Studies On Morphological And Anatomical Structure Of Taxodium Species And Hybrids

In this paper, Taxodium species and hybrids were selected as experimental materials. Physiological and morphological features, e.g. phenology, photosynthetic pigments, morphology and leaf anatomy, of the species and varieties were observed and analyzed, in order to provide a scientific basis for identification of Taxodium varieties. The main conclusions as followe:⑴The results by phenological observation and photosynthetic pigment determination indicated that their phenologies were divided into 4 categories:①early sprouting and leaf-unfolding—late defoliation,②early sprouting and leaf-unfolding—early defoliation,③late sprouting and leaf-unfolding—early defoliation, and④intermediate type. The content dynamics of total chlorophyll follows a pattern of'up—down—up—down', for the carotenoid,'down—up—down'.⑵Observation of leaf epidermis by microscopy and scanning electron microscope showed that the leaf was amphistomatic. The number and ranks of stomatas on upper epidermis were generally less than that on lower ones. In the non-stomata areas the epidermal cells arranged longitudinal lines, rectangular or nearly rectangular. The anticlinal walls of epidermal cells were mostly straight or sometimes undulate. Epidermal cells on areas with stomata were irregularly quadrilateral or polygonous. Sometimes cells were extruded flatly. Periclinal walls with cuticle were covered with dense crystalline or other massive appendages, without hairs. Stomatal apparatuses were oval, guard cells have polar layer structure. The type of stomatal apparatuses was bicyclic. Tests of various indices were significantly different.These indices can be used as indicators of varieties identification.⑶Results of leaves anatomy in Taxodium species and hybrids demonstrated that leaf was composed of upper epidermis, upper palisade tissue, spongy tissue, lower palisade tissue, and lower epidermis. Cross-section of leaves was determinated in the following shapes: elongately rod-like, irregular, inverted'W'and'∞'shape. These shapes can be used as species and varieties identification. Taxodium trees were fit to wet and shaded habitat. The leaves were isobilateral anatomically. Tests of various indices were highly significant.⑷In this paper, cluster analysis was performed for Taxodium species and hybrids. An identification key was established for these species and hybrids.