Abstract

Trivalent aluminum ions (Al3+) in acidic soils are a major constraint for crop productivity inhibiting root elongation and promoting cell death. Al3+-toxicity has adverse biochemical and physiological effects on plant root growth. Sulfur is an essential macronutrient assimilated from the soil in the form of sulfate. However, the implication of sulfate nutritional status in the modulation of short-term Al3+-tolerance mechanisms in plant roots has not been previously reported. Here, we evaluated the effects of increased sulfate supply on short-term Al3+-toxicity in roots of Lolium perenne, measuring Al, Ca, Mg and S uptake, lipid peroxidation, total SOD activity, and transcriptional levels of Cu/Zn and Fe-SOD genes. First, the nitrogen sulfur ratio (N/S) in the TF nutrient solutions used in this study were computed to confirm that L. perenne plants were grown in sulfate deficiency (120 mu M), optimal supply (240 mu M), or overdoses conditions (360 mu M), without affecting dry root biomass. Sulfate supplementation ( > 240 mu M, and N/S ratio < 16) played a significant protection to Al3+-stress that prevents morphological changes in root tips, inhibits lipid peroxidation and differentially up-regulates total SOD activity, due changes in SOD gene expression. The results support the importance of sulfate nutritional status, on plant tissue homeostasis, enhancing the physiological tolerance mechanisms modulating lipid peroxidation damage induced by short-term Al3+-toxicity.