COLOR 445 



The chief influence on color. Apples matured on the tree in an 

 abundance of sunlight show the highest color ; therefore, any- 

 thing that tends to hasten maturity or to increase the amount 

 of sunlight, such as proper pruning of the branches, thinning of 

 the fruit, and selection of site, will promote color, while factors 

 tending to retard the one or decrease the other will lessen 

 the color. 



The relation of this fact to certain others is interesting. Manure 

 and nitrogen applications, heavy soils, and excessive cultivation, 

 all tend to decrease color ; while light soils, sod or sod-mulch, and 

 possibly phosphate and potash applications tend to improve it. 

 These differences are all readily accounted for on the basis of 

 their relation to maturity, though some of them also indirectly 

 affect the amount of light. The first group of factors evidently 

 tends to retard maturity, while the second group hastens it. We 

 also know that dense tree tops, heavy foliage, and early picking 

 of fruit give us reduced color, while the reverse conditions 

 favor it. These effects are evidently due to modifications in the 

 amount of light, and in one case also to the different degree 

 of maturity. 



Our conclusions, then, are that the yellow colors in apples are 

 independent of light and of nearly all other environmental condi- 

 tions. The red colors, however, are primarily dependent on sun- 

 light, and especially on the amount received during the later stages 

 of maturity. Maturity in sunlight is therefore the dominant en- 

 vironmental influence in the production of color in apples. Hence, 

 anything that tends to hasten maturity or to increase the amount 

 of sunlight received will favor color, while the reverse conditions 

 will injure it. 



Exposure of apples to sunlight after they are harvested has in- 

 creased their redness by 35 per cent, while those kept in the dark 

 or exposed to electric light showed no definite increase. 



Effect of iron on color. The idea that iron in the soil or appli- 

 cations of iron have some definite relation to color in apples has 

 long existed. In the experiments that have been conducted, better 

 coloring was reported on both the fruit and the foliage of trees 

 receiving the applications, but the leaves and peelings contained 

 less iron than those of the checks. 



