During those sunny mornings and pleasant evenings, as you jog or stroll through a garden, you must have noticed the lush green color of plants around you. So pleasing to the eye, and yet the differences do you spy? The different shades of greens ranging from light to a dark mottled green. Have you ever wondered why is this so?
Why the Color Green?
It is common knowledge that plants derive their green color due to the presence of a pigment called Chlorophyll. Chlorophyll is derived from Greek words chloros (“green”) and phyllon (“leaf”). Chlorophyll is important for plants as it absorbs energy from light and thus helps plants get food. However it is lesser known that Chlorophyll is of 6 different types: a, b, c1, c2, d, f; each having a different molecular formula. Plants mostly have only two type of Chlorophyll in them: type “a” & type “b”. Chlorophyll a is teal-green in color whereas Chlorophyll b is yellow-green in color. A combination of these two type of chlorophyll provides them a shade of green.
But this still does not answer the question we started with. Let’s look at it now.
Why the variations in Green?
There are several reasons why there are variations in green for various leaves; let’s look at some of them.
It’s all about survival. Plants that get abundant sunlight have more chlorophyll a and thus have a lighter shade of green. Plants which grow in the shade have chlorophyll b in abundance – an adaptation for capturing low intensity light. The leaves are darker in these plants, as compared to those which grow in sunlight. More light, lighter green and less light, darker green; it’s that simple!
Some plants have thin leaves but some have thick leaves. Thicker leaves are either juicy (also called succulent) as in a cactus or non juicy (also called dicotyledons) as in Eucalyptus leaves. The leaves of dicotyledons are thick and non-juicy, are darker green because they have dense chloroplasts which highly absorb sunlight but have low reflectance. The succulent leaves tend to be lighter as their cells are quite watery, and thus the concentration of chlorophyll on the surface is less.
I thought an entire leaf must be of the same shade of green, but oh my, surprised I was! The upper part of a leaf is darker owing to the high concentrations of chloroplasts present as compared to the lighter bottom part.
Now, what did you think? Age wouldn’t affect the colour?
Young leaves have a lighter shade of green than matured and old leaves. Young leaves have yet to develop a fully functioning cell wall, and they don’t have the tidings for achieving photosynthesis as well, both of which contribute to a lighter shade. As the leaves mature, they become darker green. Many leaves even turn yellow or orange before death, resulting in beautiful fall foliage in various parts of the world.
Deficiencies in Plants
Yes, we are not alone in this, even plants get nutrient deficiencies! Nutrient deficiencies such as that of nitrogen, low magnesium and iron (also called Chlorosis) can make the plant go yellow or yellowish-green. This happens because these components are necessary for making chlorophyll.
Now that we know about various shades of green in a garden, let’s play a game! You already know everything there is to know. Look around you and observe as many leaves as you can and start categorizing plants according to their age!
- Variations in Green – UCLA
- The Department of Biology at Appalachian State
- University of California Museum of Paleontology