Autumn Leaves
Every Autumn, in temperate regions around the world, the leaves of deciduous trees undergo a transformation of color that can be quite spectacular. Leaves that spent the previous spring and summer in various shades of green now turn to brilliant shades of yellow, orange, and red. This color change is the result of transformations in leaf pigments.
The green pigment in leaves is chlorophyll, which absorbs light energy from the sun and converts it into chemical energy in the form of sugars and starches in a process called photosynthesis. Because chlorophyll is not a very stable compound, bright sunlight causes it to decompose. Therefore, plants have to continuously make more, which is a process that requires sunlight and warm temperatures.
Another pigment found in many plants is carotene, which produces yellow, orange, and brown colors. Unlike chlorophyll, carotene is very stable. When chlorophyll and carotene occur together in most leaves, the green color of the chlorophyll dominates and masks the colors of the carotene. This is why leaves appear green during the spring and summer.
A third class of leaf pigments, the anthocyanins, are red in color. Most anthocyanins are produced in the fall as a result of a reaction between high concentrations of sugars and certain proteins in the sap of the leaf cells in the presence of light. The color produced by anthocyanins is sensitive to pH. If the cell sap is highly acidic, the pigments will be a bright red color. If the cell sap has low acidity, it will be more purplish in color.
The cool nights and short days of autumn trigger a change in the trees. A corky membrane forms between the branch and the leaf stem. This membrane cuts off the flow of nutrients into the leaf, resulting in a decline in the production of chlorophyll. As a result, the remaining chlorophyll decomposes, causing the green color of the leaf to fade. If the leaf contains carotene, as do the leaves of birch and hickory, the color will change from green to yellow or orange. If it contains anthocyanins, the leaf will change to a shade of red or purple, as do the leaves of red maples, red oaks, and sumacs.
Weather also affects how bright the colors will be each season with temperature and moisture being the main influences. Lots of warm, sunny days and cool, crisp, above freezing nights produce the most spectacular color displays. Also, dry weather conditions increase the concentration of sugars in the leaf sap, which increases the amount of anthocyanins that are produced.
As the death of the leaves in the autumn produces a splendor of beauty, so the soul who surrenders his life to Christ and dies daily to self will develop a beautiful character as he beholds the life of Christ. “We need to understand how necessary it is that we die to self. Self-crucifixion will place souls on vantage ground. I entreat those [of you] who profess to be Christians to die to self that you may be stirred with a new life by the Holy Spirit’s power. Satan is working with all deceivableness of unrighteousness in them that perish. Daily we need the converting power of God, or we cannot walk in the footprints of Christ. As the mind is enlightened in regard to what is purity and sanctification, and the heart responds to the strivings of the Holy Spirit, a daily conversion will be the result.” The Upward Look, 269.
David Arbour