With arrival of fall the sky is clouded by heavy rain clouds, sunlight becomes less, foliage of trees and a grass turn yellow and over time fall down. Why in this gloomy season the leaves gain yellow color?
Instruction
1. Yellow color does not appear in foliage there is no place on wave of a magic wand with approach of fall, it is always present at it. The yellowness is given to a deciduous color of substance under the name by carotinoids. Their impact on color of leaves is shown only when "green" substance a chlorophyll which is developed in a large number only under the influence of plentiful sunshine begins to weaken.
2. When the summer passes, the sun becomes less, and the chlorophyll gradually collapses and ceases to absorb solar colors. Roles of main "dyes" of leaves pass to carotinoids, pigments of orange and yellow colors.
3. Not only the shortage of sunshine can lead to yellowing of foliage. It can occur during a drought when leaves are not able to receive a necessary amount of water. The plant dumps a part of foliage to save moisture. Suffer from a drought both wild, and houseplants, in the first case due to the lack of rains, in the second – because of dry air indoors, insufficient watering, narrowness of a pot, etc.
4. Yellow color can cause a lack of the mineral salts so necessary for synthesis of a chlorophyll. It is nitrogen, iron, magnesium. One more reason of yellowing of foliage – parasites. Leaves or roots of a plant are attacked by viruses, bacteria, pincers and so forth Besides, the houseplant can sustain mechanical damage during change or from accidental or deliberate actions of little inhabitants of the house, children or pets.
5. Why leaves turn yellow before falling down, but do not fall down green? The answer is simple: the tree or a plant takes away all remained valuable substances in roots or branches, and "pumps over" allocation products in the growing old foliage. Thus, it is possible to draw a conclusion that carotinoids are not important substances for life support of a plant.
6. Leaves of different plants turn yellow differently. For example, leaves of a birch and a linden begin to change coloring in August, at the beginning of September the maple, then an aspen turns yellow. Each plant has "biological" hours on which there are seasonal changes.