Development of a carbon accumulation model for estimating the concentration of 1^4C in Japanese radish

Atmospheric ¹⁴C released from nuclear fuel reprocessing plants can accumulate in crop plants. Japanese radish (daikon) is a major crop plant in the area surrounding the Japan's first commercial nuclear fuel reprocessing plant in Rokkasho. We previously developed a dynamic two-compartment model for ¹⁴C accumulation in the leaves and roots of Japanese radish. This model was constructed using measured data obtained under controlled experimental conditions in a growth chamber; however, it was not capable of simulating plant carbon accumulation in actual fields resulting from photosynthesis and respiration under fluctuating environments. In order to apply our previous model to actual fields, the present study aims to modify the model by incorporating the environmental responses of photosynthesis and respiration. The modified model was validated with observed temporal changes in the carbon inventories of the leaves and roots of Japanese radish in the field. The model estimates were found to be in relatively good agreement with the observed data. In addition, our modified model provides reasonable simulation results for ¹⁴C accumulation in Japanese radish exposed to ¹⁴CO₂ at different growth stages. The results of this study indicate that our modified model could contribute to the estimation of ¹⁴C accumulation in Japanese radish under field conditions. (author)