leaching with the solvent. The insoluble light-induced yellow pigment left in the tomato fruit cuticle 

 has not yet been identified. The presence or absence of this light-controlled pigment in the akin makes it, 

 respectively, either yellow or colorless. When the yellow skin is superimposed over the red, the fruit I 

 orange-red appearance, the typical color of summer field-ripened tomato fruits. The combination of red 

 flesh and a transparent skin produces a fruit that is pink. The pink color is characteristic of fruit - 

 mercially available in the North in midwinter; these have been artificially ripened in darkness by vegetable 

 wholesale distributors. If the fruits ripened in the dark have yellow-tinted skins, the fruits were too mature 

 and were already producing the light-responsive pigment at the time they were placed in the dark. 



SUPPLEMENTARY READING: 



Piringer, A. A., and Heinze, P. H. Effect of light on the formation of pigment in the tomato fruit cuticle. 



Plant Physiol. 29: 467-472. 1954. 

 U.S. Agricultural Research Service. Light link in tomato. U.S. Dept. Agr.. Agr. Res. 2: 8. 1954. 



DEMONSTRATION C-3: Localization of response to light 1>> the pigment 



in tomato skin. 



MATERIALS: 



1. Three uniformly greenish-white mature tomatoes. 



2. Other materials as in demonstration C-2. 



3. In addition, two small sheets of aluminum foil, enough to completely cover a tomato fruit. 



PROCEDURE: 



1. Completely and tightly wrap one of the tomato fruits with a sheet of aluminum foil (dark control). 



2. Remove a 5-millimeter-diameter section from the center of another sheet of aluminum foil. Completely 

 and tightly wrap another tomato fruit, being careful that the perforation exposes an area of skin on the 

 side of the fruit. 



3. Leave the remaining tomato fruit unwrapped (light control). 



4. Place all tomato fruits, both wrapped and unwrapped, in the light and allow 10 to 14 days for ripening, 

 keeping the temperature at 70° F. 



5. When the unwrapped fruit is ripe (soft and red), unwrap all fruits and note any differences in skin color. 



6. Remove and process sections of the skin as in demonstration C-2, being careful to include the area 

 exposed to the light through the perforation in the foil. 



OBSERVATIONS: 



Skins of the unwrapped fruit should be bright yellow; skins of the completely wrapped fruits should be 

 colorless; skins from the wrapped fruit with the small area exposed should be colorless except for the small 

 exposed area, which will be yellow. A novelty can be produced by tightly wrapping a green-mature fruit 

 with a sheet of aluminum foil having a number of small perforations. 



SUPPLEMENTARY READING: 



Hicks, C. B. You can make a plant do tricks. Pop. Mech. 108: 81-85, 232-236. 19:>7 



DEMONSTRATION C-4: Effect of light on coloration of apple*. 



MATERIALS: 



1. Early harvested (green) Jonathan, Rome Beauty, or Arkansas apples. Jonathan variety is preferred. 

 Store the apples before use at 32° F. in bags of 0.38-millimeter polyethylene plastic. 



2. Light and dark facilities as in demonstration C-2. 



3. Black plastic electrical tape. 



4. In addition, two small sheets of aluminum foil, enough to completely cover a fruit. 



PROCEDURE: 



1. Completely and tightly wrap one apple with a sheet of aluminum foil dark control). 



2. Wrap another apple in aluminum foil, cut holes in the foil, and place the apple under the light of the 

 growth chamber. 



15 



