Osmotic adjustment, gas exchanges and chlorophyll fluorescence of a hexaploid triticale and its parental species under salt stress

The effect of salt stress (NaCl 85.7 or 110 mmol/L) was investigated in the triticale T300 and its parental species, Triticum dicoccum farrum ( Triticum df) and Secale cereale cv. Petkus. Triticum df and T300 were more salt-tolerant than the rye (110 mmol/L NaCl was the highest concentration allowing rye growth to the three-leaf stage). Na +, K + and Cl − ions accounted for almost half of the osmotic adjustment in Triticum df and T300, and up to 90 percnt; in rye. Salinity decreased the net photosynthesis and transpiration rates of the three cereals as compared to control plants, but induced no significant change in chlorophyll a fluorescence parameters. Water-use efficiency (WUE) increased with salinity. In the presence of 110 mmol/L NaCl, the K +/Na + ratio decreased markedly in rye as compared to the other two cereals. Proline concentration, which increased in Triticum df and T300, could have protected membrane selectivity in favour of K +. Proline content remained low in rye, and increasing soluble sugar content did not appear to prevent competition between Na + and K +. The salt sensitivity of rye could be due to low K + uptake in the presence of a high NaCl concentration.