Comparison of Photosynthetic Characteristics and Resistant Enzymes in Coffee Leaves under Different Levels of Leaf Rust Damage
In order to investigate the physiological and biochemical changes of Coffea arabica after infected by leaf rust,the leaf defoliation rate(LF),relative chlorophyll content(SPAD),photosynthetic parameters,and four stress resistant enzyme activities were measured to analyze the effects of different levels of coffee leaf rust on physiological defoliation,photosynthesis,and stress resistance of coffee leaves under eight levels of leaf rust.The results showed that the LF increased with the increase of coffee leaf rust infection area,and SPAD first increased and then decreased with the increase of leaf rust infection area.The net photosynthetic rate(Pn),stomatal conductance(Gs),and transpiration rate of coffee leaves(Tr)were the highest at damage level Ⅲ.The intercellular CO2 molar fraction of coffee leaves was highest at damage level Ⅶ.The water use efficiency(Ewu)was highest at hazard level 0,and there was no significant difference between it and hazard level I,but it was significantly higher than levels Ⅱ-Ⅶ.The light energy utilization effiiciency(LUE)of hazard level Ⅳ was the highest,which was not significantly different from hazard levels Ⅱ and Ⅲ,but significantly higher than the other five hazard levels.The change in superoxide dismutase activity was not significant in hazard levels 0-Ⅵ.After being infected with coffee leaf rust,the activity of peroxidase could be increased to a certain extent;chitinase(CHT)and β-1,3-glucanase(β-1,3-GA)activities of all increased first and then decreased with the increase of hazard level.The activities of CHT,β-1,3-GA were highest at hazard level Ⅲ.Comprehensive analysis showed that under hazard level Ⅲ,coffee leaves had higher photosynthesis and stress resistance,with relatively fewer fallen leaves.
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