Free proline, soluble sugars and soluble proteins concentration as affected by salt stress in two sugarcane (Saccharum sp.) cultivars differing in their salt tolerance

Salt stress is one of the environmental stresses which affect negatively the agricultural production of the world. In this study, the effects of salt stress on free proline, soluble sugars and soluble proteins accumulation were investigated in two sugarcane (Saccharum sp.) cultivars: CP66-346 (salt- tolerant) and CP65-357 (salt-sensitive). Young plants of these cultivars were exposed, in a hydroponic system, to four concentrations of NaCl (0, 17, 34 and 68 mM). These concentrations correspond to an electric conductivity of 1; 2.83; 4.26 and 6.63 mS/cm, respectively. Free proline, soluble sugars and proteins accumulation were quantified after 2 weeks of stress. Proline and soluble sugars concentrations increased significantly in leaves and roots under salinity. Furthermore, NaCl caused an increase in soluble proteins concentration in leaves and roots of the tolerant cultivar CP66-346 and a decrease in leaves and roots of the sensitive CP65-357. Salttolerant CP66-346 plants accumulated more soluble sugars in leaves than CP65-357, while both cultivars accumulated similar quantities of proline in leaves. These results provided evidence that soluble sugars could contribute mainly to counteract the negative water potential of the outside medium and that protein synthesis stimulation was implicated in sugarcane salt tolerance. Proline appeared as a symptom in salt-stressed sugarcane plants rather than as an indicator of tolerance.Keywords: Sugarcane, Saccharum sp., proline, soluble sugars, soluble proteins, salt-toleranc

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 cultivar