Answer: Because water is an essential part of the light reactions.
Explanation: It is split in photolysis to create oxygen and hydrogen ions, and the oxygen acts as the final electron acceptor, while the ions help create ATP.
Plants cannot perform photosynthesis during a drought because there is no water available. The photosynthesis equation is co2 (carbon dioxide) + h2o (water), so there can be no way to produce the product of glucose and oxygen without water.
