六种沉香属植物叶片解剖结构研究

Leaf anatomical structure of six Aquilaria species

关键词:  沉香属, 比较解剖学, 叶片, 沉香

Key words:  Aquilaria, anatomical structure, leaf, agarwood

摘要:

为比较沉香属不同种植物间的叶片形态解剖特征,将不同来源的六种沉香属植物在海南省兴隆南药园种植,运用石蜡切片法和撕片法对其成熟叶片的解剖特征进行观察,并对叶片的上下表皮,叶脉和叶横切面等12项数量性状进行统计分析。结果表明:六种沉香属植物叶片解剖结构基本一致,均为典型的异面叶,由表皮、叶肉和叶脉组成,表现出典型的旱生形态特点。表皮细胞单层,气孔微下陷,仅分布在下表皮,上下表皮上零星分布着表皮毛。叶肉组织发达,栅栏组织由1～2层排列紧密地圆柱状细胞组成,其间分布着大量的长方晶体,海绵组织内有一层排列较整齐,染色较深的异细胞组成的下皮层。主脉维管束双韧型,呈圆环状,内含大量异细胞。方差分析表明,除栅海比外,叶片厚度、叶脉条数、主脉厚度等其余11项数量指标在六种植物间差异均达到显著水平。聚类分析将这六种植物聚成3类,Aquilaria sinensis(白木香),A. crassna和A. banaensis聚为一类,A. baillonii和A. malaccensis聚为一类; A. yunnanensis(云南沉香)单独为一类 。该研究结果为沉香属植物的物种鉴定提供了解剖学依据,同时对沉香属植物合理开发利用具有重要意义。

Abstract:

Agarwood is a resin wood, which formed in the stem of Aquilaria and may represent the most prized non-timber forest product, which can be used in fragrances, incense, medicines, aromatherapy, and religious ceremonies. Aquilaria is an endangered genus due to the excessive exploitation of its precious agarwood, while not all Aquilaria species can produce agarwood effectively or different Aquilaria species produce agarwood with distinctive fragrances and price. Therefore, it is an important task to improve the identification methods of Aquilaria species. In order to identify the Aquilaria species, the leaf anatomical structures of selected Aquilaria species were compared in this study. The mature leaves of the six Aquilaria species(Thymelaeaceae)were studied with light microscopy and paraffin sectioning, and twelve quantitative traits of the leaves were measured and analyzed. The result showed that the leaf structures of six Aquilaria species were similar. All leaves showed the xerophytic feature. All leaves were typical bifacial type and were composed of epidermis, mesophyll and vein. The epidermis consisted of single layer epidermal cells. The upper epidermis were much thicker than the lower epidermis. The sunken stomata existed only in lower epidermis which was sporadically covered by hairs. The stomata were of anomocytic type. The mesophyll was well developed which were composed of palisade parenchyma, spongy parenchyma and lithocyst. The palisade parenchyma was composed of 1-2 layers of cylindrical cells, in which many rectangular lithocyst arranged perpendicularly to the epidermis. The hypodermis was located in spongy parenchyma, which was composed of idioblasts. The micrib belonging to bicollateral bundle was well developed. The bundle sheath and pith both contain a number of idioblasts. ANOVA analysis showed that the eleven quantitative traits were significantly different among six species, except for ratio of palisade to spongy tissue. Clustering analysis showed that six species were clustered into three main groups. Group 1 consisted of A. sinensis, A. crassna and A. banaensis; Group 2 consisted of A. baillonii and A. malaccensis; Group 3 only consisted of A. yunnanensis. The results provides some new information for the species identification, but also is of great significance for the conservation and utilization of Aquilaria spp.