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A Bacterial Test for Plant Food Accessories (Auximones). 



By W. B. Bottomley, M.A., Professor of Botany, University of London, 



King's College. 



(Communicated by Prof. F. W. Oliver, F.E.S. Received June 1, 1915.) 



In a previous communication* attention was called to the significance of 

 certain accessory food substances for normal plant growth. It was pointed 

 out that the nutrition of a plant depends, not only upon the supply of 

 mineral food constituents, but also upon the presence of certain accessory 

 organic food substances, very small amounts of which are sufficient to satisfy 

 the needs of the plant. These plant food accessories are analogous in some 

 respects to the curative substances of beri-beri and scurvy which Suzuki calls 

 " oryzanine," and for which Funk has suggested the name " vitamine," 

 thinking they are of an amino nature. More recently Moore and his 

 collaborators have applied the term " torulin " to the curative substance 

 obtained from yeast. 



Experiments in progress indicate that the plant food accessories resemble 

 more closely the growth-stimulating food factors of Hopkins than the 

 vitamines of Funk, and the term " auximone " (Gr. ocvgi/xos, promoting growth) 

 is suggested for them, being descriptive of their action rather than of their 

 nature or composition, about which nothing definite is known. 



Hitherto the only means of demonstrating the presence of these plant 

 auximones has been their action on the higher plants. Unfortunately this is 

 a long process and often unsatisfactory owing to the difficulty in maintaining 

 constant environmental conditions during the comparatively long period of 

 growth, and a more ready means of demonstrating their presence is desirable 

 in order to facilitate further investigation of their constitution and properties. 



The effect of the plant food accessories obtained from an alcoholic extract 

 of bacterised peat on the growth and nitrogen fixation of Azotobacter 

 chroococcum, described in a previous paper, suggested the possibility of a 

 bacterial test for the more active fractions of the alcoholic extract. As 

 experiments had shown that the fractions of this extract of bacterised peat 

 obtained by means of phosphotungstic acid and by silver and baryta, 

 according to the method already described, gave growth results with wheat 

 plants, an investigation was made of the effect of these fractions on the 

 growth of Azotobacter. 



Eighteen flasks, each containing 100 c.c. of distilled water, 1 grm. mannite, 

 0-2 grm. K 2 HP0 4 , 0'02 grm. MgS0 4 , and 0-2 grm. CaC0 3 , were divided into 

 * 'Eoy. Soc. Proc.,' B, vol. 88, pp. 237-247 (1914). 



