落羽杉属(杉科)叶表皮结构及气孔参数

落羽杉属Taxodium Rich.现生3种植物——落羽杉T. distichum (L.) Rich.、池杉T. ascendens Brongn.和墨西哥落羽杉T. mucronatum Tenore.的条形叶为双面气孔型或单面气孔型。叶片远轴面气孔分布于中脉两侧,每侧各有4-8列气孔。叶片中部气孔数量稳定,顶部和基部气孔数量比中部略少。近轴面气孔在中脉两侧各有1-4行,有时仅少数几个气孔或没有气孔分布。非气孔分布区内,表皮细胞长方形,细胞壁直或稍微呈波状,细胞长轴与叶片长轴一致。气孔分布区内的表皮细胞有时为多边形。气孔器椭圆形,长轴与叶片长轴垂直或成一定的角度。保卫细胞壁加厚明显,极端联合形成极层结构。落羽杉属3种现生植物的气孔密度和气孔指数差异显著,不同采集地的落羽杉气孔密度和气孔指数差异不显著。这3种植物的气孔指数的变异系数均小于气孔密度的变异系数,用气孔指数指示大气CO2浓度比用气孔密度可靠。

Leaf epidermal structure and stomatal parameters of the genus Taxodium (Taxodiaceae)

The linear leaves of three species in the genus Taxodium Rich., T. distichum (L.) Rich., T. ascendens Brongn., and T. mucronatum Tenore., are amphistomatic or hypostomatic. Stomatal band comprises 4-8 lines of stomata on each side of the midvein on the abaxial surfaces of the leaves. The numbers of stomata are stable on the middle parts of the abaxial surfaces of the leaves, and decrease toward both tip and base of the leaves. On the adaxial surfaces the stomatal band comprises only 1-4 lines of stomata and sometimes no stomata were observed. In the non-stomata areas the epidermal cells are oblong and parallel to the long axis of leaves, and the anticlinal walls of epidermal cells are mostly straight or some-times undulate. Epidermal cells on areas with stomata are polygonous. Stomatal apparatuses are oval, and the long axes of stomata are mostly perpendicular or oblique to the midvein. Guard cells have thickened walls, forming polar lamellae at the polar end. The stomatal density and index of T. distichum, T. ascendens and T. mucronatum exhibits significant differences. The stomatal density and index of T. distichum from different localities show no statistically significant differences. The coefficient of variability of the stomatal index is smaller than that of the stomatal density, suggesting that the stomatal index is more reliable than stomatal density when it is utilized to study the correlation between stomatal parameter and atmospheric CO2 concentration.