Studies On The Mechanism Of Ultra-drying Tolerance Of Rice Seed And Storage Stability Of Ultra-dried Seed

1. Desiccation tolerance of rice seed in two cultivars (Zhongzu 1 and Chunjiang 15) was studied during seed developing. The results showed that the desiccation tolerance of rice seed was acquired during seed developing, which is earlier than acquiring the germination ability of fresh seed. Dehydrating slowly benefit seeds' obtain desiccation tolerance. Although there are no difference on desiccation tolerance between two developing cultivar rice seeds when their moisture content fell to ten percent of that before, distinct diversity appeared after ultra drying mature seeds, which suggested that the desiccation tolerance differed from the ultra-drying tolerance of rice seeds.2. After comparing the ultra-drying tolerance and heat-stable proteins of several cultivar rice seeds, and analyzing the possible reasons of their difference, we concluded that there were at least two kinds of heat-stable proteins which are related to the ultra-drying tolerance of rice seeds, one is not LEA protein existing in whole rice seed, the other is similar-LEA protein existing in embryo and only accumulating after seed's dehydration.3. The soluble sugars of two cultivar rice seeds with different ultra-drying tolerance were analyzed during seed developing and fresh mature seed dehydrating, respectively. The result showed that the accumulation of saccharose and the decrease of reducing sugars during the period of seed maturation and dehydration were highly related to the desiccation tolerance of rice seeds. Furthermore, this ultra-drying tolerance of rice seed was related to the accumulation and keep high content of raffinose in embryo during dehydration and ultra-drying.4. The glass transition of dehydrated rice embryo was analyzed by studying the rice seeds (Zhongzu 1) within different developing periods after 14 DAP. The results indicated that the action of glass transition was related to the desiccation tolerance of rice seed, and that high temperature DSC scanning did not affect the Tg, but led to the non-reversed change of glass transition in embryo. The actions of glass transition had no distinction among dehydrated embryos of rice seeds within different developing period after 14 DAP, which corresponded with the changes of sugars and germination ability. It could be deduced that the glass transition related to the acquiring of desiccation tolerance of rice seed.5. Using artificial methods to age the peanut seeds with different WC same time and to age them until they have the same germination rate, respectively, then analyzing the activities of anti- oxidases in these seeds, we found that the stability of peanut seeds treated with ultra-drying were enhanced during storing, but there was a moderate WC in ultra-drying. Keeping the integrity of anti-oxidases in ultra-dried seeds plays a role in enhancing the storing stability of the seeds. When the seeds sopped and germinated, these anti-oxidases rapidly activated, and then functioned in removing active oxygen and free radicals to prevent the seed from injured by peroxidatibn and to maintain the seed's vigor.