io8 



JIRICATSKY 







Fig. 5 



Figs. 5 and 6. The course of wilting of a plant in situ during decreasing soil moisture; 

 fodder cabbage (Fig. 5) and rape (Fig. 6). Abscissa: days from the beginning of 

 experiment (= days of wilting) ; ordinate: percent water saturation deficit. The figures 

 for individual curves indicate the position of the leaf on the genetic spiral begiiming 

 from the top (leaf no. i : area about 8 cm^^. 



The second methodological contribution of this paper consists in the 

 method apphed to the estimation of the actual water deficit employing discs 

 of leaf tissue. The use of discs for the estimation of the WSD possesses a 

 number of advantages over the estimation in whole plants: among others 

 (technical ones, for instance) are the rapid saturation of the tissue (and thus 

 a decrease of the extension growth effect) and further the possibihty of 

 taking representative samples without destroying leaves or whole plants. 

 Only this method makes it possible to investigate directly the course of 

 wilting. From the physiological point of view there are no serious objec- 

 tions to the use of leaf discs as is well seen in the successful work of 

 Weatherley (1947, 1950, 195 1) concerning water deficit. A basis for the 

 technical arrangement of the procedure was found in the paper by Bartos, 

 Kubin and Setlik (i960) and in the hitherto unpublished results of the same 



