种子发芽生态研究

Life history strategy is an important research area of plant population ecology and seed germination is the critical stage of plant life history.Therefore,researches on seed germination rule and strategy help to know and elucidate the evolution and ecological adaptation traits of plant species.Plants in Songnen grassland area were treated as the target to investigate the seed germination responses to constant temperature and diurnal increasing or decreasing temperature,the effect of global warming simulated by alternating temperature regimes on seed germination of C3 and C4 species,and the germination patterns and their dynamics under different temperatures.The germination response mechanisms of plants to NaCl and PEG and their interaction were also studied.Based on the results of constant temperature effect,we proposed the modified thermal time model according to the basis of thermal time model and recruited an equation describing the constant germination rate.Germination rate of C3 species was obviously lower than that of C4 species.According to thermal time model,the average base germination temperature of C3 species was lower than that of C4 species,but not significantly.The average thermal time constant of C3 species was higher than that of C4 species and the difference approached to significant level.In this study,plant seed germination pattern was divided into five categories: quick germination,delayed germination,steady germination,normal germination,and delayed-quick germination.Most annual species belonged to the quick germination pattern,while the perennial C3 species in meadow belonged to the delayed-quick germination pattern,normal germination pattern,or steady germination pattern.Being an adaptive strategy to environments,the seed germination pattern of most species changed along with different temperatures.Under global warming conditions simulated by alternating temperature regime,the germination traits of C3 and C4 species changed.C3 species was sensitive to high temperature and C4 species sensitive to low temperature.By the germination comparison of all the alternating temperature regimes,we found that sectional high or low temperature,not the difference of temperature,played an important role in the impacts of global warming on seed germination.Field experiment results indicate that more plants germinated in spring in stead of autumn in Songnen grassland.Indoor germination experiment results proved that the germination rate under diurnal increasing temperature was significantly higher than that of diurnal decreasing temperature within the small temperature range of spring(5～10℃) and autumn(10～15℃).Germination in spring could be an adaptive strategy of plants from natural selection.The relationship between germination rate and salinity under different temperatures was curvilinear for Chloris virgata Swartz.and Digitaria sanguinalis(L.) Scop.Some physiological mechanisms might be employed by plants to reduce the osmotic stress under the middle and high salinity conditions leading to the obviously increase of the germination rate.Further experiments show that these two species could germinate and germinate faster in lower water potential condition induced by NaCl in comparison with PEG treatment.The dry weight of seeds decreased with the time proceeding.The water content,seed sodium concentration,and seed solution sodium concentration of germinated seeds treated by NaCl were significantly higher than those treated by the isotonic PEG.Seed sodium concentration and seed solution sodium concentration of germinated and non-germinated seeds in NaCl treatments increased along with the decreasing of water potential.Seed water content,seed sodium concentration,and seed solution sodium concentration increased linearly along with the time proceeding.According to the results,we proposed a salinity model:θS=(Sm-S)t,in which θS is a salinity constant,Sm is the maximum salinity allowing the seed germination,S is the external salinity,and t is the germination time for a given salinity.Seed germination response to salt was divided into four stages.The first stage was mainly involved the negative osmotic effect;at the second stage,ionic effect and osmotic effect existed together with the ionic effect stronger;at the third stage,no seed germinated in PEG treatment and ionic positive effect was significantly higher than osmotic negative effect;at the fourth stage,the ionic effect began to harm the seed gradually.In summary,the results of this study has the theoretical significances and practical value for the prediction of plant germination and emergence and global warming impacts on plant growth and distribution characteristics as well as the exploitation and utilization of wild plant resources.In summary,the results of this study has the theoretical significances and practical value for the pre-diction of plant germination and emergence and global warming impacts on plant growth and distribution characteristics as well as the exploitation and utilization of wild plant resources.