AMMONIUM ENABLES ALUMINUM-INDUCED STIMULATION OF NITROGEN ASSIMILATION IN ROOTS OF AL-TOLERANT MAIZE GENOTYPES

摘要

One aluminum (Al)-sensitive (B-73) and two Al-tolerant (F-2 and L-2039) maize genotypes were subjected to Al stress (100M Al) under two nitrogen (N) treatments [13.2mM nitrate (NO3-) and 8.3mM NO3- + 4.9mM ammonium (NH4+)]. Growth parameters, chlorophyll, root N and NO3- contents, root nicotinamide adenine dinucleotide (NADH-) and nicotinamide adenine dinucleotide phosphate (NADPH)-nitrate reductase, glutamine synthetase, and glutamate dehydrogenase activities were determined. Aluminum significantly decreased growth and chlorophyll content in Al-sensitive genotype. Nitrate accumulation in roots was increased by Al in tolerant plants. In the sensitive genotype, Al suppressed all enzymes in NO3- plants, while in NO3-/NH4+ plants the suppression was less severe, and NADPH-nitrate reductase was even stimulated. In tolerant NO(3)(-)plants, glutamate dehydrogenase was stimulated in F-2 and glutamine synthetase suppressed in L-2039 genotype. In tolerant NO3-/NH4+- plants, all enzymes were stimulated by Al, which may be attributed to their participation in defense mechanisms.