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Accueil du site → Doctorat → États-Unis → 1985 → SEED YIELD, WATER USE, AND WATER USE EFFICIENCY OF COWPEA IN RESPONSE TO DROUGHT STRESS AT DIFFERENT DEVELOPMENTAL STAGES

Cornell University (1985)

SEED YIELD, WATER USE, AND WATER USE EFFICIENCY OF COWPEA IN RESPONSE TO DROUGHT STRESS AT DIFFERENT DEVELOPMENTAL STAGES

AKYEAMPONG, EKOW

Titre : SEED YIELD, WATER USE, AND WATER USE EFFICIENCY OF COWPEA IN RESPONSE TO DROUGHT STRESS AT DIFFERENT DEVELOPMENTAL STAGES

Auteur : AKYEAMPONG, EKOW

Université de soutenance : Cornell University

Grade : Doctor of Philosophy (PhD) 1985

Résumé
Cowpea is an important legume crop in the semi-arid areas of West Africa. These savanna areas have short growing periods of four months or less with annual rainfall of less than 300mm and annual potential evaporation in excess of two meters. There is therefore the potential for moisture deficits. The lack of adequate moisture is one of the most important reasons why seed yields in West Africa have tended to be low. The limitation imposed on seed yield by drought stress may be overcome by cultural management practices that exploit the inherent drought tolerance the crop must have developed over the centuries of its cultivation in West Africa. To investigate this solution, experiments were conducted to determine the responses of seed yield, water use and water use efficiency of cowpea to drought stress at various developmental stages. Three varieties of cowpea, TVu 4552, TVu 1954-01E, and TVu 4954 were grown in pots in the greenhouse. A 12-hour photoperiod was furnished between 06:00 and 18:00 hours except during the summer months. Temperatures were maintained at 29 C during the day and 21 C at night. Drought stresses were imposed at the vegetative, flowering, or pod-filling stage. Leaf water potential, stomatal conductance, transpiration, leaf area, seed yield and components of seed yield were determined when appropriate. Over the ranges of drought stress intensities imposed, drought stress at the vegetative stage did not significantly reduce seed yields of varieties TVu 4552 and TVu 1954-01E because, after resumption of irrigation, plants resumed growth and established adequate numbers of nodes and leaf areas to support flower and pod growth. Despite lower total water use, water use efficiencies of plants drought-stressed at the vegetative stage were significantly enhanced over unstressed plants. Drought stress at the flowering or pod-filling stage significantly decreased seed yield because both source and sink sizes were reduced. At the end of the stress at the flowering stage, the number of pods on the stressed plants was only 50% of the that on unstressed plants. Reduced stomatal conductance and leaf area led to the curtailment of transpiration (water use). Water was thus conserved which enabled stressed plants to maintain favorable water status as indicated by leaf water potentials.

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