Salisbury, F. B. The flowering process. Sci. Amer. 198: 109 117. L958 

 Salisbury, F. B. The initiation of flowering. Endeavour 24: 74 80. 1965 

 See Demonstration D-2. 



DEMONSTRATION D-2: Photoperiodic control of flowering of long-da) plant-. 



MATERIALS: 



1. Plants of tuberous-rooted begonia, petunia, or barley. 



2. A light-equipped chamber. Illuminate the chamber with at least two 40-watt fluorescent lamp-. 



3. A dark chamber. 



PROCEDURE: 



1. Divide the plants into lots A and B as soon as they emerge from the soil. 



2. Both lots should receive 8 to 10 hours of light daily in the light chamber. 



3. Place lot A in darkness at the close of each 8- to 10-hour light period. Place lot B (inside the light cham- 

 ber) 3 to 4 feet from a lighted 40-watt incandescent-filament lamp. 



4. If an electric time switch is available, give lot B a total daily light period of 16 to 18 hours (8 to 10 

 hours of fluorescent light plus 8 more hours of incandescent light). 



5. If an electric time switch is not available, leave the incandescent-filament lamp on throughout the night. 



6. Each morning resume the fluorescent light treatments for both lots A and B. 



7. Continue these daily treatments until flowerbuds are obvious. 



OBSERVATIONS: 



Record date of planting, date treatments began, and length of the light and dark periods; also record how 

 many long days were required to induce flowerbud formation. If the tuberous-rooted begonia is u» 

 the experimental plant, make observations on the extent of tuber formation as well as flowering. 



SUPPLEMENTARY READING: 



U.S. Agricultural Research Service. Prescription for better plant form. U.S. Dept. Agr., Agr. Res s: 



14. 1959. 

 See Demonstration D-l. 



DEMONSTRATION D-3: Photoperiodic control of growth and dormancy of 



woody plants. 



MATERIALS: 



1. Seedlings or rooted cuttings of some woody plant material such as deciduous trees (catalpa and red 

 maple), evergreen trees (spruce, loblolly pine, slash pine, or Virginia pine), and shrubs (hollies and wei- 

 gela). 



2. A light-equipped chamber. Illuminate the chamber with at least two 40-watt fluorescent lamps. 



3. A dark chamber. 



PROCEDURE: 



1. Divide rooted cuttings or seedlings into lots A and B. 



2. Both lots should receive 8 to 10 hours of light daily in the light chamber. 



3. Place lot A in darkness at the close of each 8- to 10-hour light period. Place lot B inside the light cham- 

 ber) 3 to 4 feet from a lighted 40-watt incandescent-filament lamp. 



4. If an electric time switch is available, give lot B a total daily light period o\ 16 to 18 hours 8 to 10 

 hours of fluorescent light plus 8 more hours of incandescent lighl ). 



5. If an electric time switch is not available, leave the incandescont-tilament lamp on throughout the 

 night. 



6. Each morning resume the fluorescent light treatments for both lots A and B. 



7. Continue these daily treatments until the plants on the 8- to 10-hour day those of lot A take on the 

 aspects of dormancy and there is a marked difference in the si/e o\ plants o\ lots A and B. This should 

 require at least 30 days. 



17 



