A green plant is an autotroph capable of manufacturing organic nutrients from inorganic molecules. In order to do so, specific requirements must be met.
The plant must have a sufficient supply of water which it gets through absorption via its root system. It is then transported by xylem cells which are a type of vascular tissue specialized for conducting water up from the roots to the leaves where most food-making occurs in a green plant.
Next, the plant requires a supply of carbon dioxide gas. This will enter the leaves through tiny pores known as stomata. As carbon dioxide gas enters, it travels to the air spaces in the center of the leaf and will enter different leaf cells by the process of diffusion.
Light energy is another requirement for the food-making process in plants. Inside leaf cells are chloroplasts--organelles where photosynthesis actually occurs. The green pigment chlorophyll is contained within chloroplasts and is able to absorb visible light thus it is another requirement plants must have for photosynthesis to occur.
The energy from the sun is used during the light reaction of photosynthesis to split water molecules into hydrogen and oxygen. The oxygen is a waste products that exits the stomata. Some of the light energy is converted to chemical energy in the form of the molecules ATP and NADPH which are later used in the light-independent reaction.
In the light-independent reaction, the carbon dioxide and hydrogen combine to form glucose sugar (food) and more water. This glucose can be used by the plant for energy, or stored as a larger carbohydrate like starch as an energy reserve.
In conclusion, plants require light energy, carbon dioxide, water and chlorophyll in order to produce food energy in the form of glucose.
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