Gas exchange in Plants
The requirement for gas exchange is the same for both plants and animals in
terms of respiration. However, plants also require carbon dioxide and give
oxygen out as a waste product in Photosynthesis.
This happens at different times of the day. During the day carbon dioxide
diffuses in and oxygen out for photosynthesis, and during the night – when only
respiration occurs – oxygen diffuses in and carbon dioxide out.
This is a diagram of the internal structure of a leaf showing how gas exchange
occurs for photosynthesis.
The stomata are the actual part of the leaf through which the gas exchange
takes place. It is made up of 2 guard cells which, when filled with water, swell
causing an opening between them. This is where the gases move in and out. The
main purpose of the stomata is to control water loss. During the day, when it is
hot, the stomata tend to be open to allow water out of the plant keeping it cool.
This also means it is allowing carbon dioxide in for photosynthesis.
Photosynthesis occurs up to twenty times faster when the stomata are fully
Photosynthesis is a process carried out by plants alone. This is because it
happens in the chloroplast of a plant. It is the process of using the suns’ energy
along with carbon dioxide and water to make glucose (food) and oxygen. This is
why plants are called producers – they produce their own food chemically. The
formula for gas exchange is:
Carbon dioxide + water + light oxygen + glucose (food)