Plants have leaves to absorb sunlight. On plants, the two kinds of leaves are sun and shade. These leaves differ in their size and thickness and their location on the plant. They also differ in their levels of functioning. They both contain different amounts of chlorophyll and therefore conduct photosynthesis at different rates.
Chlorophyll is a green pigment that plants use for photosynthesis. It is stored within the chloroplasts, which are organelles that photosynthesise. Each plant cell can have dozens of chloroplasts. The main function of the chlorophyll is to absorb light and transfer that into energy that the plant can utilise. It uses this energy to synthesise carbohydrates from carbon dioxide and water. These carbohydrates are then used as energy for the plant.
Sun leaves are typically smaller and thicker than shade leaves. They sit at the top and outer edges of a plant, picking up the majority of the sunlight. Sun leaves are usually around two to three cells thick. This means the cells must move around to maximise absorption. Too much sunlight will damage the chloroplast, so cells take turns at the surface absorbing sunlight then move away to process it elsewhere in the cell.
Shade leaves are larger and thinner than sun leaves. They are positioned closer to the middle and the bottom of the plant. They are thin, only one cell thick, which allows the cells to arrange themselves to maximise light absorption in minimal conditions. Even with fewer cells than sun leaves, shade leaves contain more chlorophyll, the photosynthetic chemical. Shade leaves are more efficient than sun leaves at photosynthesis and can be up to five times faster at producing energy.
Sun leaves have a higher light saturation point than shade leaves. This means they can handle the intensity of direct sunlight. Shade leaves are thinner and intense sunlight would burn through them and damage the chloroplasts. Because of these adaptations, sun leaves are only found on the top and outer edges of the plant and shade leaves are found only in the inner parts and the lower parts.
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