Relationship between Heat and Frost Resistance of Tuber-Bearing Solanum Species: Effect of Cold Acclimation on Heat Resistance

Abstract

A possible relationship between heat and freezing-stress resistance was investigated in four potato species. These species differed in degree of freezing-stress resistance and ability to acclimate to cold. The 2, 3, 5-triphenyl tetrazolium chloride reduction and the conductivity test were used to evaluate the relative heat and freezing-stress resistance of excised leaflets. Data from both tests failed to show a systematic relationship between heat and freezing-stress resistance in the four potato species. The cultivated species, Solanum tuberosum, had the lowest level of freezing-stress resistance and one of the highest levels of heat-stress resistance. One noncultivated accession had a high degree of frost and heat resistance, whereas the other three accessions had a high degree of frost but poor heat resistance. Fifteen days at 5/2 C day/night did not increase heat- and freezing-stress resistance of S. tuberosum but increased both heat- and freezing-stress resistance in S. commersonii and other species capable of cold acclimation. These results show that (1) resistance to heat and freezing stress is not always mutually exclusive; (2) if a plant is capable of increasing freezing-stress resistance during cold acclimation, it also seems to have the ability to increase heat-stress resistance; and (3) the enzymes that participate in oxidation-reduction reactions and active transport of ions are sensitive to heat injury.