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164

作者：

游学明

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摘要：

红树植物具有特殊的胎生现象,胎生分为显胎生和隐胎生两种.桐花树(Aegiceras corniculatum)属隐胎生红树植物.在以往对红树植物的胚胎学研究中,只有显胎生红树植物从受精卵(合子)到胚轴成熟这一阶段的研究,而显胎生和隐胎生红树植物早期的发育阶段(大小孢子发生和雌雄配子体发育)尚属空白.本文对桐花树胚胎发育早期阶段的大小孢子发生和雌雄配子体发育进行了显微形态观察,并测定了膜脂质过氧化和抗氧化保护酶活性及4种金属元素含量动态变化,结果如下:1,桐花树胚胎发育早期形态观察采用常规石蜡切片法,得到以下结果:(1)花药由四个花粉囊组成,药壁包括表皮,药室内壁,中层及绒毡层,绒毡层为腺质绒毡层;(2)小孢子母细胞减数分裂为同时型,四分体排列方式为四面体型;(3)成熟花粉2细胞,有4个萌发孔;(4)特立中央胎座,薄珠心,大孢子母细胞减数分裂形成T形排列的4个大孢子,合点端的大孢子具功能,成熟胚囊为7胞8核结构,胚囊发育类型为蓼型.这些结果完善了胎生现象的生物学资料.2,桐花树胚胎发育早期还具有以下特征:花药表皮不分解,花药中层细胞在发育过程中不退化,中层和内壁层细胞都发生纤维状加厚.在花药壁和子房壁处有单宁细胞,子房内部有分泌腺,结构与盐腺类似(在其他植物中均无有关报道).这些特征可能与桐花树植物的生境适应有关,有助于其繁殖器官在特殊生境下维持正常功能.3,在桐花树胚胎发育过程中,观察到胎座柄部能随胚胎发育进程而增长,在成熟桐花树胚轴中可形成长达数cm的细长"脐带",这种特殊结构在桐花树植物胚胎发育初期至胚轴成熟过程中成为胚胎和母体的营养通道.4,作为繁殖后代的重要器官,里面的雌雄配子是很敏感的,各种外界的生物和非生物压力都有可能造成可育性强烈降低.特别是在小孢子母细胞减数分裂到受精完成这个阶段,对外界压力十分敏感,例如干旱,热,冷,水淹以及营养缺乏,这些压力都会导致繁殖器官各种结构畸形和繁殖功能丧失.桐花树由于生长于海岸潮间带,其繁殖器官受盐度,水分,光照的影响都很强烈.而其能正常发育繁殖,在发育过程中过氧化保护酶体系的反应值得研究.基于形态观察的结果,依照花药的发育时期,我们把桐花树花蕾划分为5个发育阶段,测定了每个阶段花蕾的花药及非花药部分的SOD,POD,CAT保护酶活性变化及MDA含量变化,发现SOD活性在第4期出现最高值,原因可能是此时花蕾开放,海水可进入其花蕾内部;在花蕾发育的各阶段,其降解H2O2主要是依靠POD酶.5,采用湿法消化,石墨炉原子吸收法测定其花蕾的5个时期花药及非花药部分的Ca,Mg,K,Na四种金属离子的含量.结果这两部分在所有时期具有高Na,K,低Ca,Mg的特点.Mg,Ca元素在小孢子四分体时期的含量最高,可能与此时小孢子进行的细胞分裂所经历的剧烈生理生化活动有关.Mangroves possess distinctive vivipary. Vivipary is divided into two types:cryptovivipary and exposed vivipary. Aegiceras corniculatum belongs to the type of cryptovivipary .The embryo developmental stages from zygote to the seedling(hypocotyle) have been studied on the vivipary mangrove. But the early stage before zygote of cryptovivipary and exposed vivipary is still to be investigated. Megasporegenesis and microsporegenesis, male and female gametophyte of Aegiceras corniculatum had observed in this paper,and the results as follows: 1.Sporegenesis and the development of female and male gamepothytes in Aegiceras corniculatum are studied by the means of paraffin wax.the main results are as follows:(1) The wall of anther consists of four layers:epidermis,endothecium, middlelayers and tapetum from out to inside.Tapetum cell is of secretory type.(2) Cytokinesis of micro- sporocyte meioticdivision is of simultaneous type. Tetrasporophyte is tetrahedral (3) Mature pollen grain is of 2-cell type. And of four germ pores (4).The ovule is double integuments,tenuinucellate.Megasporocyte meiotic divides into T-type four megaspores .The megaspore near chalazae is the functional one.Embryo sac is of Polygonum type.These results integrated the dada of vivipary. 2,The embryo development of Aegiceras corniculatum occurred with these characters: the epidermis didn't decompose when the anther matured, endothecium and middlelayers'wall thickened in the latter developmental stages. there are groups of tanni-cells in the wall of anther,and there are secretory structures like the salt gland in the ovarys(this had not reported in other plant).all of these structures may related with the adaptations of environment. 2,We observed that the suspensor can elongate during the embyo development.It even become a several cm long "umbilical cord"in the mature hypocotyl of Aegiceras corniculatum. And this "umbilical cord" existed as the nutrition chunnel between the embryo and mather plant. 4.Productivity in plant is severely reduced by various biotic and abiotic stresses.Among these stages, reproductive development from meiosis in the spore mother cells to fertilization and early seed establishment is extremely sensitive to various stresses, such as drought,heat,cold,flooding and nutrient deficiencies. These stresses all above cause various structural and functional abnormalities in reproductive organs, leading to failure of fertilization. Aegiceras corniculatum lives in the coastal environment and it exposed to the sea water with high salts, strong light and the other disadvantages,it must have some special mechanism to protect its reproductive organs.The activities of supeloxide- dismutase(SOD), catalase (CAT) and peroxidase (POD), and concentrations of malondialdehyde have been studied during the five developmental stages of buds, which divided depending on the results of anthers developments. And

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年份：

2006