The Dynamic Of Endogenous Hormone Contents In Seeds Of Aconitum Gymnandrum Along Altitudes And Their Effects On Seed Germination

Seeds are the ending and beginning of the plant life histories.The germination and emergence of seeds are essential during ontogenesis of plants,which are directly related to the conservation of germplasm resources,population regeneration and community establishment.Seeds germination and the early stage of seedlings are the most vulnerable and critical stage of plant life histories.Seeds have evolved diverse germination behaviors and strategies due to the multiple environmental cues,the proper time of seed germination was regulated by its dormancy,which is critical to successful seedlings establishment in proper condition and can maximize the fitness of species.Seed germination and dormancy are affected by various internal and external factors,and the induction,maintenance and termination of seed dormancy related to endogenous hormones have been gained great attention.However,few studies on the regulation of endogenous hormones on seed dormancy and germination of alpine plants and the adaptation of their contents variation to environmental cues were focused on.In this study,the seeds of Aconitum gymnandrum(Ranunculaceae),a common species from degraded grassland in the alpine meadow on the eastern Qinghai-Tibet Plateau,was used to explore the influences of endogenous hormones contents of seeds in different states(dry and imbibe seeds)on seed dormancy and germination.Contents of endogenous hormones [(trans-Zeatin,ZT)?(gibberenllins,GA)?(auxins,IAA)?(abscisic acid,ABA)] and germination percentage of seeds were determined under different storage conditions,storage,germination conditions and altitudes.The dynamic changes of endogenous hormones contents during the process of seeds germination were determined.The research results showed as follows:1)Seeds germination of Aconitum gymnandrum were inhibited by light,the dormancy level of seeds from high altitude was relatively lower than those from low altitude,low temperature is beneficial to maintain seed dormancy.The percent germination of Aconitum gymnandrum at different altitudes showed a similar fluctuant trend with storage time under room temperature and cold storage,and both got a peak about every 12 months,and remaining at a high level in 12-18,24-30 and 36-month storage.Compared with seeds from low altitude,the percent germination of Aconitum gymnandrum from high altitude was significantly higher under the same germination condition,and the highest germination percentage of seeds from high altitude and low altitude were 37.33% and 28.67%,respectively.Compared with cold storage,the germination percentage in room temperature was significantly higher regardless of seeds from high or low altitudes,and the highest germination percentage under room temperature and cold storage were 37.33% and 12.67%,respectively.Compared with seeds germinated in12-h light,the germination percentage in dark was significantly higher under the same storage conditions,and the highest germination percentage in dark and in 12-h light were 37.33% and 14%,respectively.2)Contents of endogenous hormones in seeds might be related to seed dormancy.The contents of endogenous hormones showed variation during storage,the contents of ZT ranged from 3.857~33.659 ?g/g,GA ranged from 218.221~1324.539 ?g/g,IAA ranged from 24.426~110.059,and ABA ranged from 0.738~7.301 ?g/g.Seeds of Aconitum gymnandrum had been in deeper dormancy level during storage time whatever seeds were collected from high or low altitudes.The contents of endogenous hormones showed a similar variation trend with storage time under both storage conditions.Although the contents of endogenous hormones showed fluctuant trend with storage time,compared with seeds from low altitude,the seeds from high altitude had lower dormancy level.The contents of promoters,ZT?GA?IAA and ZT/ABA?GA/ABA?IAA/ABA were higher in seeds from high altitude,on the opposite,the contents of inhibitor,ABA,were lower.3)Dormancy release is not caused by the abosolutely increase of the promoters or the decrease of the inhibitors,but might be by the change of seeds sensitivity to endogenous hormones during germination.Under room temperature,only seeds with 12-month storage showed the highest germination percentage,and the highest contents of ZT,GA and IAA,while the content of ABA was the lowest.Seeds dormancy were released effectively by exogenous GA,the percent germination of seeds from low altitude and high altitude increased from 0% to 85.33% and 0% to 80.67%,respectively.Whether in light,or not,compared with dormancy-release seeds,the contents of ZT,GA,ZT/ABA,GA/ABA were higher in dormant seeds during seeds inhibition,and the decrease scale of ABA content was larger than ZT and GA contents.In addition,there was no significant difference in ABA contents before seed germination whether seeds were treated with exogenous GA or not.4)IAA might be essential to break seeds dormancy and promote seeds germination of Aconitum gymnandrum.During imbibition of dormancy-release seeds,the content of IAA and the ratio of IAA/ABA both got a peak,and those of the dormant seeds remained at a low level.In addition,the percent germination was only positively correlated with the content of IAA with storage time.