Plant measurements on African tropical Maesopsis eminii seedlings contradict pioneering water use behaviour

© 2016 Elsevier B.V. With increased drought events affecting forests globally, little is known about their future impact on Africa's forests. In particular, we need to gain a better understanding of how key African forest species will respond to drought stress. In this study, we investigated functional traits and physiological responses to drought of the light-demanding pioneer species Maesopsis eminii Engl. The study involved an experiment on potted M. eminii seedlings with three different drought treatments in which sap flow (SF), stem diameter variation (SDV) and stomatal conductance (gs) were measured. Whereas low gs rates (39 ± 30 mmol m−2 s−1) and pronounced SF-VPD (vapour pressure deficit) and gs-VPD hysteresis loops during well-watered conditions indicated conservative stomatal control on water loss, nocturnal sap flow implied M. eminii is not able to completely block transpiration. At the onset of drought, the pioneer seedlings retained high stem diameter growth despite highly reduced soil moisture (>−0.95 ± 0.03 MPa) and SF rates, indicating that growth was prioritised. Contribution of stored stem water to daily water use was limited both during drought and control conditions, which was confirmed by the absence of time lags between photosynthetic active radiation (PAR)-SDV, PAR-SF and SDV-SF in all treatments. Below a soil water potential of −0.95 ± 0.03 MPa, leaves were gradually shed, but diurnal and nocturnal SF did not turn zero, and absolute stem diameter kept decreasing for the entire experimental period (115 days), portraying that M. eminii seedlings can survive only limited drought periods. In sum, this study demonstrated that species-specific traits, as opposed to species ecological strategy, govern drought performance. For M. eminii, its leaf traits proved pivotal to its drought performance

Physico-Chemical characteristics of shea butter(Vitellaria paradoxa C.F. Gaertn.) oil from the Shea district of Uganda

Shea oil is a vegetable oil obtained from the seeds of the shea tree (Vitellaria paradoxa C.F. Gaertn.). It constitutes an important source of fat in food and cosmetics. Although shea oil can be marketed both locally and internationally, increasing demand worldwide for exportable products calls for their certification. Characterization of shea oil is one step towards developing its certification system. In this study, the physico-chemical characteristics of shea oil in different shea zones ofUganda were assessed. Samples of shea fruits were collected between the months of June-August 2007 in the districts of Pader, Lira, Katakwi and Arua representing Acholi, Lango, Teso, and West Nile shea zones, respectively. Seed oil was extracted by Soxhlet apparatus using n-hexane solvent and analysed for colour, refractive index, viscosity, oil content, acid value, peroxide value, saponification value, iodine value,ƒ¿-tocopherols and fatty acid profile. Shea oil content, colour, refractive index and viscosity ranged from 41-54%, orange to orange.yellow, 1.670-1.690 and 2.4-2.8 cP, respectively. Acid and peroxide values ranged between 2.3-12.59 mgKOH/kg and 2.10 to 2.50 meq/kg, respectively. Saponification, iodine and ƒ¿- tocopherols valueswere between 160 mgKOH/g and 192mgKOH/g, 39.21 I2g/100 and 41.37 I2g/100g and 26.3-44.4 mg/100g, respectively. Fatty acid profile for palmitic, stearic, oleic, linoleic and arachidic fatty acids ranged between 6.52-8.12%, 28.65-30.94%, 55.54-57.63%, 6.18-7.79% and 0.65-0.90%, respectively. Although there was significant variation in the oil yield (P.0.05), the physico-chemical characteristic and fatty acid profile showed no significant variation in the shea zones of Uganda (P.0.05). The fact that physico- chemical characteristics of shea oil from the different shea zones of Uganda are comparable to other high value edible vegetable oils indicates its suitability as raw material for food, cosmetic and pharmaceutical products. This characterization is a bench mark for monitoring the quality of shea oil from Uganda and can be used to enhance its local and international trade