Shade During Growth—Effects on Chemical Composition and Leaf Color of Air‐Cured Burley Tobacco1

Abstract

AbstractDevelopment of off‐color in air‐cured burley tobacco (Nicotiana tabacumL.) leaf may adversely affect the quality and value of the crop. Shading from other vegetation during growth may be a contributing factor. The purpose of this investigation was to determine the effects of shading during field growth on leaf color and chemical composition of air‐cured burley tobacco. Whole leaves and lamina from air‐cured burley tobacco (cv. Kentucky 14) grown under 0,45, or 65% shade (reduced light) conditions in field (Maury silt loam soil; clayey, mixed, mesic, Typic Paleudalf) experiments were quantitatively analyzed for parameters of color (determined by reflectance), chlorophyll isomers, carotenoids, brown pigment, total phenols, total alkaloids, and nitrate‐N. Whole leaves and lamina from tobacco grown under increased shade generally had more red hue, less yellow hue, less brightness, and more total color change. Lamina from tobacco grown under increased shade had higher levels of chlorophyll a, chlorophyll b, lutein, β‐carotene, neoxanthin, violaxanthin, and nitrate‐N, but lower contents of brown pigment and total alkaloids. Whole leaf grown under increased shade had generally higher contents of nitrate‐N and lower brown pigment, total phenols, and total alkaloids. The color changes in air‐cured whole leaf and lamina associated with increased shade during growth support the hypothesis that shade is one causative factor for the undesirable “pink leaf” characteristic that sometimes develops in air‐cured burley tobacco, although the data do not show that it is the only factor involved.