【作者】 朱诚；

【导师】 吴平；

【作者基本信息】 浙江大学 ， 植物学， 2003， 博士

【摘要】 1．在25℃恒温条件下，将花生、油菜、芝麻、黄瓜、洋葱、大豆、绿豆、水稻、玉米、小麦种子脱水干燥，定期测定种子的含水量与活力水平。结果表明，供试材料都具有较强的耐干燥的能力，种子含水量降至5—4.5％左右对种子发芽率和活力指数没有影响。若再进一步的脱水干燥，不同材料种子表现出不同的耐干燥能力。花生、油菜、黄瓜和芝麻种子含水量降至2.0％左右其发芽率和活力指数基本没有变化；洋葱、大豆、绿豆、水稻和小麦种子含水量降至约3.5％以下对种子活力都有不同程度的影响。比较不同种子内贮藏物质发现，富含脂类物质的种子脱水速率和耐超干力明显大于蛋白质类种子和淀粉类种子，但是不同品种的淀粉类种子脱水速率虽相似，且耐超干能力在品种间差异较大，供试的粳稻品种(春江15和春江683)不耐超干，当含水量降低至4.5％以下，种子发芽率和活力指数显著下降，而籼稻品种(J106和J174)耐超干能力强，含水量降低至3.5％以下时种子发芽率和活力指数没有影响，杂交稻(汕优63)和中香糯介于两者之间。 2．对较低含水量种子在萌发之前进行回水处理和电导率的测定表明，超干种子萌发前进行回水处理是很必要的，能更有效地降低种子的吸水速率，为种子再水合过程中完成膜系统的修补创造必要的条件，有利于种子活力的保持。 3．研究种子内可溶性糖、热稳定蛋白和活性氧代谢与种子耐超干之间的相关性。结果表明：(1)适度超干的花生(MC2.0％)、大豆(MC4.0％)和绿豆(4.5％)种子的种胚和子叶中非还原糖/还原糖比值高于对照(未超干种子)，而蔗糖/寡糖比值在超干过程中变化不大，说明种子的耐超干能力与种子内非还原糖/还原糖比值的变化密切相关；超干处理可降低花生、大豆和绿豆子叶内α-半乳糖苷酶活性及种胚和子叶内蔗糖酶活性，从而使超干种子在贮藏过程中减少蔗糖、寡糖等保护性物质的消耗。(2)超干处理没有引起花生、大豆和绿豆种胚和子叶产生新的热稳定蛋白，但使热稳定蛋白含量发生变化，适度超干花生和绿豆种子的种胚和子叶热稳定蛋白含量最高，大豆种子的种胚内热稳定蛋白在超干过程中变化不明显，过干导致大豆、绿豆子叶热稳定蛋白减少，说明超干能使某些蛋白的热稳定性增加。花生种子热稳定蛋白含量明显大于大豆、绿豆种子，这可能是大豆和绿豆种子耐超干能力弱的原因之一。(3)超干过程中显著增加了种子内氧自由基水平，但是种子内MDA含量和LOX活性并没有升高，这种氧自由基的急剧增加并不是由LOX引起的；超干可提高种子有机自由基清除能力，说明热稳定蛋白的含量与种子的耐超干能力密切相关。从干种子提取液中检测到SOD、CAT和AsA-POD活性，且在超干过程中活性变化不明显，说明在超干过程中种子内抗氧化酶系统保持得相当完盖 4.超干种子经人工老化或自然条件贮藏。结果表明，无论是人工老化还是自然条件下贮藏，超干处理确能提高种子的抗老化能力，延长种子的贮藏寿命，但是存在着一个适度的含水量，当脱水至某一闽值(最适含水量)以下时对种子的寿命无更大的益处。同时实验也表明利用人工老化的方式可以用来快速判断超干种子耐贮藏的性能，以及种子贮藏过程中的最适含水量。 5.分析人工老化后不同含水量种子的可溶性糖、热稳定蛋白和活性氧代谢的变化。结果表明:(1)适度超干的花生(MC2.0%)、大豆(MC4.0%)和绿豆(MC4.5%)种子人工老化后胚和子叶内非还原糖/还原糖比值比对照(未超干)高，蔗糖/寡糖比值比对照为低，此比值的变化与种子活力的变化相一致，说明非还原糖与还原糖比值及蔗糖与寡糖比值高低与种子抗老化能力有关，非还原糖/还原糖比值高、蔗糖/寡糖比值低有利于提高种子的抗老化能力。(2)花生、大豆和绿豆种子内热稳定蛋白在老化过程中变化趋势不尽相同，但老化后适度超干花生、大豆和绿豆种子的种胚具有较高水平的热稳定蛋白，有利于其在老化过程中阻止蛋白质变性。(3)超干种子内氧自由基水平高于未超干种子，但与老化前相比，未超干老化种子内氧自由基增加幅度明显大于超干种子，超干种子MDA含量和脂氧合酶活性明显低于未超干种子;说明超干处理在一定程度抑制了种子在老化过程中氧自由基的产生以及膜脂过氧化作用的加强，但是过于超干种子内部膜脂过氧化作用反而会加强;人工老化对种子内抗氧化的酶系统影响程度不同，从总体比较来看，超干种子抗氧化酶系统保持得比未超干种子好，说明超干处理可提高种子贮藏过程中的抗膜脂过氧化能力。 6.测定自然贮藏条件下不同含水量花生种子萌发过程中ATP含量、LOX活性以及活性氧代谢的变化，结果表明:超干种子萌发过程中种胚内ATP含量和抗氧化酶(s OD、CAT、AsA一POD、G一POD)活性明显高于未超干种子，MDA含量、挥发性醛和脂氧合酶活性低于未超干种子，说明超干种子在萌发过程中抗氧化酶系统活性较高，从而减轻或阻止了活性氧启动的脂质过氧化作用，避免对膜系统的损伤，保证超干种子正常的萌发。 7.不同含水量(MC 7.1%一1 .2%)的洋葱种子贮藏在35℃、室温、巧℃和5℃条件下1一3年，适度超干处理能延长种子的贮藏寿命;种子的贮藏寿更多还原

【Abstract】 In the present study, the different seed species were chosen to investigate the effect of ultradrying on seed germplasm preservation. The prominent storage substances, soluble sugars, heat-stable proteins and the metabolism of active oxygen in different seed species were evaluated for dry-tolerance and prolonging storage longevity of ultradried seeds. The aim of this study is to provide theory and to develop the technology of ultradried seed storage for germplasm preservation. The results are summarized as follows:1. Peanut, rape, sesame, cucumber, onion, soybean, mungbean, rice, corn and wheat seeds were dehydrated at 25 ℃, and the moisture content was measured at stated time intervals. Desiccation tolerance we, re observed in all of the above seeds, and The vigor indexes and germination percents of seeds with 5-4.5% moisture content did not visibly changed. However, when further dehydrated, different seed species showed dissimilar of desiccation tolerance capabilities. The vigor indexes and germination rate of peanut, rape, sesame and cucumber seeds did not changed within 2.0% moisture content, whereas onion, soybean, mungbean, rice, corn and wheat seeds showed great changes in their vigor indexes and germination rate.Higher lipid contents showed ’significantly higher speeds of dehydrating and greater ultradry-tolerant abilities than seeds of high protein or starch contents, while seeds of different starches showed parallel speeds of dehydrating, although with distinct ultradry-tolerant abilities. The germination rate and vigor index of Japonica rice seeds (Chunjiang15 and Chunjiang683) decreased rapidly when their moisture content fell to 4.5%. On the contrary, the germination rate and vigor index of Indica rice (J174 and J106) seeds changed little even when their moisture content fell to 3.5%, which indicated that Indica rice had strong ultra-drying tolerance. While the seeds’ tolerance of Waxy rice and Hybrid rice (Shanyou 63) were intervened in Japonica rice’s and Indica rice’s.2. The rehumidification treatment and a measuration of conductance of seeds with low moisture content before germination suggested that the rehumidification treatment was necessary to effectively reduce the water absorption rate and the membrane restoration during rehydration, thus maintaining the seeds’ vigor.3. The relationship between ultradry-tolerant ability and soluble sugars, heat-stable proteins or metabolism of active oxygen were investigated after ultradrying. The results showed that: (1) The ratio of non-reducing sugars/reducing sugars in embryo and cotyledons of moderately ultradried peanut seeds(MC2.0%), soybean seeds(MC4.0%), and mungbean seeds(MC4.5%) has been increased, while no significant changes in the ratio of sucrose /oligosaccarides was observed, which indicates a positive correlation between ultradry-tolerance capabilities and the ratio of non-reducing sugars/reducing sugars of seeds. Ultradrying treatments reduced the activity of invertase and a -galactosidase in embryo of peanut seeds, soybean seeds, and mungbean seeds, thus decreasing the wastage of sucrose, oligosaccarides and other protective substances. (2) Ultradrying treatments did not induce new heat-stable proteins in embryo and cotyledons of peanut seeds, soybean seeds, and mungbean seeds, although heat-stable proteins was changed. Moderate ultradrying treatments could induce to accumulate heat-stable proteins in embryo of peanut seeds and mungbean seeds, but not in soybean seeds, in the embryo of which even a decrease of heat-stable proteins was observed when excessively ultradried. This suggested that the heat-stability of some proteins was improved. The content of heat-stable proteins in peanut seeds was significantly greater than that of soybean and mungbean seeds, which cauld be one of the possible reasons of different ultradry-tolerance abilities in different seeds. (3) After ultradrying treatments, the superoxide-producing rate significantly increased, the content of MDA and the rigor of LOX did更多还原