Effect of Photoperiod, Temperature, and Certain Growth Regulators on Frost Hardiness of Solanum Species

Abstract

Cold acclimation of Solanum acaule, S. commersonii, S. multidissectum, and S. chomatophilum was achieved by exposing plants to a controlled environment of stepwise shortened photoperiods and lowered day-night temperatures. The hardiness of mature leaves of these species increased from 3 to 6 C in 3 wk under these conditions. These species also acclimated, but to a lesser extent, when they were subjected either to a regime of constant short days (8 h light) and low day-night temperatures (5/0 C) or to long days (15 h light) with day-night temperatures lowered weekly for 3 wk. Warm day-night temperatures (20/15 C) and a photoperiod shortened weekly from 12 to 10 h and then to 8 h did not induce acclimation in any of the species tested. Four S. tuberosum cultivars and Alaska Frostless failed to acclimate under any environmental regime. Treatment with 2,000 ppm CCC (2-chloroethyl-trimethyl-ammonium chloride) after 1 wk enhanced frost hardiness by about 1 C in S. acaule and S. commersonii but had no effect on S. tuberosum. Apparently S. tuberosum does not have the physiological bases for developing frost hardiness.