【作者】 吴道藩；

【导师】 宋明；

【作者基本信息】 西南农业大学 ， 蔬菜学， 2002， 硕士

【摘要】 本试验以三个甘蓝品种（西园四号、西园八号、渝丰三号）为材料，通过人工老化法获得了中、中下、低三组不同活力程度的种子。应用浸泡-干燥处理和PEG、甘露醇、赤霉素、CaCl₂、KH₂PO₁、AsA处理等方法，分别采用L₉（3⁴）正交试验设计（包括处理温度、时间、浓度或次数）组合处理上述不同品种及不同活力指数的种子，均不同程度地提高了种子活力。进而探讨了甘蓝种子活力提高后生理生化水平，细胞水平以及组织结构上的变化。结果表明： 在40℃、RH100％条件下，甘蓝种子活力随老化时间的延长而降低，活力变化的快慢与品种（基因型）有关。西园四号、西园八号分别老化3天、4天、5天，渝丰三号老化1天、2天、3天即可获得各品种的中、中下、低三组不同活力程度的种子。 浸泡-干燥处理和PEG、甘露醇、赤霉素、CaCl₂、KH₂PO₄、AsA处理等7种方法都能提高甘蓝种子活力。分析表明，种子活力提高的程度受处理方法、处理温度、时间、浓度或次数等多种因素的影响，对不同品种及不同活力程度的种子而言，这些因素的主次顺序、影响程度各不相同，最佳效果组合也不相同，一般地，低活力种子的提高效果较大一些。各种方法的最佳效果组合处理种子后，活力指数均极显著高于对照（未处理），其中PEG处理和赤霉素处理的效果最好，与其它5种方法的差异达极显著水平。 活力提高后的种子，生理生化水平上即发生了明显的变化：蛋白酶、脱氢酶、SOD、CAT、POD活性增强，都极显著高于对照，在品种及不同活力程度种子、不同方法间其活性变化的程度不相同；种子浸提液相对电导率、MDA含量显著降低，并同样存在品种及不同活力程度种子、不同处理方法间的差异。主成分分析表明，这些生理生化指标与种子活力相关性极显著，其中，相对电导率、MDA含量与种子活力指数呈极显著负相关；蛋白酶、脱氢酶、SOD、CAT、POD活性与活力指数间呈极显著正相关。结果表明它们是种子活力变化的主要原因，是衡量种子活力的可靠指标（生理生化水平上）。 根尖染色体核型分析结果，甘蓝种子在活力提高前后染色体的臂比值相同，相对长度相同，表明活力提高后染色体在形态及核型上无明显变化，而对于除中期外的其它分裂期染色体的形态特征以及染色体内部结构有无明显变异（如基因突变等）在本试验条件下尚不能确定。 胚根细胞亚显微结构电镜观察结果，甘蓝种子通过人工老化活力降低后，胚根超微结构发生了变化，主要表现为：质壁分裂，细胞膜内陷或局部断裂，细胞质空泡化，细胞器难以辨认，染色质均质化，核仁和核膜的界限模糊等现象。活力越低，上述变化越明显，亚细胞结构损伤越严重，通过各种方法处理提高种子活力后，胚根的亚细胞结构得到了不同程度的恢复。更多还原

【Abstract】 Medium, mediumlow and low vigor cabbage seeds were obtained respectively by accelerated aging of 3 cabbage varieties (xiyuan NO.4, xiyuan NO8, yufeng NO.3 ).Different methods,including imbibition/dryback treatment, polythyleneglycol (PEG),mannitol gibberellin(GA),CaCl2,KH2PO4, ascorbic acid(AsA),were used to enhance the seed vigor by Ly(3 ) orthogonal experiments.Then the probe into the changes of cabbage seeds at physiology and biochemical level,cell level and ultrastructure of cell were conducted.The results indicated that:On the condition of 40℃ and RH100% ,vigor index(VI) and germination percentage came down gradually as aging time increased,and the change rate of VI was related to varieties (genotypes).Medium, mediumlow and low vigor seeds could be acquired after different aging time (For xiyuan N0.4,aging time was respectively 3 days,4 days and 5 days,for xiyuan NO.8, aging time was respectively 3 days,4 days and 5 days,for yufeng NO.3, aging time was respectively 1 days,2 days and 3 days).All the seven methods, including imbibition/dryback treatment, polythyleneglycol (PEG),mannitol,gibberellin(GA),CaCl2,KH2PO4,ascorbic acid(AsA),could improve the vigor of cabbage seeds.The analysis showed that improving degree of vigor was affected by different temperature, time, density (or times) etc. As to the seeds of different varieties and different vigor, the order and the best combination of these factors weren’t the same.In general,the improving degree of vigor for low vigor seed was higher. The seed vigor treated by all the best combination was significantly higher than CK, and the treatments of PEG and GA were the best, moreover, the difference between PEG, GA and other methods was significant.Some physiological and biochemical changes, such as relative elelctive conductivity (REC) and the content of malondialdehyde (MDA) in seed, activities of protease, dehydrogenase, superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), were investigated before and after improving the seed vigor. The result showed that protease, dehydrogenase, SOD, CAT and POD were reduced signficantly. Moreover, the changing degree was related to different varieties or primary vigor degrees. Principal Component Analysis indicted that activities of protease, dehydrogenase, SOD, CAT and POD werecorrelated significantly and positively with VI, REC and the content of MDA were correlated significantly and negatively with VI.As a result, these parameters were the main reasons for the change of seed vigor (at physiological and biochemical level), and-they were reliable indexes for measuring seed vigor.Karyotypes of root tip chromosome showed that the arm volume ratio, the mean relative volume (as a percentage) and idiogram were identical before and after improving seed vigor, so the pattern of chromosome did not change. But we couldn’t confirm whether the pattern of other separation dates and the inner structure varied in this experiment, such as gene mutation.Observation on the ultrastructure of the radicle cell of cabbage seeds indicated that the ultrastructure changed with the seed vigor reduced, such as the segregation of cytoplasm from the cell wall, the fragmentation of cell membrane, the vesiculation of protoplasm, the homogenization of chromation, the disintegration of cytoplasm, the distinguishing of nuclear membrane and nucleous ,and so on.The lower the seed vigor ,the clearer the change .When the seed vigor was improved,the ultrastructure of cell would be resumed at different degrees.更多还原