Changes in gas exchange and antioxidant metabolism on rice leaves infected by Monographella albescens

摘要

The present study aimed to do an in-depth analysis of the effect of leaf scald on rice physiology by combining gas exchange measurements, photosynthetic pigment pools and examining the activities of enzymes involved in the antioxidant system. The size of leaf scald lesions increased from 3.1 mm at 24 h after inoculation (hai) to 25.2 mm at 120 hai. For the inoculated plants, net CO2 assimilation rate, stomatal conductance to water vapor and transpiration rate decreased while internal CO2 concentration increased in comparison to the not inoculated ones. The concentrations of chlorophyll a, chlorophyll b, total chlorophyll (a + b) and carotenoids decreased while the concentrations of malondialdehyde and hydrogen peroxide increased in the inoculated plants. The superoxide dismutase, ascorbate peroxidase, catalase, peroxidase and glutathione reductase activities significantly increased for the inoculated plants in comparison to non-inoculated ones. The results of this study show that infection by M. albencens negatively impacted the photosynthesis of rice leaves. Indeed, the CO2 fixation capacity was dramatically reduced during fungal infection, which was deeply associated with lower concentrations of photosynthetic pigments in a scenario where a more efficient antioxidative system was detrimental to remove reactive oxygen species generated over the course of fungal infection.