PHYSIOLOGICAL AND BIOCHEMICAL ASPECTS OF TOLERANCE OF 3 GRASS SPECIESTO VARYING NA+ CA(2)+ RATIOS/

The effects of decreasing Ca2+ concentrations (Na/Ca ratios were 24, 4 9, 99 and 199) of the saline growth medium (NaCl concentration 200 mM) on three grass species Cenchrus pennisetiformis Hochst. & Steud., Lep tochloa fusca L. Kunth. and Panicum turgidum Forssk. were assessed aft er 7 weeks growth in sand culture. L. fusca produced the highest dry b iomass of all the species at varying Na/Ca ratios. Number of tillers p er plant and number of green leaves per tiller were reduced significan tly only in C. pennisetiformis. Leaf water potential of C pennisetifor mis decreased at all external Na/Ca ratios, whereas in L. fusca it dec reased only at an Na/Ca ratio of 99. Leaf osmotic potential of L. fusc a consistently decreased at all Na/Ca ratios, whereas that of the othe r two species remained unchanged. The shoot and root total sugars of a ll species remained unaffected at all decreasing Ca2+ concentrations. In P. turgidum chlorophyll b and total chlorophyll decreased consisten tly at all Na/Ca ratios, but in L. fusca they decreased only at the hi ghest Na/Ca ratios. The leaf soluble proteins of all the species remai ned unaffected at all Na/Ca ratios. The leaf free amino acids decrease d significantly in L. fusca with the increase in Na/Ca ratios. The lea f proline content was only decreased in L. fusca at the highest Na/Ca ratio. The significant correlations between the growth of the three gr ass species and other variables determined in this study were not foun d.