Moderate salt stress on the physiological and morphological traits of Aloe vera L.

Aloe vera L. is a perennial liliaceous plant with succulent green leaves, it is a xerophyte with economic and social value, but little is known about its response to salt stress and its mechanisms of tolerance, especially at moderate concentrations. The objective was to investigate the effect of salinity stress (0, 30, 60, 90 and 120 mM NaCl) on Aloe by measuring physiological and morphometric traits related to growth. The results of measuring physiological traits showed no significant differences compared to the control at 30 and 60 mM (chlorophylls a, b, total, relative water content, net assimilation rate, specific leaf weight, and specific leaf area), even at 90 mM or 120 mM most parameter variations were not significantly different. Similarly, for morphological traits no significant differences were found compared to the control for all 16 morphological traits at 30 mM, or even at 60 mM since at this concentration only one trait varied significantly (1 out of 16). Although the general trend of increasing NaCl was to lower leaf fresh weight as salinity increased, presumably due to a decrease in water content. However leaf dry weight was not significantly reduced at any of the salinity concentrations applied. Thus, total dry leaf biomass was basically the same or similar, this suggesting that Aloe has an ability to withstand these levels of salinity stress. It is noteworthy to point out, that there is a general trend of lower growth (lower parameters both physiological and morphological) that is not significant at low doses (30 and 60 mM), however becoming more significant at higher doses (90 and 120 mM). Thus, we suggest that Aloe has continuum responses to NaCl stress.