Seed Vigor Index Changing Under Stresses And Test Method Screening In Non-Heading Chinese Cabbage

The non-heading Chinese cabbage (Brassica campestris ssp.chinensis Makino.) originated from China, it with tender texture and rich nutritious, which plays an important role in vegetable consumption and year round vegetable supply. Seed is the most essential production means of agriculture, also the assurance for crop yield and quality, and the seed vigor is a reliable index to measure seed quality. Seed vigor directly affects seed germination, emergence, plant growth, yield and quality. Seed harvesting, processing, storage and even sowing, can all lead to the decrease or loss of seed vigor. Therefore, studies on changing and detection methods for seed vigor in non-heading Chinese cabbage, not only can provide an easy and effective way for seed test, but also be of great importance for achieving high quality and yield.The test wrapped around the determination of seed vigor. First of all, seed vigor indexes and correlation of different aging degree were studied through artificial aging treatment at42℃and RH100%. And then, the effects of non-heading Chinese cabbage ’Aijiaohuang’seed vigor under PEG6000simulating drought, NaCl and temperature stress were studied. Subsequently,10kinds of non-heading Chinese cabbage seeds were used to screen the experimental conditions of the two common seed vigor test methods, Finally, the21indicators and methods of seed vigor were analyzed to select simple and efficient seed vigor test methods.1. In this study, using non-heading Chinese cabbage variety’Gaogengbai’as material, seed vigor indexes and correlation of different aging degree were studied through artificial aging treatment at42℃and RH100%. The results showed that the seed germination indexes(except abnormal seedling rate) and emergence indexes significantly decreased with the increase of aging degree, with abnormal seedling increase significantly; With the increase of aging degree, the activities of superoxide dismutase (SOD), peroxidase(POD) and catalase (CAT) decreased significantly; The speed of O2production firstly went up and then slowed down, the hydrogen peroxide (H2O2)content kept increasing, the content of malondialdehyde (MDA) decreased and the relative electrolyte leakage increased. Soluble sugar content, soluble protein content and dehydrogenase activity kept decreasing and a-amylase activity firstly went up and then down. Correlation analysis showed that germination energy, germination rate, SOD activity, H2O2content, the relative electric conductivity and soluble sugar content had very significant correlation with emergence indexes. Comprehensive analysis demonstrated that the changes of germination energy, germination rate, SOD activity, H2O2content, the relative electric conductivity and soluble sugar content were consistent with aging degree deepen, and they showed very significant correlation with emergence indexes, so they can serve as candidate indicators for non-heading Chinese cabbage seed vigor test.2. In this study, using non-heading Chinese cabbage variety’Aijiaohuang’as material, seed germination and antioxidant-related and osmoregulation substance were studied under PEG6000simulating drought and NaCl and temperature stress. The results illustrated that: germination energy, germination rate, germination index and vigor index decreased with increase of the three stresses, and abnormal seedling increased. With the three stresses aggravated, SOD and POD activity decreased, CAT activity firstly went up and then went down, O2production speed increased, H2O2accumulated and the relative electrolyte leakage increased. Under stress conditions, soluble sugar, soluble protein and proline content increased. Comprehensive analysis showed that under the PEG6000simulating drought, NaCl and temperature stress, the disorder of antioxidant system led to the imbalance of reactive oxygen metabolism and the ability of osmotic adjustment, which resulted in the decrease of seed vigor and even death.3.10kinds of non-heading Chinese cabbage seeds were adopted to study the change of vigor indexes under the PEG6000simulating drought and NaCl stress and to choose the suitable experimental conditions for seed vigor test. The results showed that with the PEG6000simulating drought and NaCl stress exacerbated, the seed of different varieties of non-heading Chinese cabbage, germination rate, germination energy, germination index and vigor index decreased. Under the15%PEG6000simulating drought stress, the germination rate of10varieties were significantly lower than the standard germination rate, the germination energy of8varieties showed significantly lower than the standard germination energy, and the germination index and vigor index of9varieties presented significantly lower than the standard condition. Under150mmol/L NaCl stress, the germination rate and germination energy of3varieties showed no significant difference with the control, but germination index and vigor index of all varieties were significantly lower than the control. Under the two kinds of stress, the change of the germination index and vigor index were more obvious than germination rate and germination energy. Comprehensive analysis demonstrated that the best choice of the concentration was15%PEG6000and150mmol/L NaCl when using PEG6000simulating drought and NaCl stress for determination seed vigor of non-heading Chinese cabbage.4. The multiple statistics of21vigor indexes of10non-heading Chinese cabbage varieties were analyzed. The results showed that among vigor indexes of different varieties of non-heading Chinese cabbage seeds, there were differences with diversity. Correlation analysis of21vigor indexes showed that the indexes based on the germination behavior presented significant or very significant correlation. In the physiological indexes, only the electric conductivity with germination (except vigor index) and emergence indexes showed significant correlation. By principal component analysis, the first principal component with a contributive rate accounted for52.836%, and which contained mainly indicators based on the determination of the germination behavior and soaking liquid conductivity. The vigor indexes were divided into4categories by the clustering analysis, the first category included all the germination indexes. From the definition of seed vigor, the suitable methods to determine seed vigor of non-heading Chinese cabbage were accelerated ageing test, controlled deterioration test and NaCl-stress germination test.