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Quantum plant activity.

As a biologist with some background in physics, I found the article "Living physics" (SN: 5/9/09, p. 26) probably one of the most important that you have published for a long time. Some indication that biologists are aware of the exciting developments in quantum physics and that those developments need to be applied to biological theory are much overdue. But there is still a long way to go. The article makes it plain that researchers now need to consider the implication of Bell's theorem of non-locality, which indicates that quantum "particles," such as the electrons and atoms in molecules, do not even need to be close to each other, provided they have been previously quantum entangled. I await your article on the biological effects of Bell's theorem with great anticipation.

Donald K. Edwards, Saanichton, British Columbia, Canada

In the article "Living physics," it is stated that 95 percent of the light hitting a leaf reaches the photosynthetic reaction center. If photosynthesis is so efficient, it would truly be a good way to convert sunlight into biofuels. Yet Nathan Lewis at Caltech has stated that photosynthesis is only about 0.3 percent efficient, so that enormous amounts of land would be needed to produce significant amounts of biofuels. If Lewis is correct, it is smarter to use things like photovoltaics that have far higher efficiency. Obviously, in this instance, the calculation of "efficiency" is being based on different measures of efficiency. Can you illuminate this issue for me? Perhaps the real limitation is in the production of carbohydrate plant material rather than in the absorption of light and its conversion into active electrons.

Bill Thomas, Cedar Mountain, N.C.

As the reader points out, calculating the efficiency of photosynthesis depends on what you're looking at. When calculating how much energy from the sun gets converted into the mass of the plant, the numbers can vary. Some giant grasses are extremely efficient and over a three-month growing season can convert about 8.8 percent of the light they absorb into biomass. The conversion efficiency of most plants, when averaged over the whole year, ranges from a few tenths of a percent to almost 10 percent.

In the story, the scientists discussed the "quantum efficiency" of photosynthesis, focusing on only the initial step of the transfer of energy from sunlight, which takes into account the odds that a photon that gets absorbed by a plant will actually be used and converted into energy. Scientists agree that the quantum efficiency of photosynthesis is nearly 100 percent at low light levels.

--Susan Gaidos

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Title Annotation:FEEDBACK
Author:Edwards, Donald K.; Thomas, Bill
Publication:Science News
Article Type:Letter to the editor
Date:Jul 4, 2009
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