TEMPERATURE-RELATED CHANGES IN CHLOROPHYLL FLUORESCENCE AND CONTENTS OF CHLOROPHYLL AND CAROTENOIDS IN ANDEAN AND EUROPEAN POTATO CLONES

Low-temperature adapted Andean potato clones and low-temperature sensi tive European clones cultivated at 20/10-degrees-C were compared durin g stress occurring as the result of low-temperature treatments. The st ress response of leaf tissue was assessed by measuring the decrease in chlorophyll fluorescence (Fv/Fm) in detached leaves during a period o f six days. After temperature stress combined with light Fv/Fm decreas ed only slightly in the Andean clones, but was markedly lower than the initial values in the European clones. However, after a 2-degrees-C t reatment in darkness no difference between clones of different origins was detected. In general, chlorophyll and carotenoid contents of the Andean clones were higher than those of the European clones. They were markedly lower in all clones in treatments where low temperature was combined with light, than at 20/10-degrees-C and at 2-degrees-C in the dark. The contents of carotenoids and total chlorophylls decreased mo re in the European than in the Andean clones when leaves were transfer red to a higher light intensity and when the lowest temperature used w as combined with light. Thus carotenoids and chlorophylls in the Europ ean clones were more sensitive to photo-oxidation at low temperatures than in the Andean clones. The changes in chlorophyll fluorescence in illuminated, detached leaves induced by a decrease in temperature were found to correlate with the low temperature performance of the genoty pes. The correlation between low temperature performance and photosynt hetic activity was highly significant and could be used by plant breed ers to identify plants that perform well at low temperatures.