Given below are a few statements regarding aquaporin-mediated water transport in plants.
A. The activity of aquaporins is regulated by altered pH and Ca²⁺ concentration as well as phosphorylation.
B. Aquaporin activity is also regulated by reactive oxygen species.
C. Aquaporins are restricted only to epidermis and endodermal cells and not present in xylem parenchyma.
D. Aquaporins do not mediate influx of boric acid and salicylic acid into cytosol.
Which one of the following options represents the combination of all correct statements?

Correct option is A

Correct Answer
(a) A and B
Explanation
Aquaporin activity is tightly regulated by intracellular pH, Ca²⁺ levels, and phosphorylation status, making statement A correct. Reactive oxygen species are also known to modulate aquaporin gating and expression, validating statement B. Statement C is incorrect because aquaporins are widely distributed, including in xylem parenchyma cells. Statement D is incorrect as some aquaporins facilitate transport of small neutral solutes like boric acid.
Information Booster
• Aquaporins belong to the major intrinsic protein (MIP) family
• Their gating allows rapid adjustment of plant water permeability
• ROS act as signaling molecules influencing aquaporin function
• Regulation of aquaporins is crucial during drought and stress responses
Additional Knowledge
Statement C is incorrect because aquaporins are present in multiple tissues, including cortex and xylem parenchyma. Statement D is incorrect since certain aquaporins (e.g., NIPs) transport metalloids like boric acid and other small molecules in addition to water.