Abstract

SANCHEZ, E et al. Biosynthesis of proline in fruits of green bean plants: deficiency versustoxicity of nitrogen. Phyton (B. Aires) [online]. 2007, vol.76, pp.143-152. ISSN 1851-5657.

The objective of this work was to determine the effect of deficiency versus toxicity of N on biosynthesis of proline in fruits of green bean plants (Phaseolus vulgaris L. cv. Strike). Nitrogen was applied to the nutritive solution in the form of NH₄NO₃ at 1.5 mM (N1), 3.0 mM (N2), 6.0 mM (N3, optimal level), 12.0 mM (N4), 18.0 mM (N5), and 24.0 mM (N6). Nitrogen deficiency (N1 and N2) was characterized by having lower proline accumulation in pods and seeds, mainly because proline degradation was stimulated by the enzyme proline dehydrogenase. On the other hand, N toxicity (N4, N5, and N6) was characterized for accumulation of greater amounts of proline in pods and seeds due primarily to the greater activity of the enzyme ornitine-δ-aminotransferase. These results suggest a predominance of the ornithine over the glutamine pathway. Under our experimental conditions, proline can be defined as a good bioindicator of N excess in green bean considered a good bioindicator of N toxicity in the study plant species.

Keywords : Phaseolus vulgaris L; Proline metabolism; Green bean; Nitrogen; Deficiency; Toxicity.

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