长芒草(Stipa bungeana)种子萌发与出苗对关键环境因子的响应

Responses of germination and seedling emergence of Stipa bungeana to key environmental factors

种子萌发为植物生活史的关键阶段,对植物的定居、群落演替与动态起着决定作用。通过室内控制实验的方法,研究长芒草(Stipa bungeana)种子萌发对光照和温度,水势和温度,以及幼苗出土对沙埋深度和供水的响应。使用光照、温度和湿度自动控制的生长箱,设置光照、黑暗和持续黑暗3个光处理和5个变温处理(5℃:15℃、10℃:20℃、15℃:25℃、20℃:30℃和25℃:35℃)(夜:昼);设置11个水势处理(0、-0.2、-0.4、-0.6、-0.8、-1、-1.2、-1.4、-1.6、-1.8 MPa和-2 MPa)和5个恒温处理(10、15、20、25℃和30℃),研究长芒草种子萌发对光照和温度、水势和温度的响应。设置6个沙埋深度(0.5、1、1.5、2、3、5 cm)和10个供水处理(2.5、5、7.5、10、15、20 mm和30 mm 7个单次供水处理,2.5、5、7.5 mm/3d 3个多次供水处理),研究长芒草幼苗出土对沙埋和供水的响应。结果表明:光照对长芒草种子萌发具有促进作用,黑暗与持续黑暗条件下的最终萌发百分率无显著差异。在10:20℃—15:25℃温度范围内,长芒草种子萌发快速且集中,15:25℃为种子萌发最适温度,超过最适温度时,最终萌发百分率随温度升高而下降。水势低于-1 MPa时长芒草种子不能萌发,最终萌发百分率和萌发速率均随水势的降低而降低。当温度达到30℃时,种子基本不能萌发。单次供水条件下,长芒草的最终出苗百分率和出苗速率接近为零;5 mm/3d及7.5 mm/3d供水条件下,最终出苗百分率可达到50%。5 mm/3d及7.5 mm/3d的多次供水与单次供水及2.5 mm/3d的多次供水相比更有利于长芒草出苗。适宜出苗的沙埋深度为0.5—2 cm,沙埋深度超过3 cm时最终出苗百分率和出苗速率均率接近于零。长芒草种子出苗情况随沙埋深度增加而降低,在供水量为7.5 mm/3d,沙埋深度为0.5—2 cm时,出苗最好。降低人为干扰对表层土壤的破坏,提高表层土壤含水量,是促进长芒草种子萌发和幼苗出土的有效措施。

Seed germination plays a decisive role in plant establishment,and community succession and dynamics,and forms a key stage in a plant′s life cycle.The effects of light and temperature,and water potential and temperature on seed germination,and the influence of sand burial depth and water availability during the emergence of S.bungeana seedlings were studied through controlled-environment experiments.In light-,temperature-,and air humidity-controlled growth chambers,we set up 3 different light treatments(light,dark,and continuous darkness)and 5 alternative temperature treatments(night:day,5℃:15℃,10℃:20℃,15℃:25℃,20℃:30℃,and 25℃:35℃);11 levels of water potential(0,-0.2,-0.4,-0.6,-0.8,-1,-1.2,-1.4,-1.6,-1.8,and-2 MPa)and 5 constant temperatures(10,15,20,25,and 30℃)to study the effects of light and temperature,and water potential and temperature on the final percent germination(FPG)and germination rate(GR)of S.bungeana.We set up 6 sowing depths(0.5,1,1.5,2,3,and 5 cm)and 10 water supply regimes(7 single water supply regimes 2.5,5,7.5,10,15,20,and 30 mm;and 3 multiple water supply regimes 2.5,5,and 7.5 mm/3 d)to study the effects of sand burial and water supply regimes on the final percent emergence(FPE)and emergence rate(ER)of S.bungeana.The results showed that light promoted the seed germination of S.bungeana.There was no significant difference in the FPG between dark and continuous darkness treatments.Most seeds of S.bungeana germinated quickly and germination occurred in the alternative temperature ranges of 10℃:20℃and 15℃:25℃.The optimum germination temperature range was 15:25℃.When the temperature range exceeded this optimum,the FPG decreased with increasing temperature.The seeds of S.bungeana could not germinate when water potential was lower than-1 MPa.FPG and GR decreased with decreasing water potential.When the constant temperature reached 30℃,few seeds could germinate.The FPE and ER of S.bungeana were close to zero under a single water supply.FPE reached 50%under the water supply conditions of 5 mm/3 d and 7.5 mm/3 d.A multiple water supply of 5 mm/3 d or 7.5 mm/3 d was more conducive to the emergence of S.bungeana than either a single water supply and a multiple water supply of 2.5 mm/3 d.The most suitable sowing depth for seedling emergence was 0.5—2 cm.The FPE and ER of S.bungeana were close to zero when the sowing depth was greater than 3 cm.The overall trend was that the seedling emergence decreased with an increase in sand burial depth.When the water supply was 7.5 mm/3 d and the sowing depth was 0.5—2 cm,the emergence was much higher than that in other treatments.Reducing the disturbance of the surface layer soil through human activities and increasing soil moisture in surface layer soil should be effective ways to promote germination and seedling emergence for S.bungeana.