Influence of N Stress on Leaf Senescence and N Redistribution in Soybeans1
- D. B. Egli,
- J. E. Leggett and
- W. G. Duncan2
The redistribution of nitrogen from vegetative to reproductive plant parts of soybeans (Glycine max (L.) Merr.) may be one of the factors causing leaf senescence and, consequently, it may have a direct influence on yield. Experiments were conducted for 2 years in a greenhouse hydroponics system to investigate the influence of N removal from the nutrient solution at various intervals during pod filling on the redistribution of N from vegetative plant parts to the seed and on leaf senescence. Plants were harvested at early podfill and at maturity, and all abscised leaves and petioles were collected. Subsequently, total N determinations were made on the abscised leaves and petioles, roots, pods, stems, and seed, thereby permitting an estimation of the redistribution of N. Removal of N early in the pod-filling period reduced yield, primarily as a result of smaller seed. It hastened maturity and increased the proportion of N in the seed that came from redistribution. Early N removal resulted in earlier leaf and petiole abscission, but none of the N removal treatments had a major effect on the concentration of N in the abscised material. The portion of the N in the seed that came from redistribution ranged from approximately 20% (controls) to approximately 60% (early N removal treatments). Leaves and pod walls were the major sources of redistributed N. Raising the N level in the nutrient solution above that of the control during the filling period had no effect (relative to the control) on any of the parameters measured. The data suggest that the redistribution of N from vegetative to reproductive plant parts influence plant senescence; however, other factors are involved.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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