Plant Stress Biology Lab, Department of Botany, West Bengal State University, Kolkata 700 126, West Bengal, India.
Chemosphere. 2013 Oct;93(6):906-15. doi: 10.1016/j.chemosphere.2013.05.044. Epub 2013 Jun 19.
Indiscriminate release of metal oxide nanoparticles (NPs) into the environment due to anthropogenic activities has become a serious threat to the ecological system including plants. The present study assesses the toxicity of nano-CuO on rice (Oryza sativa cv. Swarna) seedlings. Three different levels of stress (0.5 mM, 1.0 mM and 1.5 mM suspensions of copper II oxide, <50 nm particle size) were imposed and seedling growth performance was studied along control at 7 and 14 d of experiment. Modulation of ascorbate-glutathione cycle, membrane damage, in vivo ROS detection, foliar H₂O₂ and proline accumulation under nano-CuO stress were investigated in detail to get an overview of nano-stress response of rice. Seed germination percentage was significantly reduced under stress. Higher uptake of Evans blue by nano-CuO stressed roots over control indicates loss of root cells viability. Presence of dark blue and deep brown spots on leaves evident after histochemical staining with NBT and DAB respectively indicate severe oxidative burst under nano-copper stress. APX activity was found to be significantly increased in 1.0 and 1.5 mM CuO treatments. Nevertheless, elevated APX activity might be insufficient to scavenge all H₂O₂ produced in excess under nano-CuO stress. That may be the reason why stressed leaves accumulated significantly higher H₂O₂ instead of having enhanced APX activity. In addition, increased GR activity coupled with isolated increase in GSH/GSSG ratio does not seem to prevent cells from oxidative damages, as evident from higher MDA level in leaves of nano-CuO stressed seedlings over control. Enhanced proline accumulation also does not give much protection against nano-CuO stress. Decline in carotenoids level might be another determining factor of meager performance of rice seedlings in combating nano-CuO stress induced oxidative damages.
由于人为活动，金属氧化物纳米粒子（NPs）不可控制地释放到环境中，这对包括植物在内的生态系统构成了严重威胁。本研究评估了纳米氧化铜（CuO）对水稻（Oryza sativa cv. Swarna）幼苗的毒性。在实验的第 7 天和第 14 天，施加了 3 个不同水平的胁迫（0.5 mM、1.0 mM 和 1.5 mM 铜 II 氧化物悬浮液，粒径<50nm），并研究了幼苗的生长性能，同时设对照。详细研究了抗坏血酸-谷胱甘肽循环、膜损伤、体内 ROS 检测、叶片 H₂O₂和脯氨酸积累在纳米-CuO 胁迫下的变化，以全面了解水稻的纳米胁迫反应。胁迫下种子的发芽率显著降低。与对照相比，纳米-CuO 胁迫下根对 Evans 蓝的摄取量增加，表明根细胞活力丧失。经 NBT 和 DAB 组织化学染色后，叶片上出现暗蓝色和深棕色斑点，表明在纳米铜胁迫下发生严重的氧化爆发。APX 活性在 1.0 和 1.5 mM CuO 处理中显著增加。然而，在纳米-CuO 胁迫下，过量产生的 H₂O₂可能超过了 APX 活性的清除能力。这可能是胁迫叶片积累的 H₂O₂显著增加而不是 APX 活性增强的原因。此外，GR 活性的增加伴随着 GSH/GSSG 比值的单独增加，似乎并不能防止细胞受到氧化损伤，因为与对照相比，纳米-CuO 胁迫下幼苗叶片中的 MDA 水平更高。脯氨酸的积累增加也不能对纳米-CuO 胁迫提供太多保护。类胡萝卜素水平的下降可能是水稻幼苗在抵御纳米-CuO 胁迫引起的氧化损伤方面表现不佳的另一个决定因素。
