Imaging trichomes

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Published on: December 13, 2012
cryo-scanning electron microscope image of a trichome on an Arabidopsis leaf

Even if you don’t work on trichomes, you have definitely experienced them first-hand, as stings on nettles are trichomes that have evolved down a particularly nasty route. Other trichomes pack less of a punch, but they are still important for phytochemical production and herbivore defence.

Arabidopsis trichomes are rather more tame than stinging nettle trichomes, and present an excellent way to study cell differentiation as well as being a target for crop improvement. But although trichomes are easy to see using light microscopy, they are difficult to study. Manually counting them and recording their length and position is tiresome in the extreme, and imaging technologies tend to require specialized skills and software that not all labs can access.

In today’s highlighted paper, Pomeranz et al. present a new method of analysing trichomes consisting of polarizing light microscopy (PLM) and a web-based imaging tool. In fact PLM is an old technique described by Ballard in 1916, and is an excellent way of imaging trichomes because of the highly crystalline cellulose in trichome cell walls which confers polarizing (birefringent) properties. As the authors say, this new technique is a ‘repurposed’ method, and the key to the novel technique is the online resource TRICHOMENET, which allows imaging and easy analysis of trichomes, and can be linked with ImageJ.

It certainly appears that this method would be easy to set up in any lab. Preparing samples for PLM involves methanol or ethanol, lactic acid, and a water bath – the method is in the paper or in Bischoff et al. (2010). PLM itself requires polarizing filters, which can be bought in a kit, for example from Motic, or as individual filters. The image is then uploaded to TRICHOMENET, which guides the user through counting the trichomes. Once the data is recorded, TRICHOMENET can analyse trichome positional data, density, and distances.

Highlighted article: Marcelo Pomeranz, Jeffrey Campbell, Dan Siegal-Gaskins, Jacob Engelmeier, Tyler Wilson, Virginia Fernandez Jelena Brkljacic, and Erich Grotewold (2012) High-resolution computational imaging of leaf hair patterning using polarized light microscopy. The Plant Journal ‘Accepted Article’, doi: 10.1111/tpj.12075

Image credit: Emmanuel Boudet.

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