对植物茎体水分进行实时无损的在线检测成为研究植物水分生理活动的热点之一.本文提出一种基于超声射频回波技术的植物茎体水分实时无损在线检测方法,该系统硬件由超声探头、超声射频发射接收器、数据采集卡和计算机组成;软件由LabVIEW平台开发完成.通过系统获取有机溶液超声回波速度,仿真植物茎体含水率;以杨树截断样品为对象,分析其茎体吸水过程的含水率变化与超声回波速度变化的相关性,平均决定系数为0.98;以活体立木白玉兰为检测对象,完成其茎体超声波日变化检测,最高超声回波速度出现在14:00,最低值出现在22:00.实验表明超声回波速度与植物生理变化特性相符.同时,本文通过茎体样品及活立木的超声检测,验证了该方法可有效反映植物茎体轴向、径向及不同树种的结构差异,为植物茎体水分的检测提供了一种携带茎体结构特性的检测方法.%Water is directly or indirectly involved in the activities of plant physiology.One role of stems is water storage,the other is water transmission channel.Detection of plant stem water by non-destructive online method becomes one of the hot spots in the study of plant water physiological activity.A real-time online non-destructive detection system designed by LabVIEW was proposed based on ultrasonic echoes,which was composed by ultrasonic probe,ultrasonic RF transmitter receiver,data acquisition instrument and portable computer.The simulation model was built by the system with various ultrasonic velocities of different organic solutions to represent the water content of plant stems.The correlation between the changes of water content and that of ultrasonic velocity was analyzed on a set of poplar cutting samples in the process of water absorption of those samples.The average determination coefficient reached about 0.98.For 24 h detection on stem of a living Michelia alba,the highest ultrasonic velocity appeared at 14:00,and the lowest appeared at 22:00.The results showed the variations of ultrasonic velocity accorded with plant physiological characteristic.Meanwhile,the variations of velocities in radial and axial directions and in different kinds of plant stem were detected by the system,which provided a detection instrument with structural differences for the research on plant stem water physiological characteristics.
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