AP BIOLOGY

Detailed explanation-1: -Stomata also limit the entry of pathogens into leaves, restricting their invasion. Drought is accompanied by the production and/or mobilization of the phytohormone, abscisic acid (ABA), which is well-known for its ability to induce stomatal closure.

Detailed explanation-2: -Some plants limit water loss by closing their stomata when conditions are unfavorable. For example, when the humidity is low, water is more likely to evaporate quickly from the leaf surface, and plants often close or partially close their stomata to maintain a stable water balance in the leaf.

Detailed explanation-3: -Both of these predictions – stomatal closure and stomatal opening – are in fact correct: following an increase in water loss or a decrease in water supply, stomata transiently ‘pop open’ before eventually closing (e.g. Fig. 3).

Detailed explanation-4: -Water stress, high temperatures, and high carbon dioxide concentration causes stomata to close.