The pattern of radial water transport in tree stems, specifically the interaction between bark and xylem, remains elusive because few measurement techniques are not capable of independently sensing bark water content (BWC) and xylem water content (XWC). To investigate the water variations in stem, two improved flexible sensors operating at 100 MHz and equipped with small interdigital-electrode (IE) probes were developed to measure BWC and XWC independently. The performances of the flexible sensors were tested under laboratory conditions. Software simulations and laboratory measurements were performed to evaluate the volume of sensitivity (VOS) and to assess the impact of variations in stem diameter (SD) on the sensors. Concurrent measurements of BWC and XWC were performed on three trees in Malus pumila Mill. (Red Fuji). The measurements revealed that the difference in predawn water content between the bark and xylem gradually increased as the water deficit intensified. The maximum daily variation of BWC from predawn to afternoon (MDV_BWC) was greater than that of the maximum daily variation of XWC from predawn to afternoon (MDV_XWC). In addition, the dehydration-rehydration loops exhibited a time lag between BWC and XWC under water deficit conditions, with earlier dehydration and rehydration of the bark than of the xylem. Concurrent measurements of BWC and XWC provide a new perspective for examining the pattern of stem radial water transport. However, the time lag between BWC and XWC might need to be validated in other tree species.

中文翻译：

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同时测量 Malus pumila Mill 中的树皮和木质部水分含量。使用改进的柔性传感器的杆


树干中径向水分输送的模式，特别是树皮和木质部之间的相互作用，仍然难以捉摸，因为很少有测量技术无法独立感知树皮含水量 （BWC） 和木质部含水量 （XWC）。为了研究茎中的水分变化，开发了两个改进的柔性传感器，工作频率为 100 MHz，并配备了小型数字间电极 （IE） 探头，以独立测量 BWC 和 XWC。柔性传感器的性能在实验室条件下进行了测试。进行软件模拟和实验室测量以评估灵敏度体积 （VOS） 并评估茎直径 （SD） 变化对传感器的影响。同时对 Malus pumila Mill 的三棵树进行了 BWC 和 XWC 的测量。（红富士）。测量表明，随着水分亏缺的加剧，树皮和木质部之间黎明前含水量的差异逐渐增加。黎明前至下午的 BWC 最大日变化 （MDV_BWC） 大于黎明前至下午的 XWC 最大日变化 （MDV_XWC）。此外，在缺水条件下，脱水-再水循环在 BWC 和 XWC 之间表现出时间滞后，树皮的脱水和再水化早于木质部。BWC 和 XWC 的同步测量为检查茎径向水分运输模式提供了新的视角。但是，可能需要在其他树种中验证 BWC 和 XWC 之间的时间滞后。