The structures of floral organs and reproductive characteristics of an ornamental bamboo species, Pleioblastus pygmaeus
Wenjing Yao, Chuanzhe Li, Shuyan Lin, Jianping Wang, Tingting Fan, Wanqi Zhao
Abstract
As a woody grass, bamboo has special reproductive habits with an extremely long vegetative phase. Pleioblastus pygmaeus is a kind of ornamental dwarf bamboo species with high ecological and economic value in China. There was no documentary record of the flowering of P. pygmaeus until 2015, which bloomed in the Bamboo Garden of Nanjing Forestry University. Generally, bamboo plants rarely bear fruit or have a low seed setting rate, but this species has a high seed production. This study explores developmental reasons using anatomical methods. The process of flower bud differentiation and a series of important reproductive development processes including anther wall development, microsporogenesis , megasporogenesis , male and female gametophyte development, and embryonic development were investigated sequentially. Each stamen contained three tetrasporangiate anthers and the development of anther wall was of Monocotyledonous type. The microspores finally matured into 3-celled pollen grains by two successive mitoses. The pistil was composed of three carpels , with an anatropous, tenuinucellate and bitegmic ovule in a single ovary. The formation of embryo sac belonged to Polygonum type. With three mitoses, functional megaspore developed into the embryo sac with eight nuclei within seven cells. The development of stamen and pistil was synchronous in the same floret . The development of embryo followed Grass type and the development of endosperm belonged to Nuclear type. The development of endosperm was earlier than that of embryo. The study enriches basic knowledge of reproductive biology of bamboo plants and is of great fundamental significance to furtherly explore flowering mechanism of P . pygmaeus and to cultivate bamboo plants sustainably.