Efeitos da adição de alumínio, silício e selênio na fisiologia e bioquímica de Schinus terebinthifolius Raddi

Abstract

Brazilian Southern region presents acidic soils, being many of them classified as aluminum and alicytes, highlighting aluminum (Al) high levels occurrence. When in acid soils, the element is present in a trivalent form (Al +3 ), which is toxic for vegetal organisms. Studies already demonstrated the silicon (Si) and selenium (Se) efficacy as damage attenuators caused by phytotoxic elements. In this sense, our objective was to evaluate the resistance of the species to Al and Si and Se effect on Al toxicity in plants of Schinus terebinthifolius Raddi under hydroponic conditions. This study was conducted in greenhouse and in Plant Biochemistry Laboratory at Biology Department, Federal University of Santa Maria, RS. S. terebinthifolius plants were propagated via seeds in commercial substrate and later transferred to hydroponic culture in nutrient solution, where Al, Si and Se concentrations in mM were added as follows: Treatment 1: 0 Al + 0 Se and Si; Treatment 2: 2.5 Si; Treatment 3: 0 Al + 0.0025 Se; Treatment 4: 1.85 Al + 0 Se and Si; Treatment 5: 1.85 Al + 2.5 Si; Treatment 6: 1.85 Al + 0.0025 Se; Treatment 7: 3.71 Al + 0 Se and Si; Treatment 8: 3.71 Al + 2.5 Si; Treatment 9: 3.71 Al + 0.0025 Se). Following 21 days exposure to different treatments, under hydroponic cultivation were evaluated physiological variables (fresh and dry biomass, plant height, root system morphological variables, leaf area and photosynthetic variables) as well as biochemical (antioxidant enzymes, lipid peroxidation, and hydrogen peroxide content, ascorbic acid, non- protein thiols and photosynthetic pigments). Considering physiological variables, it was observed that Al is phytotoxic to this species at concentrations of 1.85 mM and 3.71 mM Al leading to significant reductions in shoot and root development. While Se did not mitigate damages caused by Al exposure, Si was able to alleviate only the damages caused by lowest Al concentrations (1.85 mM). Regarding biochemical variables, both Si and Se presented beneficial effects in Al-stress alleviation, mainly through antioxidant system activation and reduction of lipid peroxidation damages. In this way it can be concluded that the species has its performance negatively affected by Al presence, both physiologically and biochemically. However, Si was efficient in reducing physiological damage caused by Al, especially when Al concentrations were lower, whereas Se did not present this effect. Biochemically it has been noted that both Si and Se were capable of alleviating damage caused by Al through antioxidant system maintenance. Therefore, our results allow us to conclude that Si and Se elements were efficient in alleviating physiological and biochemical damages caused by aluminum in S. terebinthifolius plants.