C/N and PS/N ratios during growth and senescence of Phaseolus vulgaris L. leaves.
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Abstract
The macromolecules content (protein, nucleic acid, and carbohydrates) changes during leaf growth and senescence. However, no data are presently available concerning the changes of fundamental elements like Nitrogen and Carbon, and their relations. A hypothesis that variation in C/N and WR/N ratios may be used as an ontogenic index of leaf physiology stage is proposed. The first pair of leaves of Phaseolus vulgaris L. var Balln de Albenga was used, and two experiments were carried out: 1) Leaf growth and senescence. 2) Correlation suppression (apex excision and defoliation). The results indicated that C/N and WR/N ratios are a possible index of leaf physiological stage during growth and senescence. These findings are supported by: i) Both relations (C/N and WR/N) show a steady increase during leaf ontogeny. ii) Senescence-delaying treatments promote a decline (apex excision) or stabilization (defoliation) of C/N and WR/N ratios.
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