44G 



L. R. BLINKS 



ing to more rapid attainment of the steady state, or even with a cusp 

 shghtly above the final value, while in red light the steady level is 

 attained more slowly. These differences are not always evident, es- 

 pecially the cusp, which in thicker tissues seems to be swamped out in 

 diffusion. 



The transients become more striking when alternate exposures are 

 given to red and to green light without intervening dark periods. 

 Figure 2 is a tracing of a Speedomax recording, showing first the dark 



Fig. 3. Actual Speedomax recording of the transients on changing from red to 

 yellow or green light. The initial trace is the rate in red light (675 m/*); on exposure 

 to yellow light (580 m^) there is a very sharp oxygen gush, followed by an equal 

 depression of considerably greater length, with final recovery to a somewhat 

 higher level than in the red, which follows (675 vein). The gush and depression are 

 even sharper in the green (560 m/x). These transients represent some 15% or 20% 

 of the total photosynthesis, the base line lying well below the bottom of this record. 

 Vertical lines, 100 seconds apart. 



value, then the rather regular attainment of a steady photosynthetic 

 rate in red light (675 m/x, well above compensation but far from 

 saturation) . On shifting the monochromator setting instantly to green 

 light (540 m/i) there is an immediate cusp (oxygen gush) followed by a 

 longer depression, with recovery in about a minute to the stationary 

 state. On going again back to the red light (675 m^t) a slight depression 

 is observed, followed by recovery. These are repeated any number of 

 times, with little change in the characteristic courses, providing each 

 has gone to completion. (Alternations which are too short show smaller 

 cusps and depressions.) On darkening, the respiration value is quickly 

 attained (D). 



