The Interaction Of Nitric Oxide, Ethylene And Gibberellic Acid To Break Bunge Seed Dormancy

Nearly a decade of research shows that NO as a new signaling molecule in plants is widespread, and plays an important role in regulating a variety of physiological active-ties in plants, many scien-tists found that NO plays an important role in breaking seed dormancy. the reasons of seed dormancy are very variegated, many biological factors and abiotic factors can control seed dormancy. It has been proved that ethylene (ET) and Gibberellin acid (GA) play an important role in regulating seed dormancy of some plants. Pyrus betulifolia Bunge is a species of the Rosaceae, its seed is a dormant seed, Dormancy can be breaked by Long-term cold stratification, consuming time and bring-ing a serious loss. In this study, the Pyrus betulifolia Bunge dormant seeds as expert-menttal material, we treated its seeds with NO, ET, GA and their inhibitors, calculate and measure percentage of germina-tion, shoot length, release of ethylene content in the training process, hope to find effects and rela-tionship of NO, ET and GA on seed dormancy of Bunge. The results as follows:1. Exogenous NO can break seed dormancy for germination of Pyrus betulifolia Bunge.1,5,10, 20 mmol/L of Sodium nitroprusside(SNP) treatment all broke its seed dormancy. But the high con-centration of SNP treatment inhibited the growth of buds, even leaded to the death of buds.10 mmol/Lof SNP treatment was better in promoting germination, and didn't harm the growth of the bud. NO scavenger 2-phenyl-4,4,5,5-tetramethylimidazo-line-l-oxyl-3-oxide(PTIO) reversed the role of SNP and main-tained seed dormancy. In Breaking the dormancy of Pyrus betulifolia Bunge seed NO came from Nitric oxide synthase(NOS) but not Nitrate reductase(NR) pathway.2. Exogenous ethylene broke Pyrus betulifolia Bunge seed dormancy, increased germination rate significantly.0.5,1,2,5 mmol/L of ethephon treatment all improved the germination rate of its seed,2 and 5 mmol/L were better, but the high concentra-tion of ethephon was strongly inhibited the growth of Pyrus betulifolia Bunge buds. The results showed that 2mmol/L was optimal concen-tration to break dormancy and promote germination of Pyrus betulifolia Bunge seed. Inhibitor of ethylene action 1-Methylcyclopropene(1-MCP) can reverse the role of exogenous ethephon and reduced germina-tion rate.3. GA involved in the process of breaking Pyrus betulifolia Bunge seed dormancy.2 mmol/L exogenous GA treatment had little effect on the seeds with testa of Pyrus betulifolia Bunge, but broke seed dormancy of peeled seed. GA synthesis inhibitor paclobutrazol strongly inhibited the germination of seeds of Pyrus betulifolia Bunge.4. Breaking Pyrus betulifolia Bunge seed dormancy by NO involved the stimulation of ethylene production. Ethylene was at the downstream of NO signaling pathway in breaking Pyrus betulifolia Bunge seed dormancy.1-MCP treatment reversed the SNP effect, while PTIO had little effect on ethylene. Ethylene induced its own synthesis, ethylene accumulation broke the dormancy of Pyrus betulifolia Bunge seed. By the treatment of 10 mmol/L SNP, endogenous ethylene production of Pyrus betulifolia Bunge seed had significantly increased, both PTIO and 1-MCP reversed the effect.5. Ethylene and GA were synergy in Pyrus betulifolia Bunge seeds, collaborative breaking its dormancy, and GA was necessary for ethylene to break dormancy. The inhibitors of GA could reverse the role of ethylene, ethylene inhibitors could partially inhibit the role of GA.6. According to the experimental results, it was proposed the signals relations of NO, ET and GA in breaking the dormancy of Pyrus betulifolia Bunge seeds:NO was in the upstream signaling pathway of ethylene, promoting the accumulation of ethylene; ethylene and GA was the systematic relationship, synergy breaking the dormancy of its seed, and GA was necessary for ethylene to break dormancy.