Photosynthetic gas exchange, chlorophyll fluorescence, antioxidant enzymes, and growth responses of Jatropha curcas during soil flooding

The response of chlorophyll fluorescence, photosynthetic CO2 assimilation (PN), stomatal conductance (gs), electrolyte leakage, and transpiration (E) was observed in Jatropha curcas seedlings subjected to soil flooding. A strong reduction in growth, leaf-area expansion (64%), and stomatal conductance (45%) impaired photosynthetic CO2 assimilation (66%), which eventually reduced biomass yield. The ratio between variable-to-initial chlorophyll fluorescence (Fv/Fo) and the maximum quantum yield efficiency of the photosystem II (Fv/Fm) was used to explore damage associated with the functioning of the photosynthetic apparatus. A strong, nonlinear correlation between physiological parameters and soil flooding duration was found. Our study primarily revealed consequences of epigenetics, i.e. stagnant soil flooding, which affected growth, development, and performance of Jatropha curcas significantly. The activities of catalase (CAT), ascorbate peroxidase (APx), glutathione reductase (GR), and glutathione peroxidase (GPx) in leaves increased, implying an integrated pathway involving CAT, APx, GR, and GPx for protection against the detrimental effects of reactive oxygen species (ROS) during soil flooding.