#60 June 2022 Garden Stuff - © Sandy Lang - slang@xtra.co.nz
LIGHT MICROSCOPYThis article was written to be read in conjunction with my ‘Garden Stuff’ article SCALES, first published in the Eastbourne Herald.As you will already have discovered, Garden Stuh articles are not always very ‘gardeny’. But this one is so ‘un-gardeny’ I didn't have the cheek to publish it there in the pretence it was about gardening.Next, I did a Google search but didn't find any introductory tips on light microscopy. Maybe nobody does 'home' light microscopy any more (popular 100 years ago)...? A pity. It's been a great joy to me...!Lastly, the Herald doesn't let me mention company names - fair enough. In doing so here, I’m not seeking to promote particular products or companies - I’m just trying to get you started. A simple, cheap light microscope: Recent advances in high-quality, aspheric, plastic lenses (a spin off from mobile-phone camera development) now bring us simple, cheap, light microscopes. There are several of these on the market. One such is the Carson 60-120x LED lighted MicroBrite Plus Pocket Microscope, currently available at NZ$44.98 (see photo below) This simple light microscope will zoom from x60 to x120 and incorporates a bright LED light. This instrument is cheap and simple but it’s not a toy – it really works. But it’s just a bit fiddly compared with a professional microscope.
The Carson microscope is not as good as my professional microscope – but then it’s only about 1% of the price. But the Carson microscope is quite a bit better than my antique (Victorian) portable microscope (see below) and very much cheaper than it would have been. See photos at the bottom of this page...
Carson makes a range of similar products with different features. The more you pay, the more you get. Maybe start cheap and, if you want to do more light microscopy, then go for a more expensive instrument next time round.
Slides and cover slips: Most biological specimens are wet. To see the microscopic detail requires you must have thin samples. These dry out rapidly. You can put a drop of water on them to stop them drying and shrivelling. But the curved surface of the water drop works like a bad lens, so it severely distorts what you are trying to see.
The way round this is: (1) to place your sample on a glass microscope ‘slide’, put a tiny drop of glycerine on it, then (2) carefully place a glass ‘cover slip’ on top. The two flat glass surfaces and the glycerine allow light to pass right through your specimen with no distortion. And the glycerine will never dry out (it absorbs moisture from the air). Your slide will last for years if you don't drop it - put it in a box to keep it dust free... Glycerine (also called glycerol) is non toxic and available from any pharmacy for under NZ$10. You can't seem to buy slides and coverslips from the regular scientific suppliers as they're not intersted in retail (their clients are laboratories who order in bulk). If you are interested, I can buy and retail to you at cost. A box of 50 microscope slides (reusable) and a box of 200 coverslips (not really reusable) cost under NZ$50.
Sample preparation: You will see best if the sample on the slide is very thin. This way, the detail in the top layer of the sample is not confused by a load of just-out-of-focus detail below. There are several ways to get what you want...• Sections - Cut a super-thin slice with a new (sharp) razor blade. You know how when slicing a loaf of bread, a crooked cut will sometimes break through the surface, giving you a wedge-shape slice with a very thin edge? This is just what you want...! The very thin edge of your slice is the bit you will look at...• Peels – The outer layer of cells (epidermis) on many plant organs is stronger than the layer just below. With a pair of tweezers, you can rip off a bit of skin. Say, off a leaf, and you will get a patch of the outer cell layers of the leaf skin, but the edges of this patch will likely be only one cell-layer thick (epidermis). This edge bit is just what you want to look at…• Casts – The surfaces of most plant organs are slightly bumpy, with the individual cells each looking like a little, curved mound. If you apply a thin layer of clear nail varnish to the plant surface, let it dry thoroughly, then peel it off with tweezers, you will get a very good cast of these cells. Look at the cast under your microscope and you will see all the detail... Another way to do this is with Sellotape and acetone (hardware store). Stick tape to a glass slide, add a drop of acetone, wait a few seconds (while acetone dissolves the cellulse tape), press on a leaf (e.g.), then peel it off. The softened cellulose tape soon hardens retaining a beautiful imprint of the fine texture of the leaf. • Loose stuff – The surfaces of many plant organs are covered with fine hairs. Gently, but firmly, press a piece of clear Sellotape onto the plant surface, peel it off, the tiny hairs will be clearly visible attached to the sticky side of the tape...
Some interesting samples: The inner epidermis of an onion scale; a petal; an anther; a stigma; a wood shaving; a moss leaf; a feather; a drop of water from a muddy puddle; a fly’s leg; a fly’s eye; the 'umbrella' hairs on the bottom of an olive leaf (try the Sellotape trick for this one)…
Scale: It is useful to know how big the things are you are looking at. Use your microscope to look at a mm ruler. Write down how many mm it is from one side of the circular image to the other – for the Carson microscope (above) the circular image is about 2 mm diameter at x60 and about 1 mm diameter at x120. There are 1,000 µm (micrometres) in one 1 mm (millimetre). Get used to thinking of the things you see as being so many µm long or wide or across.
Some general tips for your microscope: • Never touch the lenses with your fingers. • If the lenses get dirty, wipe them with a new tissue (no grit). Dampen with clean water. Don’t use spit. Never use a solvent - these are plastic lenses and will be ruined by solvents.• Always start at minimum magnification then, when you’ve decided the bit you want to look at more closely, increase the magnification.• The higher magnification will certainly make things bigger but it will not necessarily make them any clearer. It depends on how good your sample is.• Try different lighting. Sometimes it’s best to have a white background behind the sample (e.g., white paper). Sometimes it’s best to have a dark background behind it (e.g. dark paper - a dark area of a photo from a glossy magazine).• Cover your microscope when not in use. You don’t want dust on the lenses. __________________________________
LIGHT MICROSCOPYThis article was written to be read in conjunction with my ‘Garden Stuff’ article SCALES, first published in the Eastbourne Herald.As you will already have discovered, Garden Stuh articles are not always very ‘gardeny’. But this one is so ‘un-gardeny’ I didn't have the cheek to publish it there in the pretence it was about gardening.Next, I did a Google search but didn't find any introductory tips on light microscopy. Maybe nobody does 'home' light microscopy any more (popular 100 years ago)...? A pity. It's been a great joy to me...!Lastly, the Herald doesn't let me mention company names - fair enough. In doing so here, I’m not seeking to promote particular products or companies - I’m just trying to get you started. A simple, cheap light microscope: Recent advances in high-quality, aspheric, plastic lenses (a spin off from mobile-phone camera development) now bring us simple, cheap, light microscopes. There are several of these on the market. One such is the Carson 60-120x LED lighted MicroBrite Plus Pocket Microscope, currently available at NZ$44.98 (see photo below) This simple light microscope will zoom from x60 to x120 and incorporates a bright LED light. This instrument is cheap and simple but it’s not a toy – it really works. But it’s just a bit fiddly compared with a professional microscope.
The Carson microscope is not as good as my professional microscope – but then it’s only about 1% of the price. But the Carson microscope is quite a bit better than my antique (Victorian) portable microscope (see below) and very much cheaper than it would have been. See photos at the bottom of this page...
Carson makes a range of similar products with different features. The more you pay, the more you get. Maybe start cheap and, if you want to do more light microscopy, then go for a more expensive instrument next time round.
Slides and cover slips: Most biological specimens are wet. To see the microscopic detail requires you must have thin samples. These dry out rapidly. You can put a drop of water on them to stop them drying and shrivelling. But the curved surface of the water drop works like a bad lens, so it severely distorts what you are trying to see.
The way round this is: (1) to place your sample on a glass microscope ‘slide’, put a tiny drop of glycerine on it, then (2) carefully place a glass ‘cover slip’ on top. The two flat glass surfaces and the glycerine allow light to pass right through your specimen with no distortion. And the glycerine will never dry out (it absorbs moisture from the air). Your slide will last for years if you don't drop it - put it in a box to keep it dust free... Glycerine (also called glycerol) is non toxic and available from any pharmacy for under NZ$10. You can't seem to buy slides and coverslips from the regular scientific suppliers as they're not intersted in retail (their clients are laboratories who order in bulk). If you are interested, I can buy and retail to you at cost. A box of 50 microscope slides (reusable) and a box of 200 coverslips (not really reusable) cost under NZ$50.
Sample preparation: You will see best if the sample on the slide is very thin. This way, the detail in the top layer of the sample is not confused by a load of just-out-of-focus detail below. There are several ways to get what you want...• Sections - Cut a super-thin slice with a new (sharp) razor blade. You know how when slicing a loaf of bread, a crooked cut will sometimes break through the surface, giving you a wedge-shape slice with a very thin edge? This is just what you want...! The very thin edge of your slice is the bit you will look at...• Peels – The outer layer of cells (epidermis) on many plant organs is stronger than the layer just below. With a pair of tweezers, you can rip off a bit of skin. Say, off a leaf, and you will get a patch of the outer cell layers of the leaf skin, but the edges of this patch will likely be only one cell-layer thick (epidermis). This edge bit is just what you want to look at…• Casts – The surfaces of most plant organs are slightly bumpy, with the individual cells each looking like a little, curved mound. If you apply a thin layer of clear nail varnish to the plant surface, let it dry thoroughly, then peel it off with tweezers, you will get a very good cast of these cells. Look at the cast under your microscope and you will see all the detail... Another way to do this is with Sellotape and acetone (hardware store). Stick tape to a glass slide, add a drop of acetone, wait a few seconds (while acetone dissolves the cellulse tape), press on a leaf (e.g.), then peel it off. The softened cellulose tape soon hardens retaining a beautiful imprint of the fine texture of the leaf. • Loose stuff – The surfaces of many plant organs are covered with fine hairs. Gently, but firmly, press a piece of clear Sellotape onto the plant surface, peel it off, the tiny hairs will be clearly visible attached to the sticky side of the tape...
Some interesting samples: The inner epidermis of an onion scale; a petal; an anther; a stigma; a wood shaving; a moss leaf; a feather; a drop of water from a muddy puddle; a fly’s leg; a fly’s eye; the 'umbrella' hairs on the bottom of an olive leaf (try the Sellotape trick for this one)…
Scale: It is useful to know how big the things are you are looking at. Use your microscope to look at a mm ruler. Write down how many mm it is from one side of the circular image to the other – for the Carson microscope (above) the circular image is about 2 mm diameter at x60 and about 1 mm diameter at x120. There are 1,000 µm (micrometres) in one 1 mm (millimetre). Get used to thinking of the things you see as being so many µm long or wide or across.
Some general tips for your microscope: • Never touch the lenses with your fingers. • If the lenses get dirty, wipe them with a new tissue (no grit). Dampen with clean water. Don’t use spit. Never use a solvent - these are plastic lenses and will be ruined by solvents.• Always start at minimum magnification then, when you’ve decided the bit you want to look at more closely, increase the magnification.• The higher magnification will certainly make things bigger but it will not necessarily make them any clearer. It depends on how good your sample is.• Try different lighting. Sometimes it’s best to have a white background behind the sample (e.g., white paper). Sometimes it’s best to have a dark background behind it (e.g. dark paper - a dark area of a photo from a glossy magazine).• Cover your microscope when not in use. You don’t want dust on the lenses. __________________________________