Answer: Acting as signaling scaffolds that activate H+ ATPase when bound to its phosphorylated C-terminus, promoting stomatal opening.
- A Forming the selective pore of the inward-rectifying K+ channel itself directly within the guard cell plasma membrane
- B Acting as signaling scaffolds that activate H+ ATPase when bound to its phosphorylated C-terminus, promoting stomatal opening
- C Hydrolyzing abscisic acid molecules directly into inactive breakdown products within the surrounding guard cell cytosol
- D Synthesizing entirely new K+ channel protein subunits specifically during the active stomatal opening response phase
Correct answer: B. Acting as signaling scaffolds that activate H+ ATPase when bound to its phosphorylated C-terminus, promoting stomatal opening
Explanation: 14-3-3 proteins bind phosphorylated H+ ATPase C-terminus (phosphorylated by protein kinase in response to light/fusicoccin), activating the pump. H+ efflux hyperpolarizes membrane, driving K+ influx and stomatal opening.
Water can travel through cell walls (apoplast) or cell-to-cell through the cytoplasm (symplast) - but the Casparian strip at the endodermis blocks the apoplast route entirely, forcing everything through a selectively permeable membrane (symplast) before it can enter the xylem.
Concept context
Water and mineral absorption, the ascent of sap, transpiration, and phloem transport via the pressure flow hypothesis.