ABSTRACT
In most of the plants opening of the keep their stomata open during the day-time to uptake CO2 for the photosynthesis, and side effect of keeping their stomata open during the day is that they lose 97% of the water they uptake to transpiration via stomata Plant hormone abscisic acid (ABA) has been considered as very crucial in drought-induced stomatal closing. The underlying mechanism of ABA triggered stomata closing is quite well understood. In succinct, during drought, plants induce accumulation and signaling of ABA in guard cells through various ways. Increased ABA signaling leads to increase of cytosolic Ca+2 levels, which consequently activates various ion channels at plasma membrane and tonoplast, which leads to efflux of K+ and various anions from the cell, leading to loss of turgor in guard cells and closing of the stomata. Although C3 plants have mechanisms to close their stomata during day-time 168when they are faced with water-deficit conditions, (but in prolonged drought conditions, continuous closing of stomata reduces plant’s capacity to: 1) regulate its temperature, (2) nutrient absorption by roots, and (3) photosynthesis, which leads to their death. Plants with crassulacean acid metabolism (CAM) have a mechanism for night-time carbon fixation, so they keep their stomata closed during day-time to avoid this high rate of day time transpiration.
