Treated by freezing,1-year-old dormant branches of four Parthenocissus species were used as test materials to determine the electro-conductivities.According to Logistic equation fitting,the semi-lethal low temperatures were calculated.The result showed that the semi-lethal low temperatures and freezing tolerance of the examined species were ranked as: Parthenocissus quinquefolia(-16.63 ℃),P.tricuspidata(-10.78 ℃),P.laetecirens(-10.29 ℃),and P.henryana(-7.72 ℃).By comparing several physiological indexes including water saturation deficit,soluble sugar,soluble protein,MDA,and proline contents,it was found that after cold stressing for a whole winter the soluble sugar and proline contents were well correlated to semi-lethal low temperatures.So both of them could be used as the physiological indexes for cold tolerance identification and selection of cold-resistant variety.
