SAMSON HUNI, HELMUT HERZOG
Humboldt-Universitšt zu Berlin, Department of Crop Science in the Tropics and Subtropics, Germany
Cowpea (Vigna unguiculata L. WALPERS) is an important source of food for hundreds of millions of people in the developing world and generally considered to be more drought tolerant than most other legumes. Nevertheless, drought is a major production constraint. Studies were conducted to determine the relationships between evapo-transpiration efficiency (ETE) and morpho-physiological characteristics [transpiration (E) and assimilation (A) rates, the ratios E/A and A/E, above-ground biomass, leaf area (LA), specific leaf area (SLA) and specific leaf weight (SLW)]. These studies were performed on 7 cowpea genotypes during the vegetative phase under well-watered conditions in the greenhouse. On two different occasions (43 and 65 days after planting, DAP) these characteristics were monitored, measured and analysed.
For all genotypes on both sampling dates significant positive correlations (p = 0.05) were found between ETE and dry matter of leaves, main stem, total shoot biomass; between E and total shoot dry matter; between E and A and branch biomass; and among LA, dry matter of leaves, main stem, branches and total shoot biomass. Negative significant correlations were observed between the following groups: ETE and SLA; A and E/A; and LA and E/A. The performance of the 7 genotypes regarding most of the mentioned characteristics also displayed significant differences, except A, A/E and branch dry matter production 43 DAP. Non-significant differences between the genotypes could be established 65 DAP for SLA, leaf DM, main stem DM, E/A and A/E.
Despite progress in the last thirty years in using morphological and physiological properties as tools for management and breeding of crops, some contradictions still exist. In the case of cowpea, this study revealed some of the relationships between ETE and some morpho-physiological properties. The hypothesis that correlations exist between ETE and A/E could not be established.
Keywords: Cowpea, evapo-transpiration efficiency, gas exchange, plant characteristics