Plants on distant hospitable planets could have developed black foliage and flowers to survive,

Plants on distant hospitable planets could have developed black foliage and flowers to survive, according to a new study.

Flora that would appear black or grey to human eyes could have evolved on planets orbiting dim "red dwarf" stars, according to unpublished research that is being presented at the National Astronomy Meeting in Llandudno, Wales.

This would enable plants to absorb more light to photosynthesise, using their star's light to convert carbon dioxide into organic compounds.

Jack O'Malley-James, a PhD student and astrobiologist at St Andrews University, focused on multiple star systems thought to be common throughout the universe.

He used models for star systems with two or three stars with various combinations of Sun-like and red dwarf stars. He then added planets to these models, orbiting around one or more of the stars.

Exotic plantlife
The research presumes first that plant life similar to that on Earth could evolve on an exoplanet in the "habitable zone" around its star - which is not a given, but the odds of which are difficult to estimate.

The idea then is that photosynthesis there would resemble that seen on our own planet, whereby plants use energy from the Sun to convert carbon dioxide and water into oxygen and organic compounds, such as sugars.

Flora on those planets would have to adapt to very different light conditions in order to photosynthesise.

"If a planet were found in a system with two or more stars, there would potentially be multiple sources of energy available to drive photosynthesis," said O'Malley-James.

"The temperature of a star determines its colour and, hence, the colour of light used for photosynthesis. Depending on the colours of their starlight, plants would evolve very differently."