Leaf gas exchange and biomass partitioning in Jatropha curcas L. young plants subjected to flooding and drought stresses

Abstract

With the purpose of assessing the physiological responses of J. curcas young plants to drought and flooding, plants were subjected to three watering regimes: Control, drought and flooding. In the same period, five plants were submitted to drought (irrigation suspension), five to flooding and five were maintained near the field capacity (control). Measurements of leaf gas exchange, chlorophyll content, biomass of each organ (leaf, stem and root), biomass ratios, as well as the root:shoot ratio were made. When compared to control, drought and flooding treatments led to significant reductions (P ≤ .05) of gas exchange rates at 14 and 7 days after imposition treatments (DAIT), respectively. At the 16th DAIT, significant reductions of leaf, root, stem and total biomass were observed, which resulted in changes of biomass partitioning of each organ. Significant reduction of leaf dry biomass (LDB) was observed in water deficit plants. Moreover, no significant effects of water deficit were observed in root dry biomass. Such response has led to a higher root:shoot ratio, suggesting an improved ability for water and nutrients uptake. In turn, flooding has induced a significant decrease in the dry biomass of all organs. Stem dry biomass ratio of flooded plants (0.67 g g-1) was significantly higher than that of control plants (0.41 g g-1), which, was seemingly due to leaf senescence and root system rotting of flooded plants. Altogether, present results reinforce the susceptibility of the studied genotype of J. curcas to flooding, as well as highlight some characteristics of drought tolerance in this species.