Autumn will always be associated with a stunning colour show. During autumn, low temperatures and short daylight hours cause trees to prepare for the coming of winter. The preparation involves the shedding of leaves.
The scene and colours created by this process are stunning and breathtaking. Green leaves turn into brilliant and striking shades of orange, red and yellow. The leaf pigment transformations create these spectacular colour changes.
That beautiful green colour of leaves is produced by the process called chlorophyll. The process involves the absorption of blue and red light from the sunlight which falls on the leaves. The light that the leaves reflect diminishes the blue and red colours to make them appear green. Some characteristics of the chlorophyll are:
- Have large molecules that are not soluble
- Not a stable compound
- Decomposes under bright sunlight
Plants continuously synthesize the chlorophyll to maintain the required amount in their leaves. The synthesizing process requires warm temperatures and sunlight. Hence, the breaking down and regeneration of chlorophyll in the leaves usually occur during summer.
Carotene is another colour pigment that can be found in plants’ leaves. The pigment absorbs the blue and blue-green light. Yellow is the colour that is created by the light reflected from the carotene. A large molecule, carotene is also an ingredient in many plants’ chloroplasts. When both chlorophyll and carotene occur in the same leaves, they remove blue, blue-green and red light from the rays of the sun that falls on the leaves. The leaves reflect a light that appears green. Some characteristics of carotene are:
- A stable compound
- Accessory absorber
- Absorbs light that is transferred to chlorophyll
- Causes leaves to appeal yellow
This colour pigment has the ability to absorb blue-green, green and blue light. The leaves that have anthocyanins reflect light that appears red. The colour that anthocyanins produced is sensitive to the cell sap’s pH. The pigment is not attached to cell membranes, unlike carotene and chlorophyll. Anthocyanin can create a vivid, bright red colour is the cell sap is acidic. A less acidic sap gives out a purple colour.
The anthocyanin is also responsible for the ripe grapes’ purple colour and the redness of ripe apples. The pigment is formed by the reaction between certain proteins and sugar in cell sap. Light is required to create the colour pigment. This is why sometimes an apple may appear green on the side that is in a shade and red on the side that is under the sun.