Accumulation, absorption et assimilation des nitrates chez différentes variétés de blé tendre marocain : influence de la lumière

Abstract

The absorption, the exsorption, and the reduction of NO3- ions were examined in light and in darkness in relation to the prior accumulated nitrates in various seedling parts of four Moroccan tender wheat genotypes: Marchouch, Jouda, Khair, and Sais. The genotype Sais has the highest quantity of accumulated nitrates, and the genotype Khair has the lowest. Distribution of nitrates between the roots and shoots of these wheat varieties showed that, for each variety, the shoot accumulates three to five times more NO3- than the roots. Seedlings of the different varieties exposed to light showed a higher absorption and reduction of nitrates than seedlings exposed to darkness. The exsorption of nitrates of plants that are subjected to light was significantly lower than that of the seedlings exposed to darkness. This suggested that the stimulation of NO3- absorption, observed in plants that were exposed to light in comparaison with darkness, could be partly explained by the diminution of nitrate exsorption. The quantitative examination of N-nitrate in roots of plants that were exposed to light showed the presence of quantities of NO3- similar to those of the seedling roots maintained in darkness. These results suggest, that by stimulating the reduction of nitrates, light contributes to a substantial increase of nitrate ion absorption by means of a diminution of ion exsorption out of root cells.