Wednesday, March 31, 2010

Botanical Flypaper

The tiny insect in the photo above, just a couple of millimetres long, is doomed. Its body and wings are held fast by the sticky leaf hairs of.....
.... this plant, a butterwort Pinguicula moranensis that originates from Guatemala and Mexico. Like all butterworts, it captures small insects on its leaf surface and then, when they die of exhaustion, slowly digests them.
Almost the whole of the plant surface is covered with these minute stalked hairs, of varying heights for maximum trapping efficiency,each tipped with a droplet of sticky mucilage.
Seen here at higher magnification and in side view, each bottle-shaped hair is composed of a single cell rising from one of the surface epidermal cells, topped with a glandular cap that at higher magnification still...
... is revealed to be made up of eight separate secretory cells, each shaped like a slice of cake, perched on the top of the stalk. Meanwhile, down below and embedded in the leaf surface.......
... there's a different kind of gland, seen here in surface view amongst the jigsaw puzzle-shaped epidermal cells of the leaf. Each leaf upper surface is studded with hundreds of these glands. Once and insect is trapped the glands nearby........
..... like this one, seen here in side view at higher magnification, secrete digestive enzymes. When the insect finally dies....
... it collapses into the pool of digestive enzymes and is slowly dissolved, until only its outer chitin exoskeleton remains, like a ghost of the plant's victim. Then the plant absorbs the resultant 'soup', rich in the essential nitrogen that's lacking in this carnivorous plant's boggy habitat. However, not all insects succumb so easily. The plants in my conservatory almost always host...
... small colonies of to these tiny aphids. Even though they are held fast, they can still use their piecing mouthparts to puncture the plant's cells and feed, and survive long enough to produce the next generation of young, which are born by virgin birth (parthenogenesis) without the need for mating.  If you double-click on this image for a larger view you'll see a pair of minute claws at the tip of each aphid leg. On most host plants these would allow the aphid to grip the plant surface and walk, but the epidermal cells of butterwort are so smooth and slippery that the claws cannot grip. If you watch under a microscope, you can see the claws simply sliding over the plant surface, so the anchored aphid can do nothing other than feed and breed before it eventually dies, leaving a ghostly shell and a clone of itself behind.


Butterworts' flypaper-like properties make them very useful plants to grow if you are troubled by the tiny mushroom flies that emerge from potting composts - a single plant will trap and kill scores of them.

4 comments:

  1. Great photos, Phil. And their story. We got these plants a few miles from my house. They grow in peace and quiet by people not being able to visit the wet bogs.
    Not a very healthy area for my wheels so.

    Did your last photo not make it through? Pity!

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  2. Amazing plants. aren't they Yoke. We've got a small area of bog not far away from us that has sundews growing in it in summer.

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  3. Thanks for this explanation of the eating habits of this great plant. I grew one last year and it must have been well fed as it bloomed non stop all Summer and Fall.

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  4. Hi barry, it's a wonderful plant - I've found that you can propagate it simply by pulling off leaves and laying them on damp sand - small plants form at the base of the leaf.

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