Room for improvement

Copyright © Charles Tambiah (All rights reserved - Worldwide).Gas exchange machines, as any other technology, are open to many sources of error, which means that a deep understanding of how the machines work and how to detect that something is not right is essential to ensure that the data obtained is sound. Poor calibration, leaks, control of temperature, extrapolation of results are some of the problems mentioned by scientists that have used them in a variety of conditions.

“Gas leaks through gaskets can also pose problems, especially when measuring outdoors in very windy area. In some instruments humidification of the airstream can be difficult, says von Caemmerer.

Another challenge is that we are usually only measuring a very small proportion of a leaf, but the photosynthetic activity of a plant can vary significantly depending on where on the plant or even on a single leaf we are measuring.

This problem is highlighted by Farquhar “The results obtained are an integration of the two sides of the leaf, which doesn’t reflect its reality as the two sides can behave quite differently.” “This means one always needs to be alert”, says von Caemmerer.

Finally, even though the machines have shrunk in size enormously, they are still not light and trying to measure hundreds of plants in the field is quite cumbersome. “It takes up to 5 minutes or even longer for a measurement to stabilise and if you are trying to measure many genotypes in a day that can be very limiting”, says George-Jaeggli.