The main variables which affect photosynthesis are light, water, CO2 concentration and temperature.
On a deeper level, other factors like amount of chlorophyll, availability of nutrients (eg Mg is needed for chlorophyll synthesis) will also affect the rate of photosynthesis, though these are rarely covered in discussion of this topic.
The thing is that photosynthesis will be held back by whichever factor is in shortest supply.
As I sit in my study in England, the sun is shining brightly, but the temperature outside is only 5ºC. I suspect the rate of photosynthesis is limited by temperature today.
Yesterday was a dull day, but in the middle of the day it was not cold and I suspect there wasn't enough light for photosynthesis. If I had turned the security lights on my house on, the plants in my garden might (possibly) have photosynthesised faster.
In summer, some farmers growing crops in glasshouses actually increase the amount of carbon dioxide in the air as all their plants have plenty of water and light and the temperature is near the best possible for photosynthesis.
A good way to investigate this might be with the help of algae and you can use the 'Immobilised Algae' practical for this.
Although water is needed as a raw material for photosynthesis, don't bother trying to investigate water as a variable - plants normally wilt and wither long before water restricts photosynthesis at the biochemical level. They need water to support the plant to face the sun as well as a raw material of photosynthesis.
The simplest equation for photosynthesis:-
Carbon dioxide + water -----(in light, with chlorophyll and enzymes)----> sugar + oxygen
Temperature speeds up all chemical reactions - photosynthesis is no exception.
Enzymes work better in warm conditions (up to about 50ºC when enzymes start to be destroyed by heat).
The idea to get across is that different conditions will be most important on different occasions. This morning, my garden could do with more warmth - yesterday, it could do with more light / sun!
Answer:
Nitrogen fixation
Explanation:
Certain soil bacteria, e.g., <em>Azobacter spp</em> can combine free nitrogen of the atmosphere with oxygen to form nitrates. This is called <u>nitrogen fixation</u>. Other nitrogen-fixing bacteria such as Rhizobium form symbiotic unions with the roots of leguminous plants called root nodules. They fix nitrogen to form nitrates which are used up by the host plant. Nitrifying soil bacteria, e.g., <em>Nitrobacter </em>convert nitrites to nitrates in a process called <u>nitrification</u>.
Answer:
- Glycine
- Ribulose 1,5-bisphosphate
- 3-phosphoglycerate
- Glyceraldehyde 3-phosphate.
- Glucose
- Sucrose
Explanation:
The glycine, among other amino acids, helps to improve chlorophyll production and promotes the process of photosynthesis.
<u>Calvin cycle</u>
During the carbon fixation phase, a CO² molecule combinate with a ribulose 1,5-bisphosphate to form 6-carbonated molecules, which will divide into two 3-phosphoglycerate molecules.
During the reduction phase, NADPH donates its electrons to reduce 3-phosphoglycerate molecules, and turn them into glyceraldehyde 3-phosphate.
During the regeneration phase, a glyceraldehyde 3-phosphate molecule leaves the cycle and goes to the cytosol to form glucose. This step can be done when three CO² enter the cycle and produce six glyceraldehyde 3-phosphate molecules. One of them leaves the cycle to form glucose, while the other five are recycled.
<u>Cytosol: </u>
Once in the cytosol, glyceraldehyde 3-phosphate molecules are used to form glucose and fructose. These two molecules are the monosaccharides that form the sucrose.
Once sucrose is formed, it is transported from the photosynthetic tissues to different parts of the plant by the phloem.
