Tiny little mouths. Swarms of them on every leaf, gaping wide open or clamping shut in order to keep their plants alive. They’re called stomata and help prevent plants from losing so much water that they dehydrate whilst allowing enough carbon dioxide into leaves that they can continue the amazing job of making their own food from what is essentially fresh air, water and sunshine. They allow plants to live on land and do things like survive droughts or forgetful gardeners and could play a big part in aiding adaptation to climate change, making them topical and important.
So, what actually are these mysterious structures? They’re basically pores on the surface of plants that let air in and out. One stoma comprises of two guard cells which control how open the pore is, an air cavity underneath that and, sometimes, a whole lovely bunch of other cells and maybe even other stomata. The science behind what controls their closing and opening is really quite complicated but what it boils down to essentially, is that when there’s more water about they open and when there’s less, they close. This is helped by their guard cell wall properties (see caption below).
As a picture is worth a thousand words (most of them about my mental age) here’s one which might make things a little clearer:
This picture also illustrates why I’m rambling about these cute little things. My MSc research project is focussed on better understanding how stomata develop in Begonia and so, for the next 2-3 months I’ll be eating, breathing and living stomata science.
As part of this I get to work with some very exciting bits of kit like a scanning electron microscope, with which I took the picture above. Preparing the samples for SEM is almost as fun as photo shopping googly eyes onto the resulting pictures, as it involves exposing your leaves to a horrifying amount of ethanol, marinating them in liquid CO2 and then coating them in platinum using a machine seemingly designed purely to mimic an alien abduction. You then load them onto a sample holder which bears more than a passing resemblance to the Starship Enterprise and BLAST THEM WITH ELECTRONS in a vacuum. Science is ridiculous when you stop to think about it.
I realise this post departs somewhat from the usual crazy plants theme of this blog, but as stomata are basically all I think about these days, it made sense somewhere in my SEM-mangled brain to write about them.
Disclaimer: Terrible Pun courtesy of my undergrad dissertation supervisor Howard, on Twitter @GriffithsHoward.
SEM image taken by yours truly on Kew’s glorious SEM.