THE FEMALE GAMETOPHYTE OF MACHAERANTHERA PATTERSONII (ASTER PATTERSONII) AND OF M. TANACETIFOLIA

The nucellus of Machaeranthera pattersonii (A. Gray) Greene (Aster pattersonii A. Gray) contains only one megaspore mother cell, and the female gametophyte develops from the chalazal megaspore of a row of four, thus conforming to the Polygonum type of development. These observations are contrary to the older work of Palm. Three nuclear divisions produce the typical eight nuclei with the egg apparatus, primary endosperm cell with two polar nuclei, and two antipodal cells, the micropylar one containing two nuclei. Usually no more antipodal cells are formed, although there is further nuclear division, apparently followed by nuclear fusion. The antipodal cells remain about the same size without forming an antipodal haustorium. Cell division accompanies the first division of the primary endosperm nucleus. The early stages of the embryo resemble those of other Compositae. Machaeranthera tanacetifolia (HBK) Nees also shows the Polygonum type of development of the female gametophyte. It is suggested that Palm may have been working on some species of Erigeron that had been wrongly identified, which would account for the difference in observations.     

Osservazioni carioembriologiche in Ornithogalum di Sardegna: Nota I. - Sporogenesi e sviluppo dei gametofiti in Ornithogalum caudatum Ait

Abstract

CARYOEMBRYOLOGICAL STUDIES in ORNITHOGALUM OF SARDINIA.

I. - SPOROGENESIS AND DEVELOPMENT OF THE GAMETOPHYTES IN ÒRNITHOGALUM CAUDATUM AIT. — After a concise synthesis of the caryoembryological knowledges regarding the taxa of Ornithogalum present in Sardinia, the embryology and morphology of Ornithogalum caudatum Ait., have been investigated.

In a three-locular ovary the ovules are anatropous, epitropous with nucellus crassinucellate and only one archesporial cell evolves a mother cell.

The development of the female gametophyte tallies with the Polygonum (Normal) Type.

The homoetypical division presents an asynchronous proceeding in the cellules of the dyad with a considerable delay in the two-nucleate arrangement, especially in the chalazal cell.

Antipodal cells present a hypertrophic growing, but they present no tendency to polyantipody.

The endosperm is of the Helobiae Type.

The divisions of the pollen mother-cells are of the successive Type.

Longest axis of 1-sulcate pollen grains about 76 micron.

A true tapetal periplasmodium isn't formed in the anthers.

The chromosome number is 2n = 54.

Raphides accour in the cataphylls, in the parenchymatous tissues of the leaf and in several parts of the floral region.     

RELATIONSHIP BETWEEN MALE AND FEMALE GAMETOPHYTE DEVELOPMENT IN RYE

The development of male gametophyte and female gametophyte within a floret of rye (Secale cereale L.) was examined. Generally, meiosis in microsporocytes and in megasporocytes occurs simultaneously in most florets, but the period from zygotene to tetrad meiosis in the megasporocyte progresses more slowly than that in the microsporocyte. When the female gametophyte has one nucleus and no vacuoles, the male gametophyte has a single, eccentric nucleus. By the time the female gametophyte develops to the vacuolated one-, two-, four-, and eight-nucleate stages and to the growth and differentiation of the egg apparatus stage, the male gametophyte reaches the two-celled pollen stage. As the female gametophyte matures, the male gametophyte also reaches maturity. The duration of male gametophyte development from microspore mother cell and the duration of female gametophyte development from megaspore mother cell are the same in most florets. The relationship between sexual development of cross-pollinated rye is similar to that of self-pollinated wheat (Triticum aestivum L.). It seems that the relationship is not related to the breeding system.     

Lo Sviluppo Del Fiore in Bupleurum Dianthifolium Guss. Con Particolare Riguardo Ad Un Corpo Citoplasmatico Fibrillare Nella Megasporogenesi

Summary

Bupleurum dianthifolium Guss., an endemic species of the small island of Marettimo just West of Sicily, is one of the few constantly hermaphroditic Umbelliferae. It is markedly protandrous. Its chromosome number is n = 8.

The flower develops acropetally from the petals to the stamens, and the carpels; the development of the sepals stops very soon.

The microspores individualise simultaneously and the reproductive nucleus divides while the pollen grain is still in the anther; the tapetum is of the secretory type.

The two carpels fuse at their tips and the ovary is divided into two chambers by the carpophore which develops from the bottom central part of the cavity. Two ovules start developing in each chamber; the upper ones cease their development while the lower ones grow into pendulous, anatropous ovules with only one integument. The ovule is tenuinucellate. The archesporium is unicellular. No parietal cell is formed.

A group of cells trophic in function is present at the basis of the embryo sac, and disappears after fertilisation has occurred. The female gametophyte is of the normal type, monosporic, 8-nucleated, with the antipodal cells sunken in the chalazal nutritive apparatus and disappearing before the polar nuclei fuse. The albumen is nuclear.

A fibrillary body has been observed in the cytoplasm of the megaspore mother-cell. This body after the meiosis remains as an exclusive property of the chalazal megaspore, i. e. the spore that will give the embryo sac. This body can still be seen in the binucleate gametophyte, and disappears during the 4-nucleated gametophyte stage.     

Ricerche Embriologiche sul Genere Thalictrum Embriologia di Thalictrum Angustifolium L. v. flavum L

Abstract

Embriologycals researches in the thalictrum genus. — Embriology of Thalictrum angustifolium L. v. flavum L.

In this research has been studied the development of the female gametophyte of Thalictrum angustifolium L. v. flavum L.; it has been found a tetrasporic bipolarized type: the Pyretrum type, with sixteen nuclei.

The gametophyte is characterized by cellularization of every antipodal nucleus.

Besides this is a new type in the Thalictrum genus, supposing that in others species of this genus, has been recognized the Normal type.

The author supposes another type in this specie, probably a development of the tetrasporic tetrapolarized type, of which he will refer when the necessary elements emerge.

In this specie the microsporogenesis is simultaneous.     

Ricerche Embriologiche Sul Genere Thalictrum. II. Embriologia e Cariologia Di Thalictrum Lucidum L. e di Thalictrum Minus L. Subsp. Minus

Abstract

Embryological researches in the «Thalictrum» genus. II. Embryology and caryology of «Thalictrum lucidum» L. and «Thalictrum minus» L. ssp. «minus». — In their development the female gametophytes of Thalictrum lucidum L. and Thalictrum minus L. ssp. minus follow the Normal type. In the female gametophytes of these species several types of antipodal cells occurs such as: their considerable enlargement, formation of many antipodals polyploid or polinucleated antipodal cells. In these various types, however, a rapid regression of the antipodals occurs. In T. lucidum some tendency to a disposition of the tetrapolarized type has been verified. The chromosome number has been confirmed to ben 2n=28 in besides, in the pollen development, many cases of regression of the microspores has been verified. The chromosome number has been confirmed to ben 2n=28 in Thalictrum lucidum L., and has been found to ben 2n=14 in Thalictrum minus L. ssp. minus, a new number in this species, which was earlier reported to have 2n=42.     

A contribution to the embryology of Desmodium motorium (Houtt.) Merr. (= D. gyrans (L.f.) DC.) (Fabaceae)

Abstract

The anthers are tetrasporangiate. The anther wall comprises epidermis, fibrous endothecium, middle layer and tapetal layer. The tapetum is of the Glandular type and its cells remain uninucleate. Meiosis in pollen mother cells is normal and simultaneous cytokinesis leads to the formation of tetrahedral and decussate microspore tetrads. The pollen grains are shed at 2-celled stage. The ovule is campylotropous, bitegmic and crassinucellate. Meiosis in megaspore mother cell results in the formation of linear or occasionally T-shaped megaspore tetrad. The chalazal megaspore develops into Monosporic Polygonum type of embryo sac. Endosperm development is of the Nuclear type.     

Embryological observations on Helichrysum rupestre (Rafin.) DC. var. errerae (Tineo) Pignatti

Abstract

The ovule and anther development of Helichrysum rupestre var. errerae from Pantelleria is studied. The ovule is anatropous, tenuinucellate, unitegmic, endotheliate and is derived from a two-zonate primordium. The archespore is one- or two-celled and all the megaspores show a functional tendency, although only the chalazal one is able to form the gametophyte according to the Polygonum type. The polar nuclei fuse before fertilization and the three antipodal cells divide further. Anthers are tetrasporangiate and their wall development conforms to the Dicotyledonous type. The epidermis persists at maturity and the endothecial cells thicken their walls. The tapetum is of the periplasmodial type and its cells become plurinucleate during microsporogenesis. The number of microsporocytes varies along the length of the same locule. Arrangement of the resulting microspores is tetrahedral, isobilateral or decussate. Pollen grains are three-celled when shed. Degenerating microsporocytes and microspores have frequently been found.     

大花君子兰大小孢子发生与雌雄配子体发育的研究

该研究运用常规石蜡切片技术,对大花君子兰(Clivia miniata Regel)大、小孢子发生及雌、雄配子体发育进程进行解剖学观察分析,以探讨君子兰生殖生物学解剖特征,为君子兰种子发育和育种提供理论依据。结果表明：(1)大花君子兰花药4室,具分泌型绒毡层。(2)小孢子母细胞减数分裂的胞质分裂为连续型,小孢子四分体为左右对称型,成熟花粉为二细胞型。(3)倒生胚珠,双珠被,厚珠心和雌配子体发育为蓼型。(4)记录了雌雄配子体发育的对应关系,发现雄配子体发育趋于同步,雌配子体发育不同步。(5)开花散粉时,雌配子体尚有处于四核、八核胚囊的时期;成熟胚囊阶段,中央细胞的2个极核位于反足细胞端,反足细胞呈退化状态。具承珠盘结构。     

DEVELOPMENT OF THE OVULE AND FEMALE GAMETOPHYTE IN EUSTACHYS PETRAEA AND E. GLAUCA (POACEAE)

The unilocular pistil in Eustachys contains a single ovule with lateral placentation. In E. petraea and E. glauca, the mature ovule is bitegmic, tenuinucellate, and amphitropous with the endostomic micropyle oriented toward the base of the locule. A single hypodermal archesporial cell enlarges to form the megasporocyte. The chalazal dyad member is larger than the micropylar one, and meiosis II is nonsynchronized. Two-thirds of the tetrads are linear and one-third T-shaped. The chalazal megaspore is functional. Initially ovoid, the two-nucleate female gametophyte becomes curved as it enlarges. The four-nucleate stage becomes wider at its extremities and constricted in the center. Synchronous mitotic divisions establish the eight-nucleate stage with four nuclei at each pole separated by a large central vacuole. In E. petraea, the maturation sequence begins with antipodal differentiation, followed by differentiation of the egg apparatus, migration of the polar nuclei to the center, and division of the antipodals to produce twelve cells. The sequence in E. glauca begins with migration of the polar nuclei followed by differentiation of the antipodals, egg apparatus, and antipodal replication to six cells. The polar nuclei fuse to form a secondary nucleus appressed to the egg cell in E. glauca and separated from it by a vacuole in E. petraea. T-tests for length measurements for various stages of development indicate that the functional megaspore and two-nucleate female gametophyte are significantly larger in E. glauca than in E. petraea. There is no significant difference in gametophyte length at the four-nucleate stage, and at the eight-nucleate stage, length in E. petraea surpasses that in E. glauca. This gap widens significantly at the mature stage. Nuclear volumes are significantly greater in E. glauca than in E. petraea in the functional megaspore and two-nucleate stage, but the volumes are similar at the four-nucleate stage. Consideration of the differences in structural complexity between the sporophyte and gametophyte generations leads to the conclusion that the female gametophytes of these species are more distinctive than are the sporophytes.     

Microsporogenesis of the feathers (fertile branches derived from annual buds) in Vitis vinifera,cv Picolit giallo

Abstract

Using light and electron microscopy, we have studied the microsporogenesis and tapetal development of the feathers in two different low producing clones of Picolit giallo (sp. Vitis vinifera). In these clones while the productivity of the main branches (fertile branches originated from buds, formed in the previous year, that remained silent during the winter) is very low, that of the feathers (fertile branches derived from annual buds) is always normal.

The microsporogenesis and tapetal development proceed normally in almost all the examined anthers; it is remarkable that at the tetrad stage the tapetal cells appear well structured without any degeneration symptom, unlike what observed for the main branches. Moreover in most of the mature anthers the pollen grains are numerous, pleinty of organelles and show sometimes thickenings in the callose layer under their wall. The tapetal cells of these anthers have disappeared. Only in few anthers we observed the presence of collapsed pollen grains and tapetal cells with anomalous development, that are still present when the pollen grains are mature. This rare situation for the feathers is on the contrary frequent for the main branches.     

Small heat shock protein LimHSP16.45 protects pollen mother cells and tapetal cells against extreme temperatures during late zygotene to pachytene stages of meiotic prophase I in David Lily

Plant meiotic prophase I is a complicated process involving the late zygotene and pachytene stages, both crucial for completing synapsis and recombination. Using David Lily (Lilium davidii var. Willmottiae) as our research material, we performed suppression subtractive hybridization to construct EST library of anthers at various stages of development by the pollen mother cells. From this library, we identified small heat shock protein LimHSP16.45 was highly expressed during the late zygotene to pachytene stages. Our results also showed that LimHSP16.45 was almost specifically expressed in the anther compared with the root, stem, or leaf, and in situ expression of LimHSP16.45 mRNAs showed strong signals in the pollen mother cells and tapetal cells. LimHSP16.45 could be induced by heat and cold in lily anthers, and its ectopic expression enhanced the viability of E. coli cells under both high and low temperatures. In vitro, it acted as molecular chaperone and could help luciferase refolding after heat shock stress. All of these data suggest that LimHSP16.45, working as molecular chaperone, possibly protects pollen mother cells and tapetal cells against extreme temperatures during late zygotene to pachytene stages of meiotic prophase I in David Lily.     

Ricerche Cito-Embriologiche E Distribuzione Geografica di Cirsium Casabonae Lam. ET DC. (Compositae)

Abstract

Cyto-embryological study and geographical distribution of CIRSIUM CASABONAE Lam. et DC. — The mature megagametophyte of Cirsium Casabonae Lam. et DC. (Compositae) is eight nucleate of the normal or Polygonum type.

In the nucellus there is only one megaspore mother cell. After meiosis the three micropylar megaspores degenerate. The three antipodal cells start to degenerate as soon as the gametophyte reaches maturity. Microsporogenesis is regular.

The chromosome number of Cirsium Casabonae Lam. et DC. is 2n = 32. This shows that also in Europe, as in America, there is at least one species of Cirsium with basis number × = 16.

The study of the geographical distribution of Cirsium Casabonae Lam. et DC. shows it to be an Atlantic-West Mediterranean endemism.     

Ovule,Female and Male Gametophyte and Fertilization of Kingdonia uniflora Balfour F. et W. W. Smith

The structure of ovule, female and male gametophyte, double fertilization and the distrubution of starch grains during the fertilization have been studied. The main results are as follows: ( 1 ) Ovule The ovule is anatropous, unitegmic and tenuinucellate. The nucetlus appears cylindric, since megaspores and embryo sac development, its internal cells of nucellus become disorganized, so that only a single layer of epidermal cells remains toward the side of the micropyle, On the other hand, the integument is not as long as nucellus, as a result micropyle is not formed. And no vascular bundle is found in the integument. (2) Female gametophyte The mature embryo sac is slender and is composed of an egg cell, two synergids, a central cell and three antipodal cells. The egg cell is situated slightly away from the tip of embryo sac. Some of them contain starch grains. Synergids occupy the tip of embryo sac. Its wall at micropylar region appears irregular in thickenes and irregular in ingrowths to form the filiform apparatus. The centrateell is very large, and strongly vacuolated Two polar nuclei come to contact closely with each other, but not fuse, or to fuse into a large secondary nucleus before fertilization. The polar nuclei or the secondary nucleus are usually situated at the middle-lower position of the central cell or nearer to the chalazal end above the antipodal cell. It is different from egg cell, no starch grains are found here. In most embryo sacs three antipodal cells are found. They are not as large as those in other plants of Ranunculaceae. But six antipodal cells or the antipodal cell with two nuclei may rarely be found. Like synergid, the wall of them appears not only irregularly thickened, but clearly with irregular ingrowths. In a few antipodal cells the starch garins are usually found near the nucleus. By the end of fertilization, antipodal cells become disintegrated. (3) Male gametophyte Most pollen grains are two-celled when shedding, and rich in starch grains. A few of them contain single nucleus or three-celled. (4) The double fertilization The fertilization of Kingdonia unifiora Balfour f. et W, W. Smith is wholly similar to some plants of Ranunculaceae studied. First, the pollen tube penetrates a degenerating synergid. And the pollen tube discharges its contents with two sperm nuclei into the degenerating synergid cell. One of the two sperms fuses with the nucleus of the egg, and the other fuses with two polar nuclei or the secondary nucleus of the central cell. If one sperm nucleus at first fuses with one of the polar nuclei, and then the fertilized polar nuclei again fuses with other polar nucleus. Secondly, the fertilization of the polar nuclei or the secondary nuclei completes earlier than that of the egg. The primary endosperm nucleus begins to divide earlier than the zygote. It seems that one of the sperm nuclei come to contact with egg nucleus, the other has already fused with polar nuclei or the secondary nucleus. The zygote with a single nucleolus appears until the endosperm with 16–20 cell. Thirdly, before and after fertilization there are one to some small nucleoli in egg nucleus and polar nuclei or secondary nucleus. However they increase in quantity from the beginning of the fusion of male nucleis. These nucleoli quite differ from male nucleoli by their small size, and most of them disappear at the end of fertilization. It may be concluded that the small nucleoli increase in quantity is related to the fusion of male and female nuclei. In the duration of fertilization, in ovule starch distribution is in the basal region of integument. But in embryo sac, onlysome egg cells, or zygotes contain starch grains, a part of which was brought in by pollen tube. Sometimes the starch grains are found in some synergids and antipodal cells. No starch grains are found in the central cell.     

Cytinus hypocistis L. embryogenesis: Some biological and ultrastructural aspects of fertilization and embryo development

Abstract

The present paper examines some biological and ultrastructural aspects of fertilization and early development of the embryo in Cytinus hypocistis, a parasitic plant belonging to the Rafflesiaceae. The probable functions of a mucilaginous substance contained in the ovary and embedding the numerous pollen tubes coming from the style are discussed.

It was ascertained that pollen tubes pass through the micropyle and enter a synergid pushing, their way through the nucellar cells that show swollen walls owing to a probable enzymatic action whose function is to facilitate pollen tube penetration. It was hypothesized that the secretion of such enzymes is attributable to the numerous pollen present in the ovary or entering the mycropyle.

Since, in all the ovules observed, synergid degeneration was never found before the arrival of the pollen tube, this degeneration was interpreted as being caused by the material disharged by the pollen tube, rather than being an essential prerequisite for pollen tube penetration into the synergid.

Pollen tube content was observed to be made up of an intensely electron-dense substance surrounding many lipidic globules and numerous polysaccharide vesicles that fuse with the pollen tube wall, clearly contributing to its growth.

The sequence of the first divisions of the developing embryo was followed and the extreme reduction of the embryo is confirmed.

In Cytinus hypocistis starch is totally absent from all the sells belonging to the female gamethophyte as well as to those belonging to the embryo, but lipidic globules are very frequent; it is therefore supposed that these bodies constitute good material for the nutrition of the zygote and early embryo.     

孝顺竹(Bambusa multiplex)大孢子发生与雌配子体发育研究

为了解孝顺竹（Bambusa multiplex）的大孢子及雌配子体的发育过程,利用扫描电镜对孝顺竹的雌蕊形态以及大孢子和雌配子体的发育进行了观察。结果表明,孝顺竹雌蕊单子房,1室,双珠被,薄珠心;大孢子母细胞是由1个雌性孢原细胞直接发育而成,大孢子四分体为线性,位于珠孔端的1个大孢子分化成为功能大孢子,然后由功能大孢子依次经历二核、四核、最终形成1卵细胞2助细胞2极核3反足细胞的成熟胚囊。此外,孝顺竹为雌雄同熟类型,根据雌、雄蕊发育的对应关系,从雄蕊形态可估测雌配子体发育阶段。有少数雌蕊出现败育现象,可能是孝顺竹结实率低的原因之一。     

山麦冬大小孢子发生及雌雄配子体发育研究

采用石蜡切片技术对百合科植物山麦冬大小孢子发生及雌雄配子体发育进行了观察研究。结果表明:(1)山麦冬花药具有4个花粉囊,花药壁的发育方式为基本型,花药壁完全分化时由表皮、药室内壁、中层及绒毡层组成。(2)绒毡层发育类型为分泌型,到四分体孢子彼此分离形成单细胞花粉阶段,绒毡层细胞开始解体退化,花粉成熟时绒毡层细胞完全消失;花粉母细胞减数分裂为连续型,四分体为左右对称形排列,成熟花粉为3-细胞花粉,单萌发沟。(3)子房3室,每室2枚胚珠,胚珠倒生型,双珠被,薄珠心,雌性孢原细胞不经过平周分裂而直接发育而成大孢子母细胞。(4)减数分裂后四分体大孢子呈线型或T型排列,合点端大孢子分化为功能大孢子,胚囊发育为蓼型;花粉母细胞减数分裂过程中,二分体、四分体细胞外方被胼胝质壁所包被,小孢子形成后胼胝质壁逐渐消失。该研究结果丰富了百合科植物生殖生物学研究的内容,也为探讨百合科植物的系统学研究提供了参考。     

云南松雌雄配子体的发育

云南松(Pinus yunnanensis Fr.)雄配子体于10月在小孢子叶腹面产生二个小孢子囊,内有许多进行分裂的造孢组织细胞。第二年一月下旬至二月初小孢子母细胞进行减数分裂。在分裂期间,细胞内所贮存的淀粉粒的分布发生变化。二月初四分体小孢子形成,绒毡层细胞解体。二日中旬单核花粉粒形成,外壁扩展形成二个异极对称的气囊。三月花粉在四细胞时期散发。 雌配子体于二月上旬在珠心皮下分化出孢原细胞。二月下旬大孢子母细胞进入减数分裂期。三月初直列四分体大孢子形成,珠孔端三个退化,合点端一个功能大孢子进入有丝分裂期,形成约32个游离核的配子体。次年三月初雌配子体形成,四月初中央细胞核分裂,四月底颈卵器成熟,卵核周围产生辐射状原生质纤丝。五月初受精开始。云南松雌雄配子体的发育与亚热带分布的P.roburghii相似。     

Embryology and embryogenesis of Spiranthes L.C.M. Richard (Orchidaceae): S. spiralis (L.) Cheval and S. aestivalis (Poiret) L.C.M. Richard

Abstract

The various stages of female gametophyte development and embryogenesis in S. spiralis and S. aestivalis are described. In both species the reproductive cycle is sexual. Some peculiarities are present: the female gametophyte is usually 6-7-8-nucleate; after double fertilization a single endospermatic cell is formed; the proembryo appears differentiated and is made up of different cells in the chalazal and micropylar ends; a single basal cell in the proembryo acts as suspensor.     

Megasporogenesis, female gametophyte development and embryonic development of Ambrosia L. in China

The megasporogenesis, female gametophyte development and embryonic development of Ambrosia artemisiifolia L. and Ambrosia trifida L. of genus Ambrosia L. in China were studied using conventional paraffin section technology and optical microscopy. The results show that both A. artemisiifolia L. and A. trifida L. have a bilobed pistil stigma, two carpels, one chamber, basal placenta, unitegmic, tenuinucellate, anatropous ovule, and well-developed integumentary tapetum. Megaspore mother cells are directly developed from archesporial cells originated from the nucellar cells under the nucellar epidermis and further undergo meiosis to form linear tetrads. The megaspore at the chalazal end develops into a functional megaspore and the other three megaspores are degraded. The development of embryo sac is monosporic type. After three consecutive mitosis, mononucleate embryo sac becomes a mature embryo sac with two synergids and one egg cell at the micropylar end, a central cell at the center and three antipodal cells at the chalazal end. Most antipodal cells are mononucleate or binucleate, only few are trinucleate. The embryonic development process contains four stages: globular embryo, heart-stage embryo, torpedo-stage embryo and mature embryo. The development of endosperm is cellular type.