continuous stomatal conductance measurements

SF-4M Sap Flow Sensor


With traditional instrumentation, stomatal conductance is difficult to measure. Traditional meters, such as a porometer, are slow and laborious. Typically, a single measurement can take several minutes and measuring many samples is very time consuming. Moreover, an instrument to measure stomatal conductance needs regular calibration and maintenance which just adds to the frustration of taking these very important physiological measurements.

Edaphic Scientific provides an easy-to-use and low maintenance solution for continuous stomatal conductance measurements. Stomatal conductance can be measured at a minimum of five-minute intervals but a single leaf can be measured continuously for several days to weeks.

As the sensor is connected to a data logger, measurements can be performed at any time of the day without the need for a researcher or technician to be present. With a modem connected to the data logger, stomatal conductance of a leaf can be viewed and monitored anywhere in the world with an internet connection.

A continuous data set of stomatal conductance over several days to weeks will provide important insights into the physiology of plants in response to experimental and environmental treatments.


the SF-4M sensor for stomatal conductance

The SF-4M is a thermometric sensor that can measure the sap flow of petioles or small stems in a diameter range of 2 to 5 mm. The sensor can be installed proximate to a lamina. Therefore, it can measure the stomatal conductance of the leaf without physically disturbing, or interrupting, the leaf’s immediate environment.

For accurate and precise measurements, it is recommended that the SF-4M sensor is calibrated. The procedure for calibration can be performed with an existing stomatal conductance meter such as the SC-1 Leaf Porometer. Figure 1 demonstrates a calibration of a SF-4M sensor where the x-axis is millivolt data from the SF-4M sensor and the y-axis is stomatal conductance data from a SC-1 Leaf Porometer. Detailed information on sensor calibration can be found here.

Sap Flow Sensor Calibration

Figure 1. A SF-4M calibrated against a SC-1 Leaf Porometer. Measured species: Hakea. R2=0.95.


continuously recording stomatal conductance measurements

Edaphic Scientific provides a complete monitoring solution where the SF-4M is connected to a data logger. The data logger controls the amount and duration of heat applied to the SF-4M sensor, and records the millivolt data from the sensor. A single data logger can support up to 16 of the SF-4M sensors. Therefore, a single data logger can potentially measure stomatal conductance, continuously, on up to 16 different leaves.

Each data logger can have telemetry communication so data can be viewed and downloaded anywhere in the world, on your PC, tablet or smart phone, as long as there is an internet connection.


example data

Figure 2 shows stomatal conductance and SF-4M data over a two day period. The red line indicates a stomatal conductance measurement with a SC-1 Leaf Porometer and the solid line indicates data recorded from the SF-4M sensor. Figure 2 demonstrates the close correlation between stomatal conductance as measured via a traditional method and the SF-4M continuous sensor.

Figure 2. An example data set displaying continuous stomatal conductance data over a two day period.


more information

Contact the scientists at Edaphic Scientific for more information on the SF-4M and how it can be integrated into your research project: