Chapter 23, Problem 20STP

Summary Introduction

To write:

The role of guard cells in regulating the amount of water in a plant.

Introduction:

A typical plant cell is identified by a large central vacuole and the presence of a cell wall. They have chloroplast, as well. There are many different cells in the plant which enable them to perform specific functions. Most plant tissues are made up of three different cell types that provide food, storage, strength and support, and flexibility.

Explanation of Solution

The outer layer of cells that form the cover of plants is known as the epidermis. Most epidermal leaf cells have small openings called stomata which allow carbon dioxide, oxygen, water and other gases to pass through. The stomata are enclosed by two bean-shaped cells, called guard cells, which result in stomata being opened and closed. The stomata on the undersides of the leaves are more numerous. The guard cells are responsible for the gaseous exchange and transpiration. The stoma opens as more water comes into the cell than out of the cells. Likewise, the stoma closes as more water goes out of the guard cells. The guard cells respond to temperature and humidity changes. Thus depending on the amount of water in the plant and the environment, the guard cells regulate the opening and the closing of stomata.

Conclusion

The guard cells control the closing and opening of the stoma and help in regulating the amount of water in the plants.