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Covering apples with foil bags about 1 month after bloom to harvest had no effect on fruit size or starch content, had inconsistent effects on fruit firmness, and reduced soluble solids, anthocyanin and chlorophyll. Uncovering fruits at various times before harvest allowed formation of anthocyanin, maximum amounts being dependent on cultivar and time of exposure.
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Proctor et al. (1976) studied this question.
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