Crescimento de milho em solução com alumínio e produção de ácidos orgânicos de baixo peso molecular

Abstract

The utilization of aluminum (Al) tolerant hybrids is a strategies employed for corn production on acid soils. To apply this strategy, the knowledge of hybrid reaction to Al as well as the mechanisms related to the Al tolerance is important. The objective of this study was to evaluate the effect of Al on corn growth and on low molecular weight organic acids production. The activities of Al tested were 0.0, 5.81, 9.9, 14, 21, and 29 μmol L-1. The effect of this factor was combined with the effect of corn hybrids (Pioneer 30F53 and 32R48, earlier and super earlier cycle, respectively), on a factorial model. The experiment was conducted in plastic greenhouse for a period of three weeks. Plants were growing in pots containing nutrient solution as growth medium. The experimental design was a randomized block design with four replications. Seminal root length, fresh and dry weight, root and shoot dry weight, stem diameter, and number of secondary roots, concentration of malic, lactic, and citric acids in the nutrient solution, in the adventitious and fasciculate roots, and in the second leave, besides Al in the roots and shoots of plants and the toxic activity of this cation that suppresses 10% of the growth attributes were evaluated. The interaction of the factors tested did not influence the evaluated variables. Increase of Al in the nutrient solution decreased the seminal root length, the stem diameter, the fresh and dry weights of seminal root and of root and shoot, but increased the concentration of malic acid on fascicular roots of hybrid 32R48. These effects were more pronounced with 29 μmol Al L-1 and less with 12 μmol Al L-1. Organic acids were not detected in the nutrient solution. Citric and lactic acids were not detected in roots and 4 shoots. The hybrid 32R48 was more tolerant to Al than the hybrid 30F53. This difference is related to the lower Al content in the biomass and the largest concentration of malic acid in fasciculate roots of the hybrid 32R48, which increase in solutions with higher activity of Al