Question

Stomata close in response to bacterial infection. Why is this response a mechanism of defense for the plant? Which hormone is most likely to mediate this response?

a) Auxin; to prevent wilting and maintain turgidity
b) Gibberellin; to stimulate growth and cell division
c) Ethylene; to regulate fruit ripening and senescence
d) Abscisic acid; to reduce water loss and prevent pathogen entry

Answer 1

Stomata close to prevent further entry of pathogens during a bacterial infection, with the responsible hormone being abscisic acid (ABA), which acts to preserve water and defend the plant.

Step-by-step explanation:

Plant Defense Mechanisms and Hormonal Responses

Stomata close in response to bacterial infection as a defense mechanism to prevent further entry of pathogens. The hormone most likely to mediate this response is abscisic acid (ABA). When a plant encounters stress, such as a bacterial infection, ABA levels increase, leading to the closure of stomata. This response helps to reduce water loss and restricts pathogen entry, as stomata are potential entry points for bacteria and other pathogens. The stomata are pores controlled by specialized cells called guard cells, which swell or shrink to open or close the pore, thereby controlling the exchange of gases and water vapor. By closing stomata, the plant can maintain internal water levels and thus, its turgidity and overall health during infection.

Other options like auxin, gibberellin, and ethylene play different roles in plant growth and development but do not primarily mediate the stomatal closure response to bacterial infection.