Jatropha curcas seedlings show a water conservation strategy under drought conditions based on decreasing leaf growth and stomatal conductance

Jatropha curcas L. has recently drawn the attention of the international research community due to its potential as a biodiesel crop. In addition, it is very well adapted to arid and semiarid climate conditions. In this research, the effects of drought on growth, leaf water relation and organic solutes, leaf and root mineral concentration, chlorophyll fluorescence parameters, leaf gas exchange and carbohydrate concentration were studied in seedlings of J. curcas to elucidate the physiological and morphological mechanisms related to their drought tolerance. Four-week-old seedlings were grown in growth chambers with five different water regimes corresponding to 100, 75, 50, 25, and 0% field capacity (FC) for four weeks. Seedlings, maintained a good water status regardless of the drought stress treatment because all water regimes affected the leaf relative water content, whereas the leaf water potential was only reduced in the water-stressed plants from the 0% and 25% FC treatments. Drought treatments reduced leaf, stem and root growth. However, the decrease in growth was higher in the aerial part of the plant than in the root, so that the root-to-shoot ratio in drought-stressed plants increased compared to that in the well-watered plants. Net assimilation of CO2 image and stomatal conductance (gs) decreased in all treatments, although image gradually declined as the water supply was decreased, while the reduction in stomatal conductance was similar in all drought stress treatments. Hence, we conclude that the strong control of transpirational water loss by reducing both stomatal conductance and biomass from aerial parts could be involved in the ability of this plant to resist drought conditions.