The green color of leaves, while other parts of a plant like the roots lack this color, can be attributed to the presence of chlorophyll and the different functions these plant parts perform.
Leaves are primarily involved in photosynthesis, the process by which plants convert sunlight into energy. Chlorophyll, the pigment that gives leaves their green color, plays a crucial role in this process. It absorbs light most efficiently at the blue and red wavelengths, which are critical for converting solar energy into chemical energy.
In contrast, roots do not have chlorophyll and are not involved in photosynthesis. Instead, their main function is to anchor the plant in the soil and absorb water and nutrients. Since roots grow underground where light is not available, the energy conversion process that necessitates chlorophyll is not needed. Therefore, roots do not develop chlorophyll, resulting in their lack of green coloration.
This differentiation in color and function can be summarized by the hypothesis that parts of a plant are adapted to their specific roles. Leaves, exposed to sunlight, need chlorophyll for photosynthesis, whereas roots, which thrive in darkness and focus on nutrient uptake, do not require this pigment.