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Current Affairs

How plants dissipate excess sunlight as heat

Date: 11 March 2020 Tags: Miscellaneous

Issue

Researchers at MIT, the University of Pavia, and the University of Verona have directly observed one of the possible mechanisms through which plants dissipate extra sunlight.

 

Background

Photosynthesis is a life-sustaining process by which plants store solar energy as sugar molecules. If sunlight is in excess, it can lead to leaves being dehydrated and damaged. To prevent such damage, plants dissipate extra light as heat.

 

Details

  • The new research has been able to determine, by using a highly sensitive type of spectroscopy, that excess energy is transferred from the pigment chlorophyll, which gives leaves their green colour, to other pigments called carotenoids.

  • During photosynthesis, light-harvesting complexes play two seemingly contradictory roles. They absorb energy to drive water-splitting and photosynthesis, but at the same time, when there’s too much energy, they have to also be able to get rid of it.

  • Previous research has shown how plants quickly adapt to changes in sunlight intensity. Even in very sunny conditions, only 30 per cent available sunlight is converted into sugar, and the rest is released as heat.

  • The excess energy, if not released, leads to the creation of free radicals that can damage proteins and other important cellular molecules.

  • Researchers developed a modification to a femtosecond spectroscopic technique, which allowed them to observe over a broader range of energy levels, spanning from red light to blue light.

  • Using the new technique, researchers could observe that chlorophylls absorb red light and carotenoids absorb blue and green light, thus being able to monitor energy transfer.

  • Broadening the spectral bandwidth, scientists could look at the connection between the blue and the red ranges, allowing us to map out the changes in energy level.