蒙古扁桃(Amygdalus mongolica)种子萌发及幼苗生长对胁迫的响应

Response of the Seed Germination and Seedling Growth of Amygdalus mongolica to Stresses

为了探讨蒙古扁桃(Amygdalus mongolica)种群退化原因和实生苗繁育的疑难问题,以祁连山中部蒙古扁桃种子为材料,采用室内控制干旱胁迫、混合盐胁迫、变温与种子剥壳相结合的处理方法,研究了种子萌发及幼苗生长对逆境生态因子的响应。结果表明:采用清水对照、-0.15 MPa PEG溶液处理,种子萌发率差异不显著(P>0.05);不同PEG溶液处理(-0.32、-0.54、-0.81 MPa)条件下,种子萌发率依次极显著降低(P<0.01);-1.15MPa处理条件下,种子不萌发;蒙古扁桃的种子萌发时间随着干旱加剧推迟,种子萌发指数、活力指数、初生芽、根长、次生根个数和幼苗鲜重随水势极显著降低(P<0.01),但在-0.32 MPa处理下壮苗指数极显著增高,-0.15MPa处理次之;种子萌发的最低渗透势阈值为-0.81 MPa。种子萌发的最低混合盐胁迫阈值为1.6%,在轻度混合盐(0.2%~0.4%)胁迫下,初生根长度和次生根数量增加,随混合盐胁迫加剧,初生芽长度、幼苗鲜重降低,表明幼苗对轻度混合盐胁迫首先采取降低生长量,促进根生长来进行适应。经低渗透势或高浓度混合盐胁迫后,部分种子休眠而保持生活力,未能萌发的种子复水后萌发率高达62%~96%,一次萌发率与恢复萌发率累计之和与对照萌发率无差异(P>0.05)。种皮障碍是制约蒙古扁桃种子萌发的主要原因,机械破除果皮可打破种子休眠,低温层积(2~5℃)能极显著提高蒙古扁桃种子活力,变温层积(5~10℃)能极显著提高蒙古扁桃种子发芽率和活力。低水势、高的混合盐胁迫、高温、种子浅的休眠及幼苗差的抗寒性是蒙古扁桃种群退化的原因,在拯救蒙古扁桃种群和人工驯化时,应选择有灌溉条件、春季气温低的区域育苗,建议土壤解冻时播种,利用早春的低温破除种子休眠,培育壮苗。

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 Amygda- lus 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 de- layed, 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 pri- mary 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 ~C ） can signifi- cantly enhance seed vitality, and stratification in variable temperatures （5--10 ~C ） 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 dor- mancy and cultivate strong seedlings.