Effect Of TiO₂ Spraying Agent On Photosynthesis And Quality Of Upper Tobacco Leaves

The main reason for upper tobacco leaves been overstocked in China is the low quality and availability,in order to avoid strong light and high temperature,traditional production changes the transplanting period to protect the mature tobacco leaves in general,this approach has its limitations.titanium dioxide has superior UV absorption,it is widely used in UV protectant and light-screening agent,in order to prevent upper tobacco leaves from strong light and high temperature,this thesis did some research on the following aspects:1.effects of different TiO₂ spraying agent on SPAD of upper tobacco leaves in vitro.2.effects of different TiO₂ spraying agent on Photosynthesis、organizational structure and quality of maturely upper tobacco leaves.The results are as follows:1.Effect of TiO₂ spraying agent on SPAD of upper tobacco leaves in vitro under different light intensityThe result of SPAD showed that TiO₂ and TiO₂ composite retard chlorophyll degradation of upper tobacco leaves in vitro,the performance in strong light environment is more obvious;the chlorophyll degradational rate at each time point is CK>T3>T1>T2 under different light intensity,the most effective treatment for retard chlorophyll degradation is the treatment of T2（titanium dioxide composite graphene oxide）;the SPAD at each time point of the same treatment decreased with the light intensity increased.2.Effect of TiO₂ spraying agent on Photosynthesis of maturely upper tobacco leaves1)The result of photosynthetic pigments showed that the treatment of spraying agents retard chlorophyll and carotenoid degradation of upper tobacco leaves,at the time of tobacco mature period（30 days after first spraying）,the maximum chlorophyll content of A2B2（0.45g/L titanium dioxide composite graphene oxide）reachs 1.18 mg/g,the treatment of CK（water comparison）had the lowest chlorophyll content of 0.74 mg/g;in the content of carotenoid,the maximum treatment of A2B2 reachs 0.181mg/g,the treatment of comparison had the lowest chlorophyll content of 0.118mg/g.2)The result of photosynthetic indexes showed that the treatment of spraying agents reduced photosynthetic rate、stomatal conductance、transpiration rate of upper tobacco leaves,on the other hand,the Intercellular CO₂ concentration of upper tobacco leaves rosed and leaf temperature was unaffected.the effects of light absorptivity decreased with the time increasing,the sparying agent of titanium dioxide composite graphene oxide peformed better in the effect of light absorptivity,two kinds of spraying agent had the biggest effect when its concentration was 0.45g/L.3)The result of chlorophyll fluorescence parameters showed that the treatment of spraying agents increased Fv/Fm、Fv/Fo、qP、ФPSⅡ（except the treatment of A1B1）,and decreased Fo、NPQ compare to the treatment of water comparison.3.Effect of Ti O₂ spraying agent on organizational structure and quality of maturely upper tobacco leaves1)The observational result of stoma showed that the treatment of spraying agents increased length and width of stomata of upper tobacco leaves,A2B3 treatment（0.6g/L titanium dioxide composite graphene oxide）had the maximum length（205.66μm）and width（148.23μm）,there were no obviously regular changes of stomatal density and length-width ratio between each treatment.2)The observational result of organizational structure showed that the treatment of spraying agents decreased thickness of leaves and epithelial cells,A2B2 treatment（0.45g/L titanium dioxide composite graphene oxide）had the minimum thickness of leaves（219.19μm）and thickness of epithelial cells（22.01μm）,there are no obviously regular change of thickness of lower epidermal cells and cell density of epidermal cells between each treatment.3)The result of physical characteristics showed that the treatment of spraying agents decreased weight per leaf and leaf thickness of flue-cured tobacco leaves,A2B2 treatment（0.45g/L titanium dioxide composite graphene oxide）had the minimum weight per leaf and thickness leaf thickness;the treatment of spraying agents increased leaf length and width of flue-cured tobacco leaves,A2B3 treatment（0.6g/L titanium dioxide composite graphene oxide）had the maximum leaf length,it reached significant difference compare to water comparsion,A2B2 treatment had the maximum leaf width,it reached extremely significant difference compare to water comparsion,there were no obviously changes of Stem ratio and equilibrium moisture content between each treatment.4)The result of chemical composition showed that the treatment of spraying agents increased total nitrogen and nicotine of flue-cured tobacco leaves,A2B3 treatment（0.6g/L titanium dioxide composite graphene oxide）had the maximum content of total nitrogen and A2B2 treatment（0.45g/L titanium dioxide composite graphene oxide）had the maximum content of nicotine;the treatment of spraying agents decreased total sugar and reducing sugar,A2B2 treatment had the minimum content of sugar and reducing sugar,it reached significant difference compare to water comparsion.there were no obviously regular changes of potassium,chlorine,starch,titanium between each treatment.at the part of chemical coordination,A2B2、A2B3 treatments had a lower ratio of sugar to nicotine,A1B2 treatment（0.45g/L titanium dioxide）had a lower ratio of potassium to chlorine,each treatment had about the same ratio of nitrogen to nicotine,A1B1 treatment（0.3g/L titanium dioxide）got the maximum score of chemical quality and A2B2 treatment got least.