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?

Short answer

Abscisic acid mediated the closing of stomata.

Step-by-step solution

Step-1 Introduction

Plant hormones play a major role in the functional regulation of growth and development such as elongation of the plant body, germination, stress tolerance, and defense against pathogens. Stomata are the cells that help in the transpiration and respiration process in plants.

Step-2 Explanation

Regulation of transpiration is mainly achieved through the stomata by its opening and closing mechanism on the leaf surface. A specialized cell known as guard cells surrounds stomata which open and close according to environmental factors such as quality and intensity of light, presence of water concentration on the leaf, and carbon dioxide concentrations.

When there is low moisture in the soil, a plant hormone called abscisic acid (ABA) is produced in high concentration and closes the stomata that helps to reduce water loss.

Stomata can be considered as a part of plant immune response as it reacts to pathogens by closing the stomata pore and preventing pathogen entry.

Step-3 Final answer

Therefore, the response of stomata toward pathogen entry can be considered a plant defense mechanism. The closing of stomata is mainly influenced by the hormone ABA which is otherwise called Abscisic acid.