A New Null Balance Leaf Porometer for Measuring Stomatal Conductance.

Stomatal conductance is useful for understanding plant response to environmental factors, transpiration rates under varying conditions, and as a way to infer plant stress. Porometers are an important tool used for measuring stomatal conductance of plant leaves. There are varying types of porometers, with one type, the null balance porometer, having especially attractive characteristics, including good performance over a wide range of environmental conditions.  Previously commercialized null balance porometers were large and bulky, requiring shoulder straps and heavy batteries. We have designed a new null balance porometer which is small, lightweight, low power, and strapless, making it easier and more comfortable to use.

The new porometer utilizes a small piezo electric blower, which reduces weight, power consumption, and cost.  Fast response humidity sensors, small cuvette volume, and cuvette mixing fan work together to give quick measurements.  Additionally, dual humidity sensors minimize error and reduce desiccant waste. Lastly, leaf temperature is measured directly using an infrared radiometer, eliminating fragile thermocouples, contact errors in estimating leaf temperature, and greatly increasing conductance measurement accuracy.