Cross-tolerance is associated with temperature and salinity stress during germination of barley seeds

Effects of temperature and salinity on germination of barley (Hordeum vulgare L. 'Pijiu') seed, and cross tolerance between temperature and salinity during seed germination were studied. The optimum temperatures for germination were 5 similar to 20 degrees C, and for germination rate were 15-20 degrees C, and for seedling growth were 25 degrees C. Germination of seeds at 35 and 40 degrees C was 5% and 0%, respectively. Concentrations of NaCl > 100 mM inhibited seed germination and seedling growth, and the sensitivity of shoot growth to salinity stress was greater than that of the radicle. Compared to germination at 35 degrees C, that of seeds pre-treated at 0 degrees C for 3 days increased by 95%, and dry weight of radicle and shot increased by 39 and 61%, respectively. After pre-treatment at 5 or 30 degrees C, the seeds were transferrd to 35 degrees C to germinate continuously. Germination and seedling growth of seeds pre-treated at 5 and 30 degrees C for different time also increased when they were at 35 degrees C, but these increases of seeds pre-treated at 0 or 5 degrees C were much greater than those of seeds pre-treated at 30 degrees C. Barley seeds pre-treated at 0 degrees C for 3 days had increased tolerance to 200 and 400 mM NaCl stress, and those pre-treated with 100-400 mM NaCl for 12 or 24 It had markedly increased tolerance to high-temperature (35 degrees C). These results provide a new concept for seed germination under stress environments. Pre-treatment at low temperature to increase tolerance to subsequent high temperature stress during germination will become an excellent model system for the study of cross tolerance.