Turgor Pressure Sensor

Note: This video show full system that using Yara original data logger; however, we cannot use full system because of Japanese radio act. Instead of using full system we use cable adaptor that can connect general data logger.

The Yara Water Sensor is a leaf turgor measuring instrument developed by YARA in Germany to improve the efficiency of nutrient and water usage. Basically, it is part of a system that collects data wirelessly, but in Japan, it is difficult to use it in a full system state due to radio law restrictions. However, if you use a dedicated cable adapter and connect it to a general-purpose data logger, you can easily use it in Japan, so we handle it as a single sensor for measuring leaf expansion pressure. At present, there are very few examples (research examples) of measurement of leaf turgor pressure, and just obtaining that data can be counted as a new attempt, so this sensor can also be used for research purposes.

Turgor pressure is one of the dynamic indicators of plant growth and fruit production, and it is a parameter that can tell the current state of the leaves. For example, when plants do not have access to enough water, their turgor pressure will drop and they begin to wilt. Turgor pressure is the pressure caused by the fluid pushing against the cell walls of plant cells and is the driving force that keeps the plant healthy and firm.

As the structure of the sensor, two magnets placed above and below the leaf are used to bring the pressure sensor into close contact. The pressure that can be detected at this time is the sum of the pressure generated by the magnet and the turgor pressure, and the pressure after subtracting the magnet pressure is the turgor pressure. The basic movement of turgor pressure is that water is lost through transpiration during the day and turgor pressure decreases, and the decreased turgor pressure recovers at night. 
If there is not enough water, the plant will undergo plasmolysis and stress will continue to increase.
The direction of water flow is soil moisture -> root -> stem -> branch -> leaf -> atmosphere. When considering the parameters associated with this movement, the following sensors are relevant.

・Soil Moisture: Soil Moisture Sensor　・Roots: Currently not detectable　・Stems & Branches: Dendrometer　・Leaves: Yara Water Sensor

Yara Water Sensor is a differential connection specification.
Since the LR5042 used in the MIJ-12 is a single-end specification, it cannot be used to drive Yara with the preheat function. Therefore, it becomes a method of continuously supplying power and using it, and the consumption of the battery becomes intense. When using the MIJ-12 and Yara together, please replace the PR-01 battery every 9 days maximum (Using 2.5V specification PR01 board).

We suggest this combination to researcher who use in short term.

If the combination with MIJ-12 is not enough, we recommend the combination with MIJ-01.
Since MIJ-01 supports differential connection, Yara can be used normally.
8 Yara sensors can be measured for 720 days at 30 minutes intervals and 240 days at 10 minutes intervals.

The advantage of combining MIJ-01 and the expansion sensor is that other parameters can be measured at the same time.
For example, it would be interesting to use a dendrometer, soil moisture meter, etc. together.

Ppatch = (Vsignal　ー Voffset) * 300 kPa / (40 mV * Vsupply)

Vsigna: Logger output when sandwiching leaves

Voffset:：Logger output when no leaf is sandwiched

Vsupply:：Preheat (Power)