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METABOLIC ASPECTS OF PHOTOPERIODISM 



1 ^ ' T 



40% 



297 



707o 



12 16 20 24 4 

 TIME OF DAY (HOURS) 



t f 



LIGHTS ON LIGHTS OFF LIGHTS OFF LIGHTS ON 

 SD LD 



Fig. 7. Carbon dioxide metabolism of Kalanchoe under long-day condi- 

 tions (broken lines), after 20 short-day cycles (solid lines), and after 21 

 short-day plus 15 long-day cycles (dotted lines). Lights on at 8:00 a.m. 

 under long- and short-day conditions. Lights off at 4:00 p.m. (16 hr) for 

 the short-day conditions, and at midnight (24 hr) for the long-day condi- 

 tions (broken and dotted lines). 



that the CO2 metabolism can be induced to develop after treatment 

 with 21 short days, although the plant is returned to long days. 



POSSIBLE RELATIONSHIP BETWEEN COo METABOLISM 



AND FLOWERING 



It is interesting to speculate on the possible relationship between the 

 CO2 metabolism and the initiation of flowering. The similarities are 

 striking. 



1 . Both are promoted by short days. 



