PDF(Pubmed)
Abstract：
The root dielectric response was measured on a minute scale to assess its efficiency for monitoring short-term cadmium (Cd) toxicity non-destructively. Electrical capacitance (CR), dissipation factor (DR) and electrical conductance (GR) were detected during the 24 to 168 h after Cd treatment (0, 20, 50 mg Cd2+ kg-1 substrate) in potted maize, cucumber and pea. Stress was also evaluated by measuring leaf chlorophyll content, Fv/Fm and stomatal conductance (gs) in situ, and shoot and root mass and total root length after harvest. CR showed a clear diurnal pattern, reflecting the water uptake rate, and decreased significantly in response to excessive Cd due to impeded root growth, the reduced tissue permittivity caused by accelerated lignification, and root ageing. Cd exposure markedly increased DR, indicating greater conductive energy loss due to oxidative membrane damage and enhanced electrolyte leakage. GR, which was coupled with root hydraulic conductance and varied diurnally, was increased transiently by Cd toxicity due to enhanced membrane permeability, but declined thereafter owing to stress-induced leaf senescence and transpiration loss. The time series of impedance components indicated the comparatively high Cd tolerance of the applied maize and the sensitivity of pea cultivar, which was confirmed by visible shoot symptoms, repeated physiological investigations and biomass measurements. The results demonstrated the potential of single-frequency dielectric measurements to follow certain aspects of the stress response of different species on a fine timescale without plant injury. The approach can be combined with widely used plant physiological methods and could contribute to breeding crop genotypes with improved stress tolerance.
摘要：
以微小尺度测量根介电响应，以评估其无损监测短期镉（Cd）毒性的效率。电容(CR),在盆栽玉米中，在Cd处理（0、20、50mgCd2kg-1底物）后24至168h内检测到耗散因子（DR）和电导率（GR），黄瓜和豌豆.还通过测量叶片叶绿素含量来评估胁迫，原位Fv/Fm和气孔导度（gs），收获后的芽和根质量以及总根长度。CR表现出清晰的昼夜模式，反映了水的吸收速率，由于根系生长受阻，对过量Cd的反应显着降低，由加速木质化引起的组织介电常数降低，和根老化。Cd暴露显著增加DR,表明由于氧化膜损坏和增强的电解质泄漏而导致的更大的导电能量损失。GR,与根部水力传导率相结合，并随昼夜变化，由于膜通透性增强，Cd毒性暂时增加，但此后由于胁迫引起的叶片衰老和蒸腾损失而下降。阻抗分量的时间序列表明，玉米对Cd的耐受性较高，豌豆品种的敏感性较高，可见的射击症状证实了这一点，重复的生理调查和生物量测量。结果表明，单频介电测量有可能在精细的时间尺度上跟踪不同物种的应激反应的某些方面，而不会对植物造成伤害。该方法可以与广泛使用的植物生理方法相结合，并且可以有助于育种具有改善的胁迫耐受性的作物基因型。
