Abstract: Cultivated Picea koraiensis Nakai, Pinus sylvestris var. mongolica Litvin, P. koraiensis Sieb et Zuce, P. tabulaeformis Carr. and P. bungeana Zucc. were studied. Changes in chlorophylls carotenoids contents, SOD activities and iso-zymograms were monitored for the needles of the 5 evergreen conifers and related to their freezing tolerance during winter of 1.987–1988 in Shenyang. It shows that the chlorophylls were degradated to various extent in the winter while the carotenoids were still synthesized during the soil-frozen period. SOD activities increased from July to November for all 5 conifers and the more tolerate the species, the higher the SOD activities during winter. The results suggest that SOD possibly has important contribution to freezing tolerance besides protecting the needles from winter photooxidation. SOD iso-zymograms and their variation showed differance among species as well, but it is hard to draw a generalized conclussion.

Key words: Conifers, Freezing resistance, SOD, Chlorophyll, Carotenoids