模拟干旱和盐碱胁迫对碱蓬、盐地碱蓬种子萌发的影响

为研究干旱和盐碱胁迫对碱蓬(Suaeda glauca)、盐地碱蓬(Suaeda salsa)种子萌发的影响,比较碱蓬和盐地碱蓬逆境生理特性的异同,本研究利用PEG6000、NaCl和Na_2CO_3分别模拟干旱、盐和碱胁迫,配制相同渗透势的PEG6000、NaCl、Na_2CO_3处理液,以蒸馏水处理为对照,对碱蓬、盐地碱蓬种子的萌发与胚的生长进行比较研究。结果表明:1)低渗处理(-0.46 MPa)对碱蓬、盐地碱蓬种子的萌发无显著影响;高渗处理(-1.38MPa、-1.84 MPa)抑制碱蓬、盐地碱蓬种子的萌发。2)当溶液渗透势相等时,NaCl处理下碱蓬种子的萌发率显著大于PEG、Na_2CO_3处理;而等渗PEG、NaCl、Na_2CO_3处理对盐地碱蓬种子萌发率的影响无显著差异。3)PEG、NaCl、Na_2CO_3处理组碱蓬、盐地碱蓬种子的最终萌发率与对照无显著差异。4)在幼苗形成阶段,PEG、Na_2CO_3处理对碱蓬、盐地碱蓬胚的抑制作用显著大于等渗NaCl处理。5)碱蓬、盐地碱蓬胚的生长对NaCl、Na_2CO_3胁迫的响应存在差异。-0.92 MPa NaCl处理抑制碱蓬胚的生长,却对盐地碱蓬产生促进作用;-0.46 MPa Na_2CO_3处理对碱蓬胚的抑制作用小于盐地碱蓬。综合分析表明:碱蓬、盐地碱蓬均具有很强的抗盐性。在种子萌发阶段,碱蓬种子的抗旱、抗碱能力低于盐地碱蓬;在幼苗形成阶段,碱蓬胚的抗盐性小于盐地碱蓬,但对轻度碱胁迫的抗性高于盐地碱蓬。

Effects of PEG, NaCl and Na2CO3 stresses on Suaeda glauca and Suaeda salsa seed germination

Suaeda glauca and S. salsa are native halophytes in China with a key role in the improvement and restoration of salt marsh ecologies. There is a lot of works on the response of Suaeda plants to salinity, but works are limited about the effects of drought and alkali stress on S. glauca and S. salsa, especially at germination stage. The aim of this study was to evaluate the impacts of PEG, NaCl and Na₂CO₃ stress on the germination of S. glauca and S. salsa seeds. The in-vitro seed germination test was carried out with various solutions of PEG-6000 (29 mmol·L^-1, 38 mmol·L^-1, 45 mmol·L^-1and 50 mmol·L^-1), NaCl (100 mmol·L^-1, 200 mmol·L^-1, 300 mmol·L^-1 and 400 mmol·L^-1) and Na₂CO₃ (70 mmol·L^-1, 140 mmol·L^-1, 210 mmol·L^-1and 280 mmol·L^-1) in iso-osmotic concentrations (-0.46 MPa, -0.92 MPa, -1.38 MPa and -1.84 MPa). We measured the germination rate, germination index, mean germination time, early seedling growth after 7-day treatment and final germination rate after another 7-day recovery. The results showed that with increasing osmotic stress intensity, the germination rates of two species were depressed under PEG, NaCl and Na₂CO₃ treatments, while -0.46 MPa treatment did not differ significantly from that of the control (fresh water). The negative effect of NaCl on S. glauca seed germination was less than iso-osmotic PEG and Na₂CO₃ treatments. By contrast, the effects of iso-osmotic PEG, NaCl or Na₂CO₃treatments on S. salsa seed germination were not significantly different. The germination rate of S. salsa was positively related to osmotic potential. Recovery study indicated that PEG, NaCl and Na₂CO₃ stress had no negative effects on the final germinate rate of S. glauca and S. salsa, meaning that the inhibition of PEG, NaCl and Na₂CO₃ stress on seed germination was due to osmotic pressure rather than ion toxicity. In addition, mild NaCl treatments (-0.46 MPa for S. glauca, and -0.46 and -0.92 MPa for S. salsa) promoted S. glauca and S. salsa seedling elongation, while PEG and Na₂CO₃ treatments inhibited it. In iso-osmotic conditions, radicle and hypocotyl lengths of S. glauca and S. salsa seedlings under NaCl treatment were greater than those under PEG and Na₂CO₃ treatments. Compared with S. glauca, S. salsa seedlings grew better under -0.46 MPa and -0.92 MPa NaCl treatments, but worse under -0.46 MPa Na₂CO₃ treatment. The findings suggested that, 1) S. salsa seeds exhibited strong resistance to PEG, NaCl and Na₂CO₃ stress, and its resistance to PEG and Na₂CO₃ stress was greater than that of S. glauca. 2) S. salsa had stronger capacity to establish seedlings under NaCl stress than S. glauca, but its tolerance to mild Na₂CO₃ stress was weaker than that of S. glauca.