Variations of superoxide dismutase(SOD)and catalase(CAT)activity,malondialdehyde(MDA) content,ultramimcroscopic structure of Machilus ichangensis seedlings at different temperatures were investigated. The data suggested that SOD and CAT activities were increased firstly and then decreased,and the number of mitochondria and starch grains increased with the temperature decline.When the temperature dropped to 5℃,SOD and CAT activities reached to the top,MDA content reached to the lowest point.As the temperature continued to decline,SOD and CAT activities both showed downward trend, MDA content began to increase gradually.When the temperature was—5℃,it was proved by transmission electron microsope observation that plasmalemma and chloroplast were damaged or destroyed.At the same time,the starch grains was degraded.

An anatomical study was conducted on the nutritive organs of Emmenopterys henryi.The results show that in the primary shoot and cortex of secondary shoot,pulp and root ′phloem of Emmenopterys henryi,many parenchyma cells are of obvious netted texture.Parenchyma cells of cortex and pulp are rich in primary structure of stem.The secondary xylem is diffuse-porous wood,vessel is simple perforation,end wall is slightly tilted,and there are few wood-parenchymatous cells.In old roots,there is no pulp in the center.The leaf is of dorsi-ventral leaf,wich developed palisade tissue,and stomata only scattering over the lower epidermis of leaf,which are the structural feature of mesophyte.

The results of structural botanical experiment on stem and leaf of Magnolia biloba(Rehd.et Wils.) Cheng show: there are secretory cavities distributed in the cortex and pith of the stem,of the rachis and the petiolule,and in the parenchyma under the main vein in the Magnolia biloba(Rehd.et Wils.) Cheng;in the walls of some cells there exist reticulate structures.The leaf is of dorsi-ventral leaf,and the stoma only scatter over the lower epidermis of the leaf,which belongs to anomocytic type.In the primare of the stem,the living thin-wall cells are very rich in the cortex and the pith.The secondary xylem is that of diffuse-porous wood.The vessel end wall,applanate and slopping is ladder-shaped compund fenestrated.The wood parenchyma is rare and has a star-scattering distribution.All these indicate that Magnolia biloba(Rehd.et Wils.) Cheng is a more primitive species in evolution.