Aluminum-induced stress differently modifies Urochloa genotypes responses on growth and regrowth: root-to-shoot Al-translocation and oxidative stress

Abstract

Forage grasses belonging to the Urochloa (Brachiaria) genus present tolerance to Al toxicity, however there are intra- and interspecific differences among the species, which in turn should be better depicted. Here we evaluate genotypic differences in Al tolerance in four Urochloa (U. decumbens cultivar Basilisk; U. brizantha cultivar Marandu; U. brizantha cultivar Piatã and U. brizantha cultivar Xaraés) cultivated in nutrient solution, during growth and regrowth. We analyzed the effect of Al uptake on epidermal and cell membrane damage, and lipid peroxidation in shoots and roots. Exposure of genotypes to Al concentration up to 1.33 mmol L⁻¹ led to different degrees of shoot yield, mainly during the growth period. Increased Al concentration decreased dry matter production in shoots and roots, reduced leaf area (LA), relative root growth, increased Al accumulation in the roots and root-to-shoot Al translocation, notably during the first growth period. However, Al translocation from roots to shoots augmented massively in all genotypes, during the regrowth. Plant roots exposed to Al were damaged, exhibiting ruptures in the epidermis and reduced number of root hairs. Lipid peroxidation in shoots ranged in all genotypes exposed to Al, however, the oxidative stress was 2–5 times higher in shoots than in roots, notably in Marandu that accumulated 95% more Al than U. decumbens. This suggests that in the genotypes that are more tolerant to Al there is maintenance of metabolic activities, including upregulated and efficient antioxidant activity, root growth, LA growth and biomass yield.