# Chalk talk: How to measure leaf transpiration

In his latest chalk talk video, Dr. Colin Campbell discusses why you can’t measure leaf transpiration with only a leaf porometer.

He teaches the correct way to estimate the transpiration from a single leaf and how a leaf porometer can be used to obtain one of the needed variables.

**Watch the video**

## Video transcript

Hello, my name is Colin Campbell. I’m a senior research scientist here at METER Group. And today we’ll talk about how to estimate the transpiration from a single leaf. Occasionally we get this question: Can I estimate the transpiration from a leaf by measuring its stomatal conductance? Unfortunately, you can’t. And I want to show you why that’s true and what you’ll need to do to estimate the total conductance, and therefore, the evaporation of a leaf.

The calculation of transpiration (E) from a leaf is given by Equation 1

where *g _{v}* is the total conductance of vapor from inside the leaf into the air,

*C*is the concentration of vapor inside the leaf and

_{vs}*C*is the concentration of vapor in the air.

_{va }**Learn more about canopy measurements**

Download the researcher’s complete guide to leaf area index—>

## Questions?

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