Study On Anatomy And Embryology Of Thellungiella Halophila

This experiment studied the anatomy and embryology of halophyte, Thellungiella halophila (C. A. Mey.) O. E. Schulz, through outside observation, measure and light microscopy of paraffin-sectioned material. The article details systematically the relationships between the anatomical structure of vegetative organs of Thellungiella halophila and its high salinity tolerance. The research included its microsporogenesis, the development of male gametophyte, megasporogenesis, the development of female gametophyte, fertilization, the development of embryo. Furthermore, the experiment studied the relationships between different stages of the processes sited above and morphological character of flower bud, flower and fruit. Conclusions as follows: 1. the structural characters of root, stem and leaf are adapted to drought and salinated environment. And its halophytic type is more likely to that of pseudohalophyte. (1) Primary structure in its roots has one layer of large, vacuolated epidermis cells. Internally, cortex is comprised of exodermis and endodermis whose cells are similar to that of epidermis in structural feature. (2) primary structure in its stem includes a ring of 8~10 different vascular bundles in size, pith and rays. There are developed vascular tissues in secondary strucrure of roots and stems. (3)Its leaf includes seperately one layer of upper and lower epidermis cells with large and highly vacuolated cells. Between the epidermises lies the indistinctly differentiated mesophyll with many big chloroplasts, surrounded by many spaces. The features commened above is adapted to drought, salination soil. The paper concludes that Thellungiella halophila is more likely to pseudohalophyte for it has no typical nature of euhalophyte or secretory structure such as salt glands before or after salt adaptation. 2. The androecium of Thellungiella halophila are tetradynamous stamen. Each anther has four pollen sac. The cytokinesis of microspore mother cell during meiosis is of simultaneaous type. Its tetrasporophyte is tetrahedral. The mature pollen grain (male gametophyte) is of 3-cell, and each has 3 germinal aperture. The development of anther wall follows the dicotyledonous type, composed of four layers, respectively epidermis, endothecium, middle layer and tapetum. Its tapetum is named as secretory tapetum. 3.The ovary is comprised of two carpels where forms parietal placentation on which many campylotropous ovules grow. The ovule is bitegminous and tenuinucellate. The archesporial cell lies under nucellus epidermis, which developes into functional megasporocyte. Megaspore tetrad is linear. The chalazal megaspore develops into an embryo sac of Polygonum type. The polar nuclei fuse before fertilization. Double fertilization is of the type of Premitotic syngamy. Endosperm formation belongs to nuclear type. Embryogeny conforms to the Onagrad type (Crucifer type) and cotyledons lean against radicle back-to-back. The mature seed has no Endosperm. 4.The archesporial cell diffentiates when the plant generates flower buds observed by naked eyes. The development of male reproductive organ is earlier than that of female. But male and female gametophytes have become mature before flower bud appears white petals which is the proof we regard Thellungiella halophila as self-pollination plant. The egg nucleus and sperm nucleus fused when flower is in full bloom. Subsequently, the fruit stretchs fast with the development of embryo.