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Dry-matter partitioning and radiation-use efficiency in cowpea cultivars (Vigna unguiculata (L.) Walp. cvs TC-9-6 and M-28-6-6) during consecutive seasonal courses in the Orinoco llanos

Published online by Cambridge University Press:  19 October 2004

J. J. SAN JOSÉ ,
R. A. MONTES ,
N. NIKONOVA ,
N. VALLADARES ,
C. BUENDIA ,
V. MALAVE  and
R. BRACHO
J. J. SAN JOSÉ
Affiliation:
Centro de Ecología, Instituto Venezolano de Investigaciones Científicas, Apartado 21827, Caracas 1020-A, Venezuela
R. A. MONTES
Affiliation:
Departamento de Estudios Ambientales, Universidad Simón Bolívar, Apartado 89000, Caracas 1080-A, Venezuela
N. NIKONOVA
Affiliation:
Centro de Ecología, Instituto Venezolano de Investigaciones Científicas, Apartado 21827, Caracas 1020-A, Venezuela
N. VALLADARES
Affiliation:
Escuela de Ingeniería Agronómica, Universidad de Oriente, Maturin, Edo. Monagas, Venezuela
C. BUENDIA
Affiliation:
Centro de Ecología, Instituto Venezolano de Investigaciones Científicas, Apartado 21827, Caracas 1020-A, Venezuela
V. MALAVE
Affiliation:
Escuela de Ingeniería Agronómica, Universidad de Oriente, Maturin, Edo. Monagas, Venezuela
R. BRACHO
Affiliation:
Centro de Ecología, Instituto Venezolano de Investigaciones Científicas, Apartado 21827, Caracas 1020-A, Venezuela
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Abstract

Field work on rainfed cowpea (Vigna unguiculata (L.) Walp. cvs TC-9-6 and M-28-6-6) was conducted in the Orinoco lowlands to explain the changes in dry-mass partitioning and radiation-use efficiency (RUE) as compared with other cultivars over four consecutive seasons. Growth features were assessed in early-maturing, prostrate-canopy (TC-9-6), and medium-maturing, erect-canopy (M-28-6-6) cowpeas. These cultivars were sown in consecutive middle-wet and late-wet seasons in double peak rainfall conditions. Dry mass accumulation by cultivars was assessed as a function of leaf-area duration and the efficiency with which radiation was converted into dry mass throughout the season (i.e. radiation-use efficiency). Cultivar differences in canopy architecture and duration of leaf area had a minor effect on the total dry mass production. In the early-maturing TC-9-6, RUE for a middle-wet and a late-wet season was 0·90±0·04 and 0·65±0·05 g/MJ, respectively. In the medium-maturing M-28-6-6, the values were 0·97±0·05 and 0·72±0·03 g/MJ, respectively. A season with rainfall below 100 mm had a negative effect on phenology and RUE. When average rainfall was above 100 mm, the total dry mass accumulation was not affected by differences in cultivars and seasons. The rate of harvest index (HI) changes was negatively related to pod-filling duration. The changes in assimilation distribution depended on the process of partitioning as modulated by the limited pod-sink and the photosynthate supply. However, the photosynthate source was not depressed by the sink activity of the pod-filling. Partitioning to non-reproductive sinks was maintained. M-28-6-6 with high dry-mass production and delayed senescence did not effectively divert a large amount of assimilate to pod-filling. Pod sink activity in cowpea was limited by genotype. Harvest index in M-28-6-6 decreased with the increasing dry mass. The final HI and rate of linear increase in HI differed between cultivars and were lower in M-28-6-6. The results of the present work in the Orinoco lowlands are relevant for a wide range of savannahs with a late wet season.

Type
Research Article
Information
The Journal of Agricultural Science , Volume 142 , Issue 2 , April 2004 , pp. 163 - 175
Copyright
© 2004 Cambridge University Press

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