Plants can make their own food using the process of photosynthesis. During photosynthesis, plants produce glucose from simple inorganic molecules such as carbon dioxide and water using light energy. The equation for photosynthesis is: Carbon dioxide + water + light → Chlorophyll → Glucose + oxygen.
The Mechanism of Photosynthesis
Photosynthesis requires energy in the form of light to drive the chemical reaction. It is an endothermic reaction, and the light energy required is absorbed by a green pigment called chlorophyll in the leaves. Chlorophyll can be found in the chloroplasts in a plant cell, particularly in the palisade and spongy mesophyll cells.
Plant cells are the main photosynthetic organ, but any part of the plant exposed to light will develop chlorophyll and photosynthesize. Carbon dioxide required for photosynthesis comes from the air and enters the leaves through the stomata, while water enters the leaves through the roots and is transported via the xylem. During the process, oxygen is formed as a waste product, some of which is used for the plant's respiration and the rest is released, making it available for respiration to animals and microorganisms.
Biosynthesis
Some glucose produced by photosynthesis is used for respiration, while the rest is the starting point for the biosynthesis of materials that plants need to live. Glucose not used for respiration is often joined into many glucose molecules to form starch, an insoluble storage form of carbohydrates. Additionally, it is used to build cell walls and add strength to the cell.
Other biosynthesis products include lipids, which are used for storage in seeds, and amino acids, which are joined into many amino acid molecules to form proteins.
Factors Affecting Photosynthesis
There are several factors that can affect the rate of photosynthesis, including light intensity, carbon dioxide concentration, and temperature. In lighting conditions unfavorable for photosynthesis, plants synthesize more chlorophyll to absorb the required light. The amount of chlorophyll affects the rate of photosynthesis and can be impacted by certain plant diseases.
Light intensity is crucial as without enough light, plants cannot photosynthesize quickly, even if there is an abundance of water and carbon dioxide and a suitable temperature. By increasing the light intensity, the rate of photosynthesis increases, but at very high light intensities, photosynthesis is slowed and eventually inhibited.
Similarly, carbon dioxide concentration is one of the reactants in photosynthesis. Increasing the concentration of carbon dioxide also increases the rate of photosynthesis, but at some point, it may become a limiting factor.
Temperature also plays a role as the chemical reactions that make up photosynthesis are controlled by enzymes, which are affected by temperature. Low temperatures limit the rate of photosynthesis, while high temperatures can denature enzymes and limit the reaction rate.
Methods of Measuring Photosynthesis Rate
There are several methods of measuring the rate of photosynthesis in the lab. However, it's important to note that these methods are not entirely accurate as the plant will also be respiring, using up some oxygen and carbohydrate and increasing carbon dioxide output. Some of the widely used methods include measuring the rate of oxygen output, rate of carbon dioxide uptake, and the rate of carbohydrate production, all of which help in determining the factors affecting the rate of photosynthesis.
