Interactive effects of light intensity and nitrogen supply on photosynthetic physiology of Cunninghamia lanceolata seedlings
To elucidate the effects of light intensity and nitrogen levels on the growth and photosynthetic physiology of Cunninghamia lanceolata seedlings,pot experiments including four light intensities(L0:100％natural light;L1:75％natural light;L2:45％natural light;L3:20％natural light)and three nitrogen levels(N0:0 g/plant;N1:4 g/plant;N2:6 g/plant)were conducted using one-year-old C.lanceolata seedlings'Yang061'.Subsequently,the changes in growth,photosynthetic physiology,and key enzymes involved in photosynthetic carbon metabolism of C.lanceolata seedlings were investigated under different light and nitrogen conditions.The results showed that(1)Shading and N supply can significantly improve the growth of seedling height and ground diameter of C.lanceolata,which increased by 7.92％-62.07％and 7.38％-71.23％,respectively,when compared with CK(L0N0);under the same light intensity,photosynthetic pigment content,PSⅡ maximum photochemical efficiency(Fv/Fm),electron transfer energy of reaction center(ETo/RC),photosynthetic performance index(Plabs),soluble sugar content,ribulose diphosphate carboxylase/oxygenase(Rubisco)(except L3N2),and glycolate oxidase activity in the leaves of C.lanceolata were increased by N fertilization to different degrees.More specifically,the above indices could be significantly increased with medium N application(N1)under medium(L2)and low light intensity(L3),which is conducive to improving the utilization of light energy and enhancing the photosynthetic rate.However,under low light intensity,higher N treatment significantly decreased the activities of Rubisco and fructose-1,6-diphosphatase,soluble sugar content,starch,and non-structural carbohydrates,thus compromising the improvement effect of N.(2)Under the same N level,with a decrease in light intensity,almost all the indices first increased and then decreased or first decreased,then increased,and again decreased,except for the dissipated energy of the reaction center and starch content indices.Among them,Fv/Fm,Plabs,the reaction center captured energy,soluble sugar content,and Rubisco enzyme activity indices reached their maximum at L2N1,which were 66.11％,992.67％,11.57％,275.96％,and 233.33％higher than CK,respectively.Under L2N1 treatment,the photosynthetic pigment content,chlorophyll a/b value,maximum fluorescence,variable fluorescence,and ETo/RC were significantly increased,which can maintain a higher photosynthetic capacity in the leaves of C.lanceolata under suitable shading conditions,whereas excessive shading significantly decreased the photosynthetic rate and non-structural carbon content,which in turn inhibited its growth.(3)There was a significant interaction between light intensity and N level for almost all indices except seedling height,initial fluorescence,and reaction center capture energy.Subordinate function analysis revealed that the L2N1 treatment,namely 45％light transmission rate and 4 g/plant N treatment,achieved the best growth under our experimental conditions.In summary,appropriate light intensity and nitrogen levels can significantly increase the capacity and efficiency of light absorption,transformation,and utilization in the leaves of C.lanceolata seedlings,thus enhancing their photosynthetic capacity and promoting the synthesis of carbon assimilation,which ultimately improves the growth and quality of seedlings.
Cunninghamia lanceolatainteraction effectphotosynthetic characteristicnon-structural carbohydratekey enzyme of sugar metabolism
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维普
