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Trees regulate photosynthesis temperature – by design?


Leaves have been found to regulate temperature to “around 21.4° Celsius plus or minus 2.2 degrees,” during photosynthesis. That appears to me to be a design to increase or optimize photosynthesis.

ID Hypothesis: Trees, and other biotic systems regulate leaf temperature to increase or optimize photosynthesis. There will be temperature and/or humidity sensors and transpiration regulation systems to achieve this temperature control.
Corollary: Net primary productivity would be substantially lower without such temperature regulation.
Global Warming Impact: This finding may invalidate tree ring temperature proxies in extrapolating to past temperatures to evaluate climate change.
Goldilocks tree leaves
by Susan Milius, June 11th, 2008,

Sweating in the heat or huddling in the cold keeps temperatures favorable
JUST RIGHTTree leaves can do plenty to keep their temperatures just right for photosynthesis.

Tree leaves do a pretty good job of achieving temperatures that are just right for photosynthesis, even if it’s too hot or too cold where they live, a new study shows.

From roughly the top to the bottom of North America, across some 50 degrees of latitude, trees all do their photosynthesizing at leaf temperatures around 21.4° Celsius plus or minus 2.2 degrees, says physiological ecologist Brent Helliker of the University of Pennsylvania in Philadelphia. That conclusion was based on a broad survey of the ratios of two forms of oxygen that vary depending on the temperature and humidity of leaves. Those properties control evaporation and make a signature in the cellulose of the tree rings, Helliker and colleague Suzanna Richter report in an upcoming Nature.

Such temperature control undermines the assumption that the insides of leaves have the same temperature as the air, Helliker says. That’s an assumption underlying studies that check oxygen ratios in old tree tissue to reconstruct past climates, he says.

. . .Trees release water, and during hot times, that botanical sweat cools them down. And trees that grow in cold places tend to cluster their leaves. These tight formations can affect the rate at which leaves lose heat on cold days, just as fingers pressed together in mittens stay warmer than fingers separated by space in gloves. . . .

See full article Goldilocks tree leaves

Isotopic ratio changes were interpreted as temperature changes,...
And how does that affect the width of tree rings? Bob O'H
ungtss The point of ID is to identify design from the object, independently of the designer. That is common in many areas of science. Design commonly incorporates regulation. Random mutation with "natural selection" has no basis or credible statistics to do so. To expand on the ID hypothesis, the temperature regulatory mechanisms involved are likely to have irreducibly complex subcomponents not amenable to evolution. On "transitional forms", the mutational history is embedded in the genomes. Almost all evidence currently points to degradation of the genome, with negligible evidence for any "beneficial" mutations. Current scientific statistics back ID. See John C. Sanford Genomic Entropy. With the 1000 genome project, this mutational history will become much more evident. DLH
Fascinating insofar as it shows another level of complexity, and insofar as it draws treering temperatures into question. But I don't think it is really an "ID hypothesis." Evolutionists will just (unfalsifiably) interpret those same temperature maintenance mechanisms as evolved. An ID hypothesis would have to falsify the alternative. That's difficult to do since neither the designer nor the transitional forms are available for examination. ungtss
Bob O'H Isotopic ratio changes were interpreted as temperature changes, assuming leaves were at the same temperature as the air. Now it appears they were at a different regulated temperature. See: ICECAP.US
Jun 13, 2008 Final Nail in Hockey Stick Coffin - Hot Climate or Cold, Tree Leaves Stay in Comfort Zone Agence France-Presse A new study that shows their internal temperature remains constant at 21.4deg could challenge the way trees are used to determine historical climate data. The internal temperature of leaves, whether in the tropics or a cold-clime forest, tends toward a nearly constant 21.4 degrees Celsius, reports a study released today. It had long been assumed that actively photosynthesising leaves - using energy from sunlight to convert carbon dioxide and water into sugar - are nearly as cold or hot as the air around them. The new findings not only challenge long-held precepts in plant biology, but could upend climate models that use tree rings to infer or predict past and present temperature changes. For decades, scientists studying the impact of global warming have measured the oxygen isotope ratio in tree-rings to determine the air temperature and relative humidity of historical climates. Oxygen atoms within water molecules evaporate more or less quickly depending on the number of neutrons they carry, and the ratio between these differently weighted atoms in tree trunk rings has been used as a measure of year-to-year fluctuations in temperatures and rainfall. “The assumption in all of these studies was that tree leaf temperatures were equal to ambient temperatures,” lead researcher Brent Helliker told AFP. “It turns out that they are not.” Helliker and University of Pennsylvania colleague Suzanna Richter turned those assumptions upside down in examining 39 tree species, across 50 degrees of latitude ranging from sub-tropical Columbia to boreal Canada. They compared current observed records of humidity and temperature against the isotope ratios in the trees, and found that tree leaves were internally cooler than surrounding air temperatures in warm climes, and warmer in cool climes. Even more startling was that in all cases the average temperature - over the course of a growing season - was about 21degC. . . .“But to think that a Canadian black spruce and a Caribbean Pine have the same average leaf temperature is quite astonishing,” he added. . . . The new findings, published in the British journal Nature, are bolstered by a recent study of a mixed species forest in Switzerland based on infrared thermal imaging. Measured across an entire growing season, the forest canopy temperatures were found to be 4degC to 5degC higher than the cool, ambient air in the Swiss Alps.
See full article ICECAP.US
Can you explain how you come to your conclusion that this invalidates tree ring temperature proxies, please. Bob O'H

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