两种铁角蕨的孢子体形态研究及水分生理测定

Sporophytic morphology characteristics comparison and water physiological indexes measurement of two pteridophytes in Asplenium

关键词:  铁角蕨, 表皮细胞, 气孔器, 管状分子, 相对含水量, 水势

Key words:  Asplenium, epidermal cells, stomatal apparatus, tubular, relative water content, water potential

摘要:

以铁角蕨属(Asplenium)两种不同植物的孢子体为材料(石生铁角蕨和变异铁角蕨),通过常规形态解剖方法和水分生理指标测定,分析探讨了这两种植物的形态特征与水分生理特点之间的适应性。结果表明:(1)石生铁角蕨和变异铁角蕨相比较,石生铁角蕨叶面积指数较大,叶片更为饱满。(2)两种铁角蕨表皮细胞的垂周壁均为不规则形,分别呈现出深波状或浅波状。(3)两种铁角蕨的气孔器全为下生气孔,且气孔器类型、形状、气孔大小及长宽比都很稳定。但是,二者之间气孔密度有很大差异,而气孔器类型以不规则四细胞型、腋下细胞型和极细胞型为主。(4)木质部维管束均为椭圆形的双柱型管状中柱,中柱内含有管状分子,呈背对月牙形分布,中柱大小约为80 μm。(5)维管束内的管状分子次生壁出现不同程度的木质化增厚,以网纹、梯纹、孔纹的形式表现出来,管状分子的直径都较小,变异铁角蕨的木质部管状分子比石生铁角蕨的稍大。(6)石生铁角蕨的自然含水量较低,相对含水量较自然含水量变化较小,束缚水与自由水比值和水势较高。从石生铁角蕨和变异铁角蕨的叶表皮形态、气孔器特征、管状中柱和管状分子特征来看,将二者划分在同一属下是比较合理的。两种植物自然生境不同,其水分生理特征差异明显,但均与各自的形态特征相适应; 石生铁角蕨的抗旱性比变异铁角蕨更强。该研究结果可为铁角蕨属植物的系统分类和抗旱性研究提供更多的资料。

Abstract:

Taking two different sporophytes of Asplenium, Asplenium saxicola and A. varians as materials, we studied the morphological characteristics through conventional anatomical method, and water physiological indexes to compare the applicability of morphological characteristics and water physiological characteristics. The results were as follows:(1)The area of pinnule of A. saxicola was about 214 mm² and its thickness was about 0.30 mm, and the leaf area index was about 0.74. The area of pinnule of A. varians was about 53 mm² and its thickness was about 0.17 mm, and the leaf area index was about 0.65. Leaf area index of A. saxicola was more larger than A. varians.(2)Their epidermal cells were irregular shape and anticlinal walls were repand or sinuate type.(3)The stomatal structure of two pteridophytes in Asplenium were all swells, which indicated that all stomata distributed in the lower epidermis, not in the adaxial epidermis. And stomatal type, shape, size and aspect ratio were stable, the average length mainly in the region of 30-36 μm, the average width of the distribution in 20-28 μm region, the aspect ratio of 1.21 in A. saxicola and the A. varians was 1.33, their aspect ratio of the difference of 0.12, not more than 0.2. But their stomatal type mainly include polocytictype, coaxillocytictype, anomotetracytictype, and the stomata density were significantly different, 72 Nun/mm² and 112 Nun/mm².(4)Xylem vascular bundle were oval double column siphonostele, tracheary elements were back-to-back crescent-shaped, the siphonostele was about 80 μm.(5)The secondary wall of tubular molecules in the vascular bundle appeared different degrees of lignification thickening,both characteristic of tubular molecules, reticulate toroid and scalariform were observed, their diameters were small, the tubular molecules of A. varians was slightly larger than A. saxicola.(6)Relative water content of A. saxicola was about 65%,and its natural moisture content was smaller than the relative water content, only increased by about 6%, ratio of bound water and free water was 1.34, and the water potential -0.71 MPa. Relative water content of A. varians was about 78%, its natural moisture content larger than the relative water content, increased by about 11%, ratio of bound water and free water was 1.16, and the water potential -0.76 MPa. And the drought resistance of A. saxicola was stronger than A. varians. The two fern plants were different in water physiological indexes, but adapted to their morphological characteristics. Therefore, it was relatively reasonable to classify A. saxicola and A. varians to be the same genus, based on the leaf epidermis morphology, stomatal characteristics, xylem vascular bundle and tubular molecules characteristics of view. The study would accumulate more information for Asplenium and drought studies.