Interactive effects of Ca2+ and NaCl salinity on the growth of two tomato genotypes differing in Ca2+ use efficiency

Two tomato (Lycopersicon esculentum Mill.) lines differing in Ca2+ use effi ciency (Ca2+ use efficient line 113 and Ca2+ use inefficient line 67) were subjected to salinity treatments in two separate experiments to determine w hether they differed in salt tolerance. In experiment I, three NaCl and two CaCl2, treatments were imposed. The Na+ concentrations were 1.1, 100 and 1 50 mM and the Ca2+ concentrations were either 1.51 or 10 mM. In experiment II, one NaCl and three Ca2+ treatments (as CaCl2, or CaSO4,) were imposed. The treatments consisted of 150 mM NaCl at either 1.51 mM CaCl2 10 mM CaCl2 or 10 mM CaSO4. Response to treatments was determined by analysis of growt h parameters (shoot and root dry weights, plant height, and root length). S hoot and root dry weight, and root length were depressed as salinity increa sed in plants lacking additional Ca2+ No significant differences in salt to lerance were detected between the two tomato lines after 24 d of salinity t reatment. An important finding of this study was that root growth and lengt h appeared to be more sensitive to the effect of CaCl2 treatment alone and to the effects of CaCl2 x NaCl treatments. This suggests that over the long term, both root growth and root length may be more sensitive indicators of salinity effects than shoots. Supplemental CaCl2 had no ameliorative effec t on NaCl stress in shoot growth. The inability of Ca2+ to counter Cl- entr y or toxicity may account for the lack of amelioration. Additional Ca2+ as CaSO4 improved shoot growth of plants exposed to 150 mM NaCl. In contrast, root growth and length were improved by 10 mM Ca2+ as either CaCl2, or CaSO 4. (C) Elsevier, Paris.