Vernalization and Photoperiodism — 4 — A Symposium 



periments were conducted with the following objects: — to determine (1) 

 the principles underlying the effect of low temperatures on flower produc- 

 tion, and (2) further details regarding (o) co-operation of the temperature 

 of germination, and temperature and other conditions during the course of 

 vegetation, and {b) the significance of tlie vegetative period in understand- 

 ing the relative peculiarities of summer and winter cereals. 



Gassn'er sowed the seed of cereals in sand at different dates between 

 January 10th and July 3rd, and subjected them to the following tempera- 

 tures during germination: 1 to 2°, 5 to 6°, 12° and 24°C. Selected seed- 

 lings were subsequently placed in pots and then planted out. Tables and 

 graphs in his paper show (o) date of sowing, (b) temperature during ger- 

 mination, (c) "appearance above ground," when the young leaf had reached 

 a length of 20 to 25 mm., and (d) shooting. The crop plants used were 

 Petkus winter rye and Petkus spring rye. The results may be summarized 

 as follows (Gassxfr, 1918'> : 



The temperature during germination had no influence on shooting of 

 spring rye ; plants germinated at the temperatures quoted above, all shoot- 

 ing at regular and uniform intervals. In winter rye, only the plants ger- 

 minated at 1 to 2°C. exhibited shooting regularly throughout the whole 

 vegetative period. Plants germinated at 5 to 6°C. only shot regularly if 

 their "appearance above ground" had occurred before the end of April, 

 and those germinated at 12° and 24°C. only if they had appeared above 

 ground before the middle of April and the end of March respectively. 



Some plants did not shoot at all, but of those which did, the plants that 

 had appeared above ground simultaneously attained shooting all the sooner, 

 the lower the temperature at which they had been germinated. Thus, 

 plants which appeared above ground in the middle of March and which had 

 been germinated at 1 to 2°C. shot about 9 days, 21 days and 41 days earlier 

 than those that had been germinated at 5 to 6°C., 12°C., and 24°C. respec- 

 tively. The illustrations in Gassner's article indicate the further difference 

 that plants germinated at a low temperature not only reached the shooting 

 stage more rapidly but also more regularly than those germinated at a higher 

 temperature. 



Gassner's conclusions regarding the physiological difference between 

 spring and winter rye were as follows : Spring rye is practically inde- 

 pendent of any need to pass through a cold period before it can achieve 

 shooting (Bliitenauslosung). The flowering (Bliitenbildung) of winter 

 rye depends on its passing through a cold period either during germination 

 or at some stage subsequent to germination. 



Gassner made some observations regarding the correlation between 

 winterhardiness, sugar content and flowering. Without going into any 

 great detail with regard to the problem of death of the plant cell through 

 cold, he stated that the following may be quoted as definite facts : 



(1) The growing of winter plants at a low temperature induces increased winter- 

 hardiness ; 



(2) low temperature is a condition for the "release of flower form^ion;" 



(3) cultivation at low temperature increases sugar content ; it may be assumed 

 that winterhardiness and sugar content are in a causal relationship, while the "release 

 of flower formation" depends on sugar content; 



(4) winterhardiness and the cold-requirement, so important for flowering, are 

 correlatively connected. 



