Abstract: 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.

Key words: cotton, NaCl stress, brassinolide, leaf physiological characteristics, differentially expressed genes.