Gaseous Exchange in Plants
Occurs in leaves, stems and roots depending on the plant’s habitat and complexity.
Mainly occurs in tiny openings called stomata found on leaves.
Structure of the Stomata
Stomata are openings between two guard cells in the epidermal layer of the leaf.
Guard cells are adjacent to the leaf epidermal cells.
Guard cells have chloroplasts and, hence are photosynthetic, unlike the adjacent epidermal cells that do not have chloroplasts.
The guard cells are curved and bean-shaped.
Their inner walls between which the stomata are found, are thicker than their outer walls which are adjacent to the leaf epidermal cells.
Have chloroplasts hence carry out photosynthesis.
Functions of Guard cells
- Regulate the opening and closing of the stomata
Difference between guard cells and the typical epidermal cells
|
Guard cells |
Typical epidermal cells |
|
Have chloroplasts |
Lack chloroplasts |
|
Have unequal wall thickness |
Have equal wall thickness |
Adaptations of Guard cells
- Have thicker inner walls and thinner outer walls to allow them to stretch unevenly when turgid to open stomata;
- Have numerous chloroplasts, to carry out photosynthesis, forming sugars to control the opening and closing of stomata;