The N-Arylphthalamic Acids 271 



33. Wittwer, S. H., and Teubnei, F. G. New practices for increasing the fruit 

 crop of greenliouse-grown tomatoes. Mich. Agr. Exp. Sta. Quart. Bui. 39: 

 198-207. 1956. 



34. Zinimernian. P. W., and Hitchcock, A. E. Flowering habit and correlation of 

 organs modified by triiodobenzoic acid. Contr. Boyce Thompson Inst. 12: 491- 

 496. 1942. 



35. , and Hitchcock, A. E. Triiodobenzoic acid influences flower formation 



of tomatoes. Contr. Boyce Thompson Inst. 15: 353-361. 1949. 



36. , Hitchcock, A. E., and Prill, E. A. Substituted benzoic acids as growth 



regulators. Contr. Boyce Thompson Inst. 16: 419-427. 1952. 



DISCUSSION 



Dr. Nitsch: Does your compound also stimulate flower formation 

 in other species? 



Dr. Teubner: We have only cursorily examined the effect on other 

 species. The tomato has a sympodial flowering habit and this may ac- 

 count for its response. We're not completely sure whether this is a 

 direct effect of the material on the developing floral primordium or 

 whether it is an indirect effect through inhibition of the sympodial 

 bud as Dr. Leopold has suggested in his recent review. However, his- 

 tological evidence indicates that it is a direct effect on the floral 

 meristem. The strawberry has a corymbose raceme which can be 

 monochotomous, dichotomous, or polychotomous. While it is more 

 difficult to work with clonal lines in this species, for large, uniform 

 populations we have observed an appreciable effect on flowering. We 

 obtained flower clusters of 50 to 100 flowers. Other plants which have 

 been examined are snapdragon and petunia. Neither of these re- 

 sponded, but of course we had little knowledge of the stage of devel- 

 opment at which floral initiation takes place. The time of applica- 

 tion is very critical at lower concentrations with the tomato and we're 

 sure this holds with other species. We know there is no response from 

 low concentrations applied 2 or 3 days before the inflorescence is laid 

 down or initiated. We previously reported this in Science (Science 

 122: 74, 1955). Apparently these compounds are so labile that when 

 low concentrations are applied prior to initiation, the amount present 

 when the flower cluster is developing is insufficient to produce the re- 

 sponse. With higher concentrations we obtained a different effect 

 if we apply 2 or 3 days prior to initiation, and reduce the number of 

 nodes which antecede the flower cluster. Similar effects are obtained 

 with 2,3,5-triiodobenzoic and a-(2-naphthoxy)phenylacetic acids. 

 Whether or not this is induction we are not in a position to state. If 

 you accept Dr. Lang's (Ann. Rev. Plant Physiol. 3: 265. 1952) thesis 

 that reduced node number is the criterion for flowering, then we are 

 inducing flowering with these chemicals. But we have to apply very 

 early, at cotyledon expansion, and at high concentrations. If you ac- 



