外源一氧化氮对镉胁迫下玉米幼苗根生长及氧化伤害的影响

摘要

Nitric oxide (NO) involves in plant response to various stresses. In the present study,maize seedlings were treated with cadmium alone or in combination with sodium nitroprusside (SNP, a NO donor), SNP plus 2-(4-carboxy-2-phenyl)-4,4,5,5- tetramethylimidazoline-l-oxyl-3-oxide (cPTIO,a NO scavenger) or K3Fe(CN)6(an analog of SNP). After 24 h,some parameters correlating with stresses were investigated to analyze the effect of NO on cadmium tolerance. We found that supplementation of Cd with SNP exhibited significantly greater root elongation and lower Cd accumulation in root tips as compared with Cd treatment a-lone. Meanwhile,Cd-induced oxidative damage including electrolyte leakage,superoxide radical (O2―· ) and hydrogen peroxide (H2O2) was alleviated by SNP supply. In addition, Cd-triggered increases in superoxide dismutase (SOD),catalase (CAT) and ascorbate peroxidase (APX) activities were also decreased by SNP addition. Although Cd stress had no effect on glutathione reductase (GR) activity, supplementing with SNP increased GR activity as compared with Cd treatment alone. The ameliorating effects of NO were specific,because K3Fe(CN)6 which did not release NO,did not show the effects of SNP. The effects of SNP were reversed by simultaneous application of cPTIO. All together,these results suggested that NO ameliorates Cd toxicity by decreasing endogenous Cd accumulation and Cd-induced oxidative damage.%以玉米幼苗为材料,通过在镉处理的同时补充外源一氧化氮(NO)供体硝普钠(SNP)及其类似物[K3Fe(CN)6]、以及NO消除剂,分析NO对植物耐镉性的影响,探讨NO在植物逆境胁迫响应中的作用及其机理.结果显示:添加20 umol·L-1 SNP能显著降低镉引发的玉米幼苗根生长抑制及根尖内源镉的积累,减少电解质的渗漏以及超氧化物自由基(O2-)和过氧化氢(H2O2)的上升幅度,抑制超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、抗坏血酸过氧化物酶(APX)活性的增加,进一步提高镉胁迫下谷胱甘肽还原酶(GR)的活性.SNP的上述效应可被NO消除剂2-(4-羧基-2-苯基)-4,4,5,5-四甲基咪唑-1-氧-3-氧化物(cPTIO)所逆转,而SNP类似物K3Fe(CN)6的应用对上述反应几乎无影响,说明该反应具有NO特异性.研究表明,外源NO能够显著缓解镉胁迫对玉米幼苗生长造成的伤害,该缓解作用主要是通过降低植株体内内源镉积累和减轻镉诱发的氧化伤害来实现的.