Temperature is one of the most important factor that affects the rate of photosynthesis in plants. Scientists proved that the temperature directly affect the enzymes of the plant. Photosynthetic organisms are able to synthesize their own food from carbon dioxide and water in presence of light. Most plants, most algae, and some bacteria like blue-green bacteria perform photosynthesis. Photosynthesis is mostly responsible for producing and maintaining the oxygen level of the Earth’s atmosphere. It also supplies all of the organic compounds and most of the energy necessary for life on Earth.Blue-green Bacteria: Blue green bacteria is a nitrogen-fixing bacteria that lives in various varieties of moist soil and water. It can live free or in symbiotic relationship with fungi. This is found in water of rice paddies or on the surface of green algae. This bacteria fix the atmospheric nitrogen in anaerobic process.Enzyme Characteristics : As temperature directly affects the plant enzymes which helps in photosynthesis that means temperature variations affects the photosynthesis as well. Enzymes are spherical proteins which act like nonliving Catalyst. These enzymes increase the rate of reactions within living organisms by lowering the activation energy. All enzymes have an optimum temperature at which they can work best. At this temperature kinetic energy of collisions increases. The temperature tends to be too high for the enzymes to function properly. The optimum temperature is 25 degrees C,for most of the plant enzymes.The temperature destroy the characteristic properties of enzymes. It also causes vibrations within the enzyme that ends up destroying the shape of the active site by breaking the hydrogen bonds in the enzyme. Due to this the enzymes are not able to function properly as it can no longer fit the specific catalyst required for the reaction. In addition this process slows down the rate of photosynthesis. At very low temperature collisions between enzymes and substrates decrease. Due to this enzymes activity decrease. At this temperature enzymes and substrates have little kinetic energy. Due to this the rate of chemical reaction slows down.Conclusion: Thus, as we know from above discussion that only at a particular temperature, photosynthesis rate is optimum. When the temperature increase beyond that temperature or decrease below that temperature,the rate of photosynthesis fall drastically.