Sun leaves and shade leaves differ structurally and metabolically and therefore adapt to sunlight on varying levels. Because of these differences, the process of photosynthesis is handled differently between the two types of leaves. While sun leaves are fully acclimated to the process, shade leaves are more sensitive and harvest the sun's energy at lower levels.
Structure of Sun Leaves vs. Shade Leaves
Shade leaves generally have a larger surface area and are thinner than sun leaves. As water is a main component in plant development, the surface area of a sun leaf is smaller to reduce water loss. As a result, less water is lost to heat and evaporation so a plant can grow.
Shade leaves harvest lower levels of light and thus contain more chlorophyll than sun leaves do. Because they're not directly exposed to sunlight, they need the extra chlorophyll to attract and absorb the sun's energy in order to produce the food needed for a plant to grow.
Light Saturation Point
Although sun leaves contain less chlorophyll than shade leaves do, they have a greater light saturation point and therefore can handle full exposure to the sun. Shade leaves are not predisposed to handle the extra saturation of light and can burn if exposed to the direct rays of the sun.
Shade leaves are located toward the lower part of a tree or grow under the shade of other leaves while sun leaves often develop on the canopy or crown of a tree in order to take full advantage of the sun's light.
Contact with Sunlight
Sun leaves are almost always in direct contact with the sun while shade leaves, being partially or fully shaded by other leaves, have minimal contact. As a result, shade-intolerant trees often have few, if any, shade leaves extending from their limbs while shade-tolerant trees can have an equal number of shade and sun leaves on their branches.
Shade leaves are often found growing at the bottom on the north side of a tree while sun leaves typically grow at the top and enjoy a southern exposure.