Effects of short-term water deficit stress on physiological characteristics of Bambara groundnut (Vigna subterranea (L.) Verdc.)

Abstract

Bambara groundnut (Vigna subterranea (L.) Verdc.) is an annual leguminous food crop native to Africa. The crop is grown in marginal soils and it is considered to be a drought-resistant species. However, there is limited information on the ways Bambara groundnut landraces respond and adapt to drought. The study was conducted to evaluate the response of Bambara groundnut landraces sourced from contrasting environments to periods of water deficit initiated at vegetative stage. Three landraces, namely Botswana-1, Getso and Gresik from Botswana, Nigeria and Indonesia, respectively, were grown in pots and irrigation was withheld 30 d after sowing in the stressed group compared with fully watered controls. The responses were studied by considering dry mass and measurements of gas exchange, chlorophyll fluorescence and biochemical parameters. Root dry mass was significantly higher (P < 0.001), whereas leaf dry mass was lower in stressed compared with control plants. Relative water content and gas exchange parameters decreased in stressed plants. Maximum photochemical efficiency of photosystem II (F_v/F_m) values also decreased after three weeks stress. Electrolyte leakage and the concentration of proline both increased in stressed plants. The results showed a possible drought avoidance strategy in Bambara groundnut in response to water deficit. The results showed the landrace Getso, sourced from a relatively drier environment, to be the most drought resistant among those studied, indicating that the origin of the landrace and the environment it is adapted to determine its response to water deficit.

Keywords: Bambara groundnut, chlorophyll fluorescence, gas exchange, photosynthesis