xylem and phloem are found in roots of a plant.
xylem and phloem are found in roots of a plant.
where are xylem and phloem found in a plant?
roots
section::::plant tissues.:permanent tissues.:complex permanent tissue.









































the complex tissue consists of more than one type of cells which work together as a unit. complex tissues help in the transportation of organic material, water, and minerals up and down the plants. that is why it is also known as conducting and vascular tissue. the common types of complex permanent tissue are:









































bullet::::- xylem or wood









































bullet::::- phloem or bast.









































xylem and phloem together form vascular bundles.









































section::::plant tissues.:permanent tissues.:complex permanent tissue.:xylem.









































xylem consists of:









































bullet::::- xylem tracheids









































bullet::::- xylem vessel









































bullet::::- xylem fibres or xylem sclerenchyma









































bullet::::- xylem parenchyma
tissue (biology)
phloem sap, which has a higher concentration of sugars and nitrogen, is under positive pressure unlike the more dilute xylem sap. most of the sternorrhyncha and a number of auchenorrhynchan groups feed on phloem. phloem feeding is common in the fulgoromorpha, most cicadellidae and in the heteroptera. the typhlocybine cicadellids specialize in feeding on non-vascular mesophyll tissue of leaves, which is more nutritious than the leaf epidermis. most heteroptera also feed on mesophyll tissue where they are more likely to encounter defensive secondary plant metabolites which often leads to the evolution of host specificity. obligate xylem feeding is a special habit that is found in the auchenorrhyncha among cicadoidea, cercopoidea and in cicadelline cicadellids. some phloem feeders may take to xylem sap facultatively, especially when facing dehydration. xylem feeders tend to be polyphagous; to overcome the negative pressure of xylem requires a special cibarial pump. phloem feeding hemiptera typically have symbiotic micro-organisms in their gut that help to convert amino acids. phloem feeders produce honeydew from their anus. a variety of organisms that feed on honeydew form symbiotic associations with phloem-feeders. phloem sap is a sugary liquid low in amino acids, so insects have to process large quantities to meet their nutritional requirements. xylem sap is even lower in amino acids and contains monosaccharides rather than sucrose, as well as organic acids and minerals. no digestion is required (except for the hydrolysis of sucrose) and 90% of the nutrients in the xylem sap can be utilised. some phloem sap feeders selectively mix phloem and xylem sap to control the osmotic potential of the liquid consumed. a striking adaptation to a very dilute diet is found in many hemipterans: a filter chamber, a part of the gut looped back on itself as a countercurrent exchanger, which permits nutrients to be separated from excess water. the residue, mostly water with sugars and amino acids, is quickly excreted as sticky "honey dew", notably from aphids but also from other auchenorrhycha and sternorrhyncha.
hemiptera