MARTYN F. CHILLMAID / SCIENCE PHOTO LIBRARY MARTYN F. CHILLMAID / SCIENCE PHOTO LIBRARY
Rosebay willowherb (Chamerion angustifolium) in autumn. Occasionally, if autumn is bright, dry and cold, but not frosty, the rosebay willowherb will turn bright red. At the end of summer the plant will recover the chlorophylls (green) from the foliage revealing the carotenoids (yellow) and anthocyanins (red). These help to block excess sunlight energy from damaging the leaf and, in dry weather, the leaf sugars become concentrated and produce more anthocyanin producing even stronger colours. In damp, dull autumns the plant will have shed its leaves before the chlorophyll can be recovered. Rosebay willowherb produces up to 20,000 parachuted seeds that will be carried by the wind for some distance from its parent. Photographed in Reykjavik, Iceland.
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