| This thesis includes four parts. In the first part, the suitable cold resistant Pharmaceuticals and their appropriate concentrations were decided by means of studying the effects of 4 kinds of cold resistant pharmaceuticals and their formulas in 3 terraced concentrations on rice seedlings under chilling stress; The cold resistant pharmaceuticals and formulas were mixed with film-forming compound in appropriate concentrations to prepare cold resistant seed-coating agents, then the physical and chemical properties of cold resistant seed-coating agents and the safety of coated seed storage were studied. In the second part, the influences of 4 kinds of cold resistant seed coating agents on rice seedlings were studied under chilling stress in growth chamber and fields, with rice varieties Jinyou974 and Xiangzaoxian31 used as materials. In the third part, the influences of 4 cold resistant seed-coating agents on 9 items of physiological and biochemical indexes, such as root vigor, chlorophyll content, proline content, soluble sugar content, soluble protein content, peroxidase(POD) > catalase(CAT) and superoxide dismutase(SOD) activities, electrolyte leakage and malondialdehyde(MDA) content, etc., were studied systematically under chilling stress in growth chamber and fields by using rice varieties Jinyou974 and Xiangzaoxian31 as materials. The fourth part, was an attempt to study the application effects of the prepared cold resistant seed coating agents. The main results are as follows:1. The suitable concentrations of HET(High-effective thiazole), YKJ, ABA (Abscisic acide) and SNC(Sodium nitro complex) were 2,0 mg/1, 2000mg/L, 10mg/L and 1000mg/1 respectively in application. The effects of YKJ, ABA and HET were better than those of SNC when used as cold resistant seed coating agents of rice. Mixture of 1000 mg/L SNC and 2000 mg/L YKJ promoted the growth and cold resistant efficiency of rice seedlings effectively.2. The cold resistant pharmaceuticals, YKJ, ABA, HET and YKJ+SNC selected in the experiment filled the film-forming compound competently. Testing results showed that the physical and chemical properties of the 4 kinds of cold resistant seed coating agents accorded with the enterprise standard Q/OUHN010-2000.3. Water content of the seed coated with YKJ+SNC seed-coating agent increased 1.0%~l.l%. The germination rate of coated and non-dried seeds had no significant changes under natural condition during 90 d storage, but decreased significantly with the lapse of storage time after 90 d. The decreasing degree was bigger than that of CK, which implied that the seed coating agent influenced the germination of coated and non-dried seeds. While the water content of coated seeds dried to less than 11.5%, the germination rate maintained more than 90% under natural condition during 180 d storage, but decreased gradually with the lapse of storage time after 180 d, and decreased by 20 percentages when stored for 365 d, 7-8 percentages more than that of coated and non-dried seeds. The change of germination rate of coated and dried seeds coincided basically with that of CK, which indicated that the seed coating agent had no significant influence on the germination rate of coated seeds dried to certain content of water, and the decrease of germination rate of the coated and non-dried seeds in storage time was because of the co-action of the seed-coating agent and water content in seeds. The germination rate of coated and dried seeds had no significant changes storing in low temperature condition for one year, which indicated that temperature and water content were the important factors affecting the storage safty of coated seeds. According to the standard about germination rate of coated seeds declared by our country, under natural condition, the coated and non-dried seeds can be safely stored for 180 d, the coated and dried seeds can be safely stored for 240 d, in low temperature of 0-3 °C, for at least pne year.4. Among the four kinds of cold resistant seed-coating agents, HET had inhibiting effects on the germination viability and germination rate of rice seeds, but not reached to significant difference degree from those of CK, with promoting effects ofthe rest three on the germination viability and germination rate under not only natural condition and low temperature condition as well. And the effects were more outstanding under chilling stress, indicating that the 4 cold resistant seed-coating agents were safe to the germination of rice seeds. Not only under natural condition but also under chilling stress, the root numbers per plant, fresh weight and dry weight per 100 plants of rice seedlings treated by the 4 cold resistant seed-coating agents were all obviously higher than those of CK, showing that the cold resistant seed-coating agents enhanced the growth of rice seedlings and the accumulation of dry matter not only under natural condition but also under chilling stress, which laid a good material foundation for enhancing the cold resistance of seedlings. Investigation in field experiment showed that the survival seedling rate of all treatments was significantly higher than that of CK, and the damage rate of treated seedlings after cold current was far less than that of CK. Synthesizing the indexes tested, we concluded that, among the 4 cold resistant seed-coating agents, YKJ+SNC seed coating agent(YKJZYJ) took the first place ,YKJ and ABA seed coating agents came second, and HET seed-coating agent came third in the aspects of promoting the germination rate, seedling rate, growth and cold resistance of rice.5. Under normal condition, the 4 kinds of cold resistant seed-coating agents raised obviously the root vigour, the contents of chlorophyll, soluble sugar, free proline, growth hormones as well as the activities of peroxidase(POD), catalase(CAT) and superoxide dismutase(SOD), decreased the content of malondialdehyde(MDA) and electrolyte leakage, which laid a physiological foundation for raising vigorous seedlings and increasing the seedling's suitability to reverse environments.Under chilling stress, the cold resistant seed-coating agents maintained a rather high level of root vigour and chlorophyll content, which guaranteed keeping seedlings a normal nutrient absorption, higher photosynthetic power and normal growth and strengthening the resistance to reverse environments. The cold resistant seed-coating agents accelerated the growth of seedlings and prolonged the functioning time of leaves by preserving a high level of growth hormones asauxin(IAA), gibberellin(GA3) and zeatin(Z) in seedlings; the membrance system was protected by enhancing large accumulation of soluble sugar, proline and abscisic acid(ABA) and reducing the decline of soluble protein, which laid a physiological foundation for strengthening the cold resistance of seedlings. The cold resistant seed coating agents reduced the electrolyte leakage and the decline of COD, CAT, POD activities, kept a low level of free oxygenic radical, decreased the accumulation of MDA, which ensured the physiological and biochemical metabolism conducted as usual. As a result, the plants were prevented from cold damage.6. The resistant frequency of 2 rice varieties coated with YKJZYJ seed-coating agent against 14 kinds of blast isolates usually seen in Hunan were 75%~93.75%, 25.5-31.25 percentages more than that of CK, which revealed that the inducing resistance were broad spectrum; The effects of inducing resistance were 74.81%~80.57%, in which the hybrid rice was superior to the conventional rice.7. In the experiment of direct seeding of 3 early-rice varieties coated with 3 kinds of seed-coating agents, HET, YKJ and YKJZYJ, adult seedling rate, seedling qualities and cold resistance were obviously enhanced, and rotten seedling rate was obviously decreased. Survival rate of seedlings increased by 10-11.6 percentages, plant damage rate decreased by 53.9-63.7 percentages and yield increased by 8.2%~17.6%. The effect of YKJZYJ was the best among three kinds of seed-coating agents tested.8. Applying under conventional condition, the total effect of YKJZYJ was superior to the effects of seed-coating agents applied in production such as Jiangsu Huanong and Sichuan Hongzhongzi produced in China and Shileshi imported from Switzerland.
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