The phloem conducts organic food such as glucose from the mesophyll to other parts of the plant. Drawing of a transverse section through a dorsiventral leaf to show the different tissues. Structure of the Stomata A stoma or pore is formed by a pair of bean-shaped guard cells . The guard cells have the ability to open and close the stoma. The inner walls of the guard cells are thick and the outer walls thin .
Guard cells differ from the translucent epidermal cells in that they contain chloroplasts .
Stomata communicate with the air chambers in the spongy mesophyll. There are more stomata on the lower epidermis of the leaf than the upper epidermis. The stomata are responsible for the interchange of gases for respiration and photosynthesis . The stomata allow for the loss of excess water in the form of water vapour , which also allows for cooling. Stomata with guard cells open and close.