Why are leaves green

A healthy leaf under proper conditions in the summer and the rainy season, is usually green. Although there are leaves that are not green in color, most are and it is due to the presence of chlorophyll in them. Green Chlorophyll is the main pigment in the process of photosynthesis but others like xanthophylls and carotenoids are also present. Xanthophylls are yellow pigments while carotenoids are mainly orange and red. The shade of green on a leaf is determined by the ratio of their presence in the leaf. This answers the question so as to the origin of the color green in plant leaves, but one may question the logic behind it, in other words, “why do the plants choose the color green?”

The question can be treated as an ironical one, because in reality, green is the only one color that is “not chosen” by plants in general. We all know that the color of an object is the color that it reflects. Plants absorb all the other colors like red and blue directly from the sunlight in order to prepare and cycle energy for their survival through photosynthesis. As they absorb all other wavelengths except green, naturally green is reflected as the only remaining unabsorbed wavelength.

If plants were transparent in nature, then their color would not have been green because in case of transparent objects, the color reflected is the same as the color absorbed, unlike in the case of that of an opaque object. In opaque objects the color wavelengths that are absorbed become invisible to our eyes, but the wavelengths that remain unabsorbed are reflected and therefore they appear to be of the same color.

Leaves are however, not always green. Other than the leaves of certain plants that have leaves of different colors throughout, most plants change the color of their leaves during autumn. In autumn we see the orange and the yellow leaves simply because the plants start storing food for the oncoming winter from this time on, that is, the green chlorophyll almost disappears from the leaves. The waste matter and the stored glucose now become the principle contents in a leaf, which of course reflect the color wavelengths of brown, yellow or orange according to their own characteristics.