TY - JOUR T1 - Dormancy and Cold Hardiness in <em>Vitis vinifera</em> L. cv. White Riesling as Influenced by Photoperiod and Temperature JF - American Journal of Enology and Viticulture JO - Am J Enol Vitic. SP - 265 LP - 272 DO - 10.5344/ajev.1987.38.4.265 VL - 38 IS - 4 AU - Barbara J. Schnabel AU - Robert L. Wample Y1 - 1987/01/01 UR - http://www.ajevonline.org/content/38/4/265.abstract N2 - Cold hardiness of Vitis vinifera L. cv. White Riesling was examined using controlled environments to establish the roles of photoperiod and temperature. Field-grown, potted plants were maintained for comparison. Gradually decreasing daylengths, when combined with constant warm temperatures, increased cane hardiness by 0.8°C, while primary bud hardiness was decreased by 2.7°C. Combining constant cool temperatures with gradually decreasing daylengths resulted in an increase in cane and primary bud hardiness of 1.3°C and 0.8°C, respectively. Long photoperiods and gradually decreasing temperatures increased cane and primary bud hardiness by 1.8°C and 1.1°C, respectively. Combining gradually decreasing temperatures and decreasing photoperiods was the most effective and caused increased hardiness of canes by 4.5°C and primary buds by 5.2°C, thus demonstrating a synergistic effect of these environmental factors. Depth of rest induced by these treatments was examined following cold hardiness evaluation. A chilling treatment facilitated the transition from dormancy to active growth. ER -