The lower surfaces of most leaves are covered in stomates, and while they require a good microscope to see them well, we can take a cast of a leaf surface and look at that, using either a clip-on or even a hand lens!
The cast is usually called ‘a peel’, and last century, peels were made with stuff called collodion. Now, there’s a simpler way. All you need is some clear nail polish, some sticky tape and a glass slide. Choose a leaf: it seems that most leaves work, but not Camellia, and leaves without hairs on their lower surface are best (use the hairy ones for Looking at leaves!).
Using a small amount of clear nail polish, paint a thin strip on the lower surface, about 1 cm wide and 3 cm long (accurate measures aren’t really important).
Leave the nail polish to dry for about 10 minutes, and then lay a strip of clear sticky tape over the nail polish. When you lift the tape off, the polish will come with it, and there will be a perfect cast of the leaf surface on the lower side. When you attach the tape to a glass slide, you are ready.
The tape, loaded with nail polish, is ready to go on the microscope slide.
Above, you can see two views of a peel from the lower surface of a bay leaf, at x100 and x400 (the inset).
Stomates let carbon dioxide in and oxygen out. They also let water vapour escape, so plants need to control their stomates, which are very tiny, about 0.05 mm (1/20 mm) across, so you won’t see them with the naked eye. Still, once you know what you are looking for, you can see them with a good hand lens, but only as closely-packed dots.
Sometimes research is just trying out ideas, and that was the case when I tried looking for stomates on fishbone fern. They are indeed there, but another form of scientific research involves reading ‘the literature’, the things other scientists have seen, noticed or discovered. That revealed that other people had already seen fern stomates. I found it has clear stomates on the under-side.
Another literature search told me that the very best plant for this exercise is Tradescantia pallida, a garden favourite with purple leaves, and one that grows easily from cuttings. Here on the left is what you can see of Tradescantia pallida with a clip-on at x15 and x65 (in the inset). Then I reached for a microscope, and the results are on the right. The same ‘peel’ is now seen through a high-end monocular microscope, at x40, x100 and x400. This is better!
Once you see this, the clip-on and hand lens views will make sense. Each stomate looks like two fat sausages (or lips) lying side by side: when they curve around, the stomatal pore opens and gases go in and out. The stomate is made up of two guard cells: these are the ‘lips’ of the ‘mouth’, but in Tradescantia pallida, there are two other cells, one at each end, making a rectangle.
It turns out that you can see the stomates on the plant’s actual leaf with a clip-on, if you know what you are doing! The shot above is not a peel: it is the actual plant that is under a clip-on. The first shot is with no digital zoom, the second is with full zoom. Look for the pale squares. This view is looking at the leaf itself, with reflected light. The stomates are the pale square shapes. The stomates are very visible at x60, but you can even see them with a hand lens offering x10, if you know what you are looking for.
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