Stomatal opening is maximum when leaf water potential is:
Correct option is C, High. In STOMATA MOVEMENT problems like this, the accurate statement is High; the others are common mix-ups. Not these: A) Low; B) Zero; D) Negative. 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.