40 



book, that the blueprint of the energetics of the living world con- 

 sists essentially of two parts only: photosynthesis and its reversal. 

 Increasing evidence is available to show that chlorophyll, in photo- 

 synthesis, is excited by light to a triplet state. In our in vhro ex- 

 periments chlorophyll behaved in ice in the same way as other 

 fluorescent dyes, going thus, in all probability, into the triplet 

 state on excitation. So triplets seem to be the main instruments of 

 energy transmission in both, photosynthesis and the biological ac- 

 tions which consume energy, which brings the analogy between 

 the two processes still closer. It seems likely that also within the 

 chloroplasts the triplet excitation of chlorophyll is made possible 

 and stable by the surrounding water structures. This interaction oi\ 

 triplets and water may also open the way to the understanding of 

 the mechanism by which the £* of chlorophyll is used to decom- 

 pose water into its elements, which is at the core of photosynthesis. 

 As will be shown later, triplet excitations in ice are stabilized by 

 SH, which may help to fit Calvin's thioctic acid into the picture. 



I have considered here only changes which may be induced in 

 the solvent, water, by its freezing, but changes may be induced 

 also in the solute, the fluorescent matter. On freezing, for instance, 

 the water crystallizes out, which m.ay lead to increased local con- 

 centrations of the solute with consequent self-quenching or poly- 

 merization which may profoundly alter excitational states and 

 light emissions. These possibilities will be studied later. 



