Abstract: Malus sieversii is precious resource of wild fruit trees in China, with strong affinity, rich provenance, strong resistance and other excellent features. In order to analyze its physiological characters under low temperature stress, peroxidase (POD) activity, proline content, malondialdehyde (MDA) content and superoxide dismutase (SOD) activity were tested after treated leaves in vitro with low temperature (4 ℃). The results show that with the increase of the low temperature stress days, the MDA content showed a trend of increasing, POD, SOD activity showed a decreased trend after the first enhancement, proline content increased at first and then reduced slowly, and chlorophyll content was slightly lower at the first day, and then reduced after the first increase. Low temperature stress on all physiological indexes related to these effects reached significant level. Correlation analyses show that the days of low temperature stress were positively correlated with MDA content and SOD activity significantly, while there was a certain correlation with POD activity, proline content and chlorophyll content. This study provides the experimental data for elucidating the mechanism of cold resistance and breeding cold resistant variety of Malus sieversii.

Key words: Malus sieversii, cold resistance, leaves in vitro testing, physiological indices