ABA induces stomatal closure mainly by causing:
Correct option is C, K⁺ efflux. In STOMATA MOVEMENT problems like this, the accurate statement is K⁺ efflux; the others are common mix-ups. Not these: A) K⁺ influx; B) Cl⁻ influx; D) Water endosmosis. Tissue transport questions usually turn on xylem vs phloem, living vs dead cells, or source vs sink.
Ref: Best CSIR NET Plant Physiology books: Master Unit 6 with Taiz & Zeiger and Salisbury & Ross. Crack Part C experimental questions with top textbooks.