大叶铁线莲大小孢子发生及雌雄配子体发育

铁线莲属植物在花部形态和结构方面存在较大差异, 遗传背景相对复杂。因此, 在杂交育种前对其进行胚胎学研究具有重要意义。利用石蜡切片技术对大叶铁线莲(Clematis heracleifolia)大小孢子发生及雌雄配子体发育过程进行研究, 结果显示, 大叶铁线莲具雄株和两性花植株。雄花中, 雄配子体发育偶见败育现象; 而两性花中多数花粉发育异常, 形成功能性雌花。正常发育的两性花中, 雄蕊较雌蕊先发育完全。花药4室, 具腺质绒毡层, 偶见变形绒毡层。胞质分裂为同时型, 以四面体型四分体为主, 偶见左右对称型。成熟花药中, 花药壁由纤维状加厚的表皮及药室内壁构成, 花粉粒为2-细胞型, 近球状, 散沟型。子房1室, 内含少量退化胚珠及1个发育正常的胚珠, 倒生, 单珠被, 薄珠心, 蓼型胚囊, 具线形大孢子四分体及双核反足细胞。大叶铁线莲可能处于相对进化的过渡地位。在杂交育种中, 建议以雄花植株作为父本, 两性花植株仅用作母本; 在两性花花芽大小为0.5-0.8 cm时进行去雄处理。

Megasporogenesis,Microsporogenesis and Development of Male and Female Gametophytes of Clematis heracleifolia

In Clematis (Ranunculaceae) species show significant differences in floral morphology and structures, consistent with their complex genetic background. Thus, it is important to study the embryological characteristics prior to any attempts of breeding by hybridization. Here, we report the characterization of microsporogenesis, microgametogenesis, megasporogenesis and macrogametogenesis of Clematis heracleifolia by floral dissection. We show that C. heracleifolia is androdioecy. Aborted microgametophyte cells are observed in the majority of bisexual flowers but occasionally found in male flowers, which results in the formation of functional female flowers. However, in a small number of normal bisexual flowers, male gametophytes mature faster than that of female gametophytes. During microsporogenesis, the tetrasporangiate anther is formed, followed by simultaneous microsporocyte cytokinesis, and the formation of glandular tapetum, occasionally with amoeboid tapetum. After meiosis, the microspores tetrads are mostly tetrahedral, and occasionally symmetrical. The wall of mature anther contains fibrous thickening epidermis and endothecium. Pollen grains are spheroidal, pantocolpate, and 2-celled. The ovary has one chamber with a normal and a few degraded ovules, which contains a anatropous, unitegmic, tenuinucellate, and Polygonum-type embryo-sac. A linear tetrad of megaspores and dikaryocyte antipodal cells can be observed. This species may belong to a transitional clade within Clematis. In breeding practice for C. heracleifolia, it is advised to use plants bearing male flowers and hermaphrodite flowers as male and female parents, respectivley, with the bisexual flowers of 0.5-0.8-cm-long to be emasculated.