Root flooding-induced changes in the dynamic dissipation of the photosynthetic energy of common bean plants

In this work, we evaluated changes in the energy dissipation on electron transport chain of photosystems of leaves of four common bean (Phaseolus vulgaris L.) genotypes (cultivars and landraces) in response to root system flooding. Common bean plants (BRS Expedito and Irai-cultivars; TB 02-24 and TB 03-13-landraces) were grown in soil and commercial substrate (1:1). At the early reproductive stages, the root system was subjected to flooding by adding distilled water up to 2 cm above the substrate surface for 4 days. Control plants were kept under normoxia. Chlorophyll a fluorescence, gas exchange, photorespiration, antioxidative enzymes and reactive oxygen species (ROS) were measured in leaves on the 4th day of flooding. Flooding of the root system reduced gas exchange in all genotypes with strong effects in CO2 assimilation. BRS Expedito genotype had a greater energy dissipation through fluorescence and heat over Irai, TB 02-24 and TB 03-13, with regard of metabolic regulation through photorespiration to alleviate the excess of ATP/NADPH produced by the electron transport chain (ETC). On the other hand, the genotypes Irai, TB 02-24 and TB 03-13 induced more efficiently the antioxidative enzyme system to cope with the deleterious effects of ROS in comparison to BRS Expedito. Further, the dynamic energy dissipation of the excess absorbed energy by the photosynthetic ETC was differentially dissipated in all four common bean genotypes.