Photosynthesis
1. Leaves have broad and flat shapes
which provide them with large surface area for absorption of carbon dioxide.
2. The thin nature of leaves enables
carbon dioxide to diffuse easily into the mesophyll cells.
3. The presence of stomata helps in gas exchange.
4. Chloroplast secrets chlorophyll which attracts light into the leaves.
5. Phloem and xylem tissues transport manufactured food from the leaves to other parts of the plants and minerals salt from the roots to the leaves.
6. Leaves are arranged in a regular pattern along the stem which prevents overshadowing and allows each leaf to receive light.
Factors which affect the rate of
photosynthesis
When plenty of carbon dioxide, sunlight and water are provided to a plant, photosynthesis will be at its maximum rate.
Sometimes the rate of photosynthesis is not
as high as expected due to inadequacy of factors that include light intensity, water, temperature and carbon dioxide concentration.
Providing plenty of each of these factors to a plant increases the rate of photosynthesis.
However, if one of these factors is not adequate, the rate of photosynthesis may become low.
A factor that is inadequate is
called a limiting factor.
Factors which affect the rate of
photosynthesis include:
1. Light intensity: In case of dim light,
the rate of photosynthesis is low. As
light intensity increases, the rate of
photosynthesis increases.
2. Carbon dioxide concentration: The
more carbon dioxide a plant is given,
the faster is the rate of photosynthesis, until a maximum is reached.
3. Temperature: Photosynthesis is an
enzyme-controlled reaction. Increase in temperature increases the rate of
photosynthesis while a decrease lowers it.
4. Stomatal opening and closing: This regulates the amount of carbon dioxide entering a plant which it uses for photosynthesis. If the stomata are closed then photosynthesis cannot take place and when they are open, carbondioxide enters and the rate of photosynthesis increases.
5. Mineral salt: Several elements are
known for normal plant growth and
development. Some of these elements are Carbon, Hydrogen and Oxygen.
6. Other elements are Nitrogen, Sulphur, Phosphorus, Potassium, Calcium and Magnesium. There are other elements called trace elements which are needed in small quantities. Plants obtain mineral salts from the soil.
The effects of these chemical elements can be discovered by growing plants in water solutions containing balanced amounts
of salts necessary for healthy plant
growth. This solution is called a
culture solution.
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