PROCEDURE: 



1. Place three sheets of filter paper in each petri dish and moisten with water. 



2. Place 20 seeds on the top filter paper of each dish, cover the dishes with the lids, and place each dish 

 in a black cloth bag, keeping the temperature at about 80° F. 



3. Allow 4 days for the seedlings to germinate and then begin treatments. 



4. Place the five dishes under fluorescent lamps for periods of 0, 4, 8, 16, and 24 hours, respectively, then 

 return the dishes to their black cloth bags. 



5. The amount of anthocyanin formed can be observed from 16 to 24 hours after irradiation. 



6. Count out a certain number of seedlings (say 10) from each dish and place each lot of 10 seedlings in 

 the solution of HC1 in 1-propanol. Place them in a refrigerator (about 40° F.) for 16 to 24 hours. 



OBSERVATIONS: 



The amount of anthocyanin formed by the various light treatments can be estimated by assigning a nu- 

 merical scale that increases with increasing color, or it can be measured by differences in optical density as 

 measured with a colorimeter or spectrophotometer. The amount of anthocyanin can then be plotted graph- 

 ically by plotting the amount of anthocyanin as a function of the time (hours of light). 



SUPPLEMENTARY READING: 



Siegelman, H. W., and Hendricks, S. B. Photocontrol of anthocyanin synthesis in turnip and red cabbage 

 seedlings. Plant Physiol. 32: 393-398. 1957. 



DEMONSTRATION C-2: Effect of light on tomato skin and fruit color. 



MATERIALS: 



1. Mature green tomato fruits from a normally red-fruited variety when ripe, such as the variety Rutgers. 

 Their skin color should be uniformly greenish-white with no visible red, pink, or yellow color. These 

 are readily obtainable from home gardens any time prior to frost and from local wholesale vegetable 

 distributors in the larger cities, where southern-grown green-mature fruits can be obtained throughout 

 the winter. 



2. A light facility, using incandescent or fluorescent lamps that provide a light intensity of 20 foot-candles 

 or more. 



3. A dark facility that provides total darkness, using light-tight black sateen cloth bags made of two layers 

 of cloth. 



4. Scalpel or similar sharp instrument. 



5. Small bottles or vials. 



6. Acetone or petroleum ether. (CAUTION: Flammable solvents.) 



PROCEDURE: 



1. Divide the green-mature fruits into two uniform lots, A and B. 



2. Ripen fruits of lot A for 10 to 14 days with illumination of daily duration of 1 hour. Longer periods may 

 be given but are not necessary. Keep the temperature at 70° F. 



3. Ripen fruits of lot B 10 to 14 days in total darkness, taking care not to remove from darkness until ripe. 

 These should ripen simultaneously with their lighted counterpart. Keep the temperature at 70° F. 



4. When the fruits are ripe, note any color differences between the two lots. Remove the skin from a tomato 

 of each lot by briefly immersing the whole fruit, or a piece, in boiling water. Be careful to keep the 

 two skins identified as to the ripening treatment of their fruits. With the scalpel scrape the adhering 

 tissue from the skins as carefully and completely as possible. Place each scraped skin in one of the small 

 containers containing acetone or petroleum ether solvent and leach the skins with several washings 

 (keeping the sections immersed) over a period of at least several hours. 



OBSERVATIONS: 



The fruits ripened in the dark will be pink; those ripened in the light will be orange-red. CAUTION: Fruits 

 will ripen faster at temperatures higher than 70° F., but at those higher temperatures the red pigment in 

 the flesh does not develop well and gives the fruit an off-color appearance. The skin of fruits ripened in 

 the dark will be colorless; the skin of those ripened in the light will have a yellow color even after prolonged 



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