Two of the most important CO2 sequestration processes on Earth are plant photosynthesis and rock chemical dissolution. Photosynthesis is undoubtedly the most important biochemical reaction and carbon sink processes on Earth. Karst geological action does not produce net carbon sinks. Photosynthesis and karstification in nature are coupled. Karstification-photosynthesis coupling can stabilize and increase the capacity of karstic and photosynthetic carbon sinks. Bidirectional isotope tracer culture technology can quantify the utilization of different inorganic carbon sources by plants. Bicarbonate utilization by plants is a driver of karstification-photosynthesis coupling, which depends on plant species and the environment. Carbonic anhydrase, as a pivot of karstification-photosynthesis coupling, can promote inorganic carbon assimilation in plants and the dissolution of carbonate rocks. Karst-adaptable plants can efficiently promote root-derived bicarbonate and atmospheric carbon dioxide use by plants, finally achieving the conjugate promotion of karstic carbon sinks and photosynthetic carbon sinks. Strengthening karstification-photosynthesis coupling and developing karst-adaptable plants will greatly improve the capacity of carbon sinks in karst ecosystems and better serve the "Carbon peak and Carbon neutralization" goals of China.