Effects of drought and salt stress on seed germination of three leguminous species
The seeds of Medicago sativa (L.), Astragalus adsurgens (Pall.) and Coronilla varia (L.) were evaluated at germination for tolerance to salt (NaCl) and drought conditions induced by polyethylene glycol (PEG) in an experiment of orthogonal design. The results reveal that the germination percentages of M. sativa and A. adsurgens were much higher than that of C. varia. The radicle and hypocotyl lengths of M. sativa were significantly longer than that of A. adsurgens and C. varia (P<0.05). The effects of PEG (PEG 6000) on the radicle length showed a trend similar to that of NaCl where the radicle length decreased significantly; additionally, the hypocotyl length was inhibited by 10 and 15% PEG and 50 and 100 mM NaCl. The fresh weights of the three species decreased as a result of the combined effects of PEG and NaCl, yet no difference was observed on the dry weights of the early seedlings in comparison with the control and the seed germination of M. sativa was not inhibited by 5% PEG + 50 mM NaCl. This study indicates that the seed germination of the three species was inhibited by PEG and NaCl but there was no inhibitory effect on M. sativa at a low concentration of PEG and NaCl.
Key words: Drought and salt stress, germination, leguminous species.