11 



There are a number of 

 these are the following: 



factors that Influence color. Among 



1. Temperature: High temperature will, of course, cause 

 fruits to ripen faster and thus accelerate the normal changes as- 

 sociated with ripening. But it can also alter these changes. It 

 is know, for example, that above 90O F lycopene (the red carotenoid) 

 will not form, and therefore, a tomato ripened above this tempera- 

 ture will not be red. There is also evidence that high tempera- 

 tures can interfere with anthocyanin synthesis. On the other hand, 

 relatively low temperatures (40-50° F) accelerate anthocyanin syn- 

 thesis, resulting in the frequently observed fact that cool weath- 

 er produces redder fruit. 



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3. Sugar content: For synthesis of either anthocyanins or 

 carotenoids to proceed, a tissue must contain a high sugar content. 

 This fact is very important for coloring of leaves and flowers 

 which have much lower sugar contents than fruit, and it is probably 

 the reason why low quality fruit are often poorly colored. 



Nutrition: It is well known that high levels of nitrogen can 

 produce poorly colored fruit, since they accentuate chlorophyll 

 and suppress anthocyanin synthesis. It has also sometimes been re- 

 ported that high potassium and high boron stimulate anthocyanin 

 Synthesis, but findings are not consistent with these elements. 



Can anything be done about fruit color? Basically, of course, 

 it is controlled by the genetics of the plant. With apples, we 

 are most interested in red color, and our problems have been great- 

 ly reduced with the selection of the anthocyanin-rich mutants (red 

 Sports) as well as through development of stop-drop sprays which 

 allow the fruit to mature more fully. Yet problems still occur as 

 a result of high temperature, overf ertil i zation , or low sugar con- 

 tent. Once we harvest apples, there is nothing we can do to im- 

 prove red color except to employ the old process of sun coloring, 

 which is seldom advisable. Considerable research has been con- 

 ducted to find a means of inducing red color, but to date no method 

 has been found to overcome the requirement for substantial quanti- 

 ties of light in order for anthocyanins to be synthesized. Never- 

 theless, color does change following harvest, because the loss of 



