448 L. R. BLINKS 



rapid fall — possibly due to inactivation of some of the chlorophyll, 

 to which energy must be transferred from phycoerythrin. Studies of 

 fluorescence during this transient phase would be desirable and will 

 be attempted. 



Another possibility is an altered respiratory rate during the first 

 moments of light absorption by phycoerythrin. Only mass spectro- 

 graphic studies could determine this, and it seems likely that their 

 time resolution might not be adequate to follow these essentially 

 second-order effects. 



It is clear, however, that the transition from chlorophyll absorp- 

 tion to phycoerythrin (or phycocyanin) absorption is not completel}^ 

 smooth, even though the final photosynthetic rate may be the same. 

 There is a "grinding of the gears" at the moment of change. When 

 this is understood, there may emerge a better understanding of the 

 remarkable "inactive chlorophyll" of the red algae. 



Discussion 



Wassink : Is there a dark period between the periods of illumination at 600 and 

 675 niM? 



Blinks : No, there is no dark period. We are simply going from one wavelength 

 to another. 



Hendley : Would the plants see these two colors of light at the same intensity? 



Blinks : They were in many cases the same intensity. They can, however, be so 

 adjusted that the steady-state photosynthesis is the same instead. The transients 

 occur in either case. 



Gaffron: Changes in light intensity cause transition effects and they are also 

 one-sided. I have not seen them, from low light to high light. However, from 

 higher light back to low light there is always a rather long disturbance. 



Blinks : It makes no difference if the intensities are alike or not, you still have 

 the transients. If you adjust intensity so that photosynthesis is equal in the 

 steady state you get them best of all. 



Brown : You say you do not see these in green algae? 



Blinks : No, not in going from the carotenoid to chlorophyll absorption regions 

 or vice versa. 



Strehler: Does it happen at very high light intensities, that is, at saturation 

 intensities? 



Blinks : No, these are at intermediate intensities. 



Emerson : We have been doing somewhat similar experiments with red and 

 green algae, looking at the subsequent respiration after exposure to different 

 wavelengths of light. In the case of red algae there is a strong promoter effect 

 of green and blue-green light on the subsequent respiration, analogous to the de- 

 pressing effect on photosynthesis described by Emerson and Lewis for Chlorella 

 at about 480 mfi in the blue. 



