THE EFFECT OF NACL ON THE GERMINATION AND EARLY SEEDLING GROWTH OF WHITE CLOVER (TRIFOLIUM-REPENS L) POPULATIONS SELECTED FOR HIGH AND LOW-SALINITY TOLERANCE

Salt tolerance at germination and seedling emergence was examined in t hree populations of white clover (Trifolium repens L.) (cv. Haifa and two lines derived from cv. Haifa, ('Low CI S2' and 'High CI S2')) whic h differed significantly in salt tolerance as mature plants. For all t hree populations, germination decreased sig nificantly (p<0.001) with increasing NaCl concentrations between 60 to 200 mol m(-3) NaCl, but t here were no differences in relative germination between the three pop ulations at any salinity level. Percentage germination began to decrea se at 60 mol m(-3) NaCl, was reduced to 50% of the viable seeds at 145 mol m(-3)) NaCl and less than 20% of the seeds that germinated at 0 m ol m(-3) NaCl germinated at 200 mol m(-3) NaCl. Rates (or time taken t o achieve 50% germination) increased significantly (p<0.001) with incr easing NaCl concentration and there were significant differences (p<0. 05) between populations. Seedling emergence was significantly more sen sitive to NaCl than was germination. The threshold concentration for a reduction in seedling emergence was 10 mol m(-3) NaCl, and seedling e mergence was reduced by 50% at 60 mol m(-3) NaCl. Although there were no differences between populations in percentage emergence, population s did differ (p<0.05) in the rate of seedling emergence, which, like g ermination, was significantly slower (p<0.001) with increasing NaCl co ncentrations. No seedlings in any population produced a trifoliolate l eaf at concentrations greater than 60 mol m(-3) NaCl. Individual seedl ing dry weights decreased significantly (p<0.001) at concentrations gr eater than 10 mol m(-3) NaCl, but there were no differences between po pulations. Concentrations of Na and Cl in the shoots did not differ be tween populations however, there were significant differences (p<0.05) in concentrations of Na, but not Cl, between salinity levels. This st udy indicates that, in T. repens, there is not necessarily a close cor relation between salt tolerance at one growth stage compared with anot her and that this should be considered when choosing plant selection c riteria for salt tolerance.