背景:根介电响应的测量是评估根生长和功能的一种有用的非破坏性方法。先前的研究通过反复进行的单次电测量来跟踪整个植物生长周期中的根发育。然而,众所周知,根系电导率和吸收活性可以迅速变化,加上光合和蒸腾速率的昼夜周期。因此,在实验室环境中使用定制的阻抗测量系统测试了在微小尺度时间分辨率下完整的根基质系统的低频介电监测。在盆栽玉米中检测了144h的电容(CR)和电导(GR)以及耗散因子(DR),在各种光照/黑暗和温度条件下生长的黄瓜和豌豆,或进行渐进的叶片切除或斩首。还测量了光合参数和气孔导度以评估胁迫响应。
结果:CR和GR数据系列显示出与所施加的光/暗和温度循环相关的显着24小时季节性。这归因于整株植物蒸腾作用的昼夜模式(通过气孔导度检测),这与根系吸水速率密切相关。CR和GR在6天黑暗治疗期间下降,随着落叶水平的增加成比例地下降,可能是由于黑暗诱导的衰老或叶片去除引起的冠层蒸腾作用的损失。暴露于6天黑暗中的植物的DR呈下降趋势,而它因斩首而显着增加,表明根膜结构和渗透性改变,和质外体与细胞间水和电流通路的比例改变。
结论:动态,完整根系的原位阻抗测量是跟踪综合根系吸水的有效方法,包括昼夜周期,和压力引起的变化。还证明了介电响应主要源于根组织极化和电流传导,受到根系实际生理活动的影响。精细时标上的介电测量,作为监测根系生理状态和环境反应的诊断工具,值得未来关注。
BACKGROUND: The measurement of root dielectric response is a useful non-destructive method to evaluate root growth and function. Previous studies tracked root development throughout the plant growing cycle by single-time electrical measurements taken repeatedly. However, it is known that root conductivity and uptake activity can change rapidly, coupled with the day/night cycles of photosynthetic and transpiration rate. Therefore, the low-frequency dielectric monitoring of intact root-substrate systems at minute-scale temporal resolution was tested using a customized impedance measurement system in a laboratory environment. Electrical capacitance (CR) and conductance (GR) and the dissipation factor (DR) were detected for 144 h in potted maize, cucumber and pea grown under various light/dark and temperature conditions, or subjected to progressive leaf excision or decapitation. Photosynthetic parameters and stomatal conductance were also measured to evaluate the stress response.
RESULTS: The CR and GR data series showed significant 24-h seasonality associated with the light/dark and temperature cycles applied. This was attributed to the diurnal patterns in whole-plant transpiration (detected via stomatal conductance), which is strongly linked to the root water uptake rate. CR and GR decreased during the 6-day dark treatment, and dropped proportionally with increasing defoliation levels, likely due to the loss of canopy transpiration caused by dark-induced senescence or removal of leaves. DR showed a decreasing trend for plants exposed to 6-day darkness, whereas it was increased markedly by decapitation, indicating altered root membrane structure and permeability, and a modified ratio of apoplastic to cell-to-cell water and current pathways.
CONCLUSIONS: Dynamic, in situ impedance measurement of the intact root system was an efficient way of following integrated root water uptake, including diurnal cycles, and stress-induced changes. It was also demonstrated that the dielectric response mainly originated from root tissue polarization and current conduction, and was influenced by the actual physiological activity of the root system. Dielectric measurement on fine timescale, as a diagnostic tool for monitoring root physiological status and environmental response, deserves future attention.