Science - November 22, 2007

Plants have dimmer switch

Green plants protect themselves against too much sunlight by transferring energy at lightning speed to lutein, the yellow pigment in plants, and then converting it into harmless warmth. An international team of scientists, including the Wageningen biophysicist Professor Herbert van Amerongen, published its findings in Nature on Thursday 22 November.

It is the first time that researchers have managed to track this very fast molecular process, which takes place in a matter of picoseconds – a millionth of a millionth of a second. Two years ago the scientists discovered in test-tube experiments that if there is excess light, the light-harvesting complex LHCII – the protein complex that plays a key role in photosynthesis – can transfer energy by changing the structure of the protein. These findings were also published in Nature.

In the latest experiments with leaves of the model plant Arabidopsis thaliana, the scientists show how chlorophyll pigment in the light-harvesting complex absorbs the light and transfers the energy to lutein. This yellow pigment, which is only found in plants, functions as a molecular dimmer switch. The mechanism explains how plants protect themselves against damage from sunlight. The knowledge is useful for growing plants in very hot areas. The development also brings a new generation of efficient solar cells closer by.

The research team was led by biophysicist Professor Rienk van Grondelle of the VU University in Amsterdam and the British biochemist Professor Peter Horten of the University of Sheffield.