Abstract This study aims to reveal the effects of light on chlorophyll fluorescence and antioxidant indexes of sun-cured tobacco leaves in yellowing period of curing. Tobacco samples under the light treatment and shading treatment (CK) were collected dynamically during yellowing period. Indexes of chlorophyll fluorescence, activities of antioxidant enzymes and contents of chlorophyll, H2O2 and MDA were measured. The results showed: 1) The degradation rate of chlorophyll under light treatment was faster than that under CK. 2) Photochemical efficiency of PS Ⅱ (PhiPS2) and electron transfer rate (ETR) decreased by 60% and 75% respectively in the first 4 days under light treatment, which was significantly greater than that under CK. On the 7th day, photochemical quenching (qP) value and the maximum photochemical efficiency (Fv/Fm) value decreased to 0.28 and 0.23, which were lower than that under CK by 38% and 43%, respectively. 3) The peak values of H2O2 and MDA contents under light treatment were 1.5 times of that under CK, and appeared 2 days earlier compared with the situation under CK. The peak values of POD and CAT activities in light treatment were also higher than that under CK. 4) Of all tested indexes, PhiPS2, MDA and H2O2 were the most affected by light treatment. In conclusion, this study demonstrates that light energy utilization efficiency of sun-cured tobacco leaves decreased rapidly in the early stage of yellowing. Part of the light energy received by tobacco leaves was converted into excess light excitation-energy, which could proliferate reactive oxygen species, aggravate oxidative stress, accelerate the degradation and transformation of chlorophyll, membrane lipid and other chemical substances in tobacco leaves and damage cell structure and function.
XIANG Huan, WANG Jun, CHEN Yong, TANG Weirong, ZHANG Fan, LIU Lei. Effects of light on chlorophyll fluorescence and antioxidant indexes of sun-cured tobacco leaves during yellowing period[J]. Acta Tabacaria Sinica, 2020, 26(4): 78-85.