Division of Forest Biodiversity, Korea National Arboretum, Pocheon, 11186, South Korea.
Division of Plant Resources, Korea National Arboretum, Yongmun, 12519, South Korea.
BMC Plant Biol. 2020 Sep 15;20(1):426. doi: 10.1186/s12870-020-02589-9.
The genus Cypripedium L. is one of the five genera of the subfamily Cypripedioideae, members of which are commonly known as lady's slipper orchids. Cypripedium japonicum is a perennial herb native to East Asia, specifically China, Japan, and Korea. Due to its limited distribution, the species is included in the Endangered category of the IUCN Red List.
We investigated gametophyte development, including complete embryogenesis, in C. japonicum. The complete reproductive cycle is presented based on our observations. Anther development begins under the soil, and meiosis of pollen mother cells begins 3 weeks before anthesis, possibly during early April. The megaspore mother cells develop just after pollination in early May and mature in mid-late June. The pattern of embryo sac formation is bisporic, and there are six nuclei: three forming the egg apparatus, two polar nuclei, and an antipodal cell in the mature embryo sac. Triple fertilization results in the endosperm nucleus, which degenerates when the proembryo reaches the eight-to-sixteen-cell stage.
Our overall comparisons of the features of gametophyte and embryo development in C. japonicum suggest that previous reports on the embryology of Cypripedium are not sufficient for characterization of the entire genus. Based on the available information, a reproductive calendar showing the key reproductive events leading to embryo formation has been prepared.
杓兰属（Cypripedium L.）是杓兰亚科的五个属之一，其成员通常被称为杓兰。日本杓兰（Cypripedium japonicum）是一种原产于东亚的多年生草本植物，具体分布在中国、日本和韩国。由于分布范围有限，该物种被列入 IUCN 红色名录的濒危类别。
我们研究了日本杓兰的配子体发育，包括完整的胚胎发生。根据我们的观察，呈现了完整的生殖周期。花药在土壤下开始发育，花粉母细胞的减数分裂在开花前 3 周开始，可能在 4 月初。大孢子母细胞在 5 月初授粉后不久发育，并在 6 月中晚期成熟。胚囊形成的模式是双核的，有六个核：三个形成卵器，两个极核和一个成熟胚囊中反足细胞。三受精导致胚乳核，当原胚达到八到十六细胞阶段时，胚乳核退化。
我们对日本杓兰配子体和胚胎发育特征的全面比较表明，以前关于杓兰属胚胎学的报告不足以描述整个属。根据现有资料，编制了一个生殖历，显示了导致胚胎形成的关键生殖事件。
