Investigation of natural auxins and growth inhibitors 



1955). Later, however, with a new supply of /iopropanol, we occasionally 

 ran into two difficulties : ( 1 ) the I AA spot was somewhat larger than when 

 ammonia was present, (2) the R^ of lAA was sometimes too high. Several 

 different alcohols were then tried systematically {Table 4). In general, 



Table 4 



Effect of various alcohol isomers on the size of the lAA spot 



The chromatograms were equilibrated overnight, then run for 8-10 hours at room 

 temperature in the dark. 2 y of the indole-3-acetic acid were applied to each strip. .\11 

 proportions are v/v. 



compact lAA spots were obtained with A?-butanol, but /Vobutanol was even 

 better, yielding consistently small, rounded spots with lAA and indole-3- 

 butyric acid (IBA). However, with zj^obutanol, the Rf of the lAA spot was too 

 low. It is known (Stowe and Thimann, 1954; Nitsch and Nitsch, 1955) that 

 increasing the percentage of water in an alcohol-water mixture brings the 

 Rf of I AA up [Figure 7) . Unfortunately, water is not very soluble in /jobutanol, 

 so that a one-phase mixtiu-e cannot be achieved with more than about 

 14 per cent water at room temperature. This difficulty was overcome by 

 adding to the uobutanol-water mixture either tertiary butanol (in which 

 water is soluble in all proportions) or methanol. Thus, the following- 

 solvents gave good results: (1) zVobutanol {p(i°/Q)-\- tertiary butanol (30%) 

 +water (20%), and (2) /^obutanol (80%)+methanol (5%)+water (15%). 

 The latter solvent was preferred because it ascends somewhat faster than the 

 first one, which moves very slowly. In conclusion, two good chromato- 

 graphic solvents for auxins are as follows : 



lAA IBA IAN lAE 

 Stowe and Thimann's 



uopropanol (80%) +28% ammonia (10%) 

 + water (10%) 



ziobutanol (80%)+methanol (5%) 

 +water(15%) 



The numbers in parentheses give the length of the spots in mm for 2 y of lAA, 

 1 y of IBA, 10 y of IAN, and 5 y of lAE when the solvent front has moved 

 20 cm. It can be judged by comparing the diagrams of Figures 2 and 3 that 



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