The granum supports the process of photosynthesis in plants due to the fact that it is composed of chlorophyll and phospholipids. Grana, which is the plural form of granum, refers to a stack of thylakoids contained within the chloroplasts of plant cells.
Chloroplasts contain compartments known as thylakoids. Grana are more simply classified as "stacks" of chloroplast thylakoids. Grana are joined together by intergranal or stromal thylakoids, allowing multiple grana to function as one unit together.
These grana resemble a stack of thylakoid "coins" or "disks." A single chloroplast can contain anywhere from 10 to 100 grana. Water oxidation, the movement of protons across thylakoid membranes and the transportation of electrons within the plant cell are all actions that are dependent upon the photosynthesis process in plants.
The process of photosynthesis is necessary for plant growth, in that it provides for the splitting, or light-driven reduction, of water, which allows for electron transport chains and the creation of a proton gradient. This reduction of water enabled by the photosynthesis process allows for the production of O2, which is necessary for cellular respiration. This is what causes plants to release oxygen into the atmosphere while providing vital support for humans and animals.