Measurements Of Physiological Indicators Of Nine Evergreen Magnoliaceae Plants In Low Temperature And Cold Tolerance Evaluations

The magnoliaceae plants characterized by its beautiful color, pleasant flower andelegant attitude, are becoming one of the main tree species in the city greening withhigh ornamental value. In the landscape greening activities, tree species ability to coldtolerance is a critical factor in the survival of the species introduction in the higherlatitudes. In the current condition, many magnolia species with high qualityornamental value have not been well applied in the activities. Therefore, themagnoliaceae plants are becoming more and more important in the green sector of thenorthern city. And it is significant to explore the relationship between cold toleranceand physiological-biochemical changes the significance of plants and then extendingnorthward.In this paper, nine species of magnoliaceae plants such as Michelia floribundaFinet et Gagnep, Michelia martinii (Levl.) Levl, M.wilsonii Finet et Gagnep,Magnolia grandiflora Linn, Michelia platypetala Hand-Mzt, Michelia chapensisDandy, Manglietia duclouxii Finet et Gagnep, Magnolia grandiflora L.var.Lanceolata Ait，Michelia maudiae Dunn had been selected as the experiment materials to research thephysiological and biochemical changes under the artificial low temperature conditions.Four low temperatures,0℃、-4℃、-8℃、-12℃were taken as cold stresses.Physiological indexes such as relative conductivity, free proline content, soluble sugarcontent, MDA content, soluble protein content were measured in cold stresses andcontrol, respectively. In addition, comprehensive analysis and evaluation of coldresistance and cold tolerance of each species were conducted and explored theprobability of overwintering in the basis of these experiments. The main results are as follows：1．In the freezing process from0℃to12℃，the changing trends of physiologicalindexes of each species of magnoliaceae plants were almost the same. The relativeconductivity, free proline content, soluble sugar content, MDA content, solubleprotein content showed an upward trend. Based on the ANOVA analysis, the relativeconductivity, free proline content, soluble sugar content, MDA content, solubleprotein content between each species and each cold temperature showed greatsignificant difference.2. The semi-lethal temperature (LT50) of Michelia floribunda Finet et Gagnep,Michelia martinii (Levl.) Levl, M.wilsonii Finet et Gagnep, Magnolia grandifloraLinn, Michelia platypetala Hand-Mzt, Michelia chapensis Dandy, Manglietiaduclouxii Finet et Gagnep, Michelia maudiae Dunn was-5.32℃,-6.65℃,-7.45℃,-8.37℃,-8.41℃,-8.12℃,-9.14℃,-14.67℃,-14.32℃, respectively.3. Comprehensive evaluation of cold resistance of above nine species ofmagnoliaceae plants was conducted based on principal component analysis, and theresults showed that the osmolyte content and cell membrane permeability wereclosely related to their cold resistance. And the cold tolerance of these nine speciesunder artificial cold condition were as follows： Magnolia grandiflora Linn>Michelia maudiae Dunn> Michelia platypetala Hand-Mzt> Michelia chapensisDandy> Manglietia duclouxii Finet et Gagnep> M.wilsonii Finet et Gagnep>Michelia floribunda Finet et Gagnep> Michelia martinii (Levl.) Levl.