Plants Conserve 44% More Water With Active Enzyme

Published on January 5th, 2010 | by

A team of biologists identified plant enzymes last month that help plants utilize raised levels of carbon dioxide to more efficiently use water. The team, led by biology professor Julian Schroeder at UC- San Diego, discovered protein censors that control the response of pores on the leaves of plants. By adding an active enzyme to plants with an inactive one, researchers were able to measure more efficient use of water by the plants and this discovery could potentially make increased food production possible without increasing the water supply.

Photo Credit: eleda 1Biologist have found a way for plants to conserve water in high CO2 environments
Biologist have found a way for plants to conserve water in high CO2 environments

We all know plants “breathe” using photosynthesis, but here’s a quick primer on the details:
1.    Plants breathe in CO2 through microscopic pores on their leaves.
2.    1 molecule of CO2 inhaled = 100’s of molecules of H20 lost.
3.    (Optional) Plants can tighten those pores to save water.

“A lot of plants have a very weak response to CO2. So even though atmospheric CO2 is much higher than it was before the industrial age and is continuing to increase, there are plants that are not capitalizing on that. They’re not narrowing their pores, which would allow them to take in CO2, while losing less water. It could be that with these enzymes, you can improve how efficiently plants use water, while taking in CO2 for photosynthesis. Our data in the lab suggest that the CO2 response can be cranked up,” – Dr. Julian Schroeder

Schroeder’s research team has isolated the pair of proteins necessary for pore tightening called carbonic anhydrases, which split CO2 into bicarbonate and protons. Plants with this gene disabled don’t respond to rising CO2 levels. Researchers also found that the enzymes work directly within what they call guard cells, which control “breathing” pores on leaves. When they added carbonic anhydrases to the genes that trigger the guard cells they successfully got plants to tighten their pores as CO2 levels rose- an exciting discovery, seeing as plants lose about 95% of the water they absorb to evaporation from their leaves.

“The guard cells respond to CO2 more vigorously. For every molecule of CO2 they take in, they lose 44 percent less water,” according to Honghong Hu, co-first author of the report.

So what’s the catch?

The researchers also looked into some possible side-effects of altering plant pore response to CO2 levels and found that plants still open pores in response to blue light so that photosynthesis can begin and the pores still shut when there is limited water- It appears, from preliminary results, that adding the enzyme could be a big help in creating higher crop yields.

The one drawback could be that if plants evaporate less water, that takes away some of their natural cooling, similar to a person wearing anti-perspirant. This could have unforeseen side effects and would have to carefully studies further.

But, with water and food supply stress looking to grow as issues in the coming decades, this is the kind of innovation I expect to see grow along with it. It will bring more and more into question the bio-ethics of food creation and the basic ethics of the human right to water.


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