3. A red chamber (a cardboard box with scams sealed with paper tape). Cut out the top and most of the 



bottom of the box. Place a light filter of two layers of red cellophane over the opening in the bottom 

 of the box, using cellophane tape to hold it in place. 



4. A far-red chamber (a cardboard box prepared in the same manner as for the red chamber excepl 



the cutout opening in the bottom with a light filter of two layers of red and two layers of dark-blue cel- 

 lophane). 



5. A dark chamber that can hold three pots. 



PROCEDURE: 



1. Plant beans in pots of sterilized soil; water and place at a temperature of 80° F. 



2. After 3 to 4 days the plants will begin to emerge from the soil. At this time all pot- should be placed 

 in the light chamber, where they should receive light from the fluorescent lamps for 8 to 10 hours each 

 day. The temperature during this growing period should be 70° to 75° F. 



3. The first pair of leaves should be about half expanded 10 to 12 days after planting. At this stage of 

 development the plants are ready to start on individual treatments, but the 8- to 10-hour fluorescent 

 lighting continues daily for all of the plants. 



4. Divide the plants into three equal lots: A, B, and C. 



5. Place plants of lot A in the dark at the close of each 8- to 10-hour light period. Place lots H and C 

 under the red and blue cellophane (the far-red filter). 



6. Turn off the fluorescent lamps, and turn on for 15 minutes a 100-watt incandescent-filament lamp 

 placed 3 feet above the red-and-blue cellophane filter. 



7. Plants of lot B are moved in darkness to the dark chamber immediately after the 15-mmute exposure 

 to far-red. Plants of lot C are moved in darkness and placed under the red cellophane filter, which is 

 under the fluorescent lamps. 



8. Turn on the fluorescent lamps for 10 minutes, then move plants of lot C in darkness to the dark chamber. 

 (Great care should be taken to assure that the plants receive no light from any other source after in- 

 dividual radiation treatments begin.) 



9. Return plants of all lots to the fluorescent-light chamber each morning. 



10. The treatments should be given daily until a response is obvious, requiring at least 5 days of treatment. 



OBSERVATIONS: 



Record date of planting, date treatments were begun, number of days treatments were given, and the 

 durations of the light period, red exposure, and far-red exposure. Measure and record daily the length of 

 the second internode. Data can be plotted as line graphs (length plotted against time). Three plots should 

 be made: The control (lot A), the far-red treatment (lot B), and the far-red followed by red (lot ( ' 



SUPPLEMENTARY READING: 



Downs, R. J., Hendricks, S. B., and Borthwick, H. A. Photoreversible control of elongation of Pinto 



beans and other plants under normal conditions of growth. Bot. Gaz. US: 99 208. L957. 

 Wassink, E. C, and Stolwijk, J. A. J. Effects of light quality on growth. Ann. Rev. Plant Physiol. 

 7: 373-400. 1956. 



C. Light and Plant Pigments 



DEMONSTRATION C-l : Effect of light on formation of anthocy anin in seedlings. 



MATERIALS: 



1. Seeds of Wheatland milo, dwarf milo, or Sumac sorgo. 



2. Five petri dishes or plastic sandwich boxes, with lids. 



3. Filter paper (Whatman No. 3). 



4. Five black bags made of two layers of black sateen cloth. 



5. A solution of 3 percent hydrochloric acid (HC1) in absolute propanol (propyl alcohol) 3 ml. HC1 in 

 97 ml. of propanol). 



is 



