Behaviour of inbred and hybrid maize lines in the presence of aluminium as evaluated by some physiological and biochemical parameters

Abstract

Four maize lines, two inbreds from northern Portugal (AMARELO and PIGARRO) and two hybrids (HB3, obtained from the cross of inbred lines adapted to soils rich in Al, and ACCO1148) that present different Al-tolerances when cultivated in field conditions, were screened for physiological and biochemical behavior in three experimental growth systems — hydropony, washed quartz sand and early germination on filter paper — in the presence of different Al concentrations. Plants in hydropony were analysed for growth parameters, nitrate uptake, pH-change of the nutrient solution and Al accumulation in shoots and roots. In vivo nitrate reductase activity (NRA) and nitrate content of the leaves were measured in plants developed in quartz sand. Root tips of three day old seedlings of ACCO1148 germinated on moistened paper were submitted to in vivo P-NMR spectroscopy to evaluate the intracellular pH and to identify mobile phosphorus compounds.

Unlike some field conditions, the experimental conditions were not limiting in water and nutrients. This may be the explanation for the absence of significant differences between the four lines when low Al quantities were added to the growth medium. As the Al concentration increased, the ACCO line was distinguished from the others by a lower Al content in shoots and roots, a lower leaf nitrate content and a higher NRA. In vivo ³¹P-NMR spectra of ACCO root tips germinated in the presence of Al allowed detection of an acidification of the cytoplasm and a net decrease in sugar phosphates, ATP and UDP-hexoses. The respiratory activity measured in this same system decreased as well.