Continuous measurements of the water use, or transpiration, of small or herbaceous plants can be difficult. A small weighing lysimeter, also known as a balance or scale, can be used however these often require a researcher to manually read the LCD screen or to have the instrument connected to a PC or laptop. Data collection is then frequently interrupted by a Windows update!
Recently, scientists at Edaphic Scientific demonstrated that the SF-4 Micro Stem Sap Flow Sensor can be reliably used to measure the water use of plants with stem diameters between 2 and 5 mm. By using a species specific calibration, the SF-4 can output plant water use as either sap flow, transpiration or stomatal conductance. The SF-4 sensor is easy to install and maintain on small stems, therefore research of plant water relations of these plants can now be significantly improved.
The following figure shows an example calibration curve between the SF-4 sensor and SC-1 Leaf Porometer. The data from the two independent instruments are highly correlated (R2 = 0.95), indicating that the SF-4 Micro Stem Sap Flow Sensor can be used for continuous plant water use measurements.