couleurs efficaces des plantes

Published online: 11 April 2007; Updated online: 12 April 2007 | doi:10.1038/news070409-7 / http://www.nature.com/news/2007/070409/full/070409-7.html

Alien plants may come in all colours but blue

Model shows the rainbow of plant life possible in the Universe.

Heidi Ledford

The local sunlight and atmosphere helps determine what colours a plant will absorb.

A picnic on a far-flung planet orbiting a red dwarf might involve spreading your blanket on black grass and munching on purple veggies, according to a new model.

Given that we have yet to find bacteria, let alone little green men or purple palms, on any other planet, it might seem slightly ridiculous to spend time working out what colour plants elsewhere in the Universe must be. But scientists say that the thought experiment could be useful in helping us to look for lush landscapes in other solar systems.

Nancy Kiang, a biometeorologist at the NASA Goddard Institute for Space Studies in New York, modelled the solar and atmospheric conditions of other planets to see which ones might be suitable for photosynthetic life, and what those photosynthesizers might look like.

Red dwarfs, for example, emit only a fraction of the visible light produced by our own Sun, meaning that plants on planets around these stars will probably hoard all the visible light they can absorb, rather than reflecting back any particular wavelength, Kiang hypothesizes. That means they would probably look black.

Is there a colour that a plant couldn't be? Kiang thinks that it's unlikely that plants will be blue, no matter what planetary environs are out there.