Dynamic changes in the Cs distribution throughout rice plants during the ripening period, and effects of the soil-K level

Abstract

Radiocesium uptake and accumulation in crops has been studied in Japan since the March 2011 nuclear power plant accident. However, few studies have reported how cesium (Cs) is distributed in aboveground parts and how it accumulates in edible parts. Here, we report the dynamics of Cs in aboveground parts of rice (Oryza sativa L.) plants throughout the cultivation period, and the effects of the amount of potassium (K) fertilizer applied to the soil. We conducted two years of pot experiments with several soil-K levels and examined the K and Cs concentrations in each plant part throughout the cultivation period. During ripening, Cs accumulated most in the panicle neck. The ratio of the Cs concentration in brown rice to that in the straw was negatively correlated with the soil-K level, indicating that the proportion of Cs accumulated in the brown rice to that in the whole-aboveground parts increased at low soil K. During ripening, transport of Cs from belowground parts and translocation from leaf blades both seemed to increase at low soil K. The Cs distribution in plant parts appears to be regulated dynamically during ripening by the soil-K level.