Degradation within plant tissues 



extend earlier findings (Wain, 1955) that substituents in certain positions of 

 the nucleus of co-phenoxyalkanecarboxylic acids can hinder /^-oxidation 

 within specific plant tissues (see Table 1). 



Table 1 

 Alternation in activity shown by homologous series of substituted co-phenoxyalkanecarboxylic acids 



>0(CH2)„C00H in three biological tests 



X 



In continuing this work on the /5-oxidation of co-phenoxyalkanecarboxylic 

 acid in plants, it was logical to study growth-regulating activity in 

 the corresponding homologous series of amides and nitriles. Accord- 

 ingly, the oj-(2:4-dichlorophenoxy)-series Cl2CgH30(CH2)„CONH2 and 

 Cl2CgH30(CHo) „CN, with n ^ I to 6, were synthesized and examined in the 

 wheat cylinder and pea curvature tests, the homologous series of acids being 

 also included. The typical alternation in the acid series which we have 

 already recorded (Wain and Wightman, 1954) was again evident in both 

 tests. The results are recorded in Figures 1 and 2. Alternation was also shown 

 in both tests by the amide series {Figures 3 and 2) and this is explicable in 

 terms of hydrolysis of amide to acid ( — CONHg— > — COOH) followed by 

 /i-oxidation. The inactivity of all nitriles except the acetonitrile in the pea 

 test {Figure 4), however, indicates that a similar hydrolysis of the — CN 

 grouping to — COOH does not readily occur with these higher homologues 

 in pea tissue. Furthermore, whereas such hydrolysis followed by ^-oxidation 

 would explain the activity of alternate homologvies of 2 :4-dichlorophenoxy- 

 acetonitrile in the wheat test, no such explanation is valid for the activity 

 shown by other members of this' series {Figure 2) . 



To elucidate these problems it was decided to expose solutions of all these 

 acids, amides, and nitriles separately to wheat and pea tissues and then 

 study the compounds present by paper chromatography. As these results 

 will be presented in detail elsewhere, they will be given only briefly here. 



The procedure adopted was to run ether extracts of the treated solutions 

 in the descending manner with «-butanol/ammonia/water ( 1 00 : 3 : 1 8) as 

 solvent for 15 hours at 20°C. After drying, the papers were divided horizon- 

 tally into ten equal segments representing Rf 0-0-1, 0- 1-0-2, 0-2-0-3, etc. 



189 



