Genotype-dependent Differential Responses of Three Forage Species to Ca Supplement in Saline Conditions.

In many crop species, supplemental Ca has reduced growth inhibition that is caused by salt stress. The objective of this study was to compare plant growth and physiological responses to interactive effects of salinity and Ca on three forage species [African millet (AM), Tall wheatgrass (TW), and Perennial ryegrass (PR)]. In a CRB design experiment with 4 replications, plants were grown in a greenhouse in culture solution containing 0, 100, and 250 mM NaCl supplemented with 0.5, 5 or 10 mM CaCl₂. Plant growth, ionic concentration, and solute (proline and glycinebetaine) concentrations of the plants were determined 2 weeks after exposure to salinity treatments. At 100 mM NaCl, there was a moderate reduction in DM of all three species. A drastic decrease in DM occurred at 250 mM NaCl. Supplemental Ca reduced the adverse effects of salinity of all three species. The TW produced higher shoot and root growth in 100 and 250 mM NaCl than AM and PR, and produced the highest DM at 5 and 10 mM Ca supplement. Shoot and root DM of TW increased by about 45 and 15 %, respectively compared to the control. Plants chemical analysis indicated that in TW, Ca restricted both uptake and transport of Na from root to shoot, and increased Ca and K concentrations in both organs. The K and Ca transport from root to shoot of AM and PR decreased by NaCl, but was restored with increased Ca in the medium. The opposite occurred for Na. In PR, more K uptake was observed in shoot at 250 mM NaCl with 10 mM Ca supplement. Accumulation of glycinebetaine and proline in leaf contributed to the NaCl tolerance of TW. The results suggest that supplemental Ca, not only improved ionic relations but also induced plant ability in production of compatible solutes.