Subjects: Biology >> Botany >> Applied botany submitted time 2023-10-22 Cooperative journals: 《广西植物》
Abstract： The taxonomy of Paphiopedilum Pfitz. has been disputed and needed more data for clarification. Floral morphology and anther development in P. purpuratum were observed using microscope and paraffin section to provide a better understanding of the systematics of Paphiopedilum, as well as those of Cypripedioideae. The results were as follows: (1) It was supported that P. purpuratum should be placed in Paph. subgenus Paphiopedilum Sect. Barbata by some floral features, including a single flower, sepal white with veins, petal spotted with blackish-maroon, pouch of a lip auriculate on both sides, and a staminode lunate. (2) At the early stage, anther primordium developed into a pair of laterally juxtaposed thecae. An incomplete sterile septa was differentiated in the center of each theca, giving rise to two arc-shaped microsporangia. When anther split, the sterile septum was discomposed and degenerated resulting in a mass of sticky pollens from two pollen sacs were fused into a unit. (3) The developed anther wall consisted of an epidermis, an endothecium, a middle layer, and a tapetum, conforming to the monocotyledonous type. Both tapetum and inner tapetum cells contained 2 nuclei. (4) Microspore mother cells underwent a simultaneous cytokinesis resulting in microspore tetrads with varied arrangements of tetrahedral, isobilateral, and decussate types. (5) Microspores produced 2-celled pollens via mitosis, which could be retained in pollen tetrads or released as monad. Based on the data available, some key features were selected for taxonomy and conservation biology of Paphiopedilum in Cypripedioideae, including the differentiation of sterile septum, the monocotyledonous type of anther wall, the binucleated tapetum, simultaneous cytokinsis, the sticky pollens and so on in Orchidaceae.
Subjects: Biology >> Botany submitted time 2023-08-25 Cooperative journals: 《广西植物》
Abstract： There are few data on the rare and endangered orchids of Renanthera Lour. Floral morphology and embryological features of anther development in R. imschootiana were investigated to provide new evidence for taxonomy and conservation of Renanthera. The results were as follows: (1) Flowers were characterized by such distinct features as tri-lobed labium with an unconspicous spur, cylindrical column, purple anther cap with yellow stripes and a pair of deeply cleft pollinia connected by a well-developed stipe and a viscidium. (2) Anther primordium was differentiated into two lateral thecae containing two densely dyed microsporangia, and then, a sterile septum was formed longitudinally and unequally which divided each microsporangium into two jointly sub-microsporangium. The septum became absorbed during microsporogenesis and collapsed when anther ripened, resulting in a pair of deeply cleft pollinia. (3) The developed anther wall comprised 5-6 layers, including an epidermis, 2-3 endothecium, a middle layer, and a tapetum, which conformed to the massive type. Tapetal cell was uni-nucleated and glandular. (4) Microspore mother cells underwent a simultaneous cytokinesis during meiosis resulting in the tetrahedral or isobilateral microspore tetrads. Finally, each microspore retained in tetrads and produced 2-celled pollen via mitosis. Pollen tetrads were compactly arranged, leading to a hard cleft pollinia in each thecae. No pollen abortion was observed during anther development. Some key floral and embryological features were discussed for taxonomy and conservation of Renanthera based on a comparative analysis with those of other orchids available.
Subjects: Biology >> Botany >> Applied botany submitted time 2023-07-13 Cooperative journals: 《广西植物》
Abstract： The genus Habenaria exhibits a highly diversity in floral morphology and has complex taxonomy problems. In order to identify key taxonomic features of this genus, floral structure and column ultrastructure of Habenaria dentata and Habenaria glaucifolia were investigated using the stereo microscope and scanning electronic microscope (SEM). The results were as follows: (1) The two Habenaria species exhibited significant differences in floral structures, specifically in terms of the presence or absence of lateral petal lobes, the morphology of the 3-lobed lip, and the ratio of the length between the spur and the ovary. (2) The column ultramicro characteristics of two Habenaria species were significantly varied, containing morphology of staminode, anther chamber exine cell, “anther-canal” exine cell, elongated stigma and papilla at the junction with style. (3) Exine sculptures of massula were distinguished in two species, the reticulate type in Habenaria dentata, and the baculate → reticulate type in Habenaria glaucifolia. This study investigates the taxonomic implications of floral features and column ultrastructure in Habenaria species, with a specific focus on the examination of Habenaria glaucifolia. Through the analysis of available data, certain selected features were identified as potentially valuable for species delimitation, including the presence or absence of lateral petal lobes, variations in spur morphology, the length ratio of the spur to the ovary, and the types of pollen exine sculpture. Additionally, the floral structure and column ultrastructure of Habenaria glaucifolia were supplemented and thoroughly analyzed based on reported data. Notably, it was not confirmed that Habenaria glaucifolia should not be treated as an independent genus from Habenaria. The results of this study provide novel insights and serve as a valuable reference for the classification of Habenaria species distributed in Asia.
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