Effects Of Chinese Gallnut On Photosynthetic Physiology Of Rhus Chinensis

Chinese gallnut is a native product of China as well as a commercial product for export. Itis formed by some aphids on the Rhus trees. Horned gall, which induced by Schlechtendaliachinensis on the sumac, Rhus chinensis, is the main commerical species which shares about70%of the total Chinese gallnut yield. The fundatrix of S. chinensis crawls to a tender leaf of R.chinensis and inserts her stylets into the upper surface of a leaf-wing or leaflet to feed andstimulates the leaf tissue abnormal growth then forms the horned gall finally. Thephotosynthetic indexes including the light response curves （Pn-PAR）, CO₂response curves（Pn-Ci） and the total nitrogen content of R. chinensis among the compound leaf with gall, thecompound leaf without gall on the same shoot and the control were analyzed. The main resultsare as follows:（1） Gall formation may changes the photosynthetic physiology indexes of R. chinensis,and these changes have related to the relative positions of the galls and the leaflets. Thephotosynthetic capacities of lateral leaflets were significant lower than the medial leaflets,including the net photosynthetic rate （Pn）, stomatal conductance （Cond）, and transpirationrate （Tr）, but the intercellular CO₂concentration （Ci） of lateral leaflets was higher than themedial leaflets. It shows that the gall changed the photosynthetic physiology indexes of themedial and the lateral leaflets. Correlation analysis among photosynthetic indexes indicate thatthe barrier of water conduction from medial leaflets to laterals caused by the gall would beresult in decreasing the photosynthetic capacity of lateral leaflets. Meanwhile the gall changethe distribution of nitrogen among different compound leafs. The total nitrogen of the gall wall,the compound leaves with gall and the compound leaves without gall on the same shoot were1.13%,1.98%, and2.14%respectively. These differences indicated that nutritions may transferfrom compound leaves without gall to the leaves with gall, and finally flowing into the galls to meet the demands of galls’ growth. This would be another reason that the lateral leaflets’photosynthetic capacity declined.（2） Gall formation may disturbs the photosynthesis of R. chinensis. Compared to thecontrol, the maximum net photosynthetic rate （Amax（L）） of compound leaves with gall increased14.49%,32.17%, and42.01%at the initial, middle and late gall stages, respectively. Thepresence of gall also rose the maximum net photosynthetic rate （Amax（L）） of compound leaveswithout gall on the same shoot at the initial gall stages, but go back to normal situation at themiddle gall stages. Compared to the initial gall stages, the light saturation point （LSP） ofcompound leaves with gall raised at the middle gall stages, however, the light saturation point（LSP） of compound leaves without gall on the same shoot droped. At the initial and middle gallstages, the light compensation point （LCP） of compound leaves with gall raised, but the lightcompensation point （LCP） of compound leaves without gall on the same shoot also droped.Compared to the control, at the initial gall stages, the dark respiration rate （Rd） of compoundleaves with gall and compound leaves without gall on the same shoot were raised, but therewas no difference at the middle and late gall stages. The extent of how galls disturb thephotosynthesis of R. chinensis is related to the position of gall and the stages of galldevelopment.（3） At the inintal stages, the compound leaves with gall’s initial carboxylation efficiency（α）, carboxylation efficiency （CE）, maximum photosynthetic efficiency under the saturatedCO₂concentration （Amax（C））, photorespiration rate （Rp） were higher than the compoundleaves without gall on the same shoot and the control. The gall also changes the photosyntheticindexes of leaflets on the compound leaves with gall. The gall causes photosynthetic indexes ofmedial leaflets higher than the lateral ones, including initial carboxylation efficiency （α）,carboxylation efficiency （CE）, maximum photosynthetic efficiency under the saturated CO₂concentration （Amax（C））, photorespiration rate （Rp）, CO₂saturation point （CSP）, and CO₂compensation point （CCP） at the initial and middle gall stages. It demonstrated that the lightutilization, CO₂fixation, ability of acclimatization, photosynthetic efficiency, photosynthetic electron transport and photophosphorylation activity of medial leaflets were exceed than thelateral ones.（4） The differences among the photosynthetic indexes caused by gall were related by thegall positions and develpoment stages. And the reasons induced these appearances as below:①The photosynthesis of compound leaves with gall may raise to meet the nutritions demand ofthe gall formation and growth.②According to raised the photosynthesis of medial leafletsfinally increased the photosynthetic capacity of the whole compound leaves with gall.③Thephotosynthesis of lateral leaflets droped because of the barrier of water and nutritions transport.