Nexu Auxins From 'Maryland Mammoth' Tobacco 09 



unsaturated fatty acid might be expected to do so. These compounds, 

 particularly in the configuration we believe ours has, do act as anti- 

 oxidants. 



Dr. Housley: Is it possible that this type of compound influences 

 cell division and that the growth you have been getting has reflected 

 this action rather than an effect on cell elongation? 



Dr. Crosby: We have not carried out microscopic examination of 

 these materials. We do note that the sections elongate; they do not 

 seem to grow in bulk. 



Dr. Osborne: Do the substances which have been isolated from 

 'Maryland Mammoth' tobacco have any effect on accelerating abscis- 

 sion? In the Agriculture Department in Oxford we are trying, with 

 Prof. E. R. H. Jones, to isolate this abscission-accelerating factor. It 

 seems likely, from what we know so far of the compound, that it 

 might fit in with your findings. As a subsidiary question, may I ask 

 if there was a large number of very old leaves in the ton of material 

 you extracted? 



Dr. Crosby: The plants were close to the flowering stage. We took 

 only the younger, bright green leaves and the apical tissue. WVt have 

 not investigated the effects of these materials on abscission. 



Dr. Fawcett: Activity in the wheat coleoptile test is shown by 

 certain compounds which do not possess a ring structure (Nature. 178: 

 972. 1956). Ethanol, ethylenediaminetetraacetic acid, certain xan- 

 thates, and chloroalkanecarboxylic acids were cited as examples. All 

 these compounds had the same low order of activity and their opti- 

 mum activity was given at a concentration just below the level at 

 which toxic symptoms were observed. Since they were inactive in 

 the pea curvature and tomato leaf epinasty tests and showed some 

 other common features, their growth-regulating activity was regarded 

 as nontypical — possibly resulting from subacute toxicity. S-carboxy- 

 methyl N.N-dimethylaminodithiocarbamate, however, was highly ac- 

 tive in the wheat, pea, and tomato tests, and we think this type of 

 nonring structure can induce a typical auxin response. Have you 

 tested the lower members of this homologous series of alcohols? 



Dr. Crosby: No, we started our examination with the C-10 alco- 

 hol. I think the physical and chemical properties of the alcohols be- 

 low C-10 fall somewhat into one class, and the properties of those 

 greater than C-10 fall into a different class. 



Dr. Thimann: It was shown recently that many algae are ex- 

 tremely sensitive to ethanol and respond to quite low concentrations. 

 The indication was that it perhaps acts as a nutrient but I would say 

 in several instances, effects on algal growth ascribed to lAA were 

 really due to the ethanol in which it was dissolved. 



