The Structure, Development And Evolution Of The Seedlings Of Antirrhinum Majus And Some Other Angiosperms

The primary structures, the genesis and the structure formed of the primary vascular system and the structural change in the process of cotyledonary senescence of the seedlings of Antirrhinum majus and other angiosperms were studied. The progress had been aquired in the aspects as follows.1.The study of comparative anatomy on the structure of seedlings of Acorus tatarinowii and Zantedeschia aethiopica suggested A. tatarinowii was more primitive "X"-shape mesarch haplostele, while Z aethiopica atactostele ; the actinostele of root of the former was di- to octoarch , but the latter only di- to pentarch ; The pattern of endothecial wall thickening in A.tatarinowii was characteristic of five-face thickened and contained passage cell, while Z. aethiopica four-faced thickened and known as casparian strip. Endocyte of the former was styloid, otherwise the latter was typical raphide. In addition, there occurred difference in the structure of cotyledonary haustrum and other storages. The results of this study support removing Acorus from Araceae as a singular family and as the basal and relative isolation of the monocotyledon.2. The process of vessel element's promotion, formation and connection in primary xylem of Antirrhinum majus, a model plant, was observed through micropolariscope and bright-field microscope. The results showed that the vessel element didn't differentiate after the seeds had imbibied for 6 hours; 6 hours after seeds germination, two loci 梠ne below the middle portion of the cotyledon and the other in the lower portion of cotyledon-node zone (CNZ) initiated the differentiation of vessel element simultaneously, then elongated towards the cotyledonary apex and hypocotyl-root region respectively; eventually the two promoter loci began to interconnect through vessel elements. 7-10 days' seedlings after the seeds germinated, the meristem in the stem apex functioned to form true leaf primordium, meanwhile, the vessel elements which differentiated from parenchymatous cells of the middle and upper portion of the CNZ connected with the vessel elements from procambium of epcotyl-shoot region. According to the space-time maturation during the development of the vessel elements in primary vascular system : the vessel elememts of the cotyledons and the lower portion of CNZ formed firstly , then downward hypocotyl-root zone, at length, the vessel elememts of the upper and middle portion of CNZ and epicotyl-shoot region connected with each other, the result uphold the seedling partition model that divides seedling into CNZ, hypocotyl-root region and epicotyl-shoot region. In addition, the paper also discusses the relation between auxin and the development of vessel element during seedling.3. The anatomical and ultrastructural research in the cotyledon of Antirrhinum majus indicated: cutin membrane and sparse epidermal trichome occurred on the surface of cotyledon. Stomata protruded appreciably over the epidermis, the ratio of palisade mesophyll and spongy mesophyll was low, the previous evidence showed structural charecater of shade leaf. Its cotyledon began to senesce in 100 days after germination. During the process of senescence, the structural abnormality occurred firstly in chloroplast in which chloroplast grana disordered and stromal lamellae twisted and in which starch grains became bigger and osmiophilic granules increased, and then converged into bigger granules. Annulate lamellaes and multi-vesicle-bodies occurred in cytoplasm and the quantity increased. The thickness of cell wall gradually became nonhomogene, and cell wall even collapsed in some place. The change in mitochondria and nucleus lagged relatively. Hereby the process of senescence of the Antirrhinum majus cotyledon as a embryonic organ appeared some features of programmed cell death (PCD).4. The studies focused on the CNZ of Dianthus barbatus and Saponaria offlcinalis seedlings appliedtwo different vascular cylinder types ,even through they both were ""-shape exarch and diarch haplostele, their patterns of protoxylem and m...