The intensity at which a cell performs photosynthesis can be assessed by the amount of oxygen it releases to the environment, or by the amount of CO2 that she consumes.
When measuring the photosynthesis rate of a plant, it is clear that this rate may increase or decrease, depending on certain parameters. These parameters are known as limiting factors of photosynthesis. Photosynthesis has some limiting factors, some intrinsic and others extrinsic.
Intrinsic Limiting Factors
Availability of photosynthetic pigments
As chlorophyll is the main responsible for the limous energy uptake, its lack restricts the energy uptake capacity and the possibility of producing organic matter.
Enzyme and cofactor availability
All photosynthetic reactions involve the participation of enzymes and cofactors such as electron acceptors and cytochromes. Its quantity must be ideal for photosynthesis to take place at its maximum intensity.
Extrinsic Limiting Factors
The concentration of CO2
The CO2 (carbon dioxide or carbon dioxide) is the substrate employed in the chemical step as a source of carbon that is incorporated into organic molecules. Plants naturally have two main sources of CO2: the gas from the atmosphere, which penetrates the leaves through small openings called stomata, and the gas released in cellular respiration.
Without the CO2, the intensity of photosynthesis is zero. Increasing CO concentration2 the intensity of the process also rises. However, this elevation is not constant and unlimited. When the entire enzymatic system involved in carbon uptake is saturated, further increases in CO2 will not be accompanied by an increase in photosynthetic rate.
In the chemical stage, all reactions are catalyzed by enzymes, and these have their activity influenced by temperature. In general, the 10 ° C rise in temperature doubles the speed of chemical reactions.
However, from temperatures around 40 ° C, enzymatic denaturation, and the speed of reactions tends to slow down.
So there is a optimum temperature where photosynthetic activity is maximum, which is not the same for all plants.
The assimilation of light by chlorophylls The and Bmainly and secondarily by accessory pigments such as carotenoids determines the action spectrum of photosynthesis.
Note the excellent photosynthetic activity in the spectrum bands corresponding to violet / blue light and red light, and the low activity in the green range.
For a green plant to perform photosynthesis with good intensity, it should not be illuminated with green light, as this light is almost completely reflected by the leaves.
When a plant is placed in complete darkness, it does not perform photosynthesis. By increasing the light intensity, the rate of photosynthesis also increases.
However, from a certain point, further increases in illumination intensity are not accompanied by an increase in the rate of photosynthesis. Light intensity is no longer a limiting factor for photosynthesis when all pigment systems are already being excited and the plant has no way of capturing this additional amount of light. Reached luminous saturation point.
Increasing the intensity of light exposure further leads to a point from which photosynthetic activity is inhibited. It is the inhibition point of photosynthesis by excess light.