WATER SATURATION DEFICIT AND ITS 

 DEVELOPMENT IN YOUNG AND OLD LEAVES 



Jmf Catsky 



Institute of Biology, Czechoslovak Academy of Sciences, 

 Praha, Czechoslovakia 



INTRODUCTION 



The origin and development of the water saturation deficit (WSD) in 

 plants in situ represents a problem not yet satisfactorily explained from the 

 point of view of ecology. The authors of the first studies on the water 

 deficit of plants (Stocker, 1928, 1929a, b; Magyar, 1930; Schanderl, 1930; 

 Vassiljev, 193 1, and a number of others) emphasised the importance of 

 this then newly-defmed value especially in ecological investigation, par- 

 ticularly in view of the fact that the values of the water deficit make it 

 possible to compare the water balance of plants from different locaHties. 

 The significance of the water deficit is, however, not restricted to this type 

 of work. Its values gain in importance especially on detailed examination 

 of wilting of plants and in studying the relationships of individual life 

 processes in plants on the supply of plant tissues with water. 



The present communication was conceived from this very point of 

 view, its aim being to be extended by further studies of the dynamics of 

 plant wilting. It attempts to correlate the existing rather varied and 

 occasionally contradictory fmdings on the water deficit from the point of 

 view of physiological ecology, to check the methods of its determination 

 and to obtain fundamental data on the course of wilting of some model 

 plants. 



LITERATURE 



The concept of water deficit as one of the most important indicators of 

 plant water balance was introduced by Stocker (1928, 1929a, b) on the 

 basis of Iljin's studies (1923). His original method of estimation of WSD 

 was used by a number of authors. Relatively very detailed data on the 

 absolute value of the water deficit under normal and extreme conditions 

 resulted from their work, together with data on its diurnal and seasonal 

 changes, relationships with climatic factors, etc. As was mentioned in a 

 previous paper (Catsky, 1959) the rehabihty of these data is unfortunately 

 rather questionable on account of the considerable error which might be 



