In order to investigate the causes of degradation and the difficult problems in seedlings breeding of Amygdalus mongolica,the response characteristics of the seed germination and seedling growth of Amygdalus mongolica to adverse ecological factors were investigated,using a method of indoor control of drought stress,mixed salt stress,variable temperatures and seed husking,with the seeds of A.mongolica in the middle section of the Qilian Mountain.The results showed insignificant difference in the germination rate (P＞0.05) of the A.mongolica seeds processed in clean water for control and-0.15 MPa PEG solution,and significant sequential decrease in the germination rate (P＜0.01) processed in the water potentials of -0.32,-0.54,and-0.81 MPa,and non-germination processed in-1.15 MPa,and non-germination processed in-1.15 MPa.As the drought worsened and water potential decreased,the germination was delayed,the germination and vitality indices,the primary bud rates,root lengths,number of secondary roots and fresh weights of seedlings were on a significantly decreasing trend (P＜0.01).But the sound seedling index were significantly increased in case of treatment in-0.32 MPa.And the lowest thresholds of osmotic potential for seed germination was-0.81 MPa.The lowest mixed salt stress threshold for seed germination was 1.6 ％.Under light mixed salt stress (0.2 ％-0.4 ％),the length of primary buds and the number of secondary roots increased.With the increase in the mixed salt stress,the dry weight of primary buds and the fresh weight of seedlings were decreased,indicating that the seedlings responded and adapted to light mixed salt stress by reducing growth to promote root growth.After the stress of low osmotic potential or high-concentration mixed salt,a certain amount of the seeds developed into dormancy to maintain life force.The ungerminated seeds showed a germination rate of 62 ％-96 ％ after rewatering,and the total of the primary germination rate and the re-germination rate was not different from the germination rate of the control seeds (P＞0.05).The obstacle of seed coat is the main factor restricting seed germination.Seed dormancy can be interrupted by mechanical peeling.Stratification of seeds in low temperature (2-5 ℃) can significantly enhance seed vitality,and stratification in variable temperatures (5-10 ℃) can significantly improve the germination rate and vigor.The causes of degradation of A.mongolica include low water potential,high salt stress,high temperature,sensitive dormancy of seeds,and poor cold resistance of seedlings.For saving and manual breeding of A.mongolica,an area with irrigation conditions and of low temperature in spring should be selected for raising of seedlings,and sowing of seeds is suggested to occur at the time of soil thawing,to take advantage of the low temperature in early spring to and wake the seeds from their dormancy and cultivate strong seedlings.

In this article,the Arnygdalus mongolica population and seeds are taken as the research object to explore its endangered factors based on the study on its physical properties and characteristics in dormancy and germination.The results showed that Amygdalus mongolica seed has large volume,heavy specific weight and grain big.It spreads in a rather aggregative pattern,which mainly relies on its own gravity,animal and water,so it could spread much further.The main factors that restrict seed germination are seed coat barriers and physiological dormancy (accounting for about 10 percent).The physiological dormancy of the seed may be stopped by peeling mechanically after 72-hours exposure in 35 ℃.Seed stratification in low temperature (2-5 ℃) will effectively improve its vitality.Meanwhile,seeds thermocline (5-10 ℃) will increase its germination rate.However,seed germination is not sensitive to light.The dormancy term of Amygdalus mongolica seed is quite short and seed germination could happen in low temperature,so the seed put into soil library before the winter would germinate quickly and die in the chilly winter,which makes Amygdalus mongolica become an endangered species.However,the seed putting into soil library during frozen period can survive and has a high seedling rate due to the protection of seed coat.In summary,it is proved that artificial breeding is the most effective measure to rescue Amygdalus mongolica from extinction.

通过研究结果表明,临泽小枣树不同年龄枣股与枣吊、枣吊结果数量及枣股结果数之间具有密切的相关关系。从开花后5d开始落花,8d时达到落花高峰,11d后落花结束,总落花率为90.9%。落果有2次高峰,第1次占总落果率的72.8%,第2次落果率占7.6%,从座果至果实成熟落果率为80.4%。总落花落果率达98.11%。