The Journal of Young Investigators: An Undergraduate, Peer-Reviewed Science Journal
Volume 20, Issue 3. September 2010
Plants’ Internal SPF Explained
Leaves, such as these beech leaves, avoid sunburn through an internal energy-dispersing mechanism called photoprotection. A new study revised the previous model of plants’ “sunscreen” by revealing that carotenoids, the molecules involved, do not have to become charged for the process to be successful. Image courtesy of Nick Fraser.
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26 June 2006 -
For humans, the arrival of summer means slathering on sunscreen to avoid burns from the sun’s intense rays. Such external protection is unnecessary for plants as they possess photoprotection, an internal defense mechanism provided by molecules called carotenoids. Now, a study in the Proceedings of the National Academy of Sciences offers a new understanding of how plants’ “sunscreen” works.
Carotenoids are pigments that, in addition to imparting yellow to red colors, normally assist plants’ chlorophyll in capturing the sun’s energy through photosynthesis. It was long known they also prevent sunburn by dispersing excess energy away from plants’ most susceptible parts in the form of electrons.
The prior model of photoprotection suggested that carotenoids are oxidized, or become charged particles, by losing electrons. In the recent study, Iris Visoly-Fisher, a postdoctoral research associate in the Biodesign Institute at Arizona State University, developed a method to measure the electrical conductance of carotenoids. Though oxidation enhanced the process, Fisher found pigments can also successfully protect plant tissues while remaining uncharged molecules.
“The result is quite unexpected," said Stuart Lindsay, an author of the study. "Carotene [a type of carotenoid] was regarded as the poster child for this molecular mechanism, but it turns out that a much simpler mechanism works just fine."
Fisher measured the transport of a single electron through a carotenoid molecule, while controlling whether the molecule was in a charged or neutral state. He found carotenoids, while far less conductive than substances such as metals, are more than sufficient to carry out photoprotection, and the speed of electron conductance measured in isolated conditions was similar to that measured within plants. The study was technically complex, as carotenoids react quickly with both water and oxygen, and must be protected from the environment as well as kept under conditions resembling a plant cell.
"The importance of this result is not only for understanding natural systems and photosynthesis, but also for the fact that technically, for the first time, we could hold a molecule in a state pretty close to the natural conditions found in the plant," explained Fisher.
Carotenoids are pigments that, in addition to imparting yellow to red colors, normally assist plants’ chlorophyll in capturing the sun’s energy through photosynthesis. It was long known they also prevent sunburn by dispersing excess energy away from plants’ most susceptible parts in the form of electrons.
The prior model of photoprotection suggested that carotenoids are oxidized, or become charged particles, by losing electrons. In the recent study, Iris Visoly-Fisher, a postdoctoral research associate in the Biodesign Institute at Arizona State University, developed a method to measure the electrical conductance of carotenoids. Though oxidation enhanced the process, Fisher found pigments can also successfully protect plant tissues while remaining uncharged molecules.
“The result is quite unexpected," said Stuart Lindsay, an author of the study. "Carotene [a type of carotenoid] was regarded as the poster child for this molecular mechanism, but it turns out that a much simpler mechanism works just fine."
Fisher measured the transport of a single electron through a carotenoid molecule, while controlling whether the molecule was in a charged or neutral state. He found carotenoids, while far less conductive than substances such as metals, are more than sufficient to carry out photoprotection, and the speed of electron conductance measured in isolated conditions was similar to that measured within plants. The study was technically complex, as carotenoids react quickly with both water and oxygen, and must be protected from the environment as well as kept under conditions resembling a plant cell.
"The importance of this result is not only for understanding natural systems and photosynthesis, but also for the fact that technically, for the first time, we could hold a molecule in a state pretty close to the natural conditions found in the plant," explained Fisher.
Journal of Young
Investigators. 2008. Volume 0.
Copyright © 2008 by Wear Emma and and JYI. All rights reserved.
Copyright © 2008 by Wear Emma and and JYI. All rights reserved.