Control and co-ordination in plants
Asked by palaksophia | 2nd Dec, 2009, 02:07: PM
Plant growth has a beginning, reproductive, and ending stage, except some plants have an additional dormant stage. The terms for these stages are: Vegetative, Reproductive, Senescence, and Dormancy.
i) In the first stage of plant growth, the Vegetative stage, the seedling absorbs moisture and nutrients from the food stored inside the seed. It penetrates the seed's protective wall and begins growth. The root grows down into the warm moist earth, while the shoot rises upwards towards the sunlight and warm air. Upon emergence, leaves unfold and the roots continue to grow and spread. This continues until the plant seedling is fully developed with extensive roots, root hairs and leaves. The roots and leaves absorb moisture and nutrients from soil, water, and air.
ii) The next stage of the plant growth is a Reproductive stage. At this point, when the seedling has matured, it will produce a flower that has either male or female parts, or both. The flower contains pollen, which is then transferred to the egg part of the flower and a transformation into new seeds, or pods containing seeds, begins to grow to maturity. The pollination can occur with the help of wind, vibrations, insects like bees, animals or by human intervention. The benefit to pollination of seeds is that gene diversity can occur, which may help survival.
iii) A third growth stage occurs after new seeds or pods have been produced and spread to make new plant life. This would be Senescence, or old age in plants. This can be seen in the fall as the leaves on certain deciduous trees change color before dropping off. Plants show deterioration similar to other organisms in old age, such as damage from free radicals and telomere shortening.
iv) Another growth stage that is different than Senescence is the Dormancy stage. In Dormancy, the plant goes into a state of hibernation, allowing it to survive intense winter weather and revive in the springtime with new growth, without going through a seed stage. Dormancy can give plants an edge because they can build on prior year's growth instead of starting over from seed. This gives them a competitive edge in competition for sunlight and soil, as they are bigger.
Answered by | 3rd Dec, 2009, 01:14: PM
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