The ability of Jatropha curcas to grow in marginal and dry soils has not been extensively explored. Given the current world energy problems of high fossil fuel consumption which plays a significant role in the greenhouse effect, J.curcas biodiesel have been considered a potential alternative source of clean energy. Although it best grows under precipitation amounts of 250-1200mm annually, this plant has been reported to be drought tolerant, but no study has been done to ascertain this in Botswana. In this study, potted plant (35 days old) from three J.curcas accessions namely Mmadinare (Central region), Thamaga (Southern region) and Maun (Northern region) in Botswana, were selected to represent the different the climatic zones with respect to rainfall per annum, were assessed for water stress tolerance. These were subjected to continuous well-watered conditions (control) and to water deficit stress (with-holding water) until they reached wilting point, (followed by a 28-day re-watering period). The maximum photochemical efficiency of PSII (estimated from dark-adapted Fv/Fm ratio) and the maximum quantum yield of PSII electron (ΦPSII) transport were measured at weekly intervals. The most rapid recovery of dark-adapted Fv/Fm ratio and ΦPSII was displayed by Mmadinare and Maun accessions than Thamaga accession. The rapid recovery in Fv/Fm ratio and ΦPSII could be attributed mainly to dissipation of excess energy harmlessly as heat. On the other hand, the slower recovery rate in dark-adapted Fv/Fm ratio and ΦPSII displayed by Thamaga accession showed that the decline could be attributed to both downregulation of PSII and possibly damage to the PSII reaction centres.

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