Root temperature and salinity: Interacting effects on tillering, growth, and sodium content of barley

Abstract

In growth chambers (day/night photoperiod of 16/8 hr and constant air temperature of 20°C) and under water-culture conditions, the effects of addition of NaCI (0, 30, and 60mmol 1^-’) to and regulation of the temperature (10, 15, 20, and 25°C) of the rooting medium on the number of tillers and the total dry matter production by barley(Hordeum vulgaris L.)were studied. Experimental design was factorial with three replications. Single factor effects of salinity and root temperature and the interactions between these two factors were significant (p <0.05) for the number of tillers, growth of tops and roots, and the concentration of Na in the plant roots and tops. The effect of salinity on growth parameters was found to be strongly dependent on the root temperature. For example, addition of 30 mmol 1^-’ NaCI to the nutrient solution stimulated the growth when root temperature was kept at 10℃C but inhibited the growth at root temperature of 25℃C. At 60 mmol l^-’, root and shoot growth were most inhibited at root temperature extremes of 10 and 25℃C and were highest when root temperature was at the intermediate level of 15℃. As the root temperature was raised from 10 to 25℃C, Na concentration in the tops generally decreased but the Na concentration in the roots increased. At the highest Na salinity level of 60 mmol 1^-’, Na concentration in the tops was lowest when the root temperature was at an intermediate level of 15 to 20℃C. At all the salinity levels tested, barley plants produced the highest number of tillers and the highest dry matter when the root temperature was at the intermediate levels of 15 to 20℃C. The results indicate that the adverse effects of salinity on the growth of barley could be minimized if the temperature of the rooting media could be kept at about 15 to 20℃C.