Is photosynthesis efficient enough? • Earth.com
Though photosynthesis has room to improve, we still have much to learn from plants, and new forms of photosynthesis are still being discovered.
04-08-2019

Is photosynthesis efficient enough?

How does photosynthesis work?

Plants and bacteria convert sunlight into sugar through the magic of photosynthesis. The evolution of this process enabled life to be what it is today. All life feeds on the sun, either directly or indirectly.

This essential process is made up of a series of complicated chemical reactions. Plants have tiny factories that control each step of this reaction. This process is complex, but the simple version is that proteins move electrons to charge machinery that produces sugar.

In the end, plants combine CO2 and water, producing sugar and oxygen.

What makes photosynthesis slow?

One of the proteins involved in photosynthesis is tasked with the essential job of grabbing CO2. This enzyme is called RuBisCO, and it is the most common protein on Earth. Part of the reason for this is that it’s not very good at its job.

It turns out that RuBisCO accidentally grabs oxygen instead of carbon dioxide about one-fifth of the time. When this happens, toxins are created rather than food. In order to decrease the harm, the plant spends energy recycling and removing these toxins. This can result in a 20-50% loss of efficiency.

This protein is so ancient and essential to life that it seems there isn’t much room for evolution to play around. RuBisCO is estimated to have originated between 720 million and 1.2 billion years ago. Because it is so essential, any decrease in the function will quickly be selected against. However, sometimes things need to get worse before they get better.

Building a better plant

We have known for a long time that the efficiency of plants could be improved. Modifying something so essential is not easy. The Realizing Increased Photosynthetic Efficiency (RIPE) project aims to do just this.

Researchers at the University of Illinois have had exciting breakthroughs in this area. They have re-engineered how plants remove the toxins produced by RuBisCO and their results are quite impressive.

The researchers edited the genes of 1700 plants to test this process. Top performers were as much as 40% larger.

RuBisCO performs worse at higher temperatures. With the climate change on the rise, this could be a real problem and researchers hope to improve food security globally. The RIPE program is committed to providing these innovations to farmers royalty-free.

Researchers in China and San Francisco have had success with similar work. They used a bioengineering approach called GOC to improve photosynthesis and photorespiration and were able to increase rice yields by 27 percent.

Modifying photosynthesis has also allowed researchers to save water. Editing the pores of plant leaves (stomata) allowed plants to grow more efficiently.

Controlling photosynthesis has exciting implications and improving technology may allow us to design our own photosynthetic organisms.

Other researchers have discovered that under the right circumstances RuBisCO may be substantially more efficient.

Are we able to do better?

Humans have created their own version of photosynthesis. Solar panels (or photovoltaic cells) achieve the same goal as photosynthesis by turning sunlight into energy.

Comparing the two processes is complicated. Photosynthesis produces sugar, which can be stored for a long time. Solar panels produce electricity, but storing this electricity is a major problem.

Batteries are inefficient and dangerous. Photosynthesis clearly has us beat when it comes to providing steady energy. Research into better battery technology is essential for all renewable energy sources.

In terms of pure energy output, photosynthesis doesn’t fare so well. About 3% of the available sunlight is stored. Solar panels, on the other hand, can convert up to 10% of available light. This discrepancy points to the inefficiencies that do exist in photosynthesis.

Advanced technologies have even been able to achieve efficiencies of up to 40%. These are not practical yet but show that there is a lot of room to improve.

Plants also provide other advantages. While producing energy, they also consume CO2, helping mitigate climate change. When the CO2 is used up, they create oxygen. This process creates breathable air, which we can all agree is pretty important.

Though photosynthesis has room to improve, we still have much to learn from plants. The diversity of plants may still reveal important secrets about collecting and storing energy, as new forms of photosynthesis are still being discovered.

By Casey Hofford, Earth.com Contributing Writer

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