Adaptations of Rice for Wet Environments:
Although rice can grow in dry conditions, it is often grown in 'paddies'- fields where the ground is intentionally flooded. Rice can tolerate growing in water, whereas most of the weeds that might compete with it are not able to do so.
Most plants cannot grow in deep water because their roots do not get enough oxygen. Oxygen is required for aerobic respiration, which provides ATP as an energy source for active transport and other energy-consuming processes such as cell division. Nor, if the leaves are submerged, can photosynthesis take place, because there is not enough CO2 available. This happens because gases diffuse much more slowly in water than they do in the air. Moreover, the concentration of dissolved O2 and dissolved CO2 in water are much less than they are in the air.Some varieties of rice respond to flooding by growing taller. this allows O2 and CO2 t obe exchanges through the stomata on the leaves.Ethanol is toxic, but the cells in rice roots can tolerate much higher levels than most plants. They also produce more alcohol dehydrogenase, which breaks down ethanol. This allows the plants to grow actively even when O2 is scarce, using ATP produced by alcoholic fermentation.The stems of the rice plants contain loosely packed cells forming tissue known as aerenchyma. Gases are able to diffuse through the aerenchyma to other parts of the plant, including those under the water.
For thousands of years, Man has been trying to produce special or improved breeds of plants to meet his needs by selective breeding. Selection is the method used to produce plants with desirable traits.
Suppose you are growing rice plants. You want seeds that contain a high nutrient.
What do you think you should do?
You should first analyze the seeds from different plants. Select those plants that produce seeds with high nutrient content and discard the rest. By doing so, you are actually selecting plants with good gene combinations for mineral production. Allow the 'good' seeds from the selected plants to grow to maturity and then allow them to either fertilize themselves or cross them with other plants showing the desired characteristics. Again, select the seeds produced by the new plants. The seeds with the best nutrient content are selected and used again as parents for the next generation. In this way, after many generations, you may be to obtain plants that produce seeds with the desirable qualities. These selected plants have desirable gene combinations. The plants can then be self-pollinated to enable the desired genes to be inherited by future generations of plants.