Conductivity Meter by the Four Electrodes Method and Measurement of Growth of Root System

根与茎一样在地下伸展，但对根的测量却很少。因为很难探测到地下的根系。他们尝试用“玻璃幕墙法”进行目测，然后尝试用电测法测量地下根系。首先，采用四电极法研制了新型电导率仪。四个栅栏式电极是为了测量根系而研制的，因为它不影响土壤中水分的渗流。用这种栅栏式电极和研制的电路制成的电导率仪具有电导率测量范围宽、线性输出与电导率成正比、重现性好、稳定性好、耐老化、不受其它因素影响和电极间相互干扰等优点，并试用该电导率仪测定了植物根系的生长情况。将四个栅栏式电极埋在土壤和琼脂中，以便进行目视比较和观察。当根从土壤或琼脂中吸收水分时，根附近的含水量发生变化。当根系靠近电极时，电极附近的含水量发生变化，电导率也随之降低。当根部距离电极5mm时出现。利用该仪器检测土壤电导率的变化，可以测量根系的生长情况。

There are quite few measurements about root which spreads under the ground as same as a stem and leves. Because it is very difficult to detect the root system in the ground. They are trying to detect it in sight by the way of "Glass-faced Profile Wall Method".Then, it is tried to measure the root system in the ground by the electric method here. At first, the new electric conductivity meter is developed by using the four electrodes method. The four hurdle-type electrodes are developed for measurement of the root system as it does not exert influence on the seepage flow of water in the soil. The conductivity meter with this hurdle-type electrodes and the developed electric circuit has good characteristics; (1) the wide conductivity range,(2) the linear output in proportion to the conductivity,(3) high accuracy in reappearance, stability, ageing, influence of other tings andmutual interference between two electrodes.Using this conductivity meter, the growth of root is tried to measure. The four hurdle-type electrodes are buried in the soil and the agar for the comparison and the observation in sight. As the root absorbs water from the soil or agar, water content changes near the root. When the root comes near the electrodes, water content near the electrodes changes and conductivity also decreases. It appears when the root reaches 5mm apart from the electrodes. The growth of root can be measured by detecting the change of conductivity using this meter.