A population of plants experiences several years of severe drought. Much of the population dies due to lack of water, but a few individuals survive. You set out to discover the physiological basis for their adaptation to such an extreme environmental change. You hypothesise that the survivors have the ability to synthesise higher levels of ________ than their siblings do.
A) auxin
B) gibberellin
C) cytokinin
D) abscisic acid

Question

Quizplus · Accepted Answer

Abscisic acid (ABA) is a plant hormone that plays a critical role in regulating water balance and stress responses. During drought conditions, plants increase their synthesis of ABA, which helps to close stomata (pores on leaves) to reduce water loss through transpiration. This allows the plant to conserve water and survive in conditions of limited water availability. Therefore, the survivors of the severe drought are likely to have the ability to synthesise higher levels of ABA than their siblings do, which would have helped them to survive by conserving water. The other hormones (auxin, gibberellin, cytokinin) are not directly involved in regulating water balance and are not likely to have been the basis for the survival of the drought-affected plants.

A Population of Plants Experiences Several Years of Severe Drought