Effect of Water Stress Imposed at Different Growth and Development Stages on Morphological Traits and Yield of Bambara Groundnuts (Vigna subterranea L. Verdc)

Two greenhouse trials were carried out to evaluate the response pattern of morphological traits of bambara groundnut to short periods of water stress imposed at different developmental stages and also their recuperative ability after rewatering. The treatments consisted of watering plants to 100% Plant Available Water (PAW), withholding water to 30% PAW at vegetative, flowering and pod filling growth stages and rewatering the plants after 21 days of each stress treatment. Water stress reduced the relative leaf expansion rate, leaf number, plant height and shoot: root ration depending on the stage of development when water stress occurred. When plants were rewatered after each stress treatment, the relative leaf expansion rate of plants stressed at pod filling and flowering stages failed to recover from water stress. Seed yield in all stressed plants was reduced by water stress due to reductions in pods per plant, seeds per pod and seed weight. The highest yield amongst the stressed plants was obtained in plants stressed during the vegetative stage, followed by the flowering and lastly the pod filling stage. Bambara groundnuts reduced growth therefore reducing transpirational area thus reducing water loss under water stress. The results also showed that bambara groundnuts have the ability to recover from water stress after rainfall or irrigation and is therefore capable of producing some yield under water limited conditions.