Studies On Inorganic Carbon Acquisition Strategies In Submerged Plants In Karst

Many submerged plant can use HCO3-as a corbon source,and thus play a role in carbon sink effect related to carbonate rock dissolution.However,different kinds of submerged plants will take different inorganic carbon acquisition strategies and have the different ability to use inorganic carbon.One species may also has different inorganic carbon utilization strategies under different inorganic carbon source.In this study,pH-drift technology,diel acidity titration,chlorophyll fluorescence kinetic parameter measurement,rapid light curve monitoring and stable carbon isotope ?13C measurement were used to measure inorganic carbon acquisition strategies of submerged plants in Karst areas of Zhaidi River.The results in Karst areas was compared with that in non-karst areas.Resusts are as follows.1.Both Vallisneria denseserrulata and Ottelia guanyangensis in the karst river of Zhaidi had HCO3-utilization capacity.Bicarbonate ion utilization capacity of O.guanyangensis in the downstream was significantly higher than that in the upstream,while the bicarbonate utilization capacity of V denseserrulata did not change between the upstream and downstream.2.Photosynthetic oxygen evolution rate experiment and chlorophyll fluorescence fast light curve results showed that O.guanyangensis and V.denseserrulata had different tendency to select CO2 and HCO3-as corbon sourse.Ottelia guanyangensis prefered to use CO2 while there was no preference for V.denseserrulata to use CO2 or HCO3-.3·Inorganic carbon source of Ottelia guanyangensis was CO2 when it was in the outlet of underground river of high concentration CO2.The inorganic carbon source changed to CO2 and HCO3-then changed to HCO3-mainly with CO2 concentration decreased along the water flow direction.Inorganic carbon source of V.denseserrulata did not change between the upstream and downstream.4.Results also showed that inorganic carbon acquisition strategies of the same species(Ottelia guanyangensis or V denseserrulata)in Karst area and non karst area is similar.However,the carbon of HCO3-in the karst area mainly comes from the rock,which leads to the difference of the ?13C values between Karst area and non karst area.