Biological paper (on seeds) 1. The germination rate of seeds generally refers to the percentage of seeds that germinate within 10 days after soaking and absorbing enough water under suitable conditions. It is the main basis for determining the quality and practical value of seeds and the amount of seeds sown and used. Different seeds often have great differences in germination ability, and the same seed germination ability will also change. The germination ability of seeds is influenced by many factors, such as cultivation conditions, maturity, climate at harvest, water content of seeds during storage, storage conditions and storage time. If germination is uncertain, blind soaking, accelerating germination or direct sowing may lead to uneven emergence, insufficient number of seedlings or even no emergence at all, which not only wastes food, but also delays the season and causes passive production. Careful measurement of seed germination ability, careful calculation of seed dosage and planned production can not only avoid the above situation, but also improve yield. The common method to measure the germination rate of rice seeds is: firstly, randomly take out a small number of seeds from the seed containers of the tested varieties, put them in different positions at the top, middle, bottom, edge and center, remove impurities, soak them at the water temperature of 20-30℃ for 24 hours, and then divide 65,438+000 seeds into 4 groups and arrange them evenly in 4 Petri dishes covered with filter paper or papyrus. Under the environmental conditions of 30-35℃, the number of germination was recorded daily from the beginning of the experiment to 10 day, and finally the germination rate was calculated in groups. The average value of the four groups is the germination rate of the seed, and its calculation formula is: germination rate (%) = number of germinated seeds * 100/ total number of tested seeds. 2. Conditions required for seed germination The necessary condition for seed germination is water. Water is the primary condition for seed germination. Seeds must absorb enough water to accelerate the physiological function of seeds, promote the activity of enzymes, facilitate the dissolution of stored nutrients and the growth of embryos, thus promoting the germination of seeds. Temperature is also one of the necessary conditions for seed germination. After absorbing enough water and oxygen, seeds need a certain temperature to germinate, and temperature is the energy source of seed germination. The function of temperature is to promote the activity of enzyme, and the optimum temperature for seed germination is also the optimum temperature for enzyme. In addition, temperature also directly affects the speed of water absorption and respiration of seeds. In a certain temperature range, the higher the temperature, the faster the seeds absorb water, the stronger the respiration and the faster the germination. Seed germination test needs a lot of oxygen. When the seeds germinate, the respiration is enhanced, such as the lack of oxygen respiration, which makes the seeds unsuitable for germination. Different crops have different reactions to light when they germinate. Most crop seeds (such as corn, cereal and other seeds) are not strict with light requirements. These seeds can germinate in light or darkness. Some seeds with good light, such as tobacco seeds and celery seeds, can germinate or promote germination only under light conditions. There are also some seeds that avoid light, such as black grass seeds, which will inhibit germination when there is light. In germination test, these seeds should be treated in the dark. Third, the process of seed germination. First of all, we should absorb water. Nutrients in cotyledons or endosperm are transported to radicle, embryo and hypocotyl. Subsequently, the radicle develops, breaks through the seed coat and forms roots. The hypocotyl is elongated and the embryo develops into stems and leaves. I have also done two experiments of seed germination, which are made of mung beans. In the first experiment, all the seeds dried up, because I always forgot to add water to them, and finally the first experiment ended in failure. Then immediately ushered in the second experiment, this time I remembered the last lesson, and my seeds finally sprouted. The theme of my thesis is about seeds, and it introduces how to measure the germination rate of seeds, the conditions and process of seed germination. This is my biology paper.