342 Morphogenetic Factors 



lateral buds that were distant from the one that was chilled and had 

 formed some time after it was treated. 



Wittwer and Teubner ( 1957 ) observed that in tomato low-temperature 

 treatment of seeds had no effect, but exposure of very young seedlings to 

 low night temperatures (10 to 13°C) for 2 or 3 weeks induced earlier 

 flowering and more flowers in the first cluster, in contrast to those grown 

 at higher temperatures (18 to 21°C). Cold treatment of older seedlings 

 increased the number of flowers in later clusters. Other factors, especially 



16 

 I2h 



• 1st Lamina 

 a 2d Lamina 

 O 'Scores' 



B 



o 



c 



la 



O 



-J 



- • 



140 



Co 



3o 3 



J L 



I I I 



an- "3 -2 -60 *l *3 

 treated Temperature of Vern. oq 



2o 



lo 



Fig. 15-3. Effect of vernalizing temperatures on length of lamina of first (A) and 

 second ( B ) leaves in winter rye, and on stage of differentiation of spike as meas- 

 ured by an arbitrary scale of "scores." Controls at left. ( From Hansel. ) 



nitrogen nutrition, also affect flower formation and complicate the prob- 

 lem of studying it. 



Hall (1950) compared buckwheat plants in culture with their roots and 

 shoots at different temperatures with others where the entire plant was 

 grown at either high or low temperature. Development was more normal 

 under the latter condition. High temperature for the shoot checked vege- 

 tative growth and hastened flowering, maturity, and senescence, and low 

 air temperature there prolonged ontogeny. Increase in duration of the 



