Theory of the experiment
A seed is a ripened ovule which encloses a miniature growing plant in the form of an embryo. A seed remains in a dormant stage till it gets the necessary required factors or conditions. Germination is nothing but the development of a seed into a seedling or young baby plant. The necessary factors required for the germination of seed are moisture (water), air (oxygen) and temperature.
Why the above three factors are essential for the germination of seeds? We explore the answers for this question from the below discussion:-
1. The necessity of water for the germination of seedsDry seeds contain 10 to 20% of the water in them. As long as they kept dry they do not germinate. When the seeds are kept in water or the seeds are provided with plenty of moisture in the soil, the seeds imbibe or absorb water through their micropyle and swell. The seeds become enlarged and seed coats become soft. The water then diffuses into the protoplasm of cells of seed. When chemicals present in the protoplasm get diluted only, the chemicals start reacting with each other to form new substances. This allows the cells in the embryo of seeds to increase their number by cell divisions and thus help to grow into a baby plant.
2. The necessity of oxygen for the germination of seedOxygen available for seed is essential for cellular aerobic respiration of seeds. Due to this cellular respiration in seed cells, energy is evolved. This energy is essential for metabolic activities (anabolic and catabolic chemical reactions) of the seed cells. Without the release of this energy, all the metabolic activities of the seed will be stopped and thus the germination of the seed also will be stopped.
3. The necessity of temperature for the germination of seedsDuring the germination of seed various chemical reactions occur in the cells of the seed. The chemicals present in the protoplasm of seed cells react with each other to form new substances. For these reactions to occur in the protoplasm of seed cells temperature is required. If the temperature available is low the formation of new substances, the formation of new cells is not possible and thus germination of the seed is not possible.
Aim of the experimentTo prove moisture (water), air (Oxygen) and temperature are very essential for the germination of seeds.
Requirements for the experimentA glass beaker, pure water, a long glass plate or a long plastic scale, dry bean seeds.
Procedure for the experimentThree healthy dry bean seeds were taken. The three seeds are tied with a string at an equal distance on the long glass plate are plastic scale. Then a glass beaker is taken and three-fourths of it is filled with water. After this, the glass plate with three seeds is arranged in such a way that one of the seed at the lower end of the glass plate is completely immersed in water, the middle seed should be half immersed at the surface of the water and the third seed should be completely away from water. The beaker with this arrangement is left in a warm place undisturbed for a few days.
ResultAfter a few days we can observe, the middle seed germinate and produce a tiny plant with new roots, small shoot, and leaves. But we find that there is no change in the seeds located at the bottom end of the plate or top end of the plate. We can explain the results observed in the following way:-
The middle seed as it is in touch with the water surface, the seed is able to imbibe water through its micropyle and get activated. In addition to that, it is able to get oxygen as it is not immersed in water completely. This oxygen supply is necessary for its respiration and energy supply for its germination. The seed is also provided with the required temperature as the experimental setup was kept in a warm place. So all the three necessary factors required for its germination helped it to germinate. But the seed present at the lower end of the glass plate is able to get moisture and warmth but no oxygen is available for it and thus it didn't germinate. The seed present at the upper end of the glass plate does not get moisture but was able to get oxygen and warmth. Because of the non-availability of moisture, this seed also fails to germinate.
So the conclusion for the above experiment is, lack of any one of the factors moisture (water), air (Oxygen) and temperature (warmth) makes the seed not to germinate. Thus all three factors are necessary for the germination of seeds.
Here are two more experiments on Osmosis and Photosynthesis