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

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Abstract
A possible relationship between heat and freezing-stress resistance was investigated in 4 potato species [S. multidissectum, S. commersonii, S. acaule, S. tuberosum]. These species differed in degree of freezing-stress resistance and ability to acclimate to cold. The 2, 3, 5-triphenyl tetrazolium chloride reaction 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 4 potato species. The cultivated species, S. tuberosum, had the lowest level of freezing-stress resistance and 1 of the highest levels of heat-stress resistance. One noncultivated accession had a high degree of frost and heat resistance; the other 3 accessions had a high degree of frost but poor heat resistance. Fifteen days at 5.degree./2.degree. C day/night did not increase heat- and freezing-stress resistance of S. tuberosum but increased both heat- and freezing-stress resistance to S. commersonii and other species capable of cold acclimation. Resistance to heat and freezing stress is not always mutually exclusive, 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. The enzymes that participate in oxidation-reduction reactions and active transport of ions are sensitive to heat injury.