硝基苯酚胁迫下外源褪黑素对水稻幼苗生长及生理特性的影响

采用液体培养实验方法,研究硝基苯酚胁迫对水稻(Oryza sativa L.)幼苗生长、抗氧化特性、光系统Ⅱ(PSⅡ)光合特性的影响,以及添加外源褪黑素对缓解硝基苯酚胁迫的作用。结果显示,随着硝基苯酚胁迫浓度的升高,水稻幼苗株高、根长、地下部干重、地上部干重、全株干重和叶片PSⅡ实际光化学效率Y(Ⅱ)]、光化学淬灭系数(q P)、PSⅡ电子传递速率(ETR)、叶绿素含量均有所下降,而叶片非光化学淬灭系数(qN、NPQ)上升;同时,根系活性氧过氧化氢(H_2O_2)和超氧阴离子(O·-2)]积累量、抗氧化酶超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT)和抗坏血酸过氧化物酶(APX)]活性,以及渗透调节物质(可溶性蛋白和可溶性糖)含量呈先升高后降低的趋势。在非硝基苯酚胁迫下,与对照组相比,添加外源褪黑素显著提高了幼苗地下部干重、根系可溶性糖含量和SOD活性、叶片PSⅡ光化学效率和叶绿素含量。与单独添加硝基苯酚处理相比,硝基苯酚+褪黑素复合处理显著缓解了硝基苯酚胁迫对幼苗生长、叶片PSⅡ光化学效率和叶绿素合成的抑制作用;降低了根系活性氧水平、抗氧化酶活性和渗透调节物质含量。研究结果表明添加外源褪黑素能够显著缓解硝基苯酚胁迫对水稻幼苗生长、根系活性氧水平、抗氧化酶活性、叶片PSⅡ光化学效率及叶绿素合成的不良影响,提高水稻幼苗对硝基苯酚胁迫的适应性。

Effects of exogenous melatonin on the growth and physiological characteristics of Oryza sativa L. seedlings under nitrophenol stress

We investigated the effects of nitrophenol stress on the growth, antioxidant properties, and PSⅡ photosynthetic characteristics of Oryza sativa L. seedlings, as well as the alleviative effects of exogenous melatonin on nitrophenol stress, through liquid culture experiments. Results showed that with the increase in nitrophenol concentration, the plant height, root length, below-ground part dry weight, above-ground part dry weight, plant dry weight, effective photochemical quantum yield of PSⅡ(Y(Ⅱ)), photochemical quenching coefficient(qP), non-cyclic electron-transport through PSⅡ(ETR), and chlorophyll content of leaves all decreased. Conversely, the non-photochemical quenching coefficient(qN, NPQ) of the leaves increased with increasing nitrophenol concentration. Simultaneously, the accumulation of reactive oxygen species(ROS)(including hydrogen peroxide and superoxide anion radicals(H₂O₂ and O₂^·-)), activity of antioxidant enzymes(including superoxide dismutase(SOD), peroxidase(POD), catalase(CAT), and ascorbate peroxidase(APX)), and content of the osmotic regulator(soluble protein and sugar) of roots first increased then decreased with increasing nitrophenol concentration. Without nitrophenol stress, the below-ground part dry weight, soluble sugar content, and SOD activity of the roots, PSⅡ photochemical efficiency, and chlorophyll content of the leaves all significantly increased under exogenous melatonin treatment compared with the control. In comparison with nitrophenol treatment, the combination of nitrophenol and melatonin treatment significantly alleviated the inhibition of nitrophenol stress on seedling growth, PSⅡphotochemical efficiency, and chlorophyll synthesis, and reduced ROS levels, antioxidant enzyme activities, and osmotic regulator content in roots. Thus, the addition of exogenous melatonin can significantly alleviate the adverse effects of nitrophenol stress on O. sativa L. seedlings.