Growth, proline and ion accumulation in sugarcane callus cultures under drought-induced osmotic stress and its subsequent relief

Calli obtained from two sugarcane cultivars (R570 and CP59-73) were exposed to different osmotic stress intensities followed by a period of stress relief. Relative rate growth, callus water content and changes in organic and inorganic solutes were determined at the end of stress and relief periods. After the stress period, calli derived from both cultivars showed a decrease in RGR, but at lesser extent in R570 than CP59-73 cultivar. Same tendency was recorded in the callus water content under mannitolinduced osmotic stress. The inorganic solutes seemed to have no contribution in the osmotic adjustment in mannitol-stressed calli since K+ and Ca2+ concentrations decreased drastically while Na+ and Mg2+ concentrations were not affected. The accumulation of proline occurred in both cultivars and was more marked in CP59-73 than R570 cultivar. At the end of the relief period, we observed that all the considered parameters have recovered completely to reach the control levels. According to these results, we conclude that the drought stress-induced changes are reversible, at the least at the cellular level, in sugarcane cultivars