Development of ovule,embryo sac,and endosperm in Dipterostemon and Dichelostemma (Alliaceae) relative to taxonomy

Dipterostemon capitatus and all species of Dichelostemma have the following characters in common: the ovule is anatropous and bitegmic; the nucellar epidermis is penetrated by the embryo sac; the remaining chalazal part of the nucellus expands, partly due to periclinal divisions in its epidermis; the micropyle is formed by the inner integument only; parietal cells are present; the embryo sac develops according to the Polygonum type; the endosperm is nuclear; after fertilization, the cells of the inner integument enlarge greatly. One difference between the genera is that the inner integument is two cells thick in Dipterostemon, but five to seven cells thick in all Dichelostemma species. In Dipterostemon, embryogenesis is of the Asterad type, and the formation of walls in the endosperm occurs much as in wheat. The absence of variation in embryological characters among the species of Dichelostemma strongly supports the view that these species all belong in one genus, despite differences in gross morphology. Dichelostemma is very closely related to Brodiaea, since species of these two genera show identical embryology. Dipterostemon must be retained as a genus because a deviating inner integument adds to uniqueness in gross morphology. Dipterostemon, Dichelostemma, and Brodiaea, are embryologically quite different from Triteleia. Neither Dipterostemon nor Dichelostemma show any close affinity with Allium.     

Embryological studies inGlaucidium palmatum Sieb. et Zucc. with a discussion on the taxonomy of the genus

Embryological features ofGlaucidium palmatum are as follows: the ovule is anatropous and bitegmic; the archesporium is hypodermal and multicelled, consisting of about 10 to 15 cells; all the archesporial, cells develop directly into megaspore mother cells, only three or four of which, however, generally complete meiotic divisions; before and during meiosis, dermal cells of the nucellar apical part undergo successive periclinal divisions forming a thick nucellar cap of as many as 20 cell-layers; embryo sac formation is of the Polygonum type; multiple embryo sacs occur frequently; antipodal cells are small in size and ephemeral or persistent; the inner integument is 3 to 5 cell-layers thick, and the outer integument 7 to 13 cell-layers thick; the outer integument is vascularized; a micropyle is formed by the inner integument alone; the endosperm is of the Nuclear type; embryogeny is of a type similar to the Onagrad type. In light of evidence from embryology and other sources it seems that there is ample reason for recognizing the family Glaucidiaceae which is distinct from the Ranunculaceae and its related families. Several common embryological features suggest an affinity between the Glaucidiaceae and the Paeoniaceae.     

Embryo sac, endosperm, and seed of Nemophila (Boraginaceae) relative to taxonomy, with a remark on embryogeny in Pholistoma

Studies on embryology and seed morphology are complementary to molecular phylogenetics and of special value at the genus level. This paper discusses the delimitation and evolutionary relationships of genera within the tribe Hydrophylleae of the Boraginaceae. The seven Nemophila species characterized by a conspicuous seed appendage are similar in embryology and seed structure. The ovule is tenuinucellate and unitegmic with a meristematic tapetum. The embryo sac penetrating the nucellar apex is of the Polygonum type, has short-lived antipodal cells, and an embryo sac haustorium. The endosperm is cellular, producing two terminal endosperm haustoria, of which the chalazal has a lateral branch. Embryogeny is of the Chenopodiad type (as in Pholistoma). The seed coat is formed from the small-celled inner epidermis of the integument. The large-celled outer epidermis of the integument disintegrates into scattered cells. Seed pits evolve from irregularly placed inner epidermal cells of the integument. The chalazal part of the ovule produces a cucullus, that functions as an ant-attracting elaiosome. Those species of Nemophila with a conspicuous cucullus form a natural genus. Nemophila is most closely related to Pholistoma. The integumentary seed pits of Nemophila might have evolved from ovular seed pits similar to those in Pholistoma.     

Embryology of theaceae — Anther and ovule development ofAdinandra,Cleyera andEurya

Anther and ovule development of the theaceous Ternstroemioideae is reported for the first time on the basis of eight specles of three generaAdinandra, Cleyera andEurya. Anthers of these three genera are similar and can be characterized by the following traits: tapetum of glandular type, anther dehiscing latrorse-introrse, both connective and anther epidermis heavily tanniniferous, and connective and even anther wall layers having abundant druses. Their ovules are also very similar in being bitegmic and tenuinucellate, and in having a micropyle formed by the inner integument only, three cell-layered integuments, a raphe bundle terminating at chalaza, usually amphitropous or less often campylotropous ovule, embryo sac formation of Polygonum type, ephemeral antipodal cells, and tanniniferous ovule epidermis. Such ovules are readily distinguishable from those of Camellioideae and all other families. It is suggested that the three genera studied are closely related, and that the degree of embryological specialization is highest inAdinandra and lowest inEurya. On the basis of the significant embryological discrepacies, the Ternstroemioideae seem to have diverged rather distantly from the other core-subfamily Camellioideae of the Theaceae.     

Embryology of the Theaceae - anther and ovule development of Camellia, Franklinia, and Schima

The anther and ovule development of Camellia, Franklinia, and Schima (Theaceae, Camellioideae) were observed. The three genera share the following embryological traits: anther wall formation of basic type, tapetum of glandular type, walls of endothecial cells with secondary thickening, and production of pseudopollen grains in connective, which are dispersed into pollen sacs at anthesis, ovule bitegmic-tenuinucellate, micropyle formed by inner integument alone, hypostase present, and both integuments generally five-to-seven cell layered. One autapomorphy of the Camellioideae found in the present study is the production of pseudopollen. The three genera surveyed differ with respect to the number of middle layers in the anther, the presence or absence of stomata on connective epidermis, morphology of pseudopollen, type of embryo sac formation, form of ovule, ovular vasculature, and the proliferation of ovular epidermis, etc. Among the three genera, Franklinia and Schima are presumed to be closer embryologically, and Schima possesses more numerous specialized features.     

The embryology ofStegnospermataceae,with a discussion on its status,affinities and systematic position

The embryology ofStegnosperma halimifolium andS. watsonii has been studied in detail. The tapetum is of the secretory type and its cells become multinucleate. Simultaneous cytokinesis in the pollen mother cells follows meiosis. The ripe pollen grains are 3-celled. The ovule is crassinucellate, bitegmic and amphitropous, with the micropyle formed by the inner integument alone. The female archesporium is one celled, and the parietal tissue 3–5 layered. The embryo sac development conforms to thePolygonum type. A central strand, 6 or 7 cells thick, differentiates inside the nucellus and extends from the base of the embryo sac to the chalazal region. The endosperm is nuclear. The embryogeny conforms to the Caryophyllad type. The seed coat is formed by the outer epidermis of the outer integument and the inner epidermis of the inner integument. Based on this evidence and other data, the status of the genus as an independent family,Stegnospermataceae (Stegnospermaceae) is confirmed. Apparently, it forms a connecting link betweenPhytolaccaceae andCaryophyllaceae.     

Embryology of the dioecious Woonyoungia septentrionalis (Magnoliaceae)

The embryological characteristics and ovular integument development of the dioecious species Woonyoungia septentrionalis (Dandy) Law (Magnoliaceae), which are poorly understood, were investigated under laser scanning confocal microscope (LSCM) and light microscope (LM). The embryological characteristics conform to most of the previously studied species in Magnoliaceae. The anther has 4 microsporangia, and the anther wall develops according to the dicotyledonous type. Cytokinesis at meiosis of the microspore mother cells follows a modified simultaneous type, giving rise to isobilateral or decussate tetrads, and a cell plate is absent, but a membrane was observed. Mature pollen grains are 2‐cellular and have high germination rates. The ovule is anatropous, crassinucellate and bitegmic, and meiotic result in linear tetrads of megaspores, the one at the chalazal end functions directly as an embryo‐sac cell. The development of the embryo sac is of the Polygonum‐type and endosperm formation is of the nuclear type. The outer integument of the ovule differentiates into an outer fleshy and an inner stony layer while the inner integument is reduced to a tanniniferous layer. The normal embryological development, high germination rates of pollen and high seed set indicate that the primary reason for the decline of the species is not to be found in these developmental processes.     

落葵的花粉粒和胚囊的形成与发育

落葵(Basella rubra L.)小孢子的发育为同时型,四分体呈四面体排列。在花粉母细胞减数分裂过程中,可清楚地看到胼胝壁的消长变化。三胞花粉,具散沟和网状纹饰。腺质绒毡层。 胚囊的发育为蓼型。反足细胞早期退化。内珠被突出形成珠被喙,同时,在其珠孔区域,有由内珠被的内表皮细胞所发育而来的类似盖状结构。 本文还注意到同一花中以及相邻花朵之间,花粉粒与胚囊发育进程的相关。花粉粒的发育略早于胚囊的发育,但以后由于胚囊母细胞形成胚囊的进程较为迅速,以致花粉粒与胚囊能够同时成熟。     

Comparative embryology of Bambusa tulda Roxb. and Thyrsostachys siamensis Gamble (Poaceae: Bambuseae)

Bambusa tulda and Thyrsostachys siamensis resemble each other in having an obovate ovary which is hairy and thickened along the apex, a pseudo-crassinucellate ovule with a wide region of attachment, poorly-developed and ephemeral outer integument, an inner integument which fails to grow beyond the nucellus, 'Polygonum' type of embryo sac ontogeny, parallel orientation of embryo sac to the long axis of the ovule, multiple antipodals which retain apical position in the embryo sac even during post-fertilization phase of development, an ephemeral nucellus, relatively small bambusoid embryos, and many-layered and apically thickened pericarp. However, they differ from each other in their gynoecial structure, the extent of the development of the outer integument, organization of megaspore tetrads and development-stage-related behaviour of the inner integument in the fertilized ovules. These taxa also differ from other members of the subfamily Bambusoideae in the structure of the mature ovule, endosperm and pericarp.     

SOME HISTOCHEMICAL,ULTRASTRUCTURAL, AND NUTRITIONAL ASPECTS OF THE OVULE OF QUERCUS GAMBELII

Histochemical analyses of the ovule of Quercus gambelii show that the major food reserves (starch grains and lipids) are located almost exclusively within the outer integument. Vascular traces are present only within this integument which contains numerous, well-developed plasmodesmata. The inner integument is virtually devoid of any food reserves and has very few plasmodesmata. The ovule has a persistent chalazal extension of residual nucellar cells (called the postament) which projects into the embryo sac. Due to the above information and the fact that the synergids rarely contain starch and no plasmodesmata are present in the walls of any of the cells of the egg apparatus (Mogensen, 1972), it is concluded that the synergids play little or no role in embryo sac nutrition. Rather, it is proposed that the pathway of available food materials in the young ovule is from the outer integument to the chalaza and through the postament into the embryo sac.     

白毛新木姜子[Neolitsea aurata var. glauca]胚胎学研究

应用光学显微镜对白毛新木姜子的胚胎学特征进行了研究,首次在非寄生性樟科植物中发现了细胞型胚乳。对樟科8属进行了胚胎学特征的比较。花药四室,药室壁的发育属于“基本型”,周原质团型绒毡层。小孢子母细胞连续型分裂。等四面体型四分体。二细胞成熟花粉,无孔沟。雌孢原多个,一般仅一个能继续发育。蓼型胚囊。助细胞具丝状器。反足细胞宿存。大孢子母细胞和合子具极性。宿存的一个助细胞具有吸器功能。细胞型胚乳,胚胎发育属于柳叶菜型的三叶变型。种皮源于外珠被,内表皮细胞壁螺旋状加厚。胚胎学特征表明,新木姜子属与木姜子属有密切的亲缘关系。较多的双胚囊异常现象,支持樟科与Monimiaceae具有紧密关系的推测。胚胎学特征不支持将无根藤属独立为科的观点。     

白毛新木姜子[Neolitsea aurata var.glauca]胚胎学研究

应用光学显微镜对白毛新木姜子的胚胎学特征进行了研究,首次在非寄生性樟科植物中发现了细胞型胚乳。对樟科8属进行了胚胎学特征的比较。花药四室,药室壁的发育属于"基本型",周原质团型绒毡层。小孢子母细胞连续型分裂。等四面体型四分体。二细胞成熟花粉,无孔沟。雌孢原多个,一般仅一个能继续发育。蓼型胚囊。助细胞具丝状器。反足细胞宿存。大孢子母细胞和合子具极性。宿存的一个助细胞具有吸器功能。细胞型胚乳,胚胎发育属于柳叶菜型的三叶变型。种皮源于外珠被,内表皮细胞壁螺旋状加厚。胚胎学特征表明,新木姜子属与木姜子属有密切的亲缘关系。较多的双胚囊异常现象,支持樟科与Monimiaceae具有紧密关系的推测。胚胎学特征不支持将无根藤属独立为科的观点。     

Morphological Studies on Circaeaster agrestis Maxim. (1) Process of Embryolo gical Development

The present paper aims at discovering the characters of embryological development of Circaeaster agrestis, which makes up a monotypic genus, Circaeaster, to establish the phylogenetic relationships of the genus. The different opinions on its systematic position among botanists are briefly explained. The embryological studies show that the most important advanced characters of the genus are as follows. The ovule is amphitropous, unitegmic and tenuinucelar; the embryo sac formation is in accordance with the Polygonum type; endosperm formation is of the cellular type, the primary endosperm nucleus dividing to form two cells and the first wall vertical; embryo formation follows the variation of the Caryophyllad type; at the early stage of development of embryo, the integument has been already atrophied and at last disappeared, so that the seed coat is absent in the mature fruit. On the basis of the embryological and some morphological evidence, the authors consider that a close relationship between the genus and Ranunculaceae and its related families seems to be unlikely. The affinities of the genus Circaeaster are still uncertain.     

小草蔻胚珠及雌配子体发育的研究

小草蔻（Alpinia henryi K.Schum）胚胎倒生,厚珠心,双珠被。内珠被独自成珠孔。造孢细胞,大孢子母细胞和四体时期,周缘细胞仅1层。四分体线形,少数三分体。合点在孢子具功能。成熟胚珠具有珠心冠原和承珠盘结构。胚囊发育属蓼型。成熟胚整,合点端狭长,形成盲囊。反足核不能构成细胞,是短命的。膜质假种皮的原基从外珠被和珠柄发生。     

甜荞pin型花与thrum型花雌雄蕊发育的比较研究

为从形态上研究甜荞(Fagopyrum esculentum)二型花发育的差异性,该文运用石蜡切片技术对甜荞pin型花和thrum型花大、小孢子发生和雌、雄配子体的发育过程进行观察比较.结果表明:(1)甜荞2种花的雌蕊、雄蕊发育的细胞学特征有很高的相似性,具直生胚珠、双珠被、厚珠心;大孢子四分体直线型排列,合点端为功能...     

Translocation of Uranin within the Living Ovules of Vanilla

In the ovules of Vanilla (Vanilla planifolia Andr.) before fertilization, outer integument surrounded the lower part of ovule. Uranin got into ovule through funiculus, forming, the first center of fluorescence at the chalaza zone of ovule. Then uranin was transported to micropyle end along inner integument, forming the second center of fluorescence at micropyle end of inner integument. Soon, fluorescence appeared in the egg apparatua. After fertilization, the outer integument ovule extended upward, forming micropyle ogerber with inner integument. After getting into ovule through funiculus, uranin spreads to- ward several directions: l. transported to outer integument at the entrance of micropyle; 2. transported downward to chalaza zone along outer integument at the side of funiculus; 3. extended from chalaza zone to the inside and to the outer integument at the side far from funiculus The ovules of Vanilla had no vascular bundles. On transporting in inner integument, however, the cells in inner layer next to the embryo sac appeared to be the major passage. In mature embryo sac, there was cuticle between inner integument and embryo sac at the half of micropyle end. But between embryo sac at the half of chalaza end and nucellus, cuticle was absent. Nutrient could get into embryo sac from chalaza end undoubtedly. As egg apparatus showed the fluorescence after formation of fluorescence center of inner integument at micropylar end, the possibility that nutrient got into embryo sac from micropyle could not be excluded.     

Embryology and relationships of Akania (Akaniaceae)

We present the first extensive study of embryology of Akania , the only genus of Akaniaceae (one of the 15 glucosinolate-producing families). Akania has a distinctive combination of embryological features, which includes bitegmic and crassinucellate ovules; thick, multiplicative and vascularized outer integument; a Polygonum-type embryo sac; albuminous seed; 'exotestal' seed coat with a palisade of columellar, thick-walled cells and a thick and sclerotic mesotesta with the inner tissue aerenchymatous. A comparison of its embryological characteristics with those of some other groups indicates that Akania closely resembles Bretschneideraceae (another glucosinolate-producing family) and Sapindaceae, but it retains some archaic embryological features and is best treated as a separate family in or near Sapindales, as in most modern general classifications. Based on evidence from embryological and other data, Akaniaceae appear to be the sister group of Bretschneideraceae, possibly near to Sapindales. With the data at hand, we cannot fully assess the recent suggestion that Akaniaceae-Bretschneideraceae are a basal group in Capparales.     

Development of ovule,fruit and seed of Xyris (Xyridaceae,Poales) and taxonomic considerations

The development of the ovule, fruit and seed of Xyris spp. was studied to assess the embryological characteristics of potential taxonomic usefulness. All of the studied species have (1) orthotropous, bitegmic and tenuinucellate ovules, with a micropyle formed by both the endostoma and exostoma; (2) a cuticle in the ovules and seeds between the nucellus/endosperm and the inner integument and between the inner and outer integuments; (3) helobial, starchy endosperm; (4) a reduced, campanulate and undifferentiated embryo; (5) a seed coat formed by a tanniferous endotegmen, endotesta with thick‐walled cells and exotesta with thin‐walled cells; and (6) a micropylar operculum formed from inner and outer integuments. The pericarp is composed of a mesocarp with cells containing starch grains and an endocarp and exocarp formed by cells with U‐shaped thickened walls. The studied species differ in the embryo sac development, which can be of the Polygonum or Allium type, and in the pericarp, which can have larger cells in either endocarp or exocarp. The Allium‐type embryo sac development was observed only in Xyris spp. within Xyridaceae. Xyris also differs from the other genera of Xyridaceae by the presence of orthotropous ovules and a seed coat formed by endotegmen, endotesta and exotesta, in agreement with the division of the family into Xyridoideae and Abolbodoideae. © 2015 The Linnean Society of London, Botanical Journal of the Linnean Society, 2015, 177 , 619–628.     

Campynemanthe (Campynemaceae): Morphology, microsporogenesis, early ovule ontogeny and relationships

Campynemanthe Baill. consists of three species endemic to New Caledonia. Two species are studied and compared. The tapetum is secretory with 2-nucleate tapetal cells. Microsprogenesis is successive, microspore tetrads are isobilateral and the pollen grains are free and inaperturate or have a weakly defined aperture. Placentation is axile with 3–4 ovules in each of the three locules. Ovules are anatropous and crassinucellate with the micropyle formed by the inner integument alone. The archesporial cell cuts off a parietal cell, which divides to form a parietal tissue. The nucellar epidermis divides periclinally at the nucellar apex to become 2-layered. The megaspore tetrad is T-shaped, in which the micropylar megaspore cells are separated by an oblique wall. The chalazal megaspore enlarges and apparently developes into a Polygonum-type embryo sac, but a mature embryo sac has not been seen. The ripe seeds are pale and non-phytomelaniferous. They have copious endosperm rich in fatty oils. The embryo is minute. These characters and gross morphological similarities support relationship with Campynema Labill., but there are also conspicuous differences. The two genera are considered related. They also closely approach genera of the variable family Melanthiaceae and there are reasons to include them in this family.     

Embryology ofCrocus thomasii (Iridaceae)

The embryology ofCrocus thomasii is described. Male meiosis is of simultaneous type, and gives rise to starchy microspores which develop into lipoid pollen grains; these are two-celled and show a spinulate acolpate, abaculate exine lacking apertures. The tapetum is glandular and its cells become bi- or sometimes multinucleate. The ovule is anatropous and bitegmic; the inner integument forms the micropyle. Megasporogenesis is heteropolar with starch accumulation in the functional chalazal megaspore. Embryo sac development conforms to thePolygonum type. The endosperm development is nuclear. The embryo develops according to the Caryophyllad type. In the ripe seed it is differentiated and enveloped by a starchy cellular endosperm. The embryological characters observed strongly favour a close relation betweenC. thomasii andC. sativus.