Wednesday, August 5, 2009

Harebell Sex-Change




Over at Stand and Stare (http://standandstare-nyctalus.blogspot.com/2009/08/humble-harebell.html) Nyctalus has recently been extolling the virtues of The Humble Harebell. It’s worth taking a close look at harebell flowers because they have a really neat fail-safe method of ensuring that they’re pollinated. When the flower is still in bud the style, with a closed stigma at its tip, is surrounded by five stamens that begin to shed pollen. As the style - which is hairy on the outside- elongates inside the bud it forces its way through the tube of stamens surrounding it, sweeping the pollen from their surface. So when the flower opens it looks like the one in the bottom photo, and any insect forcing its way down to the bottom of the harebell bell will pick up pollen from the outside of the style. At this stage the flower is functionally male, dispensing pollen. Once the pollen is all gone the tip of the style splits into three lobes that curl back (top photo) and now the flower has effectively become female, ready to receive pollen on one of those three stigma lobes from a visiting insect. But what if no pollen-laden insects turn up? No problem; those stigma lobes just keep curling back until they pick up any residual pollen that’s still left on the outside of the style, so the flower self-pollinates. Harebells are quite easy to grow from seed and if you do raise some you’ll see why their Latin name is Campanula rotundifolia, even though the plant has long, grass-like leaves: the leaves in the seedling rosette are indeed rotund.

4 comments:

  1. I saw some of these a couple of weeks ago when I went to Norfolk. They're a lovely flower, and I never knew that about the self pollination. Fascinating.

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  2. Hi Keith, I think most Campanulas have a similar pollination mechanism, including Canterbury bells.

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  3. Hi Phil. Bit slow in catching up with this but thanks for that intriguing follow-up post. I'll enjoy the harebells all the more for knowing that.

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