Nitrate accumulation, adsorption and assimilation in different varieties of Moroccan tender wheat

The absorption, the exsorption, and the reduction of NO3- ions were examine d 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 accu mulated nitrates, and the genotype Khair has the lowest. Distribution of ni trates between the roots and shoots of these wheat varieties showed that, f or each variety, the shoot accumulates three to five times more NO3- than t he roots. Seedlings of the different varieties exposed to light showed a hi gher absorption and reduction of nitrates than seedlings exposed to darknes s. The exsorption of nitrates of plants that are subjected to light was sig nificantly lower than that of the seedlings exposed to darkness. This sugge sted 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-ni trate 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 dar kness. 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.