zondag 28 oktober 2012

Plant circumnutation [plant growth trajectories with Mr Charles Darwin]

Cassia corymbosa: A, plant during day; B, same plant at night.

Charles Darwin is usually only known for his theoretical work (which arguable remain of some significance) but he was also an experimentalist who worked on barnacles and earthworms with meticulous care and for extended periods of time. Another subject he took on is the movement of plants. Below are trajectories of the circumnutation of various plants. Yes I needed to look that up as well: "cicumnation: The successive bowing or bending in different directions of the growing tip of the stem of many plants, especially seen in climbing plants." It looks neat though, like GPS tracks, and the accompanying explanations, like the following, add to the flavour. Who could have though that plants grow with such sense of exploration.
Brassica oleracea: circumnutation of radicle, traced on horizontal glass, from 9 A.M. Jan. 31st to 9 P.M. Feb. 2nd. Movement of bead at end of filament magnified about 40 times.

 Brassica oleracea: conjoint circumnutation of the hypocotyl and cotyledons during 10 hours 45 minutes. Figure here reduced to one-half original scale.

Pinus pinaster: circumnutation of young leaf, traced from 11.45 A.M. July 31st to 8.20 A.M. Aug. 4th. At 7 A.M. Aug. 2nd the pot was moved an inch to one side, so that the tracing consists of two figures. Apex of leaf 14 1/2 inches from the vertical glass, so movements much magnified.

Sida rhombifolia: circumnutation and nyctitropic (or sleep) movements of a leaf on a young plant, 9 1/2 inches high; filament fixed to midrib of nearly full-grown leaf, 2 3/8 inches in length; movement traced under a sky-light. Apex of leaf 5 5/8 inches from the vertical glass, so diagram not greatly enlarged.

Averrhoa bilimbi: angular movements of a leaflet during its evening descent, when going to sleep. Temp. 78° - 81° F.

Oxalis carnosa: movements of flower-peduncle, traced on a vertical glass: A, epinastic downward movement; B, circumnutation whilst depending vertically; C, subsequent upward movement, due to apogeotropism and hyponasty combined.













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