The Induction of Flowering with a Plant Extract 



R. H. ROBERTS 



IT IS agreed by workers who have studied the physiology of blossoming, 

 especially as related to photoperiodism, that plants contain a chemical 

 substance which induces flowering (3). This concept is based particularly 

 upon grafting experiments in which a plant in flower or a leaf from a 

 flowering plant will induce a nonflowering plant to blossom when the 

 two are grafted together under the proper experimental conditions. No 

 report of a successful extraction of the blossom-inducing chemical has 

 been seen although the name florigen has been proposed for it by 

 Cajlahjan (i). 



Several years ago Struckmeyer (4) reported that there is reduced 

 cambial activity and increased maturation of tissues at the time sexual 

 reproduction is initiated. Thus it appears that the blossom-inducing 

 substance causes maturation of tissues in contrast to the proliferation 

 of cells produced by the numerous growth substances (5), some of which 

 are used as weed killers (2). Since florigen appears to have a physiological 

 effect opposite to the so-called hormones, it was presumed that its 

 extraction should require an unlike procedure, or at least an unusual 

 solvent. 



In 1946 a solvent was found which gave promise of being useful in 

 obtaining florigen. The first successful extraction and subsequent blossom 

 induction of the short-day plant cocklebur {Xanthium echinatum) with 

 its extract was accomplished in December of that year. The fifty-second 



Editor's Note: Published with the permission of the Director of the Agricul- 

 tural Experiment Station. Tlie work reported here was supported in part by a 

 grant from the Wisconsin Alumni Research Foundation. A verbal report of this 

 work in inducing flowering with plant extracts was made before the meeting of 

 the American Society of Plant Physiologists at Cincinnati, Ohio, September 10, 

 1948. 



