Vitamin C protects plants from damaging sun rays

(NaturalNews) Although biologists have known for a couple of decades that plants create vitamin C in their chloroplasts to protect them from excess sunlight, the mechanics of that process were unknown until recently. Plant chloroplasts use chlorophyll to convert light energy of the sun into sugars that can be used by its cells.

Light is part of a process called photosynthesis that plants use to convert CO₂ into oxygen. This conversion of light energy into cellular plant food with its oxygen byproduct is the opposite of how it works with animal and human species that feed on plants and use their oxygen byproduct.

Animals and humans have mitochondria that use oxygen to help create the adenosine triphosphate (ATP) that cells need for energy. So the polar similarity of chloroplasts and mitochondria is obvious. Sunlight helps create vitamin C in plants. Most animals create their own vitamin C, but we humans need to obtain our antioxidant vitamin C from plant foods.

Sunlight is the energy source that initiates the plant process of vitamin C production, which we need from plant foods since the gene that most animals have to generate vitamin C is different in humans. Sunlight also initiates the process in our skin to create our important disease-preventing pre-hormone known as vitamin D.

But too much or too little light can disrupt the plant's ability to protect itself against self-generated oxygen free radicals that can create cellular havoc within them, inhibiting plant growth.

Going through the trouble of finding the biochemical mechanics in plants for vitamin C

It's not just the heat from sunlight that plant-generated vitamin C protects them from. The process of creating heat-shock proteins with vitamin C's help to dissipate excess energy from light has been observed even in temperature-controlled rooms.

Similar heat-shock proteins occur when there is too little light but herbicides have been applied. Think Roundup, the most commonly used herbicide on the planet.

One study by researchers from the University of California at Berkeley and the Lawrence Berkeley National Laboratory in Berkeley, California, was conducted in 2005 using the plant Arabidopsis, which is the commonly used model system for identifying plant genes and determining their functions.

As reported online by Science, the researchers discovered "that excessive sunlight triggers the formation of zeaxanthin," a carotenoid. The zeaxanthin "molecule transfers an electron to chlorophyll, rendering it incapable of generating reactive oxygen. The positively charged zeaxanthin then combines with the negatively charged chlorophyll in a reaction that disperses away excess energy as heat."

But that was evidently not enough to satisfy a group of researchers at the RIKEN Center for Sustainable Resources and Okayama University in Japan. More recently, in 2014/15, researchers there probed the exact process of what creates a plant's protective process of inhibiting oxidative damage from excess or insufficient light, using the same Arabidopsis plant that is commonly the subject for internal biochemical plant studies.

They isolated and identified PHT4;4 as the transport protein that allows vitamin C as ascorbic acid to enter chloroplasts. They discovered that, when PHT4;4 was removed, the plant was easily adversely affected by excess or insufficient light. Vitamin C is crucial as a coenzyme for developing the zeaxanthin that dissipates excess light as heat, and this protein is only in leaves, not roots.

According to lead author Takaaki Miyaji of Okayama University, "I believe that this research could lead to innovations that target PHT4;4 in order to create crop plants that can more efficiently transport vitamin C into the chloroplast."

Takahashi Kuromori of RIKEN added, "These plants would then have better than normal photoprotective properties and could prevent reduced growth in farmland that suffers from high light exposure."

Look out, Monsanto might be grabbing yet another genetic engineering project to foist on the world.

Sources:

http://www.alphagalileo.org

http://www.biology4kids.com

http://news.sciencemag.org

http://blogs.redorbit.com