Vernalization and Photoperiodism — viii — A Symposium 



If it be the meristems which are initially changed, then the subsequent 

 reactions leading to flowering may result from differences in the supply 

 system and therefore in the materials made available to the developing 

 initials. Similar effects exerted through the transporting system may be 

 operative in the thermoperiodic phenomena described by Went. 



Some of the questions are less broad and are susceptible of immediate 

 attack. One of these is the nature of the photo-receptor pigment, the 

 measurement of whose absorption spectrum by the Beltsville group is 

 described in one of the following chapters. Another is the role of sugar- 

 feeding and induced fermentation studied by Melchers, Lang and Claes, 

 and discussed in the articles by Murneek and Hamner. Still another is the 

 relation of auxin production to flowering; it is a striking fact that, in 

 pineapple, auxin greatly hastens flowering, while in other plants its effect 

 tends to be in the opposite direction. Indeed, Galston" has ascribed the 

 effect of triiodobenzoic acid in increasing the number of flower-buds in 

 soybeans to the antagonistic effect of this substance on the auxin of the 

 plant. The reduction of cambial activity preceding flowering in the plants 

 studied by Roberts and Struckmeyer would also indicate an opposition 

 between auxin and flowering. The very rapid reactions to change in day- 

 length in such plants as the soybean, of course, would not suggest that such 

 cambial changes were causative in themselves, but they could certainly be 

 an indication of decreased auxin production. Very recently, both Thurlow 

 and Bonner' and Leopold* have found, using different plants and different 

 methods, that auxin, applied externally, may inhibit to some extent the 

 normal process of flowering. A number of older observations, both botanical 

 and horticultural, point in the same direction, while the peculiar and (at 

 present) isolated case of pineapple, whose flowering is promoted by auxin, 

 cannot be overlooked. Whether auxin plays a major role in the flowering 

 process, however, (either as a promoter or an inhibitor), is far from estab- 

 lished, though there is doubtless an interesting avenue here to be opened up. 

 A more extensive discussion of this phase of the problem has been given 

 elsewhere.® 



It may be, and this is undoubtedly the usual course of research, that 

 further study of these more concrete problems will lead to a gradual 

 elucidation of the broader and more intangible unknowns. But as was 

 stated at the outset, the state of the field is such that a single clear-cut 

 result might change its whole aspect almost overnight. 



The consequences of major progress in this area are very great, not only 

 for pure science but for agriculture. In these days when so much of the 

 world is near to starvation no worker can fail to carry this thought in the 

 back of his mind, in spite of the frequent statement that research is its own 

 reward and that no further incentive is necessary. One purpose of a 

 symposium like the present publication is to enable the individual student 

 to effect something of a synthesis in his views. Such a synthesis can hardly 

 fail to engender new ideas and thus to quicken the pace of progress. 



Kenneth V. Thimann 



Harvard University 



«Galston, a. W. in Amer. J. Bot. 34:356-360, 1947. 

 ' Thurlow, J. and Bonner, J. (Abstr.) in Amer. J. Bot. 34: 603, 1947. 

 ' Unpublished data. 



* Thimann, K. V. in The Physiology and Chemistry of Hormones, Chapter 3 

 (New York: The Academic Press), 1948. 



