Which outcome disrupts C4 photosynthetic pathways in plant leaves under prolonged drought?

💡 Explanation

When water stress occurs, abscisic acid triggers stomatal closure, minimizing water loss, but preventing daytime carbon dioxide intake by mesophyll cells and thus halting initial PEP carboxylation in C4 plants. Therefore stomatal closure is the main effect, rather than photorespiration, chloroplast lysis, or Rubisco deactivation, which are indirect or less immediate consequences.

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