44 

 h 

 300- 



PLANT GROWTH SUBSTANCES 



200 



00 



o 



z 



llJ 

 o 





HOURS 



10 



20 



30 



Figure i. The change in the elastic tension of root epidermis cells during 

 the cell elongation. 



has been done both on roots and coleoptiles (2,11). Regarding roots 

 growing in a solution the conditions are simple, the cells are constantly 

 saturated with water during the whole elongation process. In coleoptiles, 

 on the contrary, there is always a large water deficit. In any event it 

 is obvious that the often advanced opinion that elongation must cease 

 in a water-saturated cell is undoubtedly erroneous, and such an opinion 

 cannot even be theoretically sound. 



The properties of the cell wall are indubitably of first-rate importance 



