Soil plant atmosphere continuum Soil plant atmosphere continuum The soil-plant-atmosphere continuum (SPAC) is the pathway for water moving from soil through plants to the atmosphere. Continuum in the description highlights the continuous nature of water connection through the pathway. The low water potential of the atmosphere, and relatively higher (i.e. less negative) water potential inside leaves, leads to a diffusion gradient across the stomatal pores of leaves, drawing water out of the leaves as vapour. As water vapour transpires out of the leaf, further water molecules evaporate off the surface of mesophyll cells to replace the lost molecules since water in the air inside
Plant life-form plant functional type, which has recently replaced "life-form" in a narrow sense. Following, some relevant schemes. Based on plant habit: Humboldt described 19 (originally 16) "Hauptformen", named mostly after some characteristic genus or family: Based upon the duration of life and the height of the ligneous stem: Based on the place of the plant's growth-point (bud) during seasons with adverse conditions (cold seasons, dry seasons): Vegetation-forms: Main life-forms ("Grundformen") system: Growth-form system: Main groups of plant life forms: Following, other morphological, ecological, physiological or economic categorizations of plants. According to the general appearance (habit): According to leaf hardness, size and