Why do Plants need sunlight?
Plants prepare their own food and do not depend on others for food. Hence, plants are known as autotrophs and they survive without eating other organisms. The process with which the plants prepare their own food and survive is called photosynthesis. Plants grow and synthesize their own food by making use of sunlight. Photosynthesis is a process going on in the plants which require sunlight. Photosynthesis is the process that can convert light energy into chemical energy.
The plants synthesize food in the inner membrane of thylakoids which are situated in the chloroplast of the plant cells. The thylakoids consist of chlorophyll pigment which is green in color and is responsible for absorbing sunlight. Photosynthesis involves basically two types of reactions. They are called as light reaction and dark reaction. Light reaction involves the transfer of electrons taken from the photon of sunlight to the electron transporters in the photophosphorylation. There are two types of chlorophyll pigments available in photo systems I and II.
Light reaction occurs with either photo system I or II and synthesizes assimilatory power. Assimilatory power consists of ATP and NADPH2. Twelve molecules of each of these two compounds were formed from the light reaction. The dark reaction will receive the assimilatory power and then synthesize the glucose. Dark reaction is otherwise called as Calvin cycle which does not require any sunlight to carry out the glucose synthesis.
The sunlight is utilized by the two photo systems of light reaction. The photo system that splits water takes in the light energy and uses it for splitting water molecule. The splitting of water results in an electron and oxygen. The other photo system transfers the water released electron from chlorophyll to NADP to form NADPH. Chlorophyll a and b absorbs red and blue light from the sunlight and helps the plant in its survival. Sunlight is necessary for the plants as they make use of it to survive and provide oxygen to the animals on the earth.