Physiological and cytological response of salt-tolerant and non-tolerant barley to salinity during germination and early growth

Seven barley cultivars (Franklin, Gairdner, YU6472, Numar, CM72, ZND3 and YUQS) were evaluated for NaCl tolerance in relation to physiological and cytological responses during germination. Standard germination techniques were employed using blotting paper saturated with different NaCl solutions (0, -0.3, -0.6, -0.9, -1.2, -1.5 or-1.8 MPa) at 20°C. The results showed significant differences among varieties for germination percentage, frequency of abnormal seedlings, and Na⁺, K⁺ uptake. Of the 7 barley cultivars, CM72 was similar in salt tolerance to Numar, while YUQS and ZND3 were the most sensitive to high salinity. The tolerant cultivars showed much higher germination percentage under salinity stress than susceptible varieties. Both CM72 and Numar maintained more than 90% germination at -1.2 MPa osmotic potential while YUQS and ZND3 had only 57% germination at the same level of salinity. The tolerant varieties also showed shorter mean germination time at low osmotic potential. The start of the first mitosis was delayed, while both the frequencies of aberrant anaphases at the first cell divisions, and the numbers of abnormal seedlings were increased in higher salt concentrations. During the seedling stage, tolerant varieties showed significantly higher K⁺ concentrations, lower Na⁺ concentrations, lower Na⁺/K⁺ ratio and higher photosynthetic rate than susceptible varieties under salinity stress. Screening of barley cultivars or breeding lines could be best achieved by a combination of germination testing and measurement of photosynthetic rate and/or Na/K balance in young seedlings.