Live-imaging evaluation of the efficacy of elevated CO<sub>2</sub> concentration in a closed cultivation system for the improvement of bioproduction in tomato fruits
To maximize fruit yield of tomatoes cultivated in a controlled, closed system such as a greenhouse or a plant factory at a limited cost, it is important to raise the translocation rate of fixed carbon to fruits by tuning the cultivation conditions. Elevation of atmospheric CO<sub>2</sub> concentration is a good candidate; however, it is technically difficult to evaluate the effect on fruit growth by comparing different individuals in different CO<sub>2</sub> conditions because of large inter-individual variations. In this study, we employed a positron-emitting tracer imaging system (PETIS), which is a live-imaging technology for plant studies, and a short-lived radioisotope <sup>11</sup>C to quantitatively analyze immediate responses of carbon fixation and translocation in tomatoes in elevated CO<sub>2</sub> conditions. We also developed a closed cultivation system to feed a test plant with CO<sub>2</sub> at concentrations of 400, 1,500 and 3,000 ppm and a pulse of <sup>11</sup>CO<sub>2</sub>. As a result, we obtained serial images of <sup>11</sup>C fixation by leaves and subsequent translocation into fruits. Carbon fixation was enhanced steadily by increasing the CO<sub>2</sub> concentration, but the amount translocated into fruits saturated at 1,500 ppm on average. The translocation rate had larger inter-individual variation and showed less consistent responses to external CO<sub>2</sub> conditions compared with carbon fixation. Our experimental system was demonstrated to be a valuable tool for the optimization of closed cultivation systems because it can trace the responses of carbon translocation in each individual, which are otherwise usually masked by inter-individual variation.
- Plant Biotechnology
Plant Biotechnology advpub(0), 2015
Japanese Society for Plant Cell and Molecular Biology