Morphophysiological changes in young plants of Jatropha curcas L. (Euphorbiaceae) subjected to water stress and recovery

To investigate drought-induced changes in morphophysiological characteristics, seedlings of two genotypes of Jatropha curcas (CNPAE 183 and CNPAE 191) were grown under two watering regimes: irrigated (-33.1 to 13.5 to kPa) and water deficit (-409.5 to 49.5 to kPa) for 55 days, followed by six days of rehydration (DAR). Withholding water led to a significant reduction (p<0.05) of leaf water potential (ΨW) and an increase in relative water content (RWC). The values of net photosynthetic rate (PN), stomatal conductance to water vapor (gS) and transpiration (E) were significantly (p<0.05) reduced 21 and 34 days after starting treatment (DAST) in plants of genotypes CNPAE 183 and CNPAE 191, respectively. After 6 DAR, only CNPAE 191 achieved a recovery of PN and E. Moreover, significantly (p<0.05) lower gS was measured in recovering plants of both genotypes, as compared to the controls. Drought stress led to reductions of 57 and 65% in whole-plant hydraulic conductance (KL) in genotypes CNPAE 183 and CNPAE 191, respectively. Full recovery of KL was observed after 6 DAR. The average water consumption was 18% lower in plants subjected to water shortage, as compared to irrigated plants. However, drought-induced reduction in growth led to lower biomass water use efficiency (WUEbiomass) in plants subjected to water deficit. The effect of water stress was more intense in CNPAE 183 than in CNPAE 191, regarding the growth variables (leaf area, height and diameter), dry mass and root volume. Moreover, a delay in the effect of water stress in genotype CNPAE 191 was also observed, which suggests a higher tolerance of this genotype as compared to CNPAE 183. Altogether, the results showed strong drought-induced stomatal limitation of carbon assimilation and growth in J. curcas. Slight genotypic differences were detected, CNPAE 191 being less sensitive to the imposed experimental conditions than CNPAE 183. Key words: Hydraulic conductivity, root volume, tolerance, leaf gas exchange, water relations, water status.