Harold Weger wrote:
>I have been following the anthocyanin/red colouration discussion, and have
>read with interest many of the ideas/hypotheses advanced to date. However, I
>have consistently wondered whether anthocyanin synthesis in the fall is
>simply a mechanism to reduce the effective light intensity (PFR), i.e. that
>anthocyanin functions as a sun screen (cytosolic carotenoids have been
>postulated to function in the same manner in the green alga Haematococcus).
>Why would a maple turn red in the fall? Is it simply to decrease the degree
>of photoinhibition induced by low temperature? That is, as temperatures
>decrease proportionally more than PFR in the fall, synthesis of anthocyanins
>would serve to screen the photosynthetic apparatus, and thus minimize the
>degree of photoinhibition. I don't know if there are experiments or data
>that support this idea, but it should be easy enough to test using a
>chlorophyll a fluorescence measurements. Does anyone know of such experiments?
>Harold Weger
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>Harold G. Weger tel: 306-585-4479
>Department of Biology fax: 306-585-4894
>University of Regina e-mail: Harold.Weger at uregina.ca>3737 Wascana Parkway
>Regina, Saskatchewan
>S4S 0A2
>Canada
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It seems to be a fresh idea. I do not beleive that plants "do it specially",
however, as a side effect of partial destruction of photosynthetic pigment
system, the rest of chlorophyll could be really "shielded" thus being kept
in an active state under limited utilization of excitation energy (i.e. at
low temperatures).
As to chlorophyll a fluorescence, this approach became extreamly popular
after PAM-type portable devices became available. You can monitor the
fluorescence quenching coefficients, the efficiency of PSII photochemistry...
Unfortunately, you cannot see the item "degree of photoinhibition" on the
screen of your fluorometer... If you discover that in certain conditions,
the PSII quantum yield decreases, it may be due to either photoinhibition or
the increase of non-radiative energy dissipation SAVING FROM photoinhibition.
You may see the photoinhibition more or less directly if you measure the dark
relaxation of chlorophyll fluorescence quenching.
As far as I know, chlorophyll a fluorescence has not been applied to the
autumn leaves. You may be the first!
Oleg Moskvin.
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Oleg V. Moskvin
Lab. of Photosynthetic Electron Transport
Inst. of Soil Sci. & Photosynthesis
Russian Academy of Sciences
142292 Russia
E-mail: omega at ibpm.serpukhov.su
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