Guard cells are paired cells found on the surface of plant leaves, forming small pores called stomata. These cells play a crucial role in plant defense by regulating transpiration, the process through which water evaporates from the leaves. When environmental conditions are favorable, guard cells open the stomata, allowing the exchange of gases for photosynthesis. However, in response to water scarcity or pathogenic threats, guard cells close the stomata, conserving water and preventing the entry of harmful pathogens. This dynamic control of the stomatal aperture not only ensures plant survival during adverse conditions but also helps in defending against diverse biotic stresses, making guard cells an indispensable part of plant defense mechanisms.#16#