Effects of Water Stress on the Physiological Behavior, the Flowering and the Fruiting of Jatropha curcas L. Under Semi-controlled Conditions

Abstract

Jatropha curcas L (J. curcas) sectors are increasingly promoted in the Sahel for biofuel production. Though, our understandings on the species responses to water deficit particularly of mature trees are still sketchy. So, this study aims at investigating the effects of water deficit on the physiological behavior, the flowering and the fruiting of J. curcas. The experimental design was a randomized complete block design with 6 replications and 4 treatments. The study was conducted at the research station of the National High School of Agriculture (ENSA) located at 4 km from Thiès, Senegal. The study lasted 113 days from April 1st to July 22nd 2013. J. curcas trees at 21 months old, grown from seeds collected at ENSA were used for the study. The experimentation was conducted in semi-controlled conditions and the 4 treatments considered are: T0 (maximal evapotranspiration); T1 (75% of maximal evapotranspiration); T2 (20% of maximal evapotranspiration) and T3 (without watering). The crop evapotranspiration, the stomatal conductance, the leaf area index (LAI) as well as the flowering and the fruiting were monitored. The results show that only severe water deficit (watering at 20% of maximal evapotranspiration) negatively affect the physiological traits (stomatal conductance and LAI) and the yields (fruits weight per tree and seed weight per tree) of J. curcas. However, only very harsh water deficit (watering at about 1% of maximal evapotranspiration) reduce flowering parameters (inflorescence size, number of male and female flowers). The flowering and the fruiting of J. curcas are less affected by water stress. The experimentation concluded to a negative effect of only severe water stress on J. curcas physiological traits but fruits and seeds production are solely affected when water uptake of J. curcas declines under 20% of maximal evapotranspiration. This question must be deeply investigated trough long-term experimentation with more treatments in order to determine the threshold of water deficit at which J. curcas yield significantly declines.