Chemical structure and biological activity 



Table 3 



Effects of 2-benzthiazolyloxyacetic acid [BTOA) 



on the growth of plant tissue cultures 



(a) Carrot root tissue 



(b) Jerusalem artichoke tuber tissue 



obtained from the immature fruit of the walnut. By analogy with this system 

 an examination was made of the immature fruit of the horse-chestnut. 

 This data was reported first to the American Society of Plant Physiologists 

 at the Gainesville meeting in 1954. It is now apparent that in the immature 

 fruit of the horse-chestnut there occurs an extremely active growth-promoting 

 effect comparable to that produced by coco-nut milk. Figure 8 shows that 

 carrot explants can be made to grow in this way in a fashion comparable to 

 that which occurs with coco-nut milk. 



This material has been collected on a relatively large scale and has been 

 fractionated by methods somewhat different from the first ones used in the 

 isolations of active substances from coco-nut milk. The present trend in this 

 laboratory has been to use techniques in which heavy metal precipitation 

 could be avoided in the attempt to isolate substances which are active in the 

 carrot tissue assay system and which have some of the ultra-violet absorption 

 properties that were thought, from the examinations of Compounds A, B, C, 

 etc., to be a guide to the active growth-promoting principles. Bv proceeding 

 in this general way and making use of an automatic Craig-Post liquid-liquid 

 separator, much progress has been made. 



The important developments from all this work may be briefly summarized 

 as follows: We now know conclusively that active growth-promoting 

 qualities reside in substances present in coco-nut milk and in Aesciibis extracts, 



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