On the Embryogeny of Three Taxa of Paepalanthoideae (Eriocaulaceae)

Embryo development in Leiothrix nubigena, Paepalanthus bifidusand Syngonanthus nitens is described. Distinct differentiationof cotyledonary and epicotyledonary sectors in the three taxais demonstrated. The cotyledonary and the epicotylary loci shareequal amounts of the embryonic shoot apex as in most monocotyledons.The cotyledon and its adjacent epicotyl are both terminal onthe embryonic axis. The basal cell of the two-celled proembryocontributes two basal rows of cells at the radicular pole inthe ripe seed. A typical radicle is not organized. Leiothrix nubigena, Paepalanthus bifidus, Syngonanthus nitens Paepalanthoideae, Eriocaulaceae, embryogeny     

Embryology ofEriocaulon setaceum (Eriocaulaceae)

Eriocaulon setaceum can be characterized by: young microsporangium wall with epidermis, endothecium (with fibrous thickenings), and glandular tapetum (uninucleate cells); pollen grains 3-celled, spiraperturate; embryo sac development according to the Polygonum type and with antipodal cyst; endosperm nuclear; embryo small, with incipient differentiation into cotyledonary and epicotylary loci; seed coat mainly from the inner layers of the integuments; pericarp 2-layered and membranous. Embryologically, theEriocaulaceae are nearer to theXyridaceae than to otherFarinosae. Their elevation to the rank of an order,Eriocaulales, therefore appears justified.     

The Origin of Epicotylary Meristem and Cotyledon in Halophila ovata Gaudich

The consensus of opinion of the organization of the monocotyledonembryo assumes a terminal origin of the cotyledon and a lateralorigin of the shoot apex. Alternative views, although they aresporadic, have not received the attention they deserve. Detailsof the embryology of Halophila ovata show that both the epicotylarymeristem and the cotyledon arise from one and the same terminallocus of the proembryo while the derivatives of the subterminalmiddle tier become incorporated into the hypocotyl region.     

Embryogenic cultures of the leguminous tree Albizia julibrissin and recovery of plants

A somatic embryogenic system was developed and plants regenerated in mimosa (Albizia julibrissin Durazz). Development of somatic embryos in the species has not previously been reported. Immature seeds, embryo cotyledons and embryo axes (cotyledons removed) at defined developmental stages were placed on induction media with different concentrations of 2,4-D. Two distinct embryogenic responses occurred: either proembryo masses or cotyledonary-stage embryos. Twenty five percent of all embryo axes cultured on basal medium produced cotyledonary somatic embryos. Six percent of in ovulo immature seed explants generated proembryo masses. These masses proliferated in liquid culture in the dark. Proembryos developed further when transferred to a growth-regulator-free semisolid medium in the light. Somatic embryos derived from either proembryo suspensions or cotyledonary embryo cultures on semisolid medium germinated to form plants that continued to grow vigorously following transfer to soil. This revised version was published online in June 2006 with corrections to the Cover Date.     

黄花油点草胚胎发育研究

利用石蜡切片技术对百合科植物黄花油点草[Tricyrtis maculata(D.Don)Machride]双受精、胚及胚乳发育进行了研究,以明确其胚胎发育的特征,为百合科植物的系统研究提供生殖生物学资料。结果表明:(1)黄花油点草为珠孔受精;进入胚囊的2枚精子分别与卵细胞和中央细胞进行正常的双受精,其受精作用属有丝分裂前型。(2)受精后的初生胚乳核立即分裂,其发育方式为核型胚乳;早期的游离胚乳核沿胚囊的边缘分布,胚囊中央部位主要为胚乳细胞质,随着游离胚乳核数量的增加,胚乳核慢慢充满整个胚囊;当发育至球形胚早期阶段,在各胚乳核周围产生胚乳细胞壁,形成完整的胚乳细胞。(3)合子有较长的休眠时间,胚的发育方式为茄型;合子第一次有丝分裂为横裂,分裂后形成基细胞和顶细胞;基细胞经过3次横裂,形成一列胚柄细胞;顶细胞经过分裂形成胚体,依次形成球形胚、棒状胚和盾形胚。(4)种子成熟时胚无器官分化;成熟种子由种皮、胚和胚乳三部分组成。     

Observations on the Neocytoplasm and Proteid Vacuoles During the Fertilization of Keteleeria evelyniana

Distributions and dynamics of the neocytoplasm and proteid vacuoles during the fertilization of Keteleeria evelyniana were studied by histochemical methods. Before fertilization cytoplasmic sheath surrounding the male and female gametes was indistinct. After fertilization, the dense neocytoplasm appeared around the zygote. Part of the neocytoplasm is invaded by mitochondria of maternal origin which had collected in large numbers in the perinuclear zone. The mitochondria contain electron compact little body which looks like a nucleus in the cytoplasm, but not observed in the rosette tier cell of proembryo and jacket cells. Hence, it was showed that the neocytoplasm participated in the development of embryo by all these observations. By using Feulgen reaction, the staining reaction of neocytoplasm was positive, the egg nucleus or zygote nucleus was weaker in positive reaction, while the proteid vacuoles were negative. When the proembryo developed, there were a few starch grains accumulated in the other three tiers except the upper tier. The Feulgen reaction was in- creased in intensity in the suspensor tier and embryonal cell tier nuclei. When the young embryo developed, Feulgen reaction became normal in the nuclei of the embryo initials. The embryo initials and Suspensor cells showed very weak Feulgen positive reaetion in the proembryo and young embryo. The development of the large proteid vacuoles was from plastid. During the early stage of egg nucleus, contents of large proteid vacuoles were less. When the zygote was formed, they reached the highest. However, after the zygote produced, the proteid vacuoles and egg cytoplasm were getting disintegrated following the course of fission of free nuclei. After the proembryo formed, the proteid vacuoles were wholly disintegrated.     

Regeneration of plant by somatic embryogenesis in <Emphasis Type="Italic">Pinus rigida</Emphasis>×<Emphasis Type="Italic">P. taeda</Emphasis>

Zygotic embryos at different developmental stages were tested for their potential in the initiation of embryogenic suspensor mass (ESM) lines using immature seeds of Pinus rigida × P. taeda. The highest frequency (1.1%) of ESM was obtained with explants from cones collected on July 1. All excised embryos of the July 1 collection were at the early proembryo stage. Two different culture media were compared. Forty-eight ESM lines were initiated on Pinus taeda basal medium (P6) (0.97%) with 13.5 μM 2,4-dichlorophenoxyacetic acid (2,4-D) and 4.4 μM benzyladenine (BA). However, only four ESM were obtained on a modified Murashige and Skoog medium (MSG; 0.55%). Most of the ESM arose from the seeds that were at the stages ranging from late cleavage polyembryony to the early staged proembryo. Out of 52 lines (0.46%) that were produced from 11,388 explants, only two viable lines (0.018%) (PRT11 and PRT28) survived. As for somatic embryo maturation, the highest number (224/g⁻¹ FW) of matured cotyledonary somatic embryos (line PRT 28) was obtained on a medium containing 100 μM abscisic acid (ABA), 0.2 M maltose, and 1.2% gellan gum. For germination of the somatic embryos, the cotyledonary somatic embryos derived from maturation medium were transferred on half-strength Litvay medium (LM) plus 0.4% gellan gum. The germination rates were high (71.4–96.3%) regardless of the concentrations of either ABA or gellan gum in the maturation medium. Approximately 500 somatic plants were recovered from the germination medium and transferred to the green house; finally most of them were transplanted successfully to the experimental field.     

云南油杉受精过程中新细胞质及蛋白泡的动态观察

云南油杉(Keteleeria evelyniana Mast)在受精前,精核与卵核周围的细胞质鞘不明显。受精后,合子核周围出现细密的新细胞质。应用孚尔根核染色法,可以较清晰地将新细胞质染出,呈现较弱的正反应,而合子的核质及受精前的精核与卵核染色极弱。卵细胞质及其中的蛋白泡均为负反应。原胚形成后,除上层外,其余几层细胞质内开始积累淀粉粒。此时胚原细胞核的孚尔根染色深度有所增加。幼胚形成后,在顶端的胚原细胞群中核的孚尔根染色反应已恢复正常。在原胚及幼胚胚原细胞质中也呈现很弱的正反应。在电镜下,胚原层细胞质及新细胞质中均含有核样电子致密小体或称作染色质小体,而原胚莲座层细胞质及四周套细胞质中的线粒体则不含这种核样小体。因此,大蛋白泡在卵核形成的早期数量不多,当合子形成时含量最高,而随着游离核的分裂进程,蛋白泡以及原卵质均逐渐地解体,在原胚形成后全部消解。     

Embryo development in Cocos nucifera L.: A critical contribution to a general understanding of palm embryogenesis

InCocos (and probably in all other palms) the embryogenesis shows a number of primitive characters, such as differentiation of the embryo proper from one cell of the pluricellular proembryo, origin of the single cotyledon from a position lateral to the terminal stem tip, and a tendency to cleavage polyembryony.     

Anatomy of the Latex System in the Dormant Embryo of Euphorbia marginata Purch : Correlative Analysis of the Histological Organization and Topographic Distribution of Laticifers

The anatomy, morphology and topography of laticifers in themature embryo of Euphorbia marginata have been studied by conventionaland fluorescence microscopy. The mature embryo consists of awell-developed embryonic axis and two cotyledons and it containsdifferentiating vascular tissue. In the hypocotyl, six procambialstrands are present which branch and extend into the cotyledons,whereas in the root they are fused in a triarch structure. Inthe embryonic axis, the latex system consists of stelar andcortical components that are first anastomized in a cotyledonaryplexus and then are joined above in a cotyledonary system. Thestelar and cortical systems are linked by horizontal branchesto a nodal latex plexus placed under the epicotylary meristem.All the vascular laticifers, 24 in number, end unbranched inthe apex of the radicle. The cortical laticifers are profuselybranched toward the epidermis in tiny veins as far as the sub-epidermallevel. The cotyledonary laticifers follow the vascular tissueand form a network surrounding the mesophyllary areoles. Thetopography of the latex system leads one to hypothesize thatthe criteria which determine the constitution of the latex systemlareonly the essential peculiarities of idioblasts, but also correlativephenomena between growing laticifers and surrounding tissues.The stelar system appears to be under the control of vascularpolar growth, while the cortical and cotyledonary latex systemsseem to be subjected both to endogenous polar stimuli and toextra-embryonal influences. Euphorbia marginata, anatomy, embryo, laticifers     

EMBRYOGENESIS AND SEEDLING DEVELOPMENT IN CASSIPOUREA ELLIPTICA (SW.) POIR. (RHIZOPHORACEAE)

Embryogenesis in Cassipourea elliptica (Sw.) Poir, begins with a first division of the zygote which may be oriented transversely, obliquely, or rarely longitudinally. The orientation of the second division is also variable. Though the differentiation of suspensor and embryo proper occurs early, some derivatives of the terminal cell sometimes contribute to the suspensor. Provascular tissue “differentiates” after the initiation of the cotyledons. The radicle apical meristem originates subterminally, 5–10 cell layers from the juncture of the embryo proper and the suspensor. After germination, during early seedling establishment, radicle apical organization is of an unspecialized, columellate type. Vascular differentiation occurs before germination, and there are two loci of initial xylem differentiation: one in the hypocotyl and another in the median trace of the cotyledons. After germination, additional xylem differentiates de novo (without lateral or longitudinal continuity with already-mature vessels) inside the arcs of phloem in the hypocotyl, a pattern reported in few angiosperms. The cotyledonary node is one-trace, unilacunar.     

The early embryogeny of the genus Fokienia with a note on its systematic position

The present investigation deals with the early embryogeny of Fokienia hodginssii (Dunn) Henry et Thomas with a note on its systematic position. The material was collected on April 17 to September 13 in 1964 from longquan, Fengyang Shan in the province of Zhejiang, at alt. 1000 to 1400 M. Fokienia Henry et Thomas, a member of the subfamily Cupressoideae of northern hemisphere, is a monotypic genus with the only species Fokienia hodginssii (Dunn) Henry et Thomas. The zygote divides three times, giving rise to eight free nuclei, then wall-formation follows. As a result, the 8 cells of the proembryo are arranged in two groups: The upper one, the open tier (O) and the lower one, the primary embryo cells (PE). The relative number of these cells (0: PE) is usually 4:4, occasionally 5:3, rarely 6:2. The cells in the upper and lower groups divide simultaneously. A proembryo of three groups of cells may be formed. The upper tier (U), the suspensor tier (P), and the embryo cells (E). U:S:E is usually 4:4:8, occasionally 5:5:6. rarely 6:6:4. The U and E are of common in origin. The primary embryo cells sometimes remain undivided though the cells of upper tier divide as usual and the prosuspensor celts elongate also. In this case, U: S: E is 4:4:4 or 5:5:3 or 6:6:2. Cleavage polyembryony occurs quite often. Generally, the cleavage polyembryony is caused by the different growth rate of the primary suspensor. Sometimes, the terminal cells cut off when cells of primary suspensor are elongating. The terminal cells elongate and divide repeatly, thus a number of successive suspensor tubes are produced.This is a derivative type in the cleavage polyembryony of Fokicnia. This specialized type of polyembryony likes that of the Juniperoid. Different view points exist in the taxonomic treatments of the Cupressaceae. Many taxonomists divide the family Cupressaceae into 2—4 subfamilies. From the view point of the early embryogeny, the author considers that Li’s (1953) treatment is a more appropriate one. According to cone structure and arrangement of ovuliferous scales. Li (1953) divides the family Cupressaceae into two subfamilies; i.e. subfamily Cupressoideae of northern hemisphere having ovuliferous scales of imbricate arrangement and Callitroideae of southern hemisphere having scales of valvate arrangement. It is interesting to note that the wall-formation of proembryo in northern hemisphere plants of Cupressaceae takes place at 8 free nuclear stage, while those in southern hemisphere ones, at 4 free nuclear stage. Apparently, the status of proembryogeny gives support to the view points of Li (1953). From the point of view of early embryogeny,however, there are still more questions to be discussed. For example, in the subfamily Cupressoideae of northern hemisphere, Li considered the tribe Cupresseae as the primitive and the genus Thujopsis of the tribe Thujopsideae derives from genus Fokienia of the tribe Cupresseae. According to the data obtained from the early embryogeny, the author considers the tribe Thujopsideae to be the most primitive of the three tribes in the subfamily Cupressoideae, then the tribes Cupresseae and finally, the tribe Junipereae. Embryogenesis of Fokienia, the northern hemisphere members of the Cupressaceae, is a specific type, whose systematic position is possibly between Chamaecyparis andSabina.     

PATTERNS OF EMBRYO AND ENDOSPERM FORMATION IN MONOTROPA HYPOPITYS (MONOTROPACEAE) FROM NORTH AMERICA AND WESTERN SWEDEN

Within the Monotropaceae. Monotropa hypopitys L. has the widest geographical distribution with sporophytes characterized as achlorophyllous, mycotrophic, and morphologically reduced. General and histochemical observations at the light microscope level concerning the postpollination changes in the numerous anatropous, unitegmic ovules reveal a precise embryogeny and endosperm development. Following double fertilization, the primary endosperm cell produces a lipid-rich cellular endosperm situated between a micropylar and a chalazal haustorium. A cytoplasmically unequal division of the elongated zygote initiates proembryo formation. The degeneration of the basal cell of the proembryo results in an isolated terminal cell that undergoes a cytoplasmically equal, transverse division establishing a two-celled embryo embedded in endosperm. Prior to final seed maturation, proteins replace the lipids as the dominant cytoplasmic reserve material. In contrast with earlier studies that depicted the mature embryo as variable in structure, here the embryo is shown to be consistently uniform within and between those populations sampled from North America and Europe.     

DEVELOPMENTAL PATTERNS IN PINE POLYEMBRYONY

Berlyn , Graeme P. (Yale U., New Haven, Conn.) Developmental patterns in pine polyembryony. Amer. Jour. Bot. 49(4): 327–333. Illus. 1962.—An investigation of multiple-embryo development in pine was undertaken. The occurrence of 4 embryos per mature seed was found in approximately one third of the seeds of Pinus lambertiana and Pinus cembra examined and in a few seeds of Pinus strobus. These embryos were derivatives of the 4 embryo-initial cells of the apical tier of the proembryo. There was a progressive reduction in size and development of embryos in a given seed, the embryo furthest from the micropyle being the largest and most differentiated. However, in many cases, histogenesis proceed even when embryo size was significantly arrested. All 4 embryos in some seeds were viable in vitro, but rarely did more than one embryo germinate in vivo. This may be associated with the more rapid reactivation of the largest embryo. Variation in the extent of multiple-embryo development reflects the apparently indeterminate pattern of competition within an embryo system.     

Reproductive development of initial sporophytes in Pinus sylvestris L

The reproductive development of Pinus sylvestris from generative primordia to sporophyte initial (embryo tier of 16-celled proembryo) was studied. In the reproductive cycle, three types of stages are distinguished and described in association with: 1) hereditary program formation; 2) a new reproductive initial origin, and 3) increase in propogative energy. The layout of disposition of these stages in the reproductive cycle is given.     

Heterochromatin and rDNA patterns in Solanum species of the Morelloid and Dulcamaroid clades (Solanaceae)

The heterochromatin distribution and the position of 18-5.8-26S, and 5S rDNA loci were determined in 13 species of Solanum of the Morelloid and Dulcamaroid clades. The CMA/DAPI staining and FISH were employed. Two types of constitutive heterochromatin were determined: CMA⁺/DAPI^? associated to NOR and CMA⁺/DAPI^? distributed as terminal bands. In the Morelloid clade, CMA⁺/DAPI^? bands were found in five species while in the Dulcamaroid clade, only S. angustifidum presented this feature. In the Morelloid clade, two to four 18-5.8-26S rDNA loci occupied terminal positions and two rDNA 5S loci were found with variable positions (terminal, intercalary, and centromeric). In the Dulcamaroid clade, two terminal 18-5.8-26S rDNA loci were detected with the exception of S. salicifolium which possessed four such loci and two to four 5S rDNA loci. Solanum crispum is the only species possessing the 5S in synteny with 18-5.8-26S rDNA loci. Karyotype features chromosome banding pattern as well as the location of ribosomal genes which varied among the species, reflecting the chromosome differentiation and evolutionary divergence. The findings obtained contributed to the development of tools that can be used for establishing chromosomic homeologies among species and hence to clarify their taxonomic relationships.     

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.     

辽藁本(Ligusticum jeholense)幼苗初生维管系统的发育

应用整体透明和石蜡连续切片等方法,对辽藁本幼苗初生维管系统的发育进行了观察。结果表明：该幼苗的轴向器官中,以子叶节区下部的初生维管系统先建立,向下发育形成了下胚轴和根的维管系统;再向上通过子叶节区中、上部的分生组织性组织与第1片真叶的叶迹相连;上胚轴一苗的维管系统向下发育与子叶迹相连,至此构成了该幼苗完整、连续的初生维管系统。此外,对幼苗侧生器官子叶片的三出一叉状脉的形成进行了观察,认为该叶脉序属于原始脉序类型。     

Influence des corrélations entre organes sur la croissance et le développement floral des bourgeons cotylédonaires chez leScrofularia arguta Sol.

The importance of various correlative influences on growth and vegetative or floral development of cotyledonary buds inScrofularia arguta Sol. is shown. The terminal bud, on the one hand, inhibits growth of cotyledonary buds and, on the other hand, induces their early flowering. The cotyledon stimulates growth of its axillary bud, but has no action on its floral development. Leaves above the cotyledonary node have the same effect as the cotyledon. Finally, roots stimulate vegetative growth of cotyledonary buds and suppress floral expression, but only when apical dominance has been removed at an early stage of development.