en Effect of salicylic acid on salt tolerance of Aloe vera plants under both salt-acclimated and non-acclimated conditions تنش شوري Salt Stress پژوهشي Research Since the role of salicylic acid (SA) in <em>Aloe vera</em> plants under salt stress is not yet clarified, this experiment was conducted to investigate the role of SA (100 and 500 &mu;M) in photosynthesis, antioxidative capacity and ion homeostasis in salt acclimated (EC 6 dS/m) and non-acclimated <em>Aloe</em> plants against subsequent salt stress (EC 21 dS/m). Salinity exerted an adverse effect on the leaf dry weight, whereas foliar spray of 100 &mu;M SA mitigated the salt-induced inhibitory effects on the plant growth, especially under acclimated conditions. While salt stress caused a significant increase in Na accumulation and a considerable decrease in K and Ca, higher levels of K/Na ratio was observed after SA treatment. SA application (100 &mu;M) also alleviated the damage to PSII function induced by salt, contributing to the improvement of electron trapping under salinity. Furthermore, <em>Aloe </em>plants exposed to EC 21 dS/m exhibited an oxidative damage, determined by increased content of oxidants (hydrogen peroxide and malondialdehyde). In contrast, foliar spray of 100 &mu;M SA increased CAT activity as well as carotenoids content, and reduced content of oxidants under salt stress. Consequently, under both salt-acclimated and non-acclimated conditions, SA at concentration of 100 &mu;M was more effective in alleviation of salt stress in <em>Aloe</em> plants via the enhancement of photochemical activity of photosynthesis, the activities of antioxidant enzymes and the ratio of K and Na under salinity. Aloe vera, antioxidant status, ion homeostasis, quantum yield of electron transport, photochemistry activity, salinity 17 24 http://jispp.iut.ac.ir/browse.php?a_code=A-10-737-6&slc_lang=en&sid=1 Ali Nakhaeia Nakhaeia nakhaeia@yahoo.com No Department of Biology, Payame Noor University (PNU), 19395-3697 Tehran, Iran Ghader Habibi Habibi gader.habibi@gmail.com Yes Department of Biology, Payame Noor University (PNU), 19395-3697 Tehran, Iran Autosa vaziri Autosa vaziri vaziri@pnu.ac.ir No Department of Biology, Payame Noor University (PNU), 19395-3697 Tehran, Iran