Proline metabolism in response to nitrogen deficiency in French Bean plants (<Emphasis Type="Italic">Phaseolus vulgaris</Emphasis> L. cv Strike)

The objective of the present work was to determine the impact of nitrogen deficiency on proline metabolism in French Bean plants (Phaseolus vulgaris L. cv. Strike). The nitrogen was applied to the nutrient solution in the form of NH4NO3 at 1.45 mM (N1), 2.90 mM (N2) and 5.80 mM (N3, optimal level). Our results indicate N deficiency is characterised by a decline in proline accumulation both in the root and leaves, fundamentally because proline degradation is encouraged by the stimulation of the enzyme proline dehydrogenase. By contrast, under conditions of adequate N (N3), proline levels rise due to the action of ornithine, suggesting predominance of the ornithine pathway over the glutamine pathway, in addition to the inhibition of proline dehydrogenase activity. Abbreviations: ATP – adenosine triphosphate, BSA – bovine serum albumin, DW – dry weight, EDDHA – ethylene diamine-di(o-hydroxyphenylaceticacid), EDTA – ethylene diamine tetraacetic acid, NAD – nicotinamide adenide dinucleotide, NADH – nicotinamide adenide dinucleotide reduced, NADP – nicotinamide adenide dinucleotide phosphate, NADPH – nicotinamide adenide dinucleotide phosphate reduced, OAT – ornithine-aminotransferase, P5CS – -pyrroline-5-carboxylate synthetase, PDH – proline dehydrogenase, PVPP – insoluble polyvinylpyrrolidone