Monitoring of Water Transportation in Plant Stem With Microneedle Sap Flow Sensor
The measurement of xylem sap flow is essential to understanding plant physiology in agriculture. Advanced hydroponics, for instance, would require sap flow measurement to observe the plant reaction to environmental variables, such as sunlight, humidity, and soil water content. However, most conventional approaches for sap flow measurement have been limited to large woody plants. Plants grown in hydroponics, e.g., tomatoes and bell peppers, are smaller and softer, and can hardly survive the invasion of thick thermal probes for flow speed measurement. This report presents a microneedle thermal probe that can be implanted into a small plant for the measurement of sap flow through the xylem. A microscale single hot wire on a single probe is used to benefit from small-scale physics in a simple configuration. The single probe enables minimally invasive measurement with a small thermal impact on plant tissues. We show that the Granier method can be modified to use the single hot wire as a heater and a temperature sensor simultaneously. Tests with a tomato stem result in a universal calibration model that can be applied to the same species. We demonstrate routine measurements of sap flow in a greenhouse tomato tree over a month, opening up the possibility for production scale application.
EXISTING SYSTEM :
Small-scale physics reveal the fundamental benefit of a microneedle thermal probes because of their size and heat transfer characteristics. The thermal capacity of the microscale system is rapidly reduced due to small control volume and mass. Thus the thermal response is quicker and more sensitive in the microscale system . These characteristics would enable rapid thermal measurement reaching to thermal equi Librium with less amount of energy and time. Most impor tantly, the target temperature of the microneedle probe can be substantially lowered. The single probe enables minimally invasive measurement with a small thermal impact on plant tissues.
PROPOSED SYSTEM :
We show that the Granier method can be modified to use the single hot wire as a heater and a temperature sensor simultaneously. Tests with a tomato stem result in a universal calibration model that can be applied to the same species. We demonstrate routine measurements of sap flow in a greenhouse tomato tree over a month, opening up the possibility for production scale application.
Microneedle sap flow sensor was designed and fabricated with MEMS fabrication process. The sensor signal was calibrated for the pipe flow and the xylem flow. The microneedle sap flow sensor showed its applicability through the calibration result. The measured values in this experiment were not extremely accurate, but relatively accurate measurements were possible compared with the accuracy of other measurement methods. The sensors were installed to greenhouse tomato plants to measure the in-vivo signal with minimum invasion for 36 days. The measured sap flow signal showed a close relationship with the solar radiation and other environmental variables. Microneedle sap flow sensor has many advantageous with its simplicity and small size. By using temperature detection via resistance, heating and temperature measurement is possible with a single electrode on a single probe. This enables simple and reliable measurement. The small size of probe minimizes the invasion and disturbance to plant growth. Small thermal capacity increases the sensitivity with better time resolution while the thermal impact on the plant is kept low. The microneedle probe has a very small sensing part. This will possibly allow measuring the local water transportation at the particular organ of a plant, which will be useful for plant physiological research. The microneedle probe platform is not limited to the sap flow measurement but can be incorporated with other in vivo sensing techniques such as electrical conductivity, ion concentration, or nutrition monitoring. The silicon-based microsensors will open up new opportunities for the agricultural applications due to their physical benefits and economical costs. Sensing quality will increase as a large number of sensors are implanted on many plants, representing the states of a whole farm. The productivity and the quality of agricultural products will be improved by accessing the key information of plants in the precision farming.