Plants produce their own natural sunscreen to protect against ultraviolet radiation

Wednesday, February 03, 2016 by: David Gutierrez, staff writer
Tags: plant defenses, natural sunscreen, ultraviolet radiation

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(NaturalNews) Scientists are beginning to uncover the mechanisms by which plants -- which depend upon sunlight to provide them with energy -- protect themselves from the damaging effects of the sun's ultraviolet rays. Most recently, in a study published in the Journal of the American Chemical Society, researchers from Purdue University helped illuminate the function of "natural sunscreens" that plants produce and use to protect their leaves.

For some time, researchers have known that the fact that plants get their energy from the sun does not make them immune to the effects of ultraviolet radiation. If anything, plants are even more vulnerable, as so much of their growth is driven by the need to maximize their exposure to sunlight. Recently, studies have begun to uncover the role that chemicals known as sinapate esters play in protecting them. Researchers have found that plants produce sinapate esters internally, then transport them to the surface of their leaves. Once there, the "natural sunscreen" blocks ultraviolet-B (UVB) radiation from penetrating the leaves and damaging the plant's structures or DNA.

Chemicals completely block dangerous rays

In the new study, the researchers made a sinapate ester gas, then bombarded that gas with UVB radiation. They found that the gas was incredibly efficient, successfully absorbing every single wavelength of UVB light.

While plants produce "natural sunscreen" to protect themselves from UVB radiation, their defenses do not end there. No matter how good the sunscreen, plants inevitably take some damage from ultraviolet radiation, just like animals do.

A 2013 study -- conducted by researchers from Dartmouth University, the Salk Institute for Biological Studies and Australian National University, and published in the Proceedings of the National Academy of Sciences -- showed that plants respond to fluctuations in sunlight by using genetic signaling proteins called Heat Shock Transcription Factors to produce enzymes that detoxify the dangerous molecules that are formed when plants are exposed to very intense light.

Finely tuned healing mechanisms

Another recent study, led by researchers from Washington State University and also published in the Proceedings of the National Academy of Sciences, further examined the mechanisms that plants use to heal themselves from excessive UV exposure. According to corresponding author Helmut Kirchhoff, UV exposure inevitably causes the production of damaging free radicals, also known as Reactive Oxygen Species (ROS). These free radicals are also produced as natural byproducts of metabolism.

Just as in humans and other animals, free radicals can damage the cells and DNA of plants, producing ill health or even death.

"ROS production can't be avoided, only minimized," Kirchhoff said. "It becomes a big problem for plants under unfavorable environmental conditions, like too much heat, too much light or insufficient nutrition."

The researchers examined the plant cell structures known as chloroplasts, which are responsible for photosynthesis. They found that free radicals tend to destroy very specific "nanomachines" found in the photosynthetic membranes of chloroplasts. These nanomachines are essentially tiny molecules that fulfill specific functions in the cell.

The study showed that just as certain nanomachines are damaged by free radicals, other nanomachines within the same membranes are responsible for repairing this damage. The repair happens in a series of discrete steps, with each step dependent upon the completion of the prior step. In each step, the repair nanomachine collects a specific protein from a unique region of the membrane, then moves to the next region to collect the next protein.

"Until now, it was not known how the order of events is guaranteed," Kirchhoff said. "Our results suggest that we have to understand the structural characteristics and dynamics of photosynthetic membranes to understand the repair of the energy-converting nanomachines. This has not been appreciated before."

Sources for this article include:

http://www.newswise.com

http://www.sciencedaily.com

http://www.sciencedaily.com