What is produces during water stress that brings stomatal closure? A. Ethylene B. Abscisic acid C. Ferulic acid D. Auxin
Option B.90% of the water taken by a plant is lost in transpiration and which takes place through stomata. Each stoma is consisting of two kidney-shaped guard cells. When the guard cells are turgid, the stoma is open. When the turgor is lost, then stoma closes. Plants experience water stress either when the water supply to their root become limiting, or when the transpiration is intense, or during the drought or high salinity. Abscisic acid is the hormone that triggers the closing of the stomata. When soil water is insufficient to keep up with the transpiration. Abscisic acid binds to the receptors present at the surface of the plasma membrane of the guard cells. The receptors activate several pathways, which converge to produce. A rise in pH in the cytosol. A transfer of Ca2+ ion from the vacuole to the cytosol. These changes stimulate the loss of negatively charged ions (anions) especially NO3−, Cl− ions from the cell and also the loss of K+ion from the cell. The loss of these solutes in the cytosol reduces the osmotic pressure of the cell and the turgor pressure also.
