关键词: 广玉兰, 类型, 抗寒性, 相对电导率, 半致死温度, 叶片组织结构

Abstract:

This study aimed at obtaining Magnolia grandiflora. varieties adaptable to high latitudes. We measured the relative electric conductivity and the semilethal temperature of six types under low temperature by collecting the detached leaves of M. grandiflora. The microstructure of leaf was investigated with electricity microscope (SEM) and the leaf tissue tightness and porosity were calculated for the different types of M. grandiflora. The results indicated that the relative electric conductivity of the six types was significantly different under the set temperature. When the temperature dropped from 5℃ to -25℃, type Ⅴ had the smallest increase in relative electric conductivity, by 31.30%, followed by the type Ⅳ, by 37.42%, and type Ⅰ had the largest increase in relative electric conductivity, by 50.72%. Type Ⅴ had the lowest semilethal temperature, followed by the type Ⅳ, and then type Ⅰ. The shape of leaf epidermal cells was elongated round or rectangular, there were needle-like trichomes on the lower epidermis, the palisade tissue was composed of a layer of the vertical arrangement square cells, and the spongy tissue cells were nearly round. The order of leaf tissue tightness of the six types was typeⅤ>typeⅣ>type Ⅵ>type Ⅱ>type Ⅲ>type Ⅰ. In general, type Ⅴ and type Ⅳ would adapted to high latitudes.

Key words: Magnolia grandiflora, types, cold resistance, relative electric conductivity, semilethal temperature, leaf tissue structure