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Cornucopia - Movement in plants

Movement in plants
Peggy Dawe

One may notice how flowers turn or grow towards the light but there are a lot of other ways that they can be seen to move. I have long been interested in the way plants move. I suppose this fascination started when I was a child and my father showed me how the evening primrose (Oenothera biennis) begins to open its flowers as the air cools on a summer evening. The petals in the bud build up a visible tension which makes them switch backwards in visible jerks and movements. Finally the sepals snap backwards against the stem. I have watched, photographed and drawn these happenings. On a cool summer evening the flower can emerge fully in about twenty minutes from the start of the process.

Most other plants are not so visibly quick. I enjoy watching the seeds of Erodium gruinum as they wind themselves round to push into the soil well away from the parent plant. If I can spot a ripening seedhead and detach one of the very long-tailed seeds before they shoot away, I will just push its tip into a piece of oasis and quite soon see it gradually rotate its long tail (maybe 3" long) until wound into a tight twist. This action is presumably to drive the seedhead into the ground. It can take about one minute for each rotation. As it is this slow I could watch and time it while I was busy in the kitchen.

Cyclamen seed heads are interesting too, as they gradually coil up, bringing the seed pod close to the parent plant. Most coil inwards from the pod tip but Cyclamen rohlfsianum coils first at the base of the seedhead stem, pulling the seed pod gradually inwards. Cyclamen flowers are another delight. They are too slow to actually watch but again the tension of the petals is very obvious as they separate and then pull backwards.

This year I have a large amaryllis bulb given to me at Christmas and what seems intriguing to me about this is that, although growing indoors near the window, the stem leans a little but the flowers do not move at all in relation to the light. The four flowers at the top of the stem ignore the light and face firmly north, south, east and west. I wonder how they can be so uncaring of the direction of light.

Another plant, new to me, that I have on my windowsill is Parochetus communis. I bought this little plant for its glorious azure blue flowers, now long over, but its leaves interest me. As it belongs to the Papilionaceae it has little clover-shaped leaves. About dusk the leaves begin to fold up for the night and they do it beautifully. First the centre leaflet turns to a vertical position between the other two. Then these others gently fold inwards to enclose the first, making a flat pack of the three. They take about 30 minutes to do this and reopen the next morning. I wonder if other leguminous plants do this.

These are a few of my favourite things!

First published in the Correspondents’ Group Newsletter, March 2009
and subsequently in Cornucopia Issue 27.
© Copyright for this article: Peggy Dawe

This article was taken from a copy of Cornucopia that was published in 2011. You could be reading these articles as they are published to a national audience, by subscribing to Cornucopia.


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