PT - JOURNAL ARTICLE AU - Richard E. Smart AU - Stephen M. Smith AU - Robert V. Winchester TI - Light Quality and Quantity Effects on Fruit Ripening for Cabernet Sauvignon AID - 10.5344/ajev.1988.39.3.250 DP - 1988 Jan 01 TA - American Journal of Enology and Viticulture PG - 250--258 VI - 39 IP - 3 4099 - http://www.ajevonline.org/content/39/3/250.short 4100 - http://www.ajevonline.org/content/39/3/250.full SO - Am J Enol Vitic.1988 Jan 01; 39 AB - The light climate of potted fruiting Cabernet Sauvignon vines was modified by shading with one, two, or three layers of 44% transmission shade cloth. Control vines and three-layer shade cloth vines were exposed to red 660 nm light from a fluorescent tube to investigate phytochrome responses. Increasing shade markedly reduced ripening, causing reduced sugar, phenol, and anthocyanin concentrations. Levels of titratable acidity, malic and tartaric acids, and juice NH4-N were increased by shade, but pH was similar despite large differences in acidity. Shade also caused major effects on mineral nutrition, especially for N metabolism. Shade caused increased concentrations of NO3-N and NH4-N in leaves, NO3-N and total N in petioles, and NH4-N and Mg in peduncles; peduncle K was decreased. Shade decreased photosynthesis, stomatal conductance, and leaf nitrate reductase activity. Red light supplementation caused increased nitrate reductase activity in leaves and earlier fruit coloration and harvest concentration of glucose and fructose, implicating phytochrome control over some aspects of fruit ripening.