3.2.3. Physiological Maturity

The content of available P at the physiological maturity of WOSR as compared to the onset of FL, as a rule, was slightly higher in 2016, and considerably lower in 2017. A significant effect of NFSs was observed only in 2016 (Table 6). A higher P content was recorded for treatments fertilized with organic N, being significant in the subsoil. The effect of N rates was non-significant, although a decreasing trend in accordance with the increasing N rates was observed. The content of available K was only affected by NFS. In 2016, as compared to FL, much lower K values were recorded in the topsoil, but an opposite trend was observed in the subsoil. In 2017, an increase in K content was noted for the subsoil.

A depletion of the available Mg content, as compared to FL, was recorded in 2016 for all soil layers. In 2017, it appeared only in the topsoil. In the subsoil, a net increase in Mg content was recorded. The impact of NFS was observed only in 2016 for the subsoil, in which a significantly higher content of Mg was recorded for the M-NFS and O-NFS. The effect of N rates was observed only for the second subsoil layer in 2016. The content of available Ca showed the highest variability. Ca status was significantly affected by both experimental factors and their interaction with a particular year. In both years, the impact of NFS was recorded for all three soil layers. As a rule, the lowest content of available Ca was found for the OM-NFS. The highest Ca values were the attribute of M-NFS. The effect of the increasing N rates was highly variable between soil layers. For the topsoil, the lowest content of Ca was generally recorded for the plot fertilized with 180 kg ha−1 of N. In the subsoil, no consistent rule governing the content of available Ca was observed.

The four PCs accounted for 69.50% of the total variance in the pooled NFSs (Table A4). PC1 had the highest and most positive loadings for the Ca content in the subsoil. PC2 was associated with Kc that exerted a negative effect in its value. PC3 explained 14.16% of the total variance, and no significant loading was recorded. PC4 was controlled by the nitrate N content at BBCH 89 (N89), having a negative loading. Yield showed a positive relationship with N89 and Pa, but the latter changed in the opposite direction to that of N89 (Table S3a; Figure S3a).

**Table 6.** The content of available nutrients along the soil layers at WOSR ripening (BBCH 89), mg kg−1 soil.

\*\*\*, \*\*, \* significant at *p* < 0.001; < 0.01; < 0.05, respectively; n.s.—non significant; a, b, c significance letters, a—the highest, c—the lowest; a means within a column followed by the same letter indicate a lack of significant difference between the treatments; a, b, c—soil layers of 0.0–0.30. 0.30–0.60. 0.60–0.90 cm, respectively.

240 55.7 31.5 20.5 117.3 66.6 58.8 66.3 56.2 66.0 369.6b 122.6b 117.1 b

F-value 0.97 0.64 0.59 0.41 2.24 0.77 1.37 0.83 2.26 5.87 \*\*\* 6.13 \*\*\* 4.89 \*\* FS × N 0.31 1.49 0.53 1.98 0.54 0.76 0.40 0.57 1.37 2.99 \*\* 8.42 \*\*\* 6.41 \*\*\*

F-value 1.99 0.08 0.33 0.41 3.37 \* 5.0 \* 1.27 0.56 1.69 5.12 \*\* 16.2 \*\*\* 5.32 \*\* Nitrogen 0 63.0 34.7 25.7 105.4 78.6 63.8 66.8 64.6 74.6 379.7b 167.1b 192.9 a,b rate 60 63.1 38.2 24.6 105.3 64.5 51.1 73.8 75.4 87.4 316.4b 180.2ab 152.4 b (N) 120 48.8 26.2 19.2 104.2 90.0 53.5 79.7 73.1 111.3 595.2a 260.3a 280.5 a kg ha−1 180 54.8 24.2 18.3 110.4 74.6 52.1 71.4 64.8 76.9 316.8b 185.1ab 226.4 a,b

For the M-NFS, three PCs accounted for 75% of the total variance. PC1 was associated with seven of fourteen variables. Positive loadings were identified for P in the subsoil and Caa, but negative values for Mg and Ca for the subsoil. Variables within each subgroup were significantly and positively correlated with each other. Yield exerted a high positive loading on PC2. PC3 had the highest and most positive loading with Ka, and Kb. Yield was weakly related to other soil variables but showed an opposite direction to Pa and Kc. The latter variable was significantly and negatively correlated with Y (Table S3b; Figure S3b).

The O-NFS was associated with three PCs, which explained 73.5% of the total variance. PC1 showed high loadings of Pb, which were positive, and of Mgb, Cab, Cac, which were negative. PC2 showed high positive loading with N89 and moderate with Y (0.65) and Kc (0.63). These three variables were significantly correlated with each other, although only N89 significantly a ffected Y. The opposite direction to that set of variables was exerted by P variables, of which Pa and Pb were significantly and negatively correlated with Y. PC3 showed a high but negative loading with Ka (Table S3c; Figure S3c).

In the OM-NFS, four PCs accounted for 81.88% of the total variance. PC1 had positive loadings for Ca, but negative for P and Mgb in the subsoil. PC2 was significantly a ffected by Mga and Mgc, which had high and positive loadings, and Pa with a negative e ffect. PC3 was dominated with Ka. PC4 was associated with N89 due to its high loading and moderately a ffected by Y (0.61). Yield was closely, but not significantly, related to Ka and N89 (Table S3d; Figure S3d).


Morpho-Anatomical Adaptation against Salinity

*Smita Srivastava*

### **Abstract**

Plants tolerant of NaCl, implement several adjustments to acclimate to salt stress, such as biochemical, physiological, and morphological modifications. Besides, plants also adjust to saline circumstances by altering their anatomical structure of roots, leaves, and morphological modifications. The leaf and roots are among the essential plant organs and are involved in the transport of water and minerals used for photosynthesis. From a plant physiology perspective, water use efficiency in the quantity of CO2 fixed in photosynthesis compared to the leaf anatomy. In this review, we provide a comparative account of the morphology of the leaf and root under normal and salt stress circumstances. There is little information on the ultrastructure changes elicited in response to salt stress. The analysis expands our knowledge of how salt may impact the leaves and root anatomy.

**Keywords:** adaptive mechanisms, arbuscular mycorrhizal fungi, trichomes, stomata, mesophyll

#### **1. Introduction**

Salt stress is among the leading abiotic causes of modifications in many physiological, anatomical, and biochemical processes [1]. Anatomical and morphological changes in leaves under restricted moisture availability play a significant role in salt stress, and they are an indication of the level of tolerance. The epidermis is the external tissue of every plant organ and serves as the initial point of contact with its environment. It is essential to preserve physiologically appropriate circumstances in all plant and environment interactions for normal metabolism [2].

In salt-stressed plants, stem vascular cell thickness was much larger than control treatment; the salinity effect was concentration-dependent. Generally, plants grown in saline solution showed higher thickness in the cuticle, vascular tissues, and vessel than unstressed plants (**Figure 1B–C**). Furthermore, we observed that, in salt-stressed plants, the number of trichomes was increased from epidermal stem cells. In other words, an increase in salinity level led to more trichomes on the epidermal layer compare with control plants [3]. There are several reports on increased trichomes density under environmental stresses such as drought and salinity [4, 5]. An increase in trichome density may be a mechanism to increase tolerance to salt stress.

The importance of the cuticular layer in regulating a plant's water status and providing protection from environmental challenges has been recognized for a long time. The cuticular layer in plants restricts non-stomatal water loss and protects plants against damage from biotic and abiotic stress [6]. Due to their role

#### **Figure 1.**

*Salt stress effects on rice plant growth under control and at 200 mM NaCl treatment(A): rice leaf anatomy, Oriza sativa; (B–C): light microscopy (cross-section) in control; (C): light microscopy (cross-section) in 200 mM NaCl; cu = cuticle, ms: mesophyll cell, Bul: bulliform cells, cp: parenchyma cells, m: mesophyll, s: stomata, vb: vascular bundles, s: stomata stomata, lv: largr vascular bundle and red line indicates the thickness of parenchyma; and scale bar = 100 μm; (D): scanning electron microscopy of the adaxial surface in control rice leaves; and (E): under stress condition (200 mmol/l), showing epicuticular wax deposition.*

in controlling water loss, specialized epidermis structures have the potential to enhance the drought tolerance and WUE ("water use efficiency") of critical crops [7–10]. The cuticular wax on the leaves of the control (non-treated rice leaves) showed less than compared with the treated rice leaves (200 mmol/l NaCl), indicating adaptation against salinity to maintain photosynthesis to control water loss (**Figure 1D–E**).

Trichomes study has conventionally centered on specialized metabolic processes understanding in glandular trichomes [11–13]. Our data showed that in salinity tolerance, rice varieties have developed dense trichomes and increased in size with the help of a layer of air trapped in trichomes to reduce the rate of water transpiration as compared to susceptible varieties under differing concentrations of salt (40–160 mmol/l) [3].

The epidermis also includes stomata, which constitute epidermal pores that directly control the exchange of gases and also water status management. They may be found on a single surface (hypostomatic) and both leaf surfaces (amphistomatic) [14]. Stomata regulate water absorption through modifications in the stomatal opening, conductance, along with density. Shortly, plants alter their stomata closure to minimize water loss and a moderate absorption of CO2 for changing circumstances [15]. Our data indicated that tolerant cultivars of rice closed stomata at the highest concentration (160 mmol/l NaCl) of salt [3]. Plant leaves can rise in stomatal density and a decreased saline area indicating a change to saline stress [16, 17]. Thus, the equilibrium between the density of stomatal and site could lead to stomatal conductance control and evaporation water loss [18, 19], which establishes equilibrium in photosynthesis [20]. Similar behavior was found for other species like "*Leptochloafusca*" [21] *Imperata cylindrical* [22], and *Triticum aestivum* [23].

Salt tolerant plants exhibit leaves thickening [23–25] which may contribute to the maintenance of turgor and content of leaf water. Wankhade et al. [26] and Hameed et al. [17] identified an optimistic association between salt stress tolerance and epidermal cells' thickening. The epidermal thickness increases the water effectiveness of plants and offers more area in which NaCl is effective for the epidermis of the leaf [27]. It can also be important to increase the region of sclerenchyma with rising salinity since it provides organ rigidity and this may be an essential characteristic for salt resistance [16]. The area of the photosynthetic leaf, parenchyma

#### *Morpho-Anatomical Adaptation against Salinity DOI: http://dx.doi.org/10.5772/intechopen.101681*

tissues exhibited a progressive reduction in salinity which is likely to influence CO2 diffusion [18].

The most challenging issues to assess by traditional microscopy methods are rice mesophyll tissues as their cells are lesser and have a greater density of chloroplast [28, 29] comparison to other plants. Thus, precise mesophyll morphology evaluation is essential for assessing photosynthetic capability [30] and maintains the leaf structure against salinity via following ways;

1.*Salt exclusion*: It inhibits salts from entering the vascular scheme.

Significant modifications were detected in salt stress chloroplast in rice leaf contrast to tolerance variety. These include; (1) Modifications in the chloroplasts number & size, and starch level. (2) Disordered membranes of the chloroplast. (3) Variations in plastoglobuli numbers and sizes. (4) Loss of the disorganization and envelope of thylakoids and grana which directly affect the chlorophyll fluorescence and photosynthetic rate, and reduced the productivity of rice (12). Chloroplast is recognized as an organelle susceptible to environmental stress [31], and its pockets [32] are known to be present in salt. Even though earlier TEM investigations have shown alterations in the chloroplast ultrastructure to salt that influence photosynthetic [32], these structural variations are specifically noticeable in the thylakoids [28] that swell under salt stress [3–32]. Therefore, mesophyll conductance decrease was correlated with the olive leaf mesophyll thickening [33]. A substantial reduction in mesophyll cell size was also a notable leaf anatomical characteristic found in *A. gomboformis*. Comparatively, small cells were found to better withstand turgor pressure than massive ones and more efficiently help to maintain turgor [34]. Thus, the decline in cell size was relatively considered to sustain tissue turgescence in *A. gomboformis* as a leaf tolerance mechanism.

On the other side, improved porosity by raising the parenchyma intercellular space did not promote the propagation conductivity of stressed plants [35]. The existence of highly vacuolated epidermal cells with poor metabolic seemed to function as a dumping mechanism in preventing mesophyll cells from stress [36]. However, decreasing the diameter of the xylem tube contributed in decreased hydraulic and ionic conductance [37] and therefore reduced photosynthesis and plant development.

The influence of salinity on leaf ultrastructure changed with the plant tolerance to NaCl, as reported in two rice species, (*Oryza sativa* L.). The sensitive rice species ('Jaya') indicated variations in the chloroplast integrity compared to the tolerant species ('Kogut'). Specifically, the majority of chloroplasts of 'Jaya' exhibited indications of damage in reaction to elevated NaCl. In comparison, 'Korgut' tolerance chloroplasts variety did not exhibit any salinity impact. This response was associated with a 53% decrease in PN in Jaya, while no substantial variation in PN was found in 'Korgut' [3] (**Figure 2**). The impact of NaCl on the ultrastructure

#### **Figure 2.**

*(A) Transmission electron microscope images of salt-tolerant variety, (a) under control (without treatment) and (b) treated with 160mM Nacl, showing thylakoid system of chloroplasts remained unaffected in control as well as under treatment. However, salt-sensitive variety, transmission electron microscope images of leaf, (c) under control, Chloroplasts had a well-developed system of thylakoids, (d) Thylakoid were damaged with loss of grana stacking under treatment; (B) Gas Exchange measurements; (C) Light reaction of photosynthesis [3].*

of leaf chloroplast was investigated in two distinct pea varieties with numerous sensitivity concentrations to NaCl, one sensitive to salt ("cv. Challis") and another relatively [38].

Aranda-Romero et al. [39] investigated anatomical disturbances generated with chloride salts (NaCl, CaCl2, KCl) in both tolerant (*Cleopatra mandarin*) and sensitive (*Carrizo citrange*) citrus cultivars. Salts in *P*N were associated with alterations in leaf anatomy, like the decrease in the thickness of the leaf and decreased mesophyll cell area (**Figure 1B–C**), enhanced leaf succulence, and decreased intercellular air space, surface, and density of the tissue. The anatomical alterations related to *Arbutus unedo* leaves in semi-thin sections were found by Navarro et al. [40]. A relationship between control plants and saline plants revealed that the cell size was not significantly changed in the 1st layer of palisade cells. Hernández et al. [38] observed in the same research that the NaCl concentration of salt and salt-tolerant pea plants had a distinct impact. Moreover, *Argyranthemum coronopifolium*, as demonstrated by Morales et al. [41], is similarly susceptible to high levels of salt. These researchers discovered that the salt in these plants does not cause modifications in the chloroplast's number, while in palisade & mesophyll cells, chloroplasts have risen significantly owing to a rise in the quantity of starch in palisade parenchyma compared to mesophyll tissues. A smaller formation of sucrose and hexoses and high activity of phosphate – sucrose synthase may explain the development of starch in leaf-chloroplasts in saline condition, which may lead to the triosephosphate path towards the synthesis of starch or/and enzymes damage included in starch deterioration through modifications in the ionic chloroplast's composition [41, 42]. The variations in the sizes of a chloroplast, as well as starch accumulation among palisade and mesophyll, parenchyma was explained by various photosynthetic leaf rate values observed by Morales et al. [41].

#### **2. Anatomy of roots**

The roots under salinity stress are essential to stress management studies since the root surfaces are initially exposed to environmental stress [43]. The root system *Morpho-Anatomical Adaptation against Salinity DOI: http://dx.doi.org/10.5772/intechopen.101681*

**Figure 3.**

*Effect of salinity on root anatomy (10x, magnification) of oryza sativa L.(A): anatomical structure of rice roots under control (without treatment); and (B):under salinity stress (200 mM NaCl). The different letter in the figures represents; a; epidermis, b; exodermis, c; sclerenchyma layers, d; mesodermis, e; endodermis, f; pericycle, g; pholem, h; metaxylem.*

anatomy correlates to root efficiency and permits plants to get nutrients and water, thus increasing the degree of replacement for lost plant water [44]. The anatomy system also prevents the salt build-up from roots, so that water from salty soils may continue [45]. Salt stress mainly controls root hair production and growth [46]. Root epidermal development demonstrates flexibility because external stimuli affect epidermal cells and root hair commencement [47]. The roots cross-section of rice species seedlings studied, in absence of stress, a greater roots thickness and wellorganized tissue were noted in rice but root thickness decreased in salt condition (**Figure 3**). Growth of the plasticity root epidermis suggests a role of root hairs in detecting environmental signals that plants adapt to stressful circumstances as a reaction to different environmental conditions [48]. Optimal root systems promote plant development and increase plant output, as roots interface plants with the earth [47]. A plant root system that is increasing thus seems better since it enables it to reach deeper soil layers and get water and nutrients [49]. Moreover, soil environmental variables (temperature fluctuations, salinity, mechanical impedance, lack of O2) may also have significant effects on the root morphology. Salt stress at a lower concentration induced plentiful root hairs, but progressively less root hair counts were calculated at increased salt levels [48]. Under the stress of salt, the root hair length and the root hair density were below 25 & 40% in comparison with untreated hydroponically cultivated wheat genotypes [36]. Two determinants of the total root surface area are total root duration and branching density – improved during moderate drought stress by comparison with "*Silene vulgaris* seedlings" [43]. Moreover, the morphology of certain plants indicates their salt sensitivity. Salinity inhibits the development of plants via osmotic & toxic effects and high sodium absorption levels because sodium raises soil tolerance, decreases root growth & root water flow by decreasing hydraulic conductivity [50]. The same behavior was also found in "*Euonymus japonica*" plants treated with a solution of NaCl and retrieved water comprising various levels of salt, which reduced the entire plant's root length, most particularly in thin ("Ø ≤ 0.5 mm") as well as average thickness ("0.5 < Ø≤2.0 mm") roots [51]. In other varieties of the plant (*Portulaca oleracea* &*Pinus banksiana*), Croser et al. [52] & Franco et al. [46] have reported a rise in root diameter as a result of salinity. The higher root density found in plants indicates better tolerance and perhaps greater reserved accumulation [45, 46] that might enhance plant resistance and accelerate the plant's establishment for farming and landscape objectives, particularly ornamental plants [53]. Root hydraulic conductivity can vary according to the salt concentration of irrigated water used in cultivated fields [54]. The root hydraulic behavior usually expresses the entire root dry weight, regardless of the root architectural function in

water absorption capacity. However, the number of fine roots that define the root and the area could vary significantly in any given relatively dry weight value, therefore influencing the degree of water absorption [55]. The detrimental impacts of abiotic stress may be reduced more by salt-tolerant rootstocks than by rootstocks sensitive to salt. Navarro et al. [54] reported lower fruit production and attribute in Carrizo grafting of the *Clemenules mandarins* ("salt-sensitive rootstock") in comparison with *Cleopatra* ("salt-tolerant rootstock"), both exposed to a solution of NaCl (30 mM). According to Penella et al. [56], the output of commercial pepper cultivars during salt irrigation was shown to be raised in salt-tolerant rootstocks. Nassar et al. [57] noted that the widths of vascular bundles and rice stems diameters reduced in NaCl. NaCl treatment in mung bean seedlings was noted by Khan et al. [58] to suppress the development of the vascular system. Gal et al. [59] found that shoot/root ratio was an essential indicator in predicting water consumption, water loss, and hydraulic conductivity in the C3 plants. The roots permeability to water is also measured by other root features, like the number of root hairs, root cortex width, xylem vessels number & diameter, and the suberin deposition in root endodermis and exodermis. This xylem structural modification may influence the capacity of water movement [60]. The xylem's capability to resist negativity depends on the specific environmental limitations [60]. Many studies show that every plant uses the same basic effectors and regulatory systems for salt tolerance and that the variation in glycophytic & halophytic species is quantitative rather than qualitative [61].

## **3. AMF ("arbuscular mycorrhizal fungi")**

The inoculation of roots AMF (that is considered an essential bio-ameliorators) for salt soils and facilitating host plants' strong growth under stressful circumstances through various complicated events of communication between the plants as well as the fungus, leading to enhancing photosynthetic activity and other features linked to gas exchanges [62] and enhanced absorption of water. Several investigations have shown that AMF's effectiveness imparts development and increase in salinity stress plants [63, 64]. AMF enhances plant nutrition by improving the availability and transport of different nutrients [65]; and also enhances soil quality by affecting its texture and structure, and therefore plant health [66, 67] and reduces Na and Cl uptake, resulting in a growth boost [68]. Good interactions between AMF-soil plants may allow reusing of recovered water, especially when roots develop in saline soil [69]. Mycorrhizal inoculation prominently increased photosynthetic rate with other gas interchange characteristics, the content of chlorophyll, and water usage effectiveness in "*Ocimumbasilicum* L." in saline circumstances [70]. AMF-inoculated plants with "*allium sativum*" exhibited increased development rates, such as the leaf area index, dry & fresh biomass in saline circumstances [71] Wang et al. [72] observed a substantial improvement in fresh & dry weights and N levels of Root & Shoot owing to inoculation with mycorrhizal in mild saline conditions.

## **4. Conclusion**

With a burgeoning population estimated to reach around 1.43 billion by 2030, India requires approximately 311 million tons of cereals and pulses to achieve food security. To meet the future food security target, it is expected to increase food grain production by 2 million tons per annum. To increase food grain production, there is a dire need to expand agricultural land and increase crop productivity. One

#### *Morpho-Anatomical Adaptation against Salinity DOI: http://dx.doi.org/10.5772/intechopen.101681*

of the possible solutions to address this problem is the genetic improvement of rice varieties in order to enhance their tolerance to salinity. In this review we have discussed morphology and anatomy review that indicates, high salinity is characterized by an increase in the leaf size, trichome and stomata size, and number, thickening of epidermis, area of vascular bundles, maintained thylakoid structure as adaptive characters for salinity stress; these characters are used as an indicator of the salinity of the soil. In addition, AMF is considered essential bio-ameliorators, which can enhance soil quality and maintain better productivity under salinity. Therefore, understanding different mechanisms enable crops to be sustained in hypersaline conditions; this may eventually contribute in improving rice yield on saline lands.

## **Author details**

Smita Srivastava Department of Botany, Goa University, Taleigao, Goa, India

\*Address all correspondence to<EMAIL_ADDRESS>
© 2022 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

## **References**

[1] Silva BRS, Batista BL, Lobato AKS. Anatomical changes in stem and root of soybean plants submitted to salt stress. Plant Biology. 2021;**23**(1):57-65. DOI: 10.1111/plb.13176

[2] Glover BJ, Airoldi CA, Moyroud E. Epidermis: Outer cell layer of the plant. In: eLS. Chichester, UK: John Wiley & Sons, Ltd.; 2016. DOI: 10.1002/<PHONE_NUMBER>902.a0002072.pub3

[3] Srivastava S, Sharma PK. Morphophysiological and biochemical tolerance mechanisms in two varieties of Oryza sativato salinity. Russian Journal of Plant Physiology. 2022;**69**:37. DOI: 10.1134/S1021443722020194

[4] Abernethy GA, Fountain DW, McManus MT. Observations on the leaf anatomy of Festuca novae-zelandiae and biochemical responses to a water deficit. New Zealand Journal of Botany. 1998;**36**(1):113-123

[5] Aguirre-Medina JF, Gallegos JAA, del Ruiz Posadas L, Shibata JK, Lopez CT. Morphological differences on the leaf epidermis of common bean and their relationship to drought tolerance. Agricultura technical en mexico. 2002;**28**(1):53-64

[6] Riederer M, Schreiber L. Protecting against water loss: Analysis of the barrier properties of plant cuticles. Journal of Experimental Botany. 2001;**52**(363):2023-2032. DOI: 10.1093/ jexbot/52.363.2023

[7] Bleeker PM, Mirabella R, Diergaarde PJ, VanDoorn A, Tissier A, Kant MR, et al. Improved herbivore resistance in cultivated tomato with the sesquiterpene biosynthetic pathway from a wild relative. Proceedings of the National Academy of Sciences of the United States of America. 2012;**109**(49):20124-20129. DOI: 10.1073/pnas.1208756109

[8] Antunes WC, Provart NJ, Williams TCR, Loureiro ME. Changes in stomatal function and water use efficiency in potato plants with altered sucrolytic activity. Plant, Cell and Environment. 2012;**35**(4):747-759. DOI: 10.1111/j.1365-3040.2011.02448.x

[9] Tian D, Tooker J, Peiffer M, Chung SH, Felton GW. Role of trichomes in defense against herbivores: Comparison of herbivore response to woolly and hairless trichome mutants in tomato (Solanum Lycopersicum). Planta. 2012;**236**(4):1053-1066. DOI: 10.1007/s00425-012-1651-9

[10] Galmés J, Ochogavía JM, Gago J, Roldán EJ, Cifre J, Conesa MÀ. Leaf responses to drought stress in mediterranean accessions of solanum lycopersicum: Anatomical adaptations in relation to gas exchange parameters. Plant, Cell and Environment. 2013;**36**(5):920- 935. DOI: 10.1111/pce.12022

[11] Franks PJ, Doheny-Adams WT, Britton-Harper ZJ, Gray JE. Increasing water-use efficiency directly through genetic manipulation of stomatal density. New Phytologist. 2015;**207**(1):188-195. DOI: 10.1111/nph.13347

[12] Schleiff U, Muscolo A. Fresh look at plant salt tolerance as affected by dynamics at the soil/root-interface using Leek and Rape as model crops. European Journal of Plant Science and Biotechnology. 2011;**5**:27-32

[13] Spyropoulou EA, Haring MA, Schuurink RC. RNA sequencing on Solanum lycopersicum trichomes identifies transcription factors that activate terpene synthase promoters. BMC Genomics. 2014;**15**:402. DOI: 10.1186/1471-2164-15-402

[14] Kang JH, McRoberts J, Shi F, Moreno JE, Jones AD, Howe GA. The flavonoid biosynthetic enzyme chalcone *Morpho-Anatomical Adaptation against Salinity DOI: http://dx.doi.org/10.5772/intechopen.101681*

isomerase modulates terpenoid production in glandular trichomes of tomato. Plant Physiology. 2014;**164**(3):1161-1174. DOI: 10.1104/ pp.113.233395

[15] Richardson F, Brodribb TJ, Jordan GJ. Amphistomatic leaf surfaces independently regulate gas exchange in response to variations in evaporative demand. Tree Physiology. 2017;**37**(7):869-878. DOI: 10.1093/ treephys/tpx073

[16] McElwain JC, Yiotis C, Lawson T. Using modern plant trait relationships between observed and theoretical maximum stomatal conductance and vein density to examine patterns of plant macroevolution. New Phytologist. 2016;**209**(1):94-103. DOI: 10.1111/ nph.13579

[17] Hameed M, Ashraf M, Naz N, Qurainy FA. Anatomical adaptations of Cynodondactylon (L.) Pers. from the Salt Range, Pakistan to salinity stress. I. Root and stem anatomy. Pakistan Journal of Botany. 2010;**42**:279-289

[18] Aasamaa K, Söber A, Rahi M. Leaf anatomical characteristics associated with shoot hydraulic conductance, stomatal conductance and stomatal sensitivity to changes of leaf water status in temperate deciduous trees. Functional Plant Biology. 2001;**28**(8):765-774. DOI: 10.1071/PP00157

[19] Zhang H, Wang X, Wang S. A study on stomatal traits of Platanus acerifolia under urban stress. Journal of Fudan Journal of Fudan. 2004;**43**:651-656

[20] Bosabalidis AM, Kofidis G. Comparative effects of drought stress on leaf anatomy of two olive cultivars. Plant Science. 2002;**163**(2):375-379. DOI: 10.1016/S0168-9452(02)00135-8

[21] Degl'Innocenti E, Hafsi C, Guidi L, &Navari-Izzo, F. The effect of salinity

on photosynthetic activity in potassiumdeficient barley species. Journal of Plant Physiology. 2009;**166**(18):1968-1981. DOI: 10.1016/j. jplph.2009.06.013

[22] Ola HAE, Reham EF, Eisa SS, Habib SA. Morphoanatomical changes in salt stressed kallar grass (Leptochloafusca L. Kunth). Research Journal of Agriculture and Biological Sciences. 2012;**8**:158-166

[23] Ali I, Abbas SQ, Hameed M, Naz N, Zafar S, Kanwal S. Leaf anatomical adaptations in some exotic species of Eucalyptus L.'Hér. (Myrtaceae). Pakistan Journal of Botany. 2009;**41**: 2717-2727

[24] Akram M, Akhtar S, Javed IUH, Wahid A, Rasul E. Anatomical attributes of different wheat (Triticum aestivum) accessions/varities to NaCl salinity. International Journal of Agriculture and Biology. 2002;**4**:166-168

[25] Nawaz T, Hameed M, Ashraf M, Ahmad MSA, Batool R, Fatima S. Anatomical and physiological adaptations in aquatic ecotypes of Cyperus alopecuroidesRottb. under saline and waterlogged conditions. Aquatic Botany. 2014;**116**:60-68. DOI: 10.1016/j.aquabot.2014.01.001

[26] Wankhade SD, Cornejo MJ, Mateu-Andrés I, Sanz A. Morphophysiological variations in response to NaCl stress during vegetative and reproductive development of rice. Acta Physiologiae Plantarum. 2013;**35**(2):323- 333. DOI: 10.1007/s11738-012-1075-y

[27] Shabala S, Hariadi Y, Jacobsen SE. Genotypic difference in salinity tolerance in quinoa is determined by differential control of xylem Na+ loading and stomatal density. Journal of Plant Physiology. 2013;**170**(10):906-914. DOI: 10.1016/j.jplph.2013.01.014

[28] Oi T, Enomoto S, Nakao T, Arai S, Yamane K, Taniguchi M. Three-dimensional intracellular structure of a whole rice mesophyll cell observed with FIB-SEM. Annals of Botany. 2017;**120**(1):21-28. DOI: 10.1093/aob/mcx036

[29] Sage TL, Sage RF. The functional anatomy of rice leaves: Implications for refixation of photorespiratory CO2 and efforts to engineer C4 photosynthesis into rice. Plant and Cell Physiology. 2009;**50**(4):756-772. DOI: 10.1093/ pcp/pcp033

[30] Burundukova OL, Zhuravlev YN, Solopov NV, P'yankov VI. A method for calculating the volume and surface area in rice mesophyll cells. Russian Journal of Plant Physiology. 2003;**50**(1):133-139. DOI: 10.1023/A:1021961123504

[31] Omoto E, Kawasaki M, Taniguchi M, Miyake H. Salinity induces granal development in bundle sheath chloroplasts of NADP-malic enzyme type C4 plants. Plant Production Science. 2009;**12**(2):199-207. DOI: 10.1626/pps.12.199

[32] Yamane K, Oi T, Enomoto S, Nakao T, Arai S, Miyake H, et al. Three-dimensional ultrastructure of chloroplast pockets formed under salinity stress. Plant, Cell and Environment. 2018;**41**(3):563-575. DOI: 10.1111/pce.13115

[33] Loreto F, Centritto M, Chartzoulakis K. Photosynthetic limitations in olive cultivars with different sensitivity to salt stress. Plant, Cell and Environment. 2003;**26**(4):595-601. DOI: 10.1046/j.1365-3040.2003.00994.x

[34] Boughalleb F, Abdellaoui R, Hadded Z, Neffati M. Anatomical adaptations of the desert species Stipa lagascae against drought stress. Biologia. 2015;**70**(8):1042-1052. DOI: 10.1515/ biolog-2015-0125

[35] Boughalleb F, Denden M, Tiba BB. Anatomical changes induced by

increasing NaCl salinity in three fodder shrubs, Nitraria retusa, Atriplex halimus and Medicago arborea. Acta Physiologiae Plantarum. 2009;**31**(5):947-960. DOI: 10.1007/ s11738-009-0310-7

[36] Tester M, Davenport R. Na+ tolerance and Na+ transport in higher plants. Annals of Botany. 2003;**91**(5):503-527. DOI: 10.1093/ aob/mcg058

[37] Van Ieperen W, Van Meeteren U, Van Gelder H. Fluid ionic composition influences hydraulic conductance of xylem conduits. Journal of Experimental Botany. 2000;**51**(345): 769-776. DOI: 10.1093/jexbot/51. 345.769

[38] Hernández JA, Olmos E, Corpas FJ, Sevilla F, del Río LA. Salt-induced oxidative stress in chloroplast of pea plants. Plant Science. 1995;**105**(2): 151-167. DOI: 10.1016/0168-9452 (94)04047-8

[39] Romero-Aranda R, Moya JL, Tadeo FR, Legaz F, Primo-Millo E, Talon M. Physiologicalandanatomical disturbances induced by chloride salts in sensitive and tolerant citrus: Beneficial and detrimental effects of cations. Plant, Cell and Environment. 1998;**21**(12):1243-1253. DOI: 10.1046/j.1365-3040.1998.00349.x

[40] Navarro A, Bañón S, Olmos E, Sánchez-Blanco MJ. Effects of sodium chloride on water potential components, hydraulic conductivity, gas exchange and leaf ultrastructure of arbutus unedo plants. Plant Science. 2007;**172**(3):473- 480. DOI: 10.1016/j. plantsci.2006.10.006

[41] Morales MA, Sánchez-Blanco MJ, Olmos E, Torrecillas A, Alarcón JJ. Changes in the growth, leaf water relations and cell ultraestructure in argyranthemum coronopifolium plants under saline conditions. Journal of Plant *Morpho-Anatomical Adaptation against Salinity DOI: http://dx.doi.org/10.5772/intechopen.101681*

Physiology. 1998;**153**(1-2):174-180. DOI: 10.1016/S0176-1617(98)80062-X

[42] Balibrea ME, Dell'Amico J, Bolarín MC, Pérez-Alfocea F. Carbon partitioning and sucrose metabolism in tomato plants growing under salinity. Physiologia Plantarum. 2000;**110**(4):503-511. DOI: 10.1111/j.1399-3054.2000.1100412.x

[43] Szabó-Nagy A, Galiba G, Erdei L. Induction of soluble phosphatases under ionic and non-ionic osmotic stresses in wheat. Journal of Plant Physiology. 1992;**140**(5):629-633. DOI: 10.1016/ S0176-1617(11)80800-X

[44] Khan MH, Panda SK. Alterations in root lipid peroxidation and antioxidative responses in two rice cultivars under NaCl-salinity stress. Acta Physiologiae Plantarum. 2007;**30**(1):81-89. DOI: 10.1007/s11738-007-0093-7

[45] Franco JA, Bañón S, Vicente MJ, Miralles J, Martínez-Sánchez JJ. Root development in horticultural plants grown under abiotic stress conditions–a review. Journal of Horticultural Science and Biotechnology. 2011;**86**(6):543-556. DOI: 10.1080/14620316.2011.11512802

[46] Munns R, Passioura JB, Colmer TD, Byrt CS. Osmotic adjustment and energy limitations to plant growth in saline soil. New Phytologist. 2020;**225**(3):1091- 1096. DOI: 10.1111/nph.15862

[47] Dwivedi SL, Stoddard FL, Ortiz R. Genomic-based root plasticity to enhance abiotic stress adaptation and edible yield in grain crops. Plant Science. 2020;**295**:110365. DOI: 10.1016/j.plantsci.2019.110365

[48] Vamerali T, Saccomani M, Bona S, Mosca G, Guarise M, Ganis A. A comparison of root characteristics in relation to nutrient and water stress in two maize hybrids. Plant and Soil. 2003;**255**(1):157-167. DOI: 10.1023/A:1026123129575

[49] Smith DM, Inman-Bamber NG, Thorburn PJ. Growth and function of the sugarcane root system. Field Crops Research. 2005;**92**(2-3):169-183. DOI: 10.1016/j.fcr.2005.01.017

[50] López-Berenguer C, García-Viguera C, Carvajal M. Are root hydraulic conductivity responses to salinity controlled by aquaporins in broccoli plants? Plant and Soil. 2006;**279**(1):13-23

[51] Gómez-Bellot MJ, Álvarez S, Castillo M, Bañón S, Ortuño MF, Sánchez-Blanco MJ. Water relations, nutrient content and developmental responses of Euonymus plants irrigated with water of different degrees of salinity and quality. Journal of Plant Research. 2013;**126**(4):567-576. DOI: 10.1007/s10265-012-0545-z

[52] Croser C, Renault S, Franklin J, Zwiazek J. The effect of salinity on the emergence and seedling growth of piceamariana, picea glauca, and pinus banksiana. Environmental Pollution. 2001;**115**(1):9-16. DOI: 10.1016/ s0269-7491(01)00097-5

[53] Sánchez-Blanco MJ, Ortuño MF, Bañon S, Álvarez S. Deficit irrigation as a strategy to control growth in ornamental plants and enhance their ability to adapt to drought conditions. The Journal of Horticultural Science and Biotechnology. 2019;**94**(2):137-150

[54] Navarro JM, Gómez-Gómez A, Pérez-Pérez JG, Botía P. Effect of saline conditions on the maturation process of clementine Clemenules fruits on two different rootstocks. Spanish Journal of Agricultural Research. 2010;**8**(S2):21-29. DOI: 10.5424/sjar/201008S2-1344

[55] Wu HI, Sharpe PJ, Walker J, Penridge LK. Ecological field theory: A spatial analysis of resource interference among plants. Ecological Modelling. 1985;**29**(1-4):215-243

[56] Penella C, Nebauer SG, Quiñones A, San Bautista A, López-Galarza S, Calatayud A. Some rootstocks improve pepper tolerance to mild salinity through ionic regulation. Plant Science. 2015;**230**:12-22. DOI: 10.1016/j. plantsci.2014.10.007

[57] Nassar RMA, Kamel HA, Ghoniem AE, Alarcón JJ, Sekara A, Ulrichs C, et al. Physiological and anatomical mechanisms in wheat to cope with salt stress induced by seawater. Plants. 2020;**9**(2):237. DOI: 10.3390/plants9020237

[58] Khan MN, Siddiqui MH, Mukherjee S, Alamri S, Al-Amri AA, Alsubaie QD, et al. Calcium–hydrogen sulfide crosstalk during K+-deficient NaCl stress operates through regulation of Na+/H+ antiport and antioxidative defense system in mung bean roots. Plant Physiology and Biochemistry. 2021;**159**:211-225. DOI: 10.1016/j. plaphy.2020.11.055

[59] Gal A, Hendel E, Peleg Z, Schwartz N, Sade N. Measuring the hydraulic conductivity of grass root systems. Current Protocols in Plant Biology. 2020;**5**(2):e20110. DOI: 10.1002/cppb.20110

[60] Brodribb TJ. Xylem hydraulic physiology: The functional backbone of terrestrial plant productivity. Plant Science. 2009;**177**(4):245-251. DOI: 10.1016/j.plantsci.2009.06.001

[61] Flowers TJ, Troke PF, Yeo AR. The mechanism of salt tolerance in halophytes. Annual Review of Plant Physiology. 1977;**28**(1):89-121. DOI: 10.1146/annurev.pp.28.060177.000513

[62] Birhane E, Sterck FJ, Fetene M, Bongers F, Kuyper TW. Arbuscular mycorrhizal fungi enhance photosynthesis, water use efficiency, and growth of frankincense seedlings under pulsed water availability conditions. Oecologia. 2012;**169**(4):895- 904. DOI: 10.1007/s00442-012-2258-3

[63] Talaat NB, Shawky BT. Protective effects of arbuscular mycorrhizal fungi on wheat (*Triticum aestivum* L.) plants exposed to salinity. Environmental and Experimental Botany. 2014;**98**:20-31. DOI: 10.1016/j.envexpbot.2013.10.005

[64] Abdel Latef AA, Miransari M. The role of arbuscular mycorrhizal fungi in alleviation of salt stress. In: Use of Microbes for the Alleviation of Soil Stresses. Vol. 23. New York: Springer; 2014. DOI: 10.1007/978-1-4939- 0721-2\_2

[65] Rouphael Y, Franken P, Schneider C, Schwarz D, Giovannetti M, Agnolucci M, et al. Arbuscular mycorrhizal fungi act as bio-stimulants in horticultural crops. Scientia Horticulturae. 2015;**196**:91-108. DOI: 10.1016/j.scienta.2015.09.002

[66] Zou YN, Srivastava AK, Wu QS. Glomalin: A potential soil conditioner for perennial fruits. International Journal of Agriculture and Biology. 2016;**18**(2):293-297. DOI: 10.17957/ IJAB/15.0085

[67] Thirkell TJ, Charters MD, Elliott AJ, Sait SM, Field KJ. Are mycorrhizal fungi our sustainable saviours considerations for achieving food security. Journal of Ecology. 2017;**105**(4):921-929. DOI: 10.1111/1365-2745.12788

[68] Evelin H, Giri B, Kapoor R. Contribution of *Glomusintraradices* inoculation to nutrient acquisition and mitigation of ionic imbalance in NaClstressed *Trigonella foenum-Graecum*. Mycorrhiza. 2012;**22**(3):203-217. DOI: 10.1007/s00572-011-0392-0

## [69] Calvo-Polanco M,

Sánchez-Romera B, Aroca R, Asins MJ, Declerck S, Dodd IC, et al. Exploring the use of recombinant inbred lines in combination with beneficial microbial inoculants (AM fungus and PGPR) to improve drought stress tolerance in tomato. Environmental and

*Morpho-Anatomical Adaptation against Salinity DOI: http://dx.doi.org/10.5772/intechopen.101681*

Experimental Botany. 2016;**131**:47-57. DOI: 10.1016/j.envexpbot.2016.06.015

[70] Elhindi KM, El-Din AS, Elgorban AM. The impact of arbuscular mycorrhizal fungi in mitigating saltinduced adverse effects in sweet basil (*Ocimumbasilicum* L.). Saudi Journal of Biological Sciences. 2017;**24**(1):170-179. DOI: 10.1016/j.sjbs.2016.02.010

[71] Borde M, Dudhane M, Jite PK. AM fungi influences the photosynthetic activity, growth and antioxidant enzymes in *Allium sativum* L. under salinity condition. Notulae Scientia Biologicae. 2010;**2**(4):64-71. DOI: 10.15835/nsb245434

[72] Wang Y, Wang M, Li Y, Wu A, Huang J. Effects of arbuscular mycorrhizal fungi on growth and nitrogen uptake of Chrysanthemum morifolium under salt stress. PLoS One. 2018;**13**(4):e0196408. DOI: 10.1371/ journal.pone.0196408

## **Chapter 12**


**3. Equatorial plasma bubble by GPS**

The study of the spatial and temporal progress of EPBs formed in the ionosphere has been carried out using two different techniques radio waves as well as optical imaging over the globe. The optical imaging techniques have a limited coverage area, but have high resolution, while the radio wave techniques have a wide coverage area but can have low resolution for the ionospheric studies. The all sky imager is widely used instrument for the optical imaging of plasma bubble while GPS receivers used to study the ionospheric irregularities using radio waves. The **Figure 2** illustrates the occurrence of EPBs as D1 and D2 in the TEC measurements. The nocturnal variation in TEC with respect to local time (Indian Standard Time) observed on April 1, 2011 and April 2, 2011. The EPBs in TEC is indicated by D1 and D2. The occurrence period of EPBs is indicated by rectangular in the **Figure 2**.

Nishioka et al. [38] did a comprehensive study of the occurrence of plasma bubbles using ground-based GPS receiver from dip equator stations. They have considered Data from 2000 to 2006 from a network of 23 GPS receivers such as network of International GNSS Service (IGS), a GPS network by the Japan Agency for Marine-Earth Science and Technology (JAMSTEC), and Scripps Orbit Permanent Array Center (SOPAC), etc. They found a different characteristic rate of EPB occurrence in different regions also the dependency of the occurrence on the solar activity was different among the regions. They concluded that the sunset time lag effect plays an important role for the monthly variation and two asymmetries which could not be explained with the sunset time lag scenario (1) asymmetry between two solstices and (2) asymmetry between two equinoxes. They also found that the plasma bubble occurrence was high and constant for a stations having height on the dip equator (HODE) was <700 km and it is began to decrease for stations having HODE was higher than 700 km and was almost zero for the stations having HODE

**61**

the bubbles.

magnetic cycle is also studied.

*Study of Equatorial Plasma Bubbles Using ASI and GPS Systems*

higher than 900 km.. They defined HODE as shown in figure as an altitude of the geomagnetic field line on the magnetic dip equator which passes 400 km altitude

*The nocturnal variation in TEC with respect to local time (Indian Standard Time) observed on 01-02 April 2011. The EPBs in TEC is indicated by D1 and D2. The occurrence period of EPBs is indicated by rectangular.*

Haase et al. [39] have studied the Propagation of plasma bubbles over Brazil from GPS and airglow data. They have mapped the airglow data to the GPS lineof-sight geometry for the direct comparison and revealing of resolvable westward tilt of the plasma depletion that may be due to vertical shear. They found the direct correspondence between integrated electron content (IEC) depletions and characteristics of depletions seen in horizontal airglow images, with very consistent

The EPB is monitored by using data provided by ground-based GNSS receiver Network over the South American continent by Takahashi et al. [40]. They have mapped the total electron content which could cover almost all of the continent within 4000 km distance in longitude and latitude. The TEC variability is monitored continuously with a time resolution of 10 min. The bubble structures are compared with simultaneous observations of OI630 nm all-sky image at Cachoeira Paulista (22.7°S, 45.0°W) and Cariri (7.4°S, 36.5°W). The formation and development of the bubble and eastward drifting features were successfully monitored and analyzed in this study. They found that the plasma bubbles observed during the December solstice has a periodic spacing, which is a periodic seeding mechanism of

The occurrence and characteristics of EPBs have been analyzed using the TEC data from GPS receivers over Hong Kong during 2001–2012 by Kumar et al. [41]. They found that the maximum occurrences of EPBs during the equinoctial months while minimum during the December solstice throughout 2001–2012. They also used the TEC data from different GNSS receivers over the Hong Kong. They concluded that the asymmetry in the EPB occurrences could be caused by the suppression of the growth rate of the instability by inter hemispheric neutral winds, which is known to be a primary cause for triggering EPB or ESF. The influence of solar and

observations of scale, amplitude, drift velocity and timing.

*DOI: http://dx.doi.org/10.5772/intechopen.85604*

above a site of GPS receiver.

**Figure 2.**

*Study of Equatorial Plasma Bubbles Using ASI and GPS Systems DOI: http://dx.doi.org/10.5772/intechopen.85604*

#### **Figure 2.**

*Geographic Information Systems in Geospatial Intelligence*

(*tL*1) at L2. The resulting equation is (Jain et al., 2011),

∆(*t*)= 40.3 × *TEC* × ( *fL*1

60°. The STEC is measured at every 30 s by the GPS receiver.

*TEC* = \_\_\_\_ 1

**3. Equatorial plasma bubble by GPS**

∆(*t*) = *tL*1 − *tL*2 (1)

Here, ∆(*t*) is a time delay in the pseudo-range (*tL*1) at L1 and pseudo-range

where *fL*1 and *fL*2 are the group path lengths corresponding to the high and low GPS frequencies *fL*1 = 1575.42 *MHz* and *fL*2 = 1227.60 *MHz*, respectively and "*c*" is speed of light in vacuum. The TEC can be obtained by rewrite above equation as,

> 2 × *fL*2 2 \_\_\_\_\_\_\_\_\_ ( *fL*1 2 − *fL*2 2 )

The signal from different GPS satellites, at random elevation angles, recorded as a TEC measurements. These different satellites are identified by a pseudo-random number (PRN). The portions of the ionosphere cross by GPS signal depend on the elevation angle of GPS satellite. Therefore, in the present work the TEC data of only those GPS satellites, having elevation angles above 30° to avoid the multipath effect of signals, are considered. The maximum elevation angle over Hyderabad station is

The study of the spatial and temporal progress of EPBs formed in the ionosphere has been carried out using two different techniques radio waves as well as optical imaging over the globe. The optical imaging techniques have a limited coverage area, but have high resolution, while the radio wave techniques have a wide coverage area but can have low resolution for the ionospheric studies. The all sky imager is widely used instrument for the optical imaging of plasma bubble while GPS receivers used to study the ionospheric irregularities using radio waves. The **Figure 2** illustrates the occurrence of EPBs as D1 and D2 in the TEC measurements. The nocturnal variation in TEC with respect to local time (Indian Standard Time) observed on April 1, 2011 and April 2, 2011. The EPBs in TEC is indicated by D1 and D2. The occurrence period of EPBs is indicated by rectangu-

Nishioka et al. [38] did a comprehensive study of the occurrence of plasma bubbles using ground-based GPS receiver from dip equator stations. They have considered Data from 2000 to 2006 from a network of 23 GPS receivers such as network of International GNSS Service (IGS), a GPS network by the Japan Agency for Marine-Earth Science and Technology (JAMSTEC), and Scripps Orbit Permanent Array Center (SOPAC), etc. They found a different characteristic rate of EPB occurrence in different regions also the dependency of the occurrence on the solar activity was different among the regions. They concluded that the sunset time lag effect plays an important role for the monthly variation and two asymmetries which could not be explained with the sunset time lag scenario (1) asymmetry between two solstices and (2) asymmetry between two equinoxes. They also found that the plasma bubble occurrence was high and constant for a stations having height on the dip equator (HODE) was <700 km and it is began to decrease for stations having HODE was higher than 700 km and was almost zero for the stations having HODE

40.3 × *c* × *fL*1

2 − *fL*2 2 ) \_\_\_\_\_\_\_\_\_ *c* × *fL*1 2 × *fL*2

2 (2)

× ∆(*t*) (3)

**60**

lar in the **Figure 2**.

*The nocturnal variation in TEC with respect to local time (Indian Standard Time) observed on 01-02 April 2011. The EPBs in TEC is indicated by D1 and D2. The occurrence period of EPBs is indicated by rectangular.*

higher than 900 km.. They defined HODE as shown in figure as an altitude of the geomagnetic field line on the magnetic dip equator which passes 400 km altitude above a site of GPS receiver.

Haase et al. [39] have studied the Propagation of plasma bubbles over Brazil from GPS and airglow data. They have mapped the airglow data to the GPS lineof-sight geometry for the direct comparison and revealing of resolvable westward tilt of the plasma depletion that may be due to vertical shear. They found the direct correspondence between integrated electron content (IEC) depletions and characteristics of depletions seen in horizontal airglow images, with very consistent observations of scale, amplitude, drift velocity and timing.

The EPB is monitored by using data provided by ground-based GNSS receiver Network over the South American continent by Takahashi et al. [40]. They have mapped the total electron content which could cover almost all of the continent within 4000 km distance in longitude and latitude. The TEC variability is monitored continuously with a time resolution of 10 min. The bubble structures are compared with simultaneous observations of OI630 nm all-sky image at Cachoeira Paulista (22.7°S, 45.0°W) and Cariri (7.4°S, 36.5°W). The formation and development of the bubble and eastward drifting features were successfully monitored and analyzed in this study. They found that the plasma bubbles observed during the December solstice has a periodic spacing, which is a periodic seeding mechanism of the bubbles.

The occurrence and characteristics of EPBs have been analyzed using the TEC data from GPS receivers over Hong Kong during 2001–2012 by Kumar et al. [41]. They found that the maximum occurrences of EPBs during the equinoctial months while minimum during the December solstice throughout 2001–2012. They also used the TEC data from different GNSS receivers over the Hong Kong. They concluded that the asymmetry in the EPB occurrences could be caused by the suppression of the growth rate of the instability by inter hemispheric neutral winds, which is known to be a primary cause for triggering EPB or ESF. The influence of solar and magnetic cycle is also studied.

Magdaleno et al. [42] studied the Climatology characterization of EPB using GPS data for the period 1998–2008. They have considered the slant total electron content (sTEC) derived from global positioning system (GPS) data from 67 International GNSS Service (IGS) stations distributed worldwide around the geomagnetic equator and the region of the ionospheric equatorial anomaly (IEA). The Ionospheric Bubble Seeker method is used to detect and distinguishes TEC depletions associated with EPBs. They found the largest occurrence rate of EPBs over the South America-Africa region and shown that the occurrence rate goes on decreasing as we go from the magnetic equator to higher latitudes.

First time study of the occurrence frequency of EPB over West Africa is done by Okoh et al. [42] using an ASI and GNSS Receivers from June 9, 2015 to January 31, 2017. This ASI is installed at Abuja (Geographic: 8.99°N, 7.38°E; Geomagnetic: 1.60°S) which covers almost the entire airspace of Nigeria. They found most occurrences of EPB during equinoxes and least occurrences during solstices also the occurrence rate of EPBs were highest around local midnight and lower for hours farther away. They also observed that the on/off status of EPB in airglow and GNSS observations are in 70% agreement.

Kumar [43] has studied the morphology of the EPB with respect of the solar activity over the Indian region from 2007 to 2012. The sTEC data are also considered from ground-based GPS receiver at Hyderabad (17.41° N, 78.55° E, Mag Lat 08.81° N) and two receivers at Bangalore (13.02°/13.03° N, 77.57°/77.51° E, Mag. Lat. 04.53°/04.55° N) in Indian region. He also observes that the occurrence of EPB is maximum in equinoctial months. He concluded that the equinox maximum in EPB occurrences for high solar activity years may be caused by the vertical F-layer drift due to pre-reversal electric field (PRE). This is expected to be maximum when daynight terminator aligns with the magnetic meridian, i.e., during the equinox months, whereas maximum occurrences during the solstice months of solar minimum could be caused by the seed perturbation in plasma density induced by gravity waves from tropospheric origins. The seasonal dependence of the EPBs occurrence is also studied.

Recently, Takahashi et al. [44] in detail studied the Occurrences of EPB (EPBs) and medium-scale traveling ionospheric disturbances (MSTIDs). They have used the GPS satellite data-based total electron content mapping, ionograms, and 630 nm all-sky airglow images observed over the South American continent during the period of 2014–2015. They observed a close relationship between the interbubble distance and the horizontal wavelength of the MSTIDs. They concluded that the MSTIDs are followed by EPBs primarily in the afternoon to the evening period due to the strong tropospheric convective activities (cold fronts and/or intertropical convergence zones) and the MSTIDs could be one of the seeding sources of EPBs.

Barros et al. [45] used ground-based network of GNSS receivers used to monitor EPB (EPBs) by mapping the total electron content (TEC map). They considered TEC data from GNSS receivers over South America for the period between November 2012 and January 2016. They found the latitudinal gradient varying from 123 ms−1 at the Equator to 65 ms−1 for 35° S latitude in the zonal drift velocities of the EPBs. They concluded that the latitudinal gradient in the inter-bubble distances seems to be related to the difference in the zonal drift velocity of the EPB from the Equator to middle latitudes and to the difference in the westward movement of the terminator.

Over the Thailand region, the statistical analysis of the separation distance between EPB is carried by Bumrungkit et al. [46]. The separation distance between EPBs is calculated using the Haversine formula technique in which the dual frequency GPS signal used. Their results show that the separation distances between EPBs on disturbed days in 2015 are in the range of 100–1200 km.

**63**

*Study of Equatorial Plasma Bubbles Using ASI and GPS Systems*

The effects of the R-T instability and EPB on the GPS signal are also studied by Panda et al. [47]. They have considered various instances of ionospheric disturbances triggered by natural processes such as earthquakes and volcanic eruption in the recent decade to investigate the spatiotemporal and seasonal effects of ionospheric irregularities on the GNSS signals. They found that the co-seismic ionospheric disturbances are difficult to study at the equatorial region due to mask of the EPBs but over the high latitude region these co-seismic ionospheric anomaly

The effects of plasma bubbles on the GPS signal path and the positioning issue is studied by Moraes et al. [48]. The analysis focused on data from November 15, 2014 to November 30, 2014 and from February 4, 2015 to February 18, 2015, at São José DOS Campos, Brazil. They found that passing through the EPB, the radio signal may take a longer propagation path and have more losses of signal lock. The posi-

Rajesh et al. [49] demonstrate that the EPBs appear to extend toward equator or pole as a result of the descending F layer and the recombination between free electrons of F layer and ions of the E layer at different latitudes. The apparent extension would vary from night to night depending on the post sunset vertical velocity of the F layer. Over equatorial region background electron density may be playing a vital role in providing the equinoctial asymmetry in the occurrence of ESF irregularities [16]. The effect of equatorial height variation of F region on ionospheric irregularities in the low latitude F region is also an important aspect. The apex height is also contributing in the occurrence of EPBs. Haaser et al. [50] suggested that EPBs occurred near the geomagnetic dip equator (<20° dip), typically within the nighttime ionospheric anomaly, while plasma blobs occurred mainly away from the geomagnetic dip equator, outside the anomaly regions (>15° dip). Yokoyama et al. [51] reported that the zonal structure of the plasma blobs in the northern hemisphere corresponded to that of the topside EPB in the southern hemisphere on a common magnetic flux tube, although the plasma blobs and the EPBs are separated

Based on satellite data, Le et al. [52] reported that the localized eastward polarized electric field plays an important role in the creation of EPBs and plasma blobs. The strength of localized eastward polarized electric field is may depend on the virtual height of the F region at dip equator. They are directly proportional to each other. The fluctuations in the virtual height of the equatorial F region creates oscillations of F region in wave nature along the latitudes which is started from the magnetic equator to low latitude (±20°) crest of a wave. The background plasma density and fluctuations in plasma density are important factors for characterizing

The eastward polarized electric field helps to combine flowing plasma with the background plasma over low latitude. Due to this combination, EPBs are generated over low latitude regions. According to literature serve, it is clear that ionospheric irregularities like EPBs or plasma blobs are not observed regularly. This may happen because of low combination or no combination of the plasma. Thus, this combination depends on the strength of eastward polarized electric field. If the strength of eastward polarized electric field is very low, then combinations will not possible while, for its particular value, low energy regions created which are captured in optical data as dark regions. These dark regions are also called as EPBs. If the strength of eastward polarized electric field is very high then, the rate of recombination will increase and high energy regions may create over low latitude regions. These high energy regions cause the enhancement in intensity of OI 630.0 nm emission, called as plasma blobs. The strength of eastward polarized electric field is also depends on the virtual height of F region at dip equator. Our results and analysis

*DOI: http://dx.doi.org/10.5772/intechopen.85604*

tioning errors may result in these cases.

by more than 20° in latitude.

plasma blobs [53].

van be studied.

*Geographic Information Systems in Geospatial Intelligence*

magnetic equator to higher latitudes.

observations are in 70% agreement.

Magdaleno et al. [42] studied the Climatology characterization of EPB using GPS data for the period 1998–2008. They have considered the slant total electron content (sTEC) derived from global positioning system (GPS) data from 67 International GNSS Service (IGS) stations distributed worldwide around the geomagnetic equator and the region of the ionospheric equatorial anomaly (IEA). The Ionospheric Bubble Seeker method is used to detect and distinguishes TEC depletions associated with EPBs. They found the largest occurrence rate of EPBs over the South America-Africa region and shown that the occurrence rate goes on decreasing as we go from the

First time study of the occurrence frequency of EPB over West Africa is done by Okoh et al. [42] using an ASI and GNSS Receivers from June 9, 2015 to January 31, 2017. This ASI is installed at Abuja (Geographic: 8.99°N, 7.38°E; Geomagnetic: 1.60°S) which covers almost the entire airspace of Nigeria. They found most occurrences of EPB during equinoxes and least occurrences during solstices also the occurrence rate of EPBs were highest around local midnight and lower for hours farther away. They also observed that the on/off status of EPB in airglow and GNSS

Kumar [43] has studied the morphology of the EPB with respect of the solar activity over the Indian region from 2007 to 2012. The sTEC data are also considered from ground-based GPS receiver at Hyderabad (17.41° N, 78.55° E, Mag Lat 08.81° N) and two receivers at Bangalore (13.02°/13.03° N, 77.57°/77.51° E, Mag. Lat. 04.53°/04.55° N) in Indian region. He also observes that the occurrence of EPB is maximum in equinoctial months. He concluded that the equinox maximum in EPB occurrences for high solar activity years may be caused by the vertical F-layer drift due to pre-reversal electric field (PRE). This is expected to be maximum when daynight terminator aligns with the magnetic meridian, i.e., during the equinox months, whereas maximum occurrences during the solstice months of solar minimum could be caused by the seed perturbation in plasma density induced by gravity waves from tropospheric

Recently, Takahashi et al. [44] in detail studied the Occurrences of EPB (EPBs) and medium-scale traveling ionospheric disturbances (MSTIDs). They have used the GPS satellite data-based total electron content mapping, ionograms, and 630 nm all-sky airglow images observed over the South American continent during the period of 2014–2015. They observed a close relationship between the interbubble distance and the horizontal wavelength of the MSTIDs. They concluded that the MSTIDs are followed by EPBs primarily in the afternoon to the evening period due to the strong tropospheric convective activities (cold fronts and/or intertropical convergence zones) and the MSTIDs could be one of the seeding

Barros et al. [45] used ground-based network of GNSS receivers used to monitor EPB (EPBs) by mapping the total electron content (TEC map). They considered TEC data from GNSS receivers over South America for the period between November 2012 and January 2016. They found the latitudinal gradient varying from

the EPBs. They concluded that the latitudinal gradient in the inter-bubble distances seems to be related to the difference in the zonal drift velocity of the EPB from the Equator to middle latitudes and to the difference in the westward movement of the

Over the Thailand region, the statistical analysis of the separation distance between EPB is carried by Bumrungkit et al. [46]. The separation distance between EPBs is calculated using the Haversine formula technique in which the dual frequency GPS signal used. Their results show that the separation distances between

EPBs on disturbed days in 2015 are in the range of 100–1200 km.

for 35° S latitude in the zonal drift velocities of

origins. The seasonal dependence of the EPBs occurrence is also studied.

**62**

sources of EPBs.

at the Equator to 65 ms−1

123 ms−1

terminator.

The effects of the R-T instability and EPB on the GPS signal are also studied by Panda et al. [47]. They have considered various instances of ionospheric disturbances triggered by natural processes such as earthquakes and volcanic eruption in the recent decade to investigate the spatiotemporal and seasonal effects of ionospheric irregularities on the GNSS signals. They found that the co-seismic ionospheric disturbances are difficult to study at the equatorial region due to mask of the EPBs but over the high latitude region these co-seismic ionospheric anomaly van be studied.

The effects of plasma bubbles on the GPS signal path and the positioning issue is studied by Moraes et al. [48]. The analysis focused on data from November 15, 2014 to November 30, 2014 and from February 4, 2015 to February 18, 2015, at São José DOS Campos, Brazil. They found that passing through the EPB, the radio signal may take a longer propagation path and have more losses of signal lock. The positioning errors may result in these cases.

Rajesh et al. [49] demonstrate that the EPBs appear to extend toward equator or pole as a result of the descending F layer and the recombination between free electrons of F layer and ions of the E layer at different latitudes. The apparent extension would vary from night to night depending on the post sunset vertical velocity of the F layer. Over equatorial region background electron density may be playing a vital role in providing the equinoctial asymmetry in the occurrence of ESF irregularities [16].

The effect of equatorial height variation of F region on ionospheric irregularities in the low latitude F region is also an important aspect. The apex height is also contributing in the occurrence of EPBs. Haaser et al. [50] suggested that EPBs occurred near the geomagnetic dip equator (<20° dip), typically within the nighttime ionospheric anomaly, while plasma blobs occurred mainly away from the geomagnetic dip equator, outside the anomaly regions (>15° dip). Yokoyama et al. [51] reported that the zonal structure of the plasma blobs in the northern hemisphere corresponded to that of the topside EPB in the southern hemisphere on a common magnetic flux tube, although the plasma blobs and the EPBs are separated by more than 20° in latitude.

Based on satellite data, Le et al. [52] reported that the localized eastward polarized electric field plays an important role in the creation of EPBs and plasma blobs. The strength of localized eastward polarized electric field is may depend on the virtual height of the F region at dip equator. They are directly proportional to each other. The fluctuations in the virtual height of the equatorial F region creates oscillations of F region in wave nature along the latitudes which is started from the magnetic equator to low latitude (±20°) crest of a wave. The background plasma density and fluctuations in plasma density are important factors for characterizing plasma blobs [53].

The eastward polarized electric field helps to combine flowing plasma with the background plasma over low latitude. Due to this combination, EPBs are generated over low latitude regions. According to literature serve, it is clear that ionospheric irregularities like EPBs or plasma blobs are not observed regularly. This may happen because of low combination or no combination of the plasma. Thus, this combination depends on the strength of eastward polarized electric field. If the strength of eastward polarized electric field is very low, then combinations will not possible while, for its particular value, low energy regions created which are captured in optical data as dark regions. These dark regions are also called as EPBs. If the strength of eastward polarized electric field is very high then, the rate of recombination will increase and high energy regions may create over low latitude regions. These high energy regions cause the enhancement in intensity of OI 630.0 nm emission, called as plasma blobs. The strength of eastward polarized electric field is also depends on the virtual height of F region at dip equator. Our results and analysis

gives strong support for this statement. Herein, one more thing is that the flowing of plasma is in wavy nature, travel from the dip equator to low latitude. This nature of the flowing of plasma also makes an effect on the combination or recombination of plasma over low latitude regions. Thus to explain this nonlinear problem we need of more theoretical models.


**2.2 The chelate effect**

314 Soybean Physiology and Biochemistry

the Cosmetic Ingredient Review Expert Panel found that these ingredients are safe as used

Ethylenediaminetetraacetic acid (EDTA) is a very effective chelating agent but has the disadvantage that is quite persistent in the environment owing to its low biodegradability. For that reason different chelating agents were investigated, such as [S,S,] ethylenediaminedisuccinic acid, iminodisuccinic acid, methylglycine diacetic acid, etc. but the problem is the dependence of the pH on the extraction efficiency. (Tandy et al., 2004) Major industrial processes involve the sequestration of metal ions in an aqueous solution. In the textile industry, this prevents metal ion impurities from modifying colors of dyed products. In the pulp and paper industry, EDTA inhibits the ability of metal ions, especially Mn2+, to catalyze disproportionate amounts of hydrogen peroxide, which is used in "chlorine-free bleaching." Similarly, EDTA is added to some foods as a preservative or stabilizer to prevent a catalytic oxidative discoloration which is catalyzed by metal ions. Oral exposures have been noted to cause reproductive and developmental effects (Elliot & Brown, 1989). The same study by Lanigan also found that both dermal exposure to EDTA in most cosmetic formulations and inhalation exposure to EDTA in aerosolized cosmetic formulations would produce systemic effects below those seen to be toxic in oral dosing

A crucial factor to be considered in comparing studies on chelating agent is the pH of the extraction solution. While extraction was investigated at various pH values in some studies (Elliot & Brown, 1989 ,; Pichtel, 1998; Pichtel, 1997; Kim, 2003; Ghestem, 1998), some only stated the pH of the solution (Reed, 1996; Cline, 1995; Van Benschoten, 1997), while others did not consider pH at all (Pichtel, 2001; ). In general, the lower the pH of the chelating

The history and chemistry of the industrial use of natural products and their derivatives have a rich technological tradition. Many modern products, such as plastics, fuels, chemical intermediates and fibers, find their origins in natural products derived from plants and animals. Given the recent social emphasis on the environment and resource renewability, utilizing natural materials as potential resources for industrial products receives a ready

Together, the oil and protein contents of dry soybeans account for about 60% of the weight; protein being 40% and oil 20%. The remainder consists of 35% carbohydrate and about 5% ash. Most soy protein is a relatively heat-stable storage protein. This heat stability enables the manufacture of soy food products requiring high temperature cooking, such as tofu, soy

This article focuses on the application of natural "green" textured soya extract as a

The word chelation is derived from Greek, meaning "claw." The ligands lie around the

The IUPAC definition of chelation is the formation or presence of two or more separate bindings between a polydentate (multiple bonded) ligand and a single central atom. Usually these ligands are organic compounds and are called chelants, chelators, chelating agents, or

agent solution, the greater is the extraction efficiency of the toxic metals.

substitute for EDTA in its role as a metals-sequestering agent in foods.

welcome. Among the most versatile of raw materials is the soybean. (Liu, 1997)

in cosmetic formulations.

studies (Lanigan & Yamarik, 2002).

milk and textured vegetable protein (soy flour).

**2. Antecedents**

**2.1 What is a chelating agent?**

sequestering agents. (IUPAC)

central atom like the claws of a lobster.

The increased stability of complexes containing chelating ligands over those containing comparable monodentate ligands can be envisaged as having the following physical basis. Suppose we have a metal ion in solution, and we attach to it a monodentate ligand, followed by a second monodentate ligand, figure 1. These two processes are completely independent of each other. But suppose we have a metal ion and we attach to it one end of a chelating ligand (it is reasonable to assume that when we put a chelate ligand onto a metal, it happens in a stepwise fashion, i.e. one end attaches first and then the other end). The point is that the attachment of the second end of the chelate is now no longer an independent process: once one end is attached, the other end, rather than floating around freely in solution, is anchored by the linking group in reasonably close proximity to the metal ion, and is therefore more likely to join onto it than a comparable monodentate ligand would be.

Fig. 1. Complexes formation.

The figure 2 shows the EDTA ligand binding to a central copper ion.

Fig. 2. Copper ion complexes with EDTA.

Amino acids are classified into different ways base don polarity, structure, nutricional requirement, metabolic fate, etc.

Generally used classification is based on polarity. Based on polarity amino acids are classified into four groups.

Chelates of glycine with cations such as iron, zinc and copper have been fully studied. The chelates usually contain two moles of ligand (glycine) and one mol of metal as demonstrated in the figure 3.

Fig. 3. Chelate of glycine with some metal M.

Consider the two equilibriums, in an aqueous solution, between the copper (II) ion, Cu2+ and ethylenediamine (en) on the one hand and methylamine, MeNH2 on the other.

$$\mathrm{Cu^{2+} + en} \rightleftharpoons [\mathrm{Cu(en)}]^{2+} \tag{1}$$

$$\text{Cu}^{2+} + 2\text{ MeNH}\_2 \rightleftharpoons [\text{Cu(MeNH}\_2)\_2]^{2+} \tag{2}$$

In (1) the bidenate ligand ethylene diamine forms a chelate complex with the copper ion. Chelation results in the formation of a five–member ring. In (2) the bidentate ligand is replaced by two monodentate methylamine ligands of approximately the same donor power, meaning that the enthalpy of formation of Cu—N bonds is approximately the same in the two reactions. Under conditions of equal copper concentrations and when the concentration of methylamine is twice the concentration of ethylenediamine, the concentration of the complex (1) will be greater than the concentration of the complex (2). The effect increases with the number of chelate rings so the concentration of the EDTA complex, which has six chelate rings, is much higher than a corresponding complex with two monodentate nitrogen donor ligands and four monodentate carboxylate ligands. Thus, the phenomena of the chelate effect are a firmly established empirical fact.

The thermodynamic approach to explaining the chelate effect considers the equilibrium constant for the reaction: the larger the equilibrium constant, the higher the concentration of the complex.

The formation of a chelant compound is an equilibrium reaction as shown in the reaction (3)

aM n+ + b L < ==> c ML (3)

Metal Ligand Metal-chelate

The reaction rates of the forward and reverse reactions are generally not zero but, being equal; there are no net changes in any of the reactant or product concentrations. Since forward and backward rates are equal:

$$\mathbf{k}\_1 \begin{bmatrix} \mathbf{M} \mathbf{r}^\flat \end{bmatrix} \mathbf{\hat{u}} \begin{bmatrix} \mathbf{L} \end{bmatrix} \mathbf{\hat{v}} = \mathbf{k}\_2 \begin{bmatrix} \mathbf{M} \mathbf{L} \end{bmatrix} \mathbf{\hat{c}} \tag{4}$$

and the ratio of the rate constants is also a constant, now known as an equilibrium constant.

$$K = \frac{[ML]^c}{[M^{n+}]^a [L]^b} \tag{5}$$

The concentration of ligand does not change during the reaction. For that reason the equilibrium constant can be expressed only in function of metal ion and metal-complex, as showing in the equation 6.

$$K = \frac{[ML]^c}{[M^{n+}]^a} \tag{6}$$

#### **2.3 Common chelating agents**

316 Soybean Physiology and Biochemistry

Amino acids are classified into different ways base don polarity, structure, nutricional

Generally used classification is based on polarity. Based on polarity amino acids are

• *Non-polar amino acids.- They have equal number of amino and carboxyl groups and are neutral. These amino acids are hydrophobic and have no charge on the 'R' group. The amino acids in this group are alanine, valine, leucine, isoleucine, phenyl alanine, glycine, tryptophan, methionine*

• *Polar amino acids with no charge.- These amino acids do not have any charge on the 'R' group. These amino acids participate in hydrogen bonding of protein structure. The amino acids in this*

• *Polar amino acids with positive charge.- Polar amino acids with positive charge have more amino groups as compared to carboxyl groups making it basic. The amino acids, which have positive charge on the 'R' group, are placed in this category. They are lysine, arginine and histidine.*  • *Polar amino acids with negative charge.- Polar amino acids with negative charge have more carboxyl groups than amino groups making them acidic. The amino acids, which have negative charge on the 'R' group are placed in this category. They are called as dicarboxylic mono-amino*

Chelates of glycine with cations such as iron, zinc and copper have been fully studied. The chelates usually contain two moles of ligand (glycine) and one mol of metal as demonstrated

M

O - - - - - N

Consider the two equilibriums, in an aqueous solution, between the copper (II) ion, Cu2+

Cu2+ + en [Cu(en)]2+ (1)

 Cu2+ + 2 MeNH2 [Cu(MeNH2)2]2+ (2) In (1) the bidenate ligand ethylene diamine forms a chelate complex with the copper ion. Chelation results in the formation of a five–member ring. In (2) the bidentate ligand is replaced by two monodentate methylamine ligands of approximately the same donor power, meaning that the enthalpy of formation of Cu—N bonds is approximately the same in the two reactions. Under conditions of equal copper concentrations and when the concentration of methylamine is twice the concentration of ethylenediamine, the concentration of the complex (1) will be greater than the concentration of the complex (2). The effect increases with the number of chelate rings so the concentration of the EDTA complex, which has six chelate rings, is much higher than a corresponding complex with two monodentate nitrogen donor ligands and four monodentate carboxylate ligands. Thus,

and ethylenediamine (en) on the one hand and methylamine, MeNH2 on the other.

the phenomena of the chelate effect are a firmly established empirical fact.

 They are aspartic acid and glutamic acid.*

O

Fig. 3. Chelate of glycine with some metal M.

C

H C2

requirement, metabolic fate, etc.

classified into four groups.

*and proline.*

in the figure 3.

There are many chelating agents used in the industry as Na, Ca-ethylenediaminetetraacetic (EDTA), diethylenetriaminepentaacetic acid (DTPA), nitriloacetic acid, ethylene glycolbis8aminoethyl)tetraacetic acid (EGTA), D,L-mercaptosuccinic acid (MSA), meso-2-3 dimercaptopropanesuccinic acid (DMSA), D,L-2,3-dimercaptopropane-1-sulfonic acid (DMPS), penicillamine (PA), N-acetylpenicillamine (NAPA), vitamins as: thiamine (B1), pyridoxine (B6), cobalim (B12) and ascorbic acid, and many more. The most common is EDTA.

#### **2.4 Naturals chelating agents**

Virtually all biochemicals exhibit the ability to dissolve certain metals cations. Thus, proteins, polysaccharides, and polynucleic acids are excellent polydentate ligands for many metal ions. In addition to these adventitious chelators, several biomolecules are produced to specifically bind certain metals. Histidine, malate and phytochelatin are typical chelators used by plants. (U Kramer, 1996; Jurandir, 2006 & Suk-Bomg Há, 1999)

Virtually all metalloenzymes feature metals that are chelated, usually to peptides or cofactors and prosthetic groups (Lippard & Berg, 1994). Such chelating agents include the porphyrin in hemoglobin and chlorophyll. Many microbial species produce water-soluble pigments that serve as chelating agents, termed sideropho. For example, species of *Pseudomonas* are known to secrete pycocyanin and pyoverdin that bind iron. Enterobactin, produced by E. coli, is the strongest chelating agent known.

In earth science, chemical weathering is attributed to organic chelating agents, *e.g.* peptides and sugars that extract metal ions from minerals and rocks. (Michael) Most metal complexes in the environment and in nature are bound in some form of chelate ring, *e.g.* with a humic acid or a protein. Thus, metal chelates are relevant to the mobilization of metals in the soil, the uptake and the accumulation of metals into plants and micro-organisms. Selective chelating of heavy metals is relevant to bioremediation *e.g.* removal of 137Cs from radioactive waste. (Prasad, 2001)