Carbon Dioxide + Water (+ Light Energy) -> Glucose + Oxygen
During photosynthesis light energy is absorbed by the chlorophyll in the chloroplasts. It is used to convert carbon dioxide and water into sugar (glucose). Oxygen is released as a by-product.
Glucose is converted into starch for storage.
Leaves are well adapted to allow the maximum photosynthesis to take place:
- most leaves are broad, they have a big surface area for light to fall on
- contain chlorphyll in the chloroplasts to absorb the light energy
- they have air spaces which allow carbon dioxide to get to the cells, and oxygen to leave them
- they have veins, which bring plenty of water to the cells of the leaves
We can artificially change the environment in which we grow plants. We can use this to observe the effect of different factors on the rate of photosynthesis. We can also use it to control their rate of photosynthesis.
LIGHT: If there is plenty of light, lots of photosynthesis can take place. If there is little or no light, photosynthesis will stop regardless of the other conditions around the plant. The brighter the light, the faster the rate of photosynthesis.
TEMPERATURE: As temperature rises, the rate of photosynthesis will increase as the reaction speeds up. Photosynthesis takes place in living organisms, this means it is controlled by enxymes. Enzymes are destroyed once the temperature rises to around 40 to 50 degrees. This means that if the tempterature gets too high, the rate of photosyntheis will fall as the enzymes contolling it are denatured.
CARBON DIOXIDE LEVELS: Plants need carbon dioxide to make glucose. The atmosphere only contains about 0.04% carbon dioxide, this limits the amount of photosynthesis which can take place. Increased rates of carbon dioxide will increase the rate of photosynthesis.
How Plants Use Glucose
Plant cells use some of the glucose they make during photosynthesis or respiration.
Some of the soluble glucose produced during photosynthesis is converted into insoluble starch for storage.
Plant cells respire all the time. They break down glucose using oxygen to provide energy for their cells. Carbon dioxide and water are the waste products of the reaction. The energy released in respiration is then used to build up smaller molecules into bigger molecules. Some of the glucose is converted into starch for storage. Plants use some of the energy from respiration to combine sugars with other nutrients from the soil to make amino acids.
Plants make food by photosynthesis in their leaves and other green parts. The food is needed all over the plant. It is moved around the plant in a special transport system. The phloem is made up of living tissue, it transports sugars made by photosynthesis from the leaves to the rest of the plant. The xylem carries water and mineral ions from the soil around the plant.
Why do plants need minerals?
Plant roots absorb mineral salts including nitrate needed for healthy growth.
Nitrates are needed from the soil to make protein, without them the plant does not grow properly.
Magnesium is needed to make chlorophyll, without it the plants turns pale with yellow leaves.
Chlorophyll is vital to plants. It absorbs the energy from light which makes it possible for plants to photosynthesise. So if the plant
The most recent development in growing crops is hydroponics. You don't plant your crops in soil, instead you plant them in water to which you add the minerals your plants need to grow as well as possible.