Effects of salt stress on the seed germination and seedling growth of Pennisetum alopecuroides and Spodipogon sibiricus

In order to understand the adaptive features of r-strategists at their germination and seedling stages under salt stress, Pennisetum alopecuroides and Spodipogon sibiricus were chosen as the objects, and two single-factor experiments of seed germination and seedling growth were conducted to compare the germination ability, embryo growth, and seedling growth of the plants as well as their physiological and biochemical properties under the salt treatments of 1∶1∶3 (mol) of NaCl∶Na2SO4∶NaHCO3 at six levels (0.0%, 0.1%, 0.2%, 0.4%, 0.8%, and 1.6%). At germination stage, the germination rate, germination index, and germination vigor of P. alopecuroides and S. sibiricus decreased significantly with the increase of salt concentration. The germination ability of P. alopecuroides was less than S. sibiricus at low salt concentrations (≤0.4%), but in adverse at high salt concentrations (≥ 0.8%). With the increase of salt concentration, the plumule length, radicel length, and embryo weight of the two plants decreased significantly, but the inhibition degree was higher for S. sibiricus. At seedling stage, the growth of P. alopecuroides and S. sibiricus was significantly inhibited by the salts, but the inhibition degree was lower for S. sibiricus than for P. alopecuroides, and the contents of physiological active calcium and malondialdehyde in P. alopecuroides were higher than those in S. sibiricus. These results suggested that P. alopecuroides had a stronger salt-resistance than S. sibiricus at germination stage but a lower salt-resistance than S. sibiricus at seedling stage, implying the risk-sharing countermeasures of r-strategists.