The polarization of fluorescence and energy transfer in grana.
نویسندگان
چکیده
The results of several experiments suggest that t,he first step in green plant photosynt,hesis is a cooperative act carried out by a few hundred chlorophyll molecules. By using very short flashes of light, spaced far apart so as not to interfere with each other, Emerson and Arnold (1) found that the maximum number of carbon dioxide molecules reduced per flash was some 2500 times less 6han the number of chlorophyll molecules. Tamiya (2) repeated the experiments using very much longer flashes and found t.hat. t’he maximum amount of carbon dioxide reduced per flash by 1 g. dry weight of algal cells was 7.3 X 10-S moles at 25°C. and 3.7 X 1w8 moles at 7°C. The longer flash times used by Tamiya would allow a part of the photosynthetic mechanism to “recycle” during the flash. Since this effect should be less at t’he lower temperature, the 7°C. measurement and the chlorophyll content of 7.0 X 1F5 moles/g. of dried algae, given by Tamiya, will be used to calculate t,he ratio of chlorophyll to photosynthesis. This ratio is 1900. This large number of chlorophyll molecules [which can be determined by other methods than by flash experiments, as shown by Gaffron and Wohl (3)], is for the reduction of one carbon dioxide molecule, and thus must be divided by the number of quanta used to reduce one carbon dioxide molecule in order to obtain the number of chlorophyll molecules involved in the absorption of one quantum. The exact number of quanta used by the plant t.o reduce one molecule of carbon dioxide is still uncertain, but it is probably between 4 and 10. Thus the number of chlorophyll molecules per quantum used will be between 200 and 500.
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عنوان ژورنال:
- Archives of biochemistry and biophysics
دوره 60 1 شماره
صفحات -
تاریخ انتشار 1956