The Microscopist's Mate, part 5 of many

Just for the record, all of what you find here, and in the other blogs in this series, is now available in fuller detail in my e-book Looking at Small Things.  Go to this link to find out more about how to get the free low-resolution copy, or the cheap high-resolution version: I'm a professional writer, so I like selling books, but I'm also a professional educator, so I like sharing ideas.

There's a similar free or cheap deal on offer for my Playwiths ebook as well, and to see what else I have been doing (LOTS!), go to this link.

Here are the links to Part 1, Part 2, Part 3 and Part 4.

Sorry about the delay, but I have been busy having fun, like this study, where I was looking at stomates, the little pores on leaves that plants breathe through, and which you can see above. Now I have started writing up.

You need some suitable leaves, clear nail polish, clear sticky tape, a piece of glass like a microscope slide, a device and a Go Micro.

Risks and dangers: Spillage or sniffing of the nail varnish. If you have never mentioned Material Safety Data Sheets before,  search on <MSDS acetone>. Microscope slides are fragile, and cuts are possible.

Stomates (or stomata) are pores that are mainly found in the lower surfaces of leaves, and they let carbon dioxide in and oxygen out. They also let water vapour escape, so plants need to control their stomates, which are very tiny. One of the best is a common garden plant with purple leaves, known as Tradescantia pallida.

Old botanists say it has large and clear stomates, ones that can be seen with a 30x hand lens. The stems break off easily, and when pushed into the ground, they take root.

This is what the plant looks like.

The flowers of Tradescantia pallida.

The lower surface of most leaves will be rich 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. All you need is some clear nail polish, some sticky tape, a microscope slide and a way to light the slide from below.

Stomates are very small, about 0.05 mm (¹/₂₀ mm) across, so you won’t see them with the naked eye, but once you know what you are looking for, you can see them with a good hand lens, just as closely-packed dots. The cast, by the way, is usually called “a peel”, and in my youth, they were made with stuff called collodion.

Now, there’s a simpler way, but I will take you through some of my steps, including some false ones.

Choose a leaf: most leaves work, but ones without hairs on their lower surface are probably best, and if you can find that purple Tradescantia anywhere, get a leaf of that.

Then, using a small amount of clear nail polish, paint a thin layer on the lower surface, no more than 1 cm wide and 3 cm long (size isn’t really important). Leave this to dry for about 10 minutes, then press a strip of clear sticky tape down over the nail polish. I used ivy first, then a Camellia and a bay leaf. 

It is worth noting in passing that with a bit of effort, you can break a Camellia leaf in the same way as breaking a piece of onion (I'll get to that some other time), to yield a small scrap of real epithelium, the leaf’s surface layer.

The bay leaf was better. Those tiny dots are stomates, and the first picture below is like the unconvincing view from a hand lens, taken through the Go Micro with no digital zoom.

The next one is at full digital zoom with the Go Micro: this is a bit more convincing!

So you can see these stomates with the Go Micro, but to show you what is visible with a professional level microscope, there is a shot on the next page of a peel from a bay leaf, taken at x100, though the lower right inset is at x400. Once you see this, the lower magnification views will make sense. Each stomate looks like two fat sausages (the guard cells) lying side by side: when they curve around, the stomatal pore opens and gases go in and out.

Two views of a peel from the lower surface of a bay leaf, at x100 and x400 (inset).

As I said, the best plant (and certainly the best I have found so far) for this exercise is Tradesacantia pallida, a purple garden favourite with purple leaves, and one that grows easily from cuttings. Here is what you can see with the 60x at two magnifications:

Stomates of Tradescantia pallida, seen with the 60x.

The rig for this: the slide sat on jar with a light source and a diffusing film, my phone sat on top of the two boxes and the lens rested on the microscope slide.

The same slide, seen through a high-end microscope, at 40x, 100x and 400x

Each 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 is important to note this, because it turns out that you can see the stomates on the plant’s actual leaf with the Go Micro, if you know what you are doing! The next two shots are looking at the actual leaf surface, with the gadget.

This view is looking at the leaf itself, with reflected light. The stomates are the pale square shapes.

Here, the stomates are very visible at x60, but you can even see them, once you know what you are looking for, with a 10x handlens. I think that’s neat!