208 



GROWTH OF PLANTS 



Table 24. Dependence of Activity for Cell Elongation Upon the Position 

 of Substituents, Groups, or Atoms 



CH2COOH 



1NO2 



CH2COOH 



Inactive 



JNO2 

 Active 



CH2COOH 



NO2 

 Inactive 



CH2COOH 



A 



NH2 



CH2COOH 



i 



Inactive 



,NH2 

 Inactive 



CH2COOH 



A 



NH2 



Active 



CH2COOH 



CH2COOH 



i 



Active 



CI 

 Active 



CH2COOH 

 O 



CI 

 Active 



CH2COOH 

 O 



CH2COOH 



A 



NO2 



NO2 



Inactive 



CH2COOH 

 ^CH3 



CH3 

 Active 



ethylene gas, is a satisfactory species. The coleoptile can be used only to 

 detect the cell-elongating power of a substance. With one treatment the 

 tomato plant detects the capacity of a chemical to induce cell elongation, 

 cell division, adventitious roots, and formative effects. The time required 

 varies \vith the response. Detection of cell elongation requires only from 

 20 minutes to two hours, cell division 48 to 72 hours, initiation of roots 

 five to ten days, and formative effects four to ten days. The four types of 

 response are illustrated in Figs. 75 and 76. If the chemical does not induce 

 at least one of these responses, it is listed as inactive. 



