Chapter 35.4, Problem 2CC

Summary Introduction

To explain: The reason why stomata need to be closed, but lenticels do not.

Concept introduction:

The woody plants possess an outer hard layer called periderm in the trunks of plants. The periderm is derived from the cork cambium, a component of lateral meristem. This layer protects trees from microbial attack and insect invasions. Lenticels are loose aggregate of cells in the periderm. They help in gaseous exchange between the atmosphere and the living tissue inside the bark.

The stomata are openings in the epidermis of the leaf that allow exchange of gases. These are also the sites where the maximum evaporation takes place. The stomata are surrounded by guard cells that control their opening and closing.