how to Photosynthesis In Plants

Plants synthesize their food by themselves and hence they are termed as "autotrophs". The leaves and stems in most of the plants except in few crotons appear green in color. The parts of the plant which appears green in color contribute for synthesis of sugars. The synthesis of sugars is carried out by the process called photosynthesis. Photosynthesis is the process of synthesizing the food materials in the plant with the help of carbon-di-oxide, water and sunlight. The entire process is divided into light reaction and dark reaction. Light reaction attained this name, as it involves sunlight releasing photons which participate in the first step of the reaction. The energy from photons is absorbed by the water molecule to get split into electron, hydrogens and oxygen. The oxygen atom released from water will be later converted to oxygen molecule in the electron transport chain of plant respiration.

The leaves or green part of the plant cells consist of a special cell organelle known as chloroplast. The chloroplasts are organelles present in every plant cell inside which the thylakoids are stacked. Thylakoids are sub cellular structures that are bound by a membrane. The thylakoids membrane possesses pigment molecules called as chlorophylls. Chlorophyll is the green pigment that comprises of four Porphyrin rings with a magnesium ion in the center. Chlorophyll molecules exist in and around the photo systems I and II that are available in the thylakoid membranes. Chlorophyll molecule acts as the reaction center of photo system I and II. The reaction center of photo system I absorbs light of one particular wavelength (680nm) and the other center absorbs another wavelength of light (700nm). The chlorophyll in the photo system II absorbs electron given out from splitting of water. Chlorophyll from photo system I take the electron that has travelled through many electron transporters in the photo system II. The electron transfers across many electron transporting substances which get reduced and oxidized while accepting and donating electron. The process of electron transport aids in release of ATP and NADPH molecules which is called as Assimilatory power. The assimilatory power is useful as the source of energy for the dark reaction to be initiated and carried out.

Dark reaction is the series of reaction mechanisms that involve various carbon compounds getting inter converted by absorbing the energy and releasing at the end, glucose molecules. The glucose molecules are the source of food for the plant. They are utilized in the respiration as substrate. Dark reaction does not require any light or energy. It makes use of precursors that are released from light reaction and prepare the hexoses.