A New Method for Parametric Imaging of Photosynthesis with C-11 Carbon Dioxide and Positron Emitting Tracer Imaging System (PETIS)

The positron emitting tracer imaging system (PETIS) and carbon-11-labeled carbon dioxide (¹¹CO₂) can image carbon movement during photosynthesis in a plant leaf, and ¹¹C kinetics make it possible to estimate physiological function parameters in those photosynthesis processes. With an exposure ¹¹CO₂ gas to a leaf, PETIS experiments were performed iteratively under dark and light environments on a single leaf. In order to estimate the rate constants of photosynthetic parameters, time activity curves of ¹¹CO₂ gas input and leaf response were fitted to an appropriate compartmental tracer kinetic model, which applies influx and efflux for photo-assimilation and sucrose export rate constants respectively. Results obtained from the kinetic analysis are consistent with physiological knowledge and important to discuss photosynthesis in plant physiology and agriculture. In addition, the proposed method in this paper produce parametric images of photosynthetic functions on a pixel-by-pixel basis successfully, in other words, molecular imaging for plant study is demonstrated.