A Short Fall
JACKSONTOWN- Brilliant autumn colors are few and far between this year. A lackluster autumn is particularly disappointing to Mike Becker, director of horticulture at Dawes Arboretum, whose favorite season is autumn. He said this year's dry summer caused the less than stellar display.
"The trees were already stressed from the dryness," he said. Becker explained that fall colors depend upon photosynthesis continuing in the fall leaf even after it is no longer green; photosynthesis continues until shortly before the leaf drops. It requires plenty of moisture. He said a leaf's autumn colors are already in the leaf, hidden behind the summer green. As winter approaches, the green color drains from the leaf, exposing the color behind it.
According to about. com: chemistry, chlorophyll, which makes the leaf green, is produced in response to sunlight. As the season changes and the amount of sunlight decreases, less chlorophyll is produced, and the leaf appears less green. Other compounds within the leaf determine its fall color, such as xanthophyll, which is yellow, and carotene and lycopene, which make yellow, orange, and red. Several other compounds are responsible for other colors.
Interestingly, a deciduous tree-one that drops its leaves in autumn-must go dormant during the winter to survive. Becker said a deciduous tree kept in a controlled environment with even temperature and light all year will die. A deciduous tree doesn't have enough energy to survive a whole year and rests in dormancy through the winter. If it doesn't drop its leaves in the fall, it can't recharge itself.