抄録
It is very important to measure growth of plant for analyzing its physiology, growth mechanism and producing it efficienty in agriculture.
There are many reports about measurment of a stem diameter, a plant height, a leaf area, water transportation in a stem and so on. There are quite few measurments 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 electiric conductivity meter is developed by using the four electrodes method. The four hurdle-type electrodes are developed for measurment 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 and mutual interference between two electrodes.
Using this conductivity meter, the growth of root is tried to measure. The four hurdle-type electrodes are beried in the soil and the agar for the comperison 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.
