Vernalization and Photoperiodism —40— A Symposium 



Photoperiod — Lmgth of daily exposure to light (Garner and Allard). 



Photoperiodism — Response of plants to photoperiod (Garner and Allard). 



Photoperiodicity — Response of animals to photoperiod. Used by some zoologists (Bis- 

 sonette). . . 



Long-day platits — Species, varieties and strains in which the flowering period is ac- 

 celerated by a relatively long daily exposure to light, usually more than 12 to 14 

 hours (Garner and Allard), or which require minimum photoperiods or con- 

 tinuous light, but not darkness (Lysenko), or which require short dark periods 

 (Hamner). . . 



Short-day plants — Species, varieties and strains in which the flowering period is ac- 

 celerated by a relatively short daily exposure to light, usually less than 12 to 14 

 hours (Garner and Allard), or which require photoinductive cycles containing 

 photoperiods of minimum intensity and dark periods of minimum duration (Ham- 

 ner). 



Day-neutral (indeterminate) plants — Species, varieties and strains in which flowering 

 is not influenced by length of daily exposure to light (Garner and Allard). 



Photoperiodic inditction — Formerly, the carry-over effect of a photoperiod conducive 

 to sexual reproduction to one opposite to it (Lubimenko and Sceglova). Now, 

 the stimulation of flowering by exposure to photoinductive cycles (Hamner). 



Photoperiodic after-effect — The same as photoperiodic induction (Maximov). Plants 

 may exhibit also temperature and possibly other "after-effects." 



Photoperiodic adaptation — The adaptation of plants in their native or artificial 

 habitat, to a definite length of day or to latitude (Lubimenko). 



Photoperiodic inhibition — Inhibition or retardation of growth primarily of the main 

 axis, by certain photoperiods (Murneek). 



Photothermal induction — The induction of reproduction by a combination of photo- 

 periods and temperature (Owen et al.). 

 Thermo-photoperiodic induction — The same as photothermal induction (Whyte). 

 Thermoperiodicity — Response of plants to alterations in day and night temperatures 



(Went). 

 Thermoperiodic adaptation — The adaptation of plants, in their native or artificial 

 habitat, to specific temperature requirements (Lubimenko). 



Reviews on Photoperiodism and Related Subjects: — For a more 

 detailed discussion of literature on photoperiodism in plants, and subjects 

 appertaining thereto, than is possible to present here, the reader is referred 

 to the following comparatively recent reviews : 



Garner, W. W. Biol. Effects of Radiation, Ch. 19, 1936 and Hot. Rev. 3 :2S9-275, 

 1937. 



BuRKHOLDER, P. R. Bot. Rev. 2: 1-52, 97-168, 1936. 



Gregory. F. G. Sci. Hort. 4: 143-154, 1936. 



Bowman, E. T. Journ. Austral. Inst. Agr. Sci. 4: 25-32, 1938. 



TiNCKER, M. A. H. Sci. Hort. 6 : 133-149, 1938. 



Hamner, K. C. Ann. Rev. Biochem. 13 : 575-590, 1944. 

 Sex expression in plants: — 



LoEHWiNG, W. F. Bot. Rev. 4: 581-625, 1938. 

 Nutrition in relation to photoperiodism: — 



Murneek, A. E. Mo. Agr. Exp. Sta. Res. Bui. 268, 1937. 



Murneek, A. E. Growth 3 : 295-315, 1939. 



Loehwing, W. F. Proc. Iowa Acad. Sci. 49: 61-112, 1942. 

 Temperature responses: — 



Thompson, H. C. Proc. Amer. Soc. Hort. Sci. 37 : 672-679, 1939. 

 Theories related to flower formation: — 



Cajlachjan, M. H. Hormonal theory of plant development, Moscow, 1937 (in 

 Russian) . 



Whyte R O. and Oljhovikov, M. A. Chron. Bot. 5 : 327-331, 1939. 



Cholodny, N. G. Herbage Revs. 7: 223-247, 1939. 



Abler, F. Forschungsdienst 9 : 332-367, 1940. 



