ON THE PROBLEM OF THE RELATIONSHIP 



BETWEEN HYDRATION OF LEAF TISSUE AND 



INTENSITY OF PHOTOSYNTHESIS AND 



RESPIRATION 



BOHDAN SlAVIK 



Institute of Biology, Czechoslovak Academy of Sciences, 

 Praha, Czechoslovakia 



INTRODUCTION 



A considerable number of papers has been devoted to the relationship 

 between the intensity of photosynthesis and hydration of photosynthesising 

 tissues. Papers will not be mentioned in the sequel which do not take into 

 consideration the intensity of carbon dioxide assimilation but rather the 

 fmal yield (of the more recent ones, e.g. Baumann, I957; Kreeb, 1958). 



Concerning the lower poikilohydric plants (algae, bryophytes, hchens) 

 there exists a fundamental unity of view that hydration directly affects the 

 intensity of CO2 assimilation (BrilHant, 1924; Mayer and Plantefol, 1926; 

 Stocker, 1927; Walter, 1928, 1929; Smyth, 1934; Stocker and Holdheide, 

 1937; Stalfelt, 1937, 1938; Danilov, 1938; Kaltwasser, 1939; Ellee, 1939; 

 Romose, 1940; Ried, 1953; Ensgraber, 1954 and others). 



On the other hand, papers where this relationship is considered in higher 

 dry-land homoiohydric (hydrostable) plants without interaction of the 

 stomata, have not reached a common basis so far. For instance, Pisek and 

 Winkler (1955) did not fmd in their results any experimental support for 

 the view that photosynthesis should decrease on water loss in any other way 

 than by virtue of stomatal closure. A similar standpoint is maintained by 

 Larcher (i960). An ehmination of the influence of the hydroactivity of 

 stomata is rather difficult from the experimental point of view. Iljin (1923) 

 worked with plants with closed stomata and he still found a relationship to 

 exist between water content and intensity of photosynthesis, different in 

 different taxons. Brilliant (1924, 1925, a review of 1949) and ChrelashviH 

 (1940) carried out experiments on small segments of leaf tissue after having 

 ascertained that the state of the stomata did not Hmit the saturation of the 

 tissues with CO 2 which took place through the planes of section. In addition 

 to a dependence of the intensity of photosynthesis on water content in the 

 tissue they demonstrated the existence in higher plants of an optimal water 

 deficit at which the intensity of photosynthesis was in some cases higher 



