铁皮石斛花粉块结构及发育过程的解剖学特征研究北大核心CSCD

兰科植物的有性生殖特殊,每朵花只有1个花药,且花粉有聚集成块发育的特征。为了揭示铁皮石斛花粉块的发育特征,该研究以野生铁皮石斛不同时期的花药为材料,采用半薄切片和植物组织化学方法对其发育过程进行解剖学观察分析,并对成熟花粉块进行离体培养,观察花粉管的萌发状况。结果表明:(1)铁皮石斛花药壁由1层表皮细胞,2层药室内壁细胞,1层中层细胞和1层绒毡层细胞组成。开花时,绒毡层细胞退化,中层细胞没有退化,药室内壁细胞则形成纤维状细胞壁;药室中的小孢子母细胞没有明显的胼胝质壁结构。(2)小孢子发生属同时型,减数分裂后四分体小孢子不分散,以四合花粉状态发育,并进一步连接形成花粉块。(3)在小孢子发育中,孢粉素覆盖在整个花粉块表面形成花粉外壁,但花粉块内部的花粉没有花粉外壁结构;在花粉块表面的花粉外壁上未见花粉萌发孔。(4)在花粉离体萌发实验中,具有花粉外壁的花粉块表面花粉未见萌发,仅由花粉块内部的花粉萌发出花粉管。

Study on Anatomical Characteristics of Pollinium Structure and Development of Dendrobium officinale

The sexual reproduction of Orchidaceae is special, each flower has only a anther and pollens have aggregated into pollinium is one of its characteristics. In this study, the anthers of wild Dendrobium officinale at different stages are used as materials, the anatomical observation of anther development were carried out by semi thin section and plant histochemical methods. The mature pollinium is cultured in vitro to observe the germination of pollen tubes. The results show that: (1) the anther wall of D. officinale is composed of one layer of epidermis cells, two layers of endothecium cells, one layer of middle layer cells and one layer of tapetal cells. At anthesis, the tapetal cells degenerate, while layer of middle layer cells do not, and the endothecium cells form fibrous bands in its cell wall. The microspore mother cells have no obvious callose wall structure. (2) Its microsporogenesis is simultaneous type. After meiosis, four microspores in tetrad do not disperse and sequentially develop as pollen tetrads, which stick together to form pollinia. (3) During microspore development, sporopollen covers the surface of whole pollinium and forms the extine of the pollinium, while the pollen tetrads inside the pollinium have no extine structure. No pollen germ pore was observed in the extine of pollinium. (4) When pollen germinates in vitro, pollen grains with extine on the surface of pollinium do not germinate, and pollen tubes are mainly produced in pollen grains inside the pollinium.