Study On Cold Resistance For Two Kinds Of Forsythia

The branches and petals of Three-years-old Forsythia×intermedia zabel andForsythia suspensa Vahlas were used as test materials to research their cold resistance inBaoding. Supercooling point,superoxide dismutase (SOD) activity、 peroxidase (POD)activity、MDA content、 soluble protein content and other indicators under natural andartificial low-temperature stress were determined, the main research The results were asfollows:（1）whether it is artificial low temperature stress, or natural wintering process,forsythia branches relative conductivity higher than that of the United States Admiraltyforsythia, conductivity and temperature change was negatively correlated.（2）Combined with the logistic equation, obtained lethal temperature by fitting theconductivity of the two forsythia branches tip,middle and base. The semi-lethaltemperature of the the two forsythia’s various parts: The tip of Forsythia suspensa(Thunb.) Vahl-14.13℃、The central of Forsythia suspensa (Thunb.) Vahl-16.51℃、thebase of Forsythia suspensa (Thunb.) Vahl-17.59℃、The tip of Forsythia×intermediazabel-14.26℃、The central of Forsythia×intermedia zabel-17.12℃、the base ofForsythia×intermedia zabel-18.78℃. In contrast, regardless of the tip, the centraland thebase, Forsythia×intermedia zabel were more hardy than Forsythia suspensa (Thunb.)Vahl.（3）Soluble protein content and cold tolerance of plant are positively correlated.Whether under artificial low temperature stress or natural wintering process, soluble proteincontent showed a trend of increased and then decreased. Under artificial cold stress, thesoluble protein content of Forsythia×intermedia zabel is higher than that of Forsythiasuspensa (Thunb.) Vahl. During natural wintering process, the soluble protein content ofForsythia suspensa (Thunb.) Vahl is higher than that of Forsythia×intermedia zabel.（4）MDA content are negatively correlated with the plant cold tolerance. Under theartificial cold stress, MDA content showed a rising trend. During the natural winteringprocess, the MDA content showed a trend of increased and then decreased.Whether under artificial low temperature stress or during natural wintering process,MDA levels of Forsythia×intermedia zabel branches were lower than that of Forsythiasuspensa (Thunb.) Vahl. （5）The two forsythia SOD activity showed a trend of first increased and thendecreased whether in the process of artificial low temperature stress and natural wintering.POD activity in the natural cooling process showed a significant trend of "Twin Peaks".（6）The super-cooling points in different flowering stage of2forsythia petals havesignificant difference. For the same species the super-cooling point of the bud stage wasthe highest, first stage second and full stage the lowest. In the buds and first stage, theForsythia suspensa (Thunb.) Vahl flower petals had a lower super-cooling point. In thesecond stage, the Forsythia×intermedia zabel had a lower super-cooling point.（7）As the temperature decreases, Soluble protein and MDA content of the twoforsythia petals showed a continuous increasing trend. SOD and POD activity increased atfirst and then decreased. Forsythia×intermedia zabel had a higher content of solubleprotein. SOD, POD activity peak appeared earlier. MDA content was not significantlydifferent.