Plant-based sensors that measure the electrical capacitance of leaves can tell farmers when to activate their irrigation systems, preventing both water waste and parched plants.
Continuously monitoring plant “water stress” is particularly critical in arid regions. Traditionally,
Plant-based sensors that measure the electrical capacitance of leaves can tell farmers when to activate their irrigation systems, preventing both water waste and parched plants.
Continuously monitoring plant “water stress” is particularly critical in arid regions. Traditionally, water stress has been tested through measuring soil moisture content or developing evapotranspiration models that calculate the sum of ground surface evaporation and plant transpiration. New technology that more accurately detects when plants need to be watered, however, could potentially increase water-use efficiency.
For this study, lead researcher Amin Afzal, a doctoral degree candidate in plant science at Penn State, integrated the capability to simultaneously measure leaf thickness and leaf electrical capacitance into a leaf sensor.
Researchers worked with tomato plants in a growth chamber with a constant temperature and 12-hour on/off photoperiod for 11 days. They used peat potting mixture, with water content measured by a soil-moisture sensor, as a growth medium. They maintained the soil water content was at a relatively high level for the first three days and allowed it to dehydrate thereafter, over a period of eight days.
The researchers randomly chose six leaves that were exposed directly to light sources and mounted leaf sensors on them, avoiding the main veins and the edges. They recorded measurements at five-minute intervals.
“I believe these sensors could improve water-use efficiency considerably…”
The daily leaf-thickness variations were minor, with no significant day-to-day changes when soil moisture contents ranged from high to wilting point. Leaf-thickness changes were, however, more noticeable at soil-moisture levels below the wilting point, until leaf thickness stabilized during the final two days of the experiment, when moisture content reached 5 percent.
The electrical capacitance, which shows the ability of a leaf to store a charge, stayed roughly constant at a minimum value during dark periods and increased rapidly during light periods, implying that electrical capacitance was a reflection of photosynthetic activity. The daily electrical-capacitance variations decreased when soil moisture was below the wilting poi