INTRODUCTION 



Equation (i.i) expresses the qualitative facts of plant 

 respiration and photosynthesis. Further analysis of the two 

 processes became possible only when the quantitative 

 relationships of plant metabolism were studied. For such 

 investigations it was found necessary to investigate cells 

 from many types of plant, from the more specialized of the 

 higher plants to the simpler unicellular forms represented 

 by the algae and bacteria. Each type offered certain advan- 

 tages in the investigation of a particular aspect of photo- 

 synthesis. But before such data could be analysed quantita- 

 tively the effect of the vast differences in physical structure 

 had to be taken into consideration. This is the subject of the 

 second chapter of this book which is concerned with plant 

 structure as it affects the study of photosynthesis. In the 

 fourth chapter the general relations between the rate of 

 photosynthesis and various environmental factors are con- 

 sidered and we shall see how important plant structure may 

 be in determining a relationship such as that between rate 

 of photosynthesis and the external concentration of carbon 

 dioxide. Physiological studies led to a formulation of the 

 mechanism of photosynthesis in general terms which was 

 subsequently interpreted in chemical terms as the result 

 largely of work with photosynthetic bacteria. This is dis- 

 cussed in Chapter 5. The subsequent chapters discuss more 

 recent researches in biochemistry which are relevant to the 

 problem of photosynthesis and which may ultimately per- 

 mit the formulation of the mechanism of photosynthesis in 

 specific chemical terms. 



