Photosynthetic rate and chlorophyll fluorescence in leaves of stem mustard (Brassica juncea var. tsatsai) after turnip mosaic virus infection

The growth, photosynthetic gas exchange and chlorophyll fluorescence were studied in stem mustard (Brassica juncea var. tsatsai) plants infected with turnip mosaic virus. The infected plants showed decreased plant weight, leaf area, plant height although they had similar leaf number. Chlorophyll content was significantly reduced in infected plants after 2 weeks of virus infection as compared to control plants. Decreased net photosynthetic rate, transpiration and stomatal conductance, and a slightly higher intercellular CO2 concentration were observed in infected plants. For the chlorophyll fluorescence parameter Fv/Fm, Fv′/Fm′, ETR and qP, there were no differences between infected and control plants, but qN showed a reduction in infected plants. AES was always higher in infected plants than in control plants after 3 weeks of infection, which may a causal factor of plant growth suppress. From the present experiment, it is suggested that TuMV infection caused a reduction in photosynthesis in stem mustard by a series of processes, including stomatal and non-stomatal limitations during disease stress.