Growth and Oxidative Stress of Brittlewort (Nitella pseudoflabellata) in Response to Cesium Exposure

The present study evaluated the impact of cesium (Cs-133) at four concentrations (0, 0.001, 0.01, and 0.1 mg L-1) on growth, concentrations of chlorophyll and carotenoid pigments, and oxidative stress responses in the charophyte, Nitella pseudoflabellata, over 30 days. Oxidative stress was quantified by measuring anti-oxidant enzyme activities and H2O2 content. When compared with the control, significantly elevated activity levels of the anti-oxidative enzymes ascorbic peroxidase, catalase and guaiacol peroxidase were observed at 0.1 mg L-1 (all p < 0.05), even though the H2O2 level was not significantly elevated. Carotenoid and chlorophyll a and b pigment levels were significantly reduced (all p < 0.05) at Cs exposures of 0.01 and 0.1 mg L-1. Photosynthetic efficiency (i.e., F-v/F-m) was significantly reduced (p < 0.05) at Cs concentrations a parts per thousand yen0.001 mg L-1. Significant reduction (p < 0.05) of plant growth (i.e., shoot length) was also observed after 1 week of exposure at Cs concentrations a parts per thousand yen0.001 mg L-1. Our results suggested that Cs exposure reduced plant growth and affected plant functioning via activating the defense mechanism against oxidative stress in Nitella.