Germination test is one of the main measures to evaluate the seed quality. The purpose is to determine the maximum germination potential of the seed sample, so as to estimate the sowing value of the seed batch in the field; second is to compare the seed use value of different seed batches. Germination and proper identification of seedlings under appropriate conditions are a very important issue in the germination test. It is directly related to the accuracy of the germination test results and even to the consistency of the field emergence rate. The author combines the problems encountered in practical work and talks about the problems that should be paid attention to in the seed germination test. The seed germination conditions can be provided by the seed germination box.
1 Coordinated control of germination conditions Adequate water, suitable temperature, and adequate oxygen are prerequisites for seed germination and growth. Only coordinated relationships between moisture, oxygen, and temperature can promote seed germination and good seedling growth. The highest germination rate was measured. The moisture and oxygen in the sprouting bed is a contradiction. More water will form a water film around the seeds, hindering oxygen from entering the embryo and affecting germination. Therefore, the moisture content of the germination bed should be appropriate so as not to form a water film. When seeds germinate, radicle elongation is more sensitive to oxygen demand than to embryo elongation. More water and less oxygen produce longer shoots, less water, and more oxygen than long roots. These conditions can cause unbalanced growth of seedlings. Therefore, it is necessary to keep the sprouting bed moist in the seed germination box, but also to maintain enough oxygen, the germination box should often open the cover ventilation.
The temperature of the germination test should be selected based on the optimum temperature of the seeds of each crop listed in GB 3534.4-919 (5 Crop Seed Inspection Regulations). For newly harvested dormant seeds, a lower temperature or a variable temperature is generally used, which is conducive to seed seepage. Human oxygen promotes enzyme activation and accelerates germination.
2 Understanding the characteristics of seeds The object of germination tests is seeds, so first of all the characteristics of seeds of different crops should be mastered. Due to the different ecological environment of origin and evolution, different kinds of crop seeds result in different seed structure, differentiation and physiological characteristics. These characteristics make it possible to differentiate seedlings for germination conditions and seedling identification. For example, soybean seeds contain more protein, and proteins have a strong hydrophilicity, so the seeds of soybeans must germinate enough water, especially the seeds and seeds that have a lower moisture content. But at the same time, we must also consider the appropriateness of moisture. If too much water causes oxygen deficiency and the seeds undergo anaerobic respiration, they will produce carbon dioxide and alcohol, poisoning the seeds, causing rotten species, rotted roots, and rotting buds.
Another example is the physiological characteristics of rice seeds is the first long "buds" (actually the elongation of the coleoptile) long roots after germination. Although rice seeds are less sensitive to moisture, if they do not understand this physiology, if the water is too large and the seeds are immersed in water, they only grow “budsâ€, do not grow roots, and they cannot form normal seedlings. Corn seeds are also less sensitive to moisture, but some smaller, thin, lean seeds have higher starch content, require less water, and require more oxygen. If the moisture is high, it will naturally cause decay due to lack of oxygen.
Second, there are differences in seedling identification due to differences in seed structure and differentiation. The bean seeds are structurally complete and have a high degree of differentiation. Therefore, the structures considered during seedling identification should be more, such as the identification of roots, hypocotyls, epicotyls, apical buds, and primary leaves. The cotyledon of the grass seed has been reduced to a scutellum. The scutellum remains in the soil. The first photosynthesis is true leaf, so the cotyledon does not need to be considered during the identification. However, dicotyledonous seedlings such as soybeans must consider the cotyledon, which is the first place for photosynthesis and energy supply. Therefore, mastering seed characteristics is a basic premise for cultivating normal seedling growth and identification of seedlings.
3 Grasp the seedling characteristics The key to the identification of seedlings is to grasp the structural characteristics of the seedlings. The main structure of the seedlings is based on the different species being examined. The structure of the seedlings is observed in the tissue culture chamber and it is found that they are usually roots, seedlings, axes, cotyledons, and coleoptiles. And other specific combinations. The five types of seedling development types of monocotyledonous plants and the four types of seedling development types in dicotyledonous plants are listed in GB/T3543.4-1995 “Agronomic Seed Inspection Regulationsâ€. In the identification of seedlings, the characteristics of these seedling types must be fully taken into consideration, and the observations, analyses, and judgments must be emphasized. For example, abnormal seedlings of Oryza and Maize species mainly consider roots, hypocotyls, coleoptiles, and first leaves and whole seedlings. This type of seedling usually produces a large number of secondary roots, so the primary and secondary roots are primarily considered in the identification. In addition, this type of seedling coleoptile often cracks, so another consideration is the degree of coleoptile cracking, especially the degree of separation from the leaves, if the separation is obviously abnormal seedlings; if natural cracking, but keep close to the leaves Contact is judged as normal seedlings.
Another example is the dicotyledonous soybean genus, a typical cotyledon unearthed seedling. Identification of abnormal seedlings mainly from roots, hypocotyls, cotyledons, primary leaves, apical buds, and seedlings, with secondary roots and hypocotyls being taken into consideration. For example, in the identification of seedlings, there are defects such as primary root loss, fineness, and shortness, but as long as there are enough secondary roots, they are normal seedlings. From this we can see that seedling identification must fully consider the characteristics of the seedling structure and identify it in a targeted manner.
4 correctly distinguish between primary and secondary infections How to distinguish between primary infections and secondary infections, is a principle issue to identify the normal or not. The primary infection (ie, the seeds themselves carry pathogens) causes the major structural morbidity and rot of the seedlings, and impedes their normal growth to be judged as abnormal seedlings. If the source of infection is caused by other seedlings, etc., rather than the secondary infection caused by the seed itself, even severe rot or disease should be classified as normal seedlings. Since it is difficult to distinguish between a primary infection and a secondary infection only from the appearance of a seedling, it is difficult to determine whether it is a normal seedling. Therefore, seedlings can only be correctly identified if they are fundamentally distinguished from primary infections and secondary infections.
First, measures should be taken to prevent secondary infections. The germination bed and the water are controlled and treated, that is, the paper bed is applied with sterile clean germination paper, and the sand bed should be used after disinfection; the water should be selected with clean water to avoid germination bed and moisture carrying the source of the infection, resulting in secondary infection. Second, primary and secondary infections should be identified during the seedling growth period. Because the germs have not yet spread or are not deeply infected, it is easier to distinguish. It mainly depends on whether the new seedlings are normal in color and healthy in growth. Seedlings that are newly infected should be removed immediately to prevent the spread of infection. If the source of infection has contaminated nearby surrounding seedlings, wash the seedlings immediately and transfer to a clean sprouted bed. If the seedlings are heavily rot or pathogenic, the samples should be retested. Re-experiment should increase seed spacing, reduce moisture, try to use sand bed or soil as a culture medium to reduce the possibility of secondary infection in the seed.
1 Coordinated control of germination conditions Adequate water, suitable temperature, and adequate oxygen are prerequisites for seed germination and growth. Only coordinated relationships between moisture, oxygen, and temperature can promote seed germination and good seedling growth. The highest germination rate was measured. The moisture and oxygen in the sprouting bed is a contradiction. More water will form a water film around the seeds, hindering oxygen from entering the embryo and affecting germination. Therefore, the moisture content of the germination bed should be appropriate so as not to form a water film. When seeds germinate, radicle elongation is more sensitive to oxygen demand than to embryo elongation. More water and less oxygen produce longer shoots, less water, and more oxygen than long roots. These conditions can cause unbalanced growth of seedlings. Therefore, it is necessary to keep the sprouting bed moist in the seed germination box, but also to maintain enough oxygen, the germination box should often open the cover ventilation.
The temperature of the germination test should be selected based on the optimum temperature of the seeds of each crop listed in GB 3534.4-919 (5 Crop Seed Inspection Regulations). For newly harvested dormant seeds, a lower temperature or a variable temperature is generally used, which is conducive to seed seepage. Human oxygen promotes enzyme activation and accelerates germination.
2 Understanding the characteristics of seeds The object of germination tests is seeds, so first of all the characteristics of seeds of different crops should be mastered. Due to the different ecological environment of origin and evolution, different kinds of crop seeds result in different seed structure, differentiation and physiological characteristics. These characteristics make it possible to differentiate seedlings for germination conditions and seedling identification. For example, soybean seeds contain more protein, and proteins have a strong hydrophilicity, so the seeds of soybeans must germinate enough water, especially the seeds and seeds that have a lower moisture content. But at the same time, we must also consider the appropriateness of moisture. If too much water causes oxygen deficiency and the seeds undergo anaerobic respiration, they will produce carbon dioxide and alcohol, poisoning the seeds, causing rotten species, rotted roots, and rotting buds.
Another example is the physiological characteristics of rice seeds is the first long "buds" (actually the elongation of the coleoptile) long roots after germination. Although rice seeds are less sensitive to moisture, if they do not understand this physiology, if the water is too large and the seeds are immersed in water, they only grow “budsâ€, do not grow roots, and they cannot form normal seedlings. Corn seeds are also less sensitive to moisture, but some smaller, thin, lean seeds have higher starch content, require less water, and require more oxygen. If the moisture is high, it will naturally cause decay due to lack of oxygen.
Second, there are differences in seedling identification due to differences in seed structure and differentiation. The bean seeds are structurally complete and have a high degree of differentiation. Therefore, the structures considered during seedling identification should be more, such as the identification of roots, hypocotyls, epicotyls, apical buds, and primary leaves. The cotyledon of the grass seed has been reduced to a scutellum. The scutellum remains in the soil. The first photosynthesis is true leaf, so the cotyledon does not need to be considered during the identification. However, dicotyledonous seedlings such as soybeans must consider the cotyledon, which is the first place for photosynthesis and energy supply. Therefore, mastering seed characteristics is a basic premise for cultivating normal seedling growth and identification of seedlings.
3 Grasp the seedling characteristics The key to the identification of seedlings is to grasp the structural characteristics of the seedlings. The main structure of the seedlings is based on the different species being examined. The structure of the seedlings is observed in the tissue culture chamber and it is found that they are usually roots, seedlings, axes, cotyledons, and coleoptiles. And other specific combinations. The five types of seedling development types of monocotyledonous plants and the four types of seedling development types in dicotyledonous plants are listed in GB/T3543.4-1995 “Agronomic Seed Inspection Regulationsâ€. In the identification of seedlings, the characteristics of these seedling types must be fully taken into consideration, and the observations, analyses, and judgments must be emphasized. For example, abnormal seedlings of Oryza and Maize species mainly consider roots, hypocotyls, coleoptiles, and first leaves and whole seedlings. This type of seedling usually produces a large number of secondary roots, so the primary and secondary roots are primarily considered in the identification. In addition, this type of seedling coleoptile often cracks, so another consideration is the degree of coleoptile cracking, especially the degree of separation from the leaves, if the separation is obviously abnormal seedlings; if natural cracking, but keep close to the leaves Contact is judged as normal seedlings.
Another example is the dicotyledonous soybean genus, a typical cotyledon unearthed seedling. Identification of abnormal seedlings mainly from roots, hypocotyls, cotyledons, primary leaves, apical buds, and seedlings, with secondary roots and hypocotyls being taken into consideration. For example, in the identification of seedlings, there are defects such as primary root loss, fineness, and shortness, but as long as there are enough secondary roots, they are normal seedlings. From this we can see that seedling identification must fully consider the characteristics of the seedling structure and identify it in a targeted manner.
4 correctly distinguish between primary and secondary infections How to distinguish between primary infections and secondary infections, is a principle issue to identify the normal or not. The primary infection (ie, the seeds themselves carry pathogens) causes the major structural morbidity and rot of the seedlings, and impedes their normal growth to be judged as abnormal seedlings. If the source of infection is caused by other seedlings, etc., rather than the secondary infection caused by the seed itself, even severe rot or disease should be classified as normal seedlings. Since it is difficult to distinguish between a primary infection and a secondary infection only from the appearance of a seedling, it is difficult to determine whether it is a normal seedling. Therefore, seedlings can only be correctly identified if they are fundamentally distinguished from primary infections and secondary infections.
First, measures should be taken to prevent secondary infections. The germination bed and the water are controlled and treated, that is, the paper bed is applied with sterile clean germination paper, and the sand bed should be used after disinfection; the water should be selected with clean water to avoid germination bed and moisture carrying the source of the infection, resulting in secondary infection. Second, primary and secondary infections should be identified during the seedling growth period. Because the germs have not yet spread or are not deeply infected, it is easier to distinguish. It mainly depends on whether the new seedlings are normal in color and healthy in growth. Seedlings that are newly infected should be removed immediately to prevent the spread of infection. If the source of infection has contaminated nearby surrounding seedlings, wash the seedlings immediately and transfer to a clean sprouted bed. If the seedlings are heavily rot or pathogenic, the samples should be retested. Re-experiment should increase seed spacing, reduce moisture, try to use sand bed or soil as a culture medium to reduce the possibility of secondary infection in the seed.
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