黄芪种子萌发对光温条件和旱盐胁迫的响应特征

Responses of seed germination of Astragalus membranaceus to light and temperature conditions accompanied with drought and salt stresses

以膜荚黄芪Astragalus membranaceus种子为材料,设置光照(连续光照、光照12 h/黑暗12 h交替、连续黑暗)和温度(15℃恒温、15℃12 h/30℃12 h交替和30℃恒温)处理分别与等渗的PEG和Na Cl(0,-0. 1,-0. 3,-0. 5,-0. 7 MPa)溶液进行交互实验。结果显示:①在光温2因素处理中,高温抑制最终发芽率且高温下的连续光照也成为最终发芽率的限制因素,光照模式不能影响平均发芽时间,黑暗和低温有利于根系伸长生长,光照和高温有利于叶片生长,黑暗和高温有利于胚轴生长。②光温处理结合PEG和NaCl胁迫条件下,轻微的渗透胁迫能促进种子萌发,但是随着渗透胁迫的加剧,种子萌发和生长所受到的抑制逐渐加强;在等渗条件下,PEG比Na Cl对最终发芽率和平均发芽时间的影响要剧烈。结果表明,黄芪种子可能随着温度的升高由光中性型转变为厌光型或者在干旱和连续光照交互作用下降低萌发率也是一种避旱的适应策略。黄芪胚轴在全黑暗处理中加速生长的现象也符合植物在光照不足时增加对茎和株高的分配投入以便获取更多光照的生态特性。Na^+引起的种内水势降低从而促进吸水,或许可以解释高浓度NaCl处理下种子发育略优于高浓度PEG处理的现象。

We studied the seed germination of Astragalus membranaceus under PEG and Na Cl osmotic stress gradients(0,-0.1,-0.3,-0.5,-0.7 MPa)respectively applied with light(continuous light,light 12 h/dark 12 h circulation and continuous dark)and temperature(constant 15℃,15℃12 h/30℃12 h circulation and constant 30℃)treatments.The results showed as following:①Under the light and temperature interactive treatments,total germination percentage(TGP)was restrained by high temperature and continuous light also decreased TGP under high temperature.Mean germination time(MGT)was not changed by light mode.Root development was enhanced by dark and low temperature.Shoot development was enhanced by light and high temperature.Hypocotyl length was enhanced by dark and high temperature.②Under the light and temperature interactive treatments combined respectively with PEG and NaCl stress conditions,although the inhibitions of seed germination and growth were gradually strengthened with the increases of osmotic stresses,slight osmotic stress can promote seed germination.Under the same osmotic potential,the effects of PEG on TGPs and MGTs were stronger than that of NaCl.As the temperature increase,the seeds may change from photo-neutrality to photo-phobia.Decreased TGP under drought and continuous light interactive treatment is an adaptation strategy to avoiding drought.Hypocotyl growth accelerated under continuous dark treatment is an ecological trait which could increase dry matter input in stem and height for more light.Seed development under high concentration of NaCl treatment is better than that of PEG treatment due to low water potential caused by Na^+,which can enter into seed coat and promote water absorption.