多壁碳纳米管对水稻幼苗的生理学效应及对1,2,4-三氯苯毒性的缓解

Multi-walled carbon nanotubes:their effects on the physiological responses of Oryza sativa L.seedlings and the toxicity of trichlorobenzene

研究多壁碳纳米管(multi-walled carbon nanotubes,MWCNTs;1 g/L)对水稻幼苗生理学反应的影响是否具粒子尺寸依赖效应,并在受试外径范围内筛选出对水稻幼苗生理学反应无不良影响的MWCNTs,探究其在培养基质中的存在能否有效缓解1,2,4-三氯苯(TCB)对水稻幼苗的生理学胁迫作用.结果显示:将水稻幼苗暴露于不同外径MWCNTs(<8 nm,20-30 nm,>50 nm)的悬浮液中培养10 d后,与对照相比,<8 nm或20-30 nm MWCNTs处理抑制了水稻幼苗的生长,降低了根系可溶性糖和可溶性蛋白含量、超氧化物歧化酶(SOD)活性、过氧化物酶(POD)活性和抗坏血酸过氧化物酶(APX)活性,以及叶片光系统II(PS II)光化学活性和叶绿素含量;而根系超氧阴离子(O2^·-)积累量和过氧化氢酶(CAT)活性则上升.相较<8 nm MWCNTs处理,20-30 nm MWCNTs处理对幼苗上述不良影响有所减轻.然而,>50 nm MWCNTs处理则显著优化了幼苗的生长,维持了根系活性氧(reactive oxygen species,ROS)代谢平衡,并且提高了根系可溶性糖和可溶性蛋白含量,以及叶片PSⅡ光化学活性和叶绿素含量.非TCB处理条件下,添加外源MWCNTs(>50 nm,1g/L)显著提高了根系可溶性糖含量、叶片PSⅡ光化学活性和叶绿素含量;与单独TCB(40 mg/L)处理相比,TCB(40 mg/L)+MWCNTs(>50 nm,1 g/L)复合处理显著缓解了TCB对水稻幼苗的生理学胁迫作用.上述结果表明,MWCNTs对水稻幼苗的生理效应具有粒子尺寸依赖性,且外径>50 nm的MWCNTs在培养基质中的存在能够显著缓解TCB对水稻幼苗的生理学胁迫作用.

In this study, we investigate whether multi-walled carbon nanotubes(MWCNTs;1 g/L) have a particle size-dependent effect on the physiological responses of Oryza sativa L. seedlings. We also investigated the alleviative effects of MWCNTs(those found to have no adverse effects on the physiological responses of O. sativa seedlings in initial testing) on 1,2,4-trichlorobenzene(TCB) toxicity. Initially, MWCNTs with two different outer-diameters(< 8 nm and 20-30 nm;1 g/L) were applied to the roots of O. sativa seedlings grown for 10 d under hydroponic conditions. Results showed that, compared to controls, such application inhibited seedling growth, and decreased the soluble protein and soluble sugar content, superoxide dismutase(SOD) activity, peroxidase(POD) activity, and ascorbate peroxidase(APX) activity of roots. Additionally, such treatment also resulted in reduced leaf PS Ⅱ photochemistry activity and chlorophyll content. Conversely, the root superoxide anion(O2·-) production rate and catalase(CAT) activity were increased under this treatment. However, the adverse physiological effects to O. sativa seedlings were alleviated with treatment using 20-30 nm MWCNTs, in contrast to treatment with < 8 nm MWCNTs. Importantly, MWCNTs with an outer-diameter of < 50 nm presented in medium effectively enhanced seedling growth, maintained the ROS(reactive oxygen species) metabolism balance of roots, increased the soluble protein and sugar content of roots, improved PS Ⅱ photochemistry activity, and increased chlorophyll content of leaves. We further investigated the alleviative effects of MWCNTs with outer-diameter > 50 nm on the toxicity of TCB in O. sativa seedlings. Without TCB stress, MWCNTs presented in medium increased the root soluble sugar content, leaf PS Ⅱ photochemistry activity, and chlorophyll content. With TCB stress, MWCNTs presented in medium significantly alleviated the TCB-induced negative physiological effects. These results suggest that MWCNTs with moderately sized outer-diameters can be an advantageous additive during the growth of O. sativa seedlings and can protect them from TCB toxicity.