. Cell chemistry; a collection of papers dedicated to Otto Warburg on the occasion of his 70th birthday. Warburg, Otto Heinrich, 1883-; Biochemistry. — ?6 X cell ; iff) U e 12 16 I X cell voL/t) " 16x cv/h (V) °\ / '' \ 72 cmm/rae^^) o 36cmm/ra6^4). P~- ;^^ (16') ^ 32xcell vol/h 10 15 l-MIV) '' 15 X c v/ti 350cmm/f(U36-b^^) 25 20 25 30 35 W —»- t mm 45 Fig. 6. Quantum yields at high hght intensities, in the virtual steady-state (galvanometer read visually). times that needed for respiration compensation. The quantum requirement, calculated in the usual
. Cell chemistry; a collection of papers dedicated to Otto Warburg on the occasion of his 70th birthday. Warburg, Otto Heinrich, 1883-; Biochemistry. — ?6 X cell ; iff) U e 12 16 I X cell voL/t) " 16x cv/h (V) °\ / '' \ 72 cmm/rae^^) o 36cmm/ra6^4). P~- ;^^ (16') ^ 32xcell vol/h 10 15 l-MIV) '' 15 X c v/ti 350cmm/f(U36-b^^) 25 20 25 30 35 W —»- t mm 45 Fig. 6. Quantum yields at high hght intensities, in the virtual steady-state (galvanometer read visually). times that needed for respiration compensation. The quantum requirement, calculated in the usual manner to include respiration correction, was at the lowest intensity emplo^^ed, and at the highest. At the highest level of light intensity, the calculated quantum requirement is not greatly changed if the dark oxygen consumption is left out of the calculation ( instead of ), since the dark respiration is only one tenth of the total photosynthesis. This result is in agreement with the similar manometric results reported in the accompanying paper^. In Fig. 6 the oxygen exchanges in photo- synthesis and in respiration are both reported in terms of "times cell volume per hour" for purposes of facilitated comparison. SUMMARY 1. The electrochemical method of Todt for the determination of oxygen gas has been applied to the measurement of (i) the quantum requirement of photosynthesis and (2) the course of the light reaction and the dark back-oxidation over very short time periods (seconds). 2. With this new and independent, galvanometric method, the earlier results obtained by us with manometry have been confirmed, that is, attainment of a limiting quantum recjuirement of about 3 in the cycle of light and dark reactions. All significant objections raised regarding the time lag of manometry, as used by us, are thereby refuted. 3. Quantum requirements with single illumination periods as short as 5 seconds have been reported, and much shorter periods are sh
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