A Report on the Effect of Light on Pigment Formation in Apples

Investigations have been carried out in recent years in an effort to improve the color of various fruits. Citrus and other semitropical fruits, in particular, have received the most attention. Several studies of the factors influencing the formation of the red pigment of apples have been made. In general, such studies have included the influence of light, fertilization, pruning, and artificial tree and fruit feeding. Overholser (1) has shown that light is one of the most important factors in the development of anthocyanin pigments, not only in the apple, but in other kinds of fruit as well, such as pears, peaches, plums, nectarines, etc. Magness (2) has presented data which indicate that apples must reach a certain state of maturity before red color will develop on exposure to light. In other words, certain substances must be present in the fruit before the anthocyanin pigments can be produced by the action of light. Since light is such an important factor in anthocyanin formation, it becomes essential to determine which wave-lengths of light are most influential. The present paper is a preliminary report on the effect of various wave-lengths of light on development of color in McIntosh apples. Before going further, it is desirable to establish an arbitrary range for the main divisions of the spectrum. According to Luckiesh (3) the ultra-violet range is from 0 to 3000 8., the near ultra-violet from 3000 to 4000 A., and the visible spectra from 4000 to 7600 li.