In which layer of the plant tissue Guard cells are present?

Guard cells are specialized cells located in the epidermis, which is the outermost layer of the plant tissue [3]. These cells occur in pairs and surround the stomatal pores, primarily on the lower surface of leaves [1]. Unlike other epidermal cells, guard cells contain chloroplasts and are responsible for regulating gas exchange and transpiration by opening and closing the stomata [3]. This regulation is achieved through changes in turgor pressure; when water flows into the guard cells, they swell and bow outward to open the pore, and when they lose water, they become flaccid and close the pore [1]. While the mesophyll layers (palisade and spongy) are the primary sites for photosynthesis, they rely on the stomata in the epidermal layer for the diffusion of carbon dioxide and the release of oxygen [2].

Sources

1. [3] https://pmc.ncbi.nlm.nih.gov/articles/PMC5462021/
2. [1] Science , class X (NCERT 2025 ed.) > Chapter 5: Life Processes > Activity 5.1 > p. 83
3. [2] https://en.wikipedia.org/wiki/Guard_cell