Impacts of soil type and drought stress on growth and cesium accumulation in Napier grass.

In our previous study, the decontamination efficiency of cesium-137 ( ¹³⁷ Cs) by Napier grass (Pennisetum purpureum Schum.) in the field was shown to be variable and often influenced by natural environmental factors. To elucidate the factors influencing this variable ¹³⁷ Cs-decontamination efficiency, we investigated the influences of soil type and drought stress on Cs accumulation using cesium-133 ( ¹³³ Cs) in Napier grass grown in plastic containers. The experiment was performed using two soil types (Soil A and B) and three different soil moisture conditions: well-watered control (CL), slight drought stress (SD), and moderate drought stress (MD). Overall, our results indicate that soil type and drought have a significant impact on plant growth and ¹³³ Cs accumulation in Napier grass. Plant height (PH), tiller number (TN), leaf width (W _leaf ), and dry matter weight of aboveground parts (DW _above ) and root parts (DW _root ) in Soil B were greater than those in Soil A. Drought stress negatively affected chlorophyll fluorescence parameters (maximal quantum efficiency of photosystem (PS) II photochemistry and potential activity of PS II), PH, TN, W _leaf , DW _above , DW _root , and total ¹³³ Cs content (TCs), but it had a positive effect on ¹³³ Cs concentration. The ¹³³ Cs concentration in the aboveground parts (Cs _above ) was increased by MD approximately 1.62-fold in Soil A and 1.11-fold in Soil B compared to each CL counterpart. The TCs in the aboveground parts (TCs _above ) decreased due to drought by approximately 19.9%-39.0% in Soil A and 49.9%-62.7% in Soil B; however, there was no significant effect on TCs _above due to soil type. The results of this study indicate that soil moisture is a key factor in maintaining Napier grass ¹³⁷ Cs-decontamination efficiency.
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