Effects of titanium dioxide spraying agents on photosynthesis and chlorophyll fluorescence parameters of upper tobacco leaves

Objective  To explore the effect of TiO₂ spraying agent on photosynthesis and chlorophyll fluorescence parameters of upper tobacco leaves, and provide a reference for improving the availability of upper tobacco leaves.

Method  TiO₂ spraying agent was preparated by means of sol-gel method. The effects of different concentrations and formulas of TiO₂ spraying agent on photosynthetic pigment content, photosynthetic physiological indexes and chlorophyll fluorescence parameters of upper tobacco leaves at maturity were studied.

Result  TiO₂ spraying agents retarded the degradation rates of chlorophyll and carotenoid of upper tobacco leaves. The spraying agents reduced photosynthetic rate, stomatal conductance and transpiration rate of upper tobacco leaves, increased the intercellular CO₂ concentration in upper tobacco leaves, but leaf temperature was unaffected. Photosynthesis and chlorophyll fluorescence parameters of upper tobacco leaves were significantly affected by TiO₂ spraying agents. Compared with the spraying water control, the spraying agents increased F_v/F_m, F_v/F_o and qP , and decreased F_o and NPQ. The absorption efficiency of light intensity of tobacco leaves sprayed titanium dioxide or titanium dioxide composite graphene was the best at the concentration of 0.45 g·L^–1.

Conclusion  Tobacco leaves can absorb ultraviolet (UV) to a certain extent, and the efficiency of spraying titanium dioxide composite graphene was better. There was a threshold of spraying agent concentration for light absorption efficiency.