Nutrition in Plants Flashcards
How do you destarch a leaf?
Put the leaf in boiling water for two minutes.
Put the boiled leaf in a boiling tube containing alcohol or ethanol. Place the boiling tube in a hot water bath.
What is photosynthesis?
Photosynthesis is the process in which light energy absorbed by chlorophyll is transformed into chemical energy. The chemical energy is used to synthesise carbohydrates from water and carbon dioxide. Water and carbon dioxide are the raw materials for photosynthesis. oxygen is released during the process.
What are the limiting factors in photosynthesis?
- Light intensity
- Concentration of carbon dioxide
- Temperature
What happens to the glucose that is formed during photosynthesis?
- Used immediately in respiration or cell wall formation
- Excess glucose is converted into starch
- Converted to sucrose for storage organs
- Reacts with nitrates to form amino acids, which can form proteins or be used for synthesis of new protoplasm
- Forms fats for storage, respiration or synthesis of new protoplasm
How is the petiole adapted for photosynthesis?
It holds the leaf in position to absorb maximum light energy.
How is the lamina adapted for photosynthesis?
The thin lamina provides a short diffusion distance for gases and enables light to reach all mesophyll cells.
The broad lamina provides a large surface area for maximum absorption of light.
How is the waxy cuticle on the epidermal layers adapted for photosynthesis?
The cuticle is transparent to allow sunlight to reach the mesophyll cells.
It is waxy to reduce water loss through evaporation from the leaf.
How is the stomata in the epidermal layers adapted for photosynthesis?
It opens in the presence light to allow carbon dioxide to diffuse in and oxygen to diffuse out of the leaf.
How is the chloroplasts adapted for photosynthesis?
It absorbs and converts light energy to chemical energy used in the manufacture of sugars.
Why are there more chloroplasts in the upper palisade tissue?
More light energy can be absorbed near the leaf tissue, making photosynthesis more efficient.
Why is there an interconnecting system of air spaces in the spongy mesophyll layer?
It allows for rapid diffusion of carbon dioxide and oxygen into and out of mesophyll cells.
How do the guard cells control the size of stomata in sunlight?
In sunlight, the guard cells photosynthesise. Chemical energy produced is used to pump potassium ions into the guard cells via active transport. The water potential of guard cells is lowered and water from neighbouring epidermal cells will enter the guard cells by osmosis. This makes the guard cells become turgid and swollen, allowing them to become more curved, and thus pulling the stoma open.
How do the guard cells control the size of stomata at night?
At night, the potassium ions accumulated in the guard cells diffuse out. The water potential in the guard cells is increased, resulting in water leaving the cells by osmosis. The guard cells become flaccid and thus the stoma closes.
How does carbon dioxide enter the leaf?
During photosynthesis, the carbon dioxide is rapidly used up. Since the concentration of carbon dioxide in the leaf becomes lower than that of atmospheric air, carbon dioxide diffuses from the surrounding air into the leaf, through the stomata.
The surfaces of the mesophyll cells are covered by a thin film of water so carbon can dissolve in it. The dissolved carbon dioxide then diffuses into cells.
