Effects of saline and alkaline stresses in varying temperature regimes on seed germination of Leymus chinensis from the Songnen Grassland of China

Leymus chinensis is a dominant and most promising grass species in the Songnen Grassland of Northern China. Experiments were conducted to determine the effect of temperature, salinity, alkalinity and their interactions on seed germination. Seeds were germinated at four alternating temperatures (1020, 1525, 2030 and 2535 degrees C), with saline stress (9 similar to 1 molar ratio of NaCl similar to Na2SO4) and alkaline stress (9 similar to 1 molar ratio of Na2CO3 similar to NaHCO3). Germination percentage and rate were inhibited by either an increase or decrease in temperature from the optimal temperature range of 2030 degrees C, and were also inhibited by an increase in salinity and alkalinity at all temperatures. The inhibitory effects of high salinity on germination were greater at 2535 degrees C, but seeds were subjected to more stress even though the alkalinity was low under this temperature. Recovery percentage was highest at 400 mm salinity at 2030 degrees C, but only at 100 mm alkalinity, and 2535 degrees C also resulted in lower recovery percentage under both stresses. Results suggest that saline stress and alkaline stress have different impacts on seed germination and that saline-alkaline tolerance of L. chinensis seeds is affected by the interactions of temperature and salinity-alkalinity. Early July sowing in the field is recommended when temperature is optimal and salinity-alkalinity concentrations are reduced by the high rainfall.