566 THE STRUCTURE OF ECONOMIC PLANTS 



pigment determine the variation in the shade and intensity of 

 color. 



There are differences of opinion in regard to pigmentation in 

 tomato fruits and two viewpoints are here reported. Jones and 

 Rosa (i6) state that 



"In lemon-yellow fruit, carotin occurs in the pericarp, but the 

 epidermis is colorless; in orange-colored fruit, carotin occurs both in 

 pericarp and epidermis; in pink fruit, lycopersicin occurs in the peri- 

 carp, but the epidermis is colorless; in red fruit, lycopersicin occurs 

 in the pericarp and carotin in the epidermis and probably in the pericarp 

 as well. Albino, or white, fruit lacks all pigments." 



Smith (x8) sums up the matter as follows: 



"It has long been advocated that there are yellow and transparent 

 tomato skins which, combined with yellow or red fruit color, give 

 rise to light yellow, dark yellow, pink, and orange-red tomatoes. 

 These transparent skins have often been called colorless. This is erro- 

 neous. All skins of commercial red and pink tomato fruits are colored. 

 The cell walls of yellow skins are yellow or golden, the color being 

 due to an unidentified pigment. The cell walls of pink skins lack this 

 pigment and therefore are colorless. The color of the pink skin is 

 due to the presence of lycopene crystals, and often carotene also, as 

 a part of the cell contents. Light intensity and quality appear to have 

 an effect on the pigment content of the skins of tomato fruits by altering 

 the quantity of any or all of the three pigments which constitute 

 tomato-skin color." 



In studies of fruit pigments, Howard (15) points out that 

 Willstatter and Escher (37) have demonstrated that lycopersicin 

 is identical in general composition and molecular weight with 

 carotin. Her work on tomato indicates that lycopersicin is the 

 principal pigment and that carotin is present in small amounts. 

 The lycopersicin crystals which occur in the ripe fruits are brownish 

 rose to carmen red and are usually in the form of needles or elon- 

 gated prisms. In some instances, crystal aggregates are formed, 

 while in others the crystals appear as long fine hair-like structures. 



On the basis of Smith's investigations it appears that protection 

 of the fruit from intense light favors lycopene formation; but that 



"the carotenoid content of both the skin and the flesh of fruits ripened 

 in the light is higher than in fruits ripened in the dark when the early 

 growth has occurred under the same light conditions. To attain 

 maximum carotenoid content, the fruits should be grown in complete 

 exposure to light and allowed to mature on the vine." 



