54 GROWTH HORMONES IN PLANTS 



Compound Avena Test 



3-Indole pyruvic acid . 2 



'2-Methyl-3-indole methyl acetate Inactive 



Phenylacetic acid . 0002 1 



Phenylpropionic acid Inactive 



Cinnamic acid Inactive 



Allocinnamic acid O.OOO61 



Cis-o-methoxycinnamic acid Inactive 



Isatinic acid . 002 



Atrolactic acid Inactive 



Vulpinic acid Inactive 



' The curvature is confined to a short region at the top of the coleoptile. 



The foregoing compounds tested by Haagen Smit and Went on 

 the Avena coleoptile are also more or less active in the pea test 

 (with the exception of cinnamic acid). 



The following compounds were found inactive in the pea test: 

 2-ethyl-3-indole acetic acid, coumarin, o-coumaric acid, cinnamic 

 acid, a-methyl cinnamic acid, a-phenylcinnamic acid, trans-o- 

 methoxycinnamic acid, p-methoxycinnamic acid, cinnamic-ethyl 

 ester, benzilic acid, phenylglyoxylic acid, benzoic acid, benzal- 

 malonic acid, r-mandelic acid, phenylacetamid, diphenylacetic 

 acid, phenylvalerianic acid, p-nitrophenylacetic acid, 2-4-dinitro- 

 phenylacetic acid, phenylalanin, indole carbonic acid, phenyl- 

 aminoacetic acid, acetic acid, propionic acid, butyric acid, 

 chloracetic acid, iodacetic acid, malonic acid, maleic acid, adipinic 

 acid, serine, cysteine, isatin, angelic acid, tiglic acid, crotonic acid, 

 acetophenone, tyrosine, eosin. 



Coleoptile cylinders 5 mm. in length were placed in solutions of 

 numerous of the foregoing compounds, and the increase in length 

 measured after 12 hours. The same compounds which brought 

 about linear growth of coleoptile cylinders also gave positive 

 results with the pea test, but in numerous instances the same 

 compounds failed to induce curvature in the Avena coleoptile. 



Thimann (1935c) has recently studied the physiological activity 

 of 3-indole acetic acid (/3-indole acetic) and its analogues which 

 contain no nitrogen; these are 3-indene acetic and 1-coumaryl 

 acetic acid. They contain carbon and oxygen atoms, respec- 

 tively, in place of nitrogen. All three compounds possess the 

 unsaturated five-membered ring, fused to benzene, with the 

 acetic acid side chain. Both analogues produce cell elongation in 

 the Avena coleoptile, are active in root formation, inhibit root 



