Matéria seca e acúmulo de nutrientes em genótipos de milho contrastantes quanto a aquisição de fósforo

Abstract

With the objective of evaluating the effect of phosphorus stress on morphological attributes of the root system of corn genotypes contrasting in relation to phosphorus efficiency, an experiment was carried out in nutrient solution in greenhouse at Embrapa Milho e Sorgo, Sete Lagoas, MG, in the months of november and december of 2001. The experiment design was totally at random, in an 8 x 2 factorial scheme with three repetitions, corresponding to eight genotypes (three lineages: L1 = inefficient, L2 and L3 = efficient, and five hybrids: H1,H2 and H3 = efficient, H4 and H5 = inefficient) and two phosphorus levels (low = 2.3 mM and high = 129 mM). The seedlings were grown in nutrient solution with a following composition: in mg L-1: N-NO3 152; N-NH4 18,2; Ca 141,1; K 90,1; Mg 20,8; S 18,8; Fe 4,3; Mn 0,5; B 0,27; Cu 0,04; Zn 0,15; Mo 0,08; Na 0,04 e HEDTA 20,06. At 18 days after transplanting, the results showed that, under conditions of P stress in nutritive solution, the hybrids H5, H1 and H2 presented the largest values of total and shoot dry matter, in relation to the others. In general, the hybrids and inbred lines when were grown in solution with low level of P, they presented larger root-shoot relationship, than the materials grew in solution with high level of the nutrient. The concentration of N in the shoot of the plants was superior in the treatment with low level of P. The hybrids H1 and H2 and the inbred line L3 accumulated the largest amounts of P in the shoot, independently of the level of P in the solution. Independent of P level, there was variation in the nutrient content in the shoot of the hybrid, while in inbred lines were not observed the same behavior.