烟草单倍体植株的大孢子发生和雌配子体败育

单倍体植株小孢子母细胞减数分裂现象,一些作者曾作过大量观察,但有关大孢子发生过程中减数分裂和胚囊发育情况,工作和报道较少。本文较为系统地观察了花药培养得到的再生单倍体植株大孢子母细胞减数分裂和胚囊发育过程,从大孢子角度为单倍体植物增添了具体的细胞学和胚胎学内容。供试材料烟草(Nicotiana tabacum c.)“金星”品种(2n=48)花药接种于附加KT 2毫克/升,IAA 0.5毫克/升的H固体培养基上。约40天形成愈伤组织后转移到NAA 0.15毫克/升,IAA 0.375毫克/升的MS固体培养基上,待分化出小苗后经盆栽适应,再定植于大田中。用FAA和纳瓦兴液固定单倍体植株不同长度花     

喜树大小孢子发生和雌雄配子体的发育

喜树子房下位,一室,有1枚倒生胚珠,悬垂,具单珠被。假厚珠心胚珠类型,胚囊发育为蓼型。喜树小孢子母细胞减数分裂胞质分裂方式为同时型,四分体主要为四面体形和左右对称形,单核小孢子呈三角形,成熟花粉粒有三角形、四边形和圆形。本文主要研究喜树大小孢子发生和雌雄配子体的发育过程,并初步探讨了喜树部分雌蕊败育的原因。     

凹叶厚朴大、小孢子发生和雌、雄配子体发育的研究

凹叶厚朴花药四囊型,腺质绒毡层有1-2层细胞,小孢子形成时胞质分裂方式为修饰性同时型,小孢子四分体排列方式为左右对称型．成熟花粉粒为二细胞型。四分体和小孢子在发生时有不规则变形。子房单心皮,心皮腹面壁上着生2个胚珠,胚珠倒生型,厚珠心,双珠被;孢原细胞一个,并且自表皮下第2层细胞处分化。胚囊发育为单孢蓼型。凹叶厚朴的胚胎学特征与木兰科其它植物的胚胎学特征基本相同,属于较原始的被子植物胚胎类型。在凹叶厚朴大、小孢子发生和雌、雄配子体发育过程中存在部分败育现象。本文初步探讨了凹叶厚朴濒危的生殖生物学原因。     

藠头大小孢子的发生及雌雄配子体败育的细胞学研究

对栽培头4个品种大小孢子发生和雌雄配子体发育的细胞学观察表明,头小孢子母细胞减数分裂过程基本正常,四分体左右对称或四面体型,部分单核小孢子解体。散粉时,多数花粉粒空瘪,无萌发沟;部分花粉粒具单核或二核;极少数花粉粒具生殖核和营养核。花粉粒生活力低或无,无花粉管萌发。胚囊发育属葱型,部分能发育形成四核胚囊,大部分发育异常,出现二核至五核胚囊,未观察到正常七细胞八核胚囊的形成。结果表明,雌雄配子体败育导致头不结实。     

ROLE OF SETTLEMENT DENSITY ON GAMETOPHYTE GROWTH AND REPRODUCTION IN THE KELPS PTERYGOPHORA CALIFORNICA AND MACROCYSTIS PYRIFERA (PHAEOPHYCEAE)1

Laboratory studies were used to examine how variation in the density of spore settlement influences gametophyte growth, reproduction, and subsequent sporophyte production in the kelps Pterygophora californica Ruprecht and Macrocystis pyrifera (L.) C. Ag. In still (non-aerated) cultures, egg maturation in both species was delayed when spores were seeded at densities 300 · mm^?2. Although the density at which this inhibition was first observed was similar for both species, the age at which their eggs matured was not. P. californica females reached sexual maturity an average of 4 days (or ～ 30%) sooner than did M, pyrifera. As observed previously in field experiments, per capita sporophyte production was negatively density dependent for both species when seeded at spore densities of 10 · mm^?2. Total sporophyte production (i.e. number · cm^?2) for both species, however, was greatest at intermediate densities of spore settlement (～ 50 spores · mm^?2). In contrast, total sporophyte production by P. californica steadily increased with increasing spore density in aerated cultures; highest sporophyte density was observed on slides seeded at a density of 1000 spores · mm^?2. Preliminary experiments with P. californica involving manipulation of aeration and nutrients indicate that inhibition of gametophyte growth and reproduction at higher densities of spore settlement in non-aerated cultures was probably caused by nutrient limitation.     

COMPARATIVE MEGASPOROGENESIS IN PAPILIONACEAE

Megasporogenesis in 16 species of Papilionaceae has been investigated. Archesporial development in Papilionaceae is usually hypodermal, but subhypodermal origin has been observed. The archesporial cell develops directly into the megasporocyte, or divides to produce a parietal cell and a primary sporogenous cell. The parietal cell is always oriented toward the micropylar end of the developing ovule. It may or may not divide to contribute to the nucellar mass as the primary sporogenous cell enlarges to form the megasporocyte. A single megasporocyte is produced in most species investigated. Of those species that form more than one megasporocyte, few develop more than one tetrad of megaspores, and in no case is more than one megagametophyte produced. Meiosis occurs in the megasporocyte to form a tetrad of megaspores. Several variations in tetrad patterns are explored here. Monosporic development is the prevalent condition in Papilionaceae; however, bisporic development does occur.     

MALE GAMETOPHYTE SELECTION IN A NATURAL POPULATION OF HAPLOPAPPUS GRACILIS (COMPOSITAE)

Distributions of two forms of the A chromosome of Haplopappus gracilis in a hybrid natural population and in artificial crosses are analyzed. Pollen bearing the standard type A chromosome is generally superior to that bearing the Mexican type A when they compete on homozygous pistils of either type, but there is no selection on heterozygous pistils. The distribution of sporophyte karyotypes in the natural population is not in equilibrium, and it is surmised that the standard type A chromosome is increasing in frequency in the population.     

POLLEN APERTURE POLYMORPHISM AND GAMETOPHYTE PERFORMANCE IN VIOLA DIVERSIFOLIA

Pollen aperture polymorphism is studied in Viola diversifolia, where all plants produce three- and four-apertured pollen grains. We tested whether there are genetic differences among plants for the proportions of the different pollen morphs, and whether the morphs differ in gametophytic performance. Results show that the more apertures a pollen grain has, the more quickly it germinates but that few-apertured pollen grains have faster growing pollen tubes and longer life expectancies. The proportions of the different pollen morphs, together with pollen tube growth rates, may be inherited traits based on differences among maternal families. These results suggest that the different pollen morphs are favored in different pollination ecology situations. The production of several pollen morphs by the same individual could therefore be evolutionarily advantageous.     

INITIATION AND DEVELOPMENT OF INFLORESCENCE AND FLOWER IN ANEMOPSIS CALIFORNICA (SAURURACEAE)

All flowers of Anemopsis californica, the most specialized taxon of the family Saururaceae, are initiated as individual primordia subtended by previously initiated bracts, in contrast to the common-primordium initiation of all flowers of Saururus cernuus and of most flowers of Houttuynia cordata. Floral symmetry is bilateral and zygomorphic, and the sequence of initiation among floral parts is paired or whorled. In A. californica, the six stamens arise as three common primordia, each of which later bifurcates to form a pair. The three common primordia occupy sites corresponding to the positions of the three stamens in H. cordata flowers. In Anemopsis, the filaments of each pair are connate. Each stamen pair is vascularized by a single bifurcating vascular bundle. The three carpels per flower are usually initiated simultaneously although there may be some variation. Adnation between stamens and carpels results from zonal growth. Downward extension of the locule, and proliferation and expansion of receptacular tissue and inflorescence cortical tissue around the locule below the bases of the carpels produce the inferior ovary. The inflorescence terminates its activity as a flattened apical residuum, surrounded by bracts subtending reduced flowers most of which have stamens only.     

INCOMPATIBILITY OF MERISTEMATIC AND FILAMENTOUS GROWTH IN THE FERN GAMETOPHYTE

Gametophytes of Pteridium aquilinum can be maintained in red light as either 1- or 2-dimensional structures. The mode of growth realized in red light is dependent upon the activity of the meristem. An active meristem in a 2-dimensional structure will permit a continued development of that structure. A breakdown in meristematic activity results in filament formation. It is suggested that a group of actively dividing cells in some manner inhibits cell elongation and thus prevents filament formation in red light.     

STUDIES ON THE PATTERN OF MEGASPOROGENESIS AND MICROTUBULAR CYTOSKELETON CHANGES IN CYMBIDIUM SINENSE

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