Journal of Experimental Botany, Vol 49, 853-862, Copyright © 1998 by Oxford University Press
C Sanetra, O Ito, S Virmani and P Vlek
Remobilization of life nitrogen during the seed filling stage was
investigated in relation to patterns of leaf abscission with three
pigeonpea genotypes (Cajanus cajan L.) of different
maturity duration [extra-short (ESD), short (SD), and medium (MD)].Leaflet
abscission (trifoliate leaf) started from the bottom of the plants. The
life span of defined leaf layers in the canopy differed among the genotypes
and tended to be longer toward the top of the plants. At harvest, the leaf
layer close to the pod-bearing top of the plant had a survival rate of 75%
and 31% in ESD and SD pigeonpea, respectively, indicating that a large
number of leaves in ESD was not entirely exploited for nutrient
redistribution to the seed.Net remobilization of nitrogen from leaves
during the reproductive stage was obtained from an above-ground plant
budget for N and amounted to 35%, 47%, and 37% of the pod's requirement for
N in ESD, SD, and MD, respectively. The amount of nitrogen in the defined
leaf layers decreased exponentially with time, and the rate of N loss was
calculated from the regressions in terms of half-life. For most of the
layers half-life was longest in ESD pigeonpea indicating slower abscission
and remobilization compared to both other genotypes.The present study
compares two pigeonpea hybrids (ESD and SD) with a conventional genotype
(MD). The results imply (1) that the efficiency to remobilize leaf nitrogen
for seed development is related to the pattern of leaf abscission in
pigeonpea, and (2) that SD pigeonpea remobilizes leaf N more efficiently
than ESD and MD.Keywords: Cajanus
cajan, nitrogen remobilization, leaf senescence, leaf
abscission, leaf life span.
ARTICLES
Remobilization of nitrogen from senescing leaves of pigeonpea (Cajanus cajan (L.) Millsp.): genotypic differences across maturity groups?
Georg-August-Universitat Gottingen, Institut fur Pflanzenbau und Tierproduktion in den Tropen und Subtropen, Grisebachstr. 6, D-37077 Gottingen, Germany; International Rice Research Institute, PO Box 933, 1099 Manila, Philippines; International Crops Research Institute for the Semi-Arid Tropics, Patancheru 502 324, Andhra Pradesh, India; Corresponding author; e-mail: csanetr@gwdg.de
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