Ovule-to-seed development in Dovyalis caffra (Salicaceae: Flacourtieae) with notes on the taxonomic significance of the extranucellar embryo sac

Bothalia ◽  
2005 ◽  
Vol 35 (1) ◽  
pp. 101-108 ◽  
Author(s):  
E. M. A. Steyn ◽  
A. E. Van Wyk ◽  
G. F. Smith
Keyword(s):  
Seed Development ◽  
Embryo Sac ◽  
Taxonomic Significance ◽  
Polygonum Type

Dovyalis caffra (Hook.f. Harv.) Hook.f. is a widespread and horticulturally important southern African endemic. Here described, ovule-to-seed development represents the first embryological information on this genus of the tribe Flacourtieae, Salicaceae  sensu lato. Results are discussed in the light of data available on the embryology of the order Malpighiales in general and on the tribe Flacourtieae in particular. It is clear that Dovyalis E.Mey. ex Am. shares many characters with other members of the Flacourtieae. Ovules of D. caffra are anatropous. bitegmic and crassinucellate with both bisporic Allium- and monosporic Polygonum-type embryo sacs. One of the most characteristic embryological features of the tribe is the pres­ence of an unusual, extranucellar embryo sac that stretches halfway up into the micropyle. Since this extraordinary-shaped embryo sac also defines the embryo sacs of Salix L. and Populus L., it is suggested that the character provides strong sup­port for the proposed close phylogenetic link between tribes Flacourtieae and Saliceae of Salicaceae sensu lato.

scholarly journals Desarrollo del gametofito femenino de Tagetes patula (Asteraceae)

2017 ◽  
pp. 5
Author(s):  
Marcelina García-Aguilar ◽  
E. Mark Engleman ◽  
Eulogio Pimienta-Barrios
Keyword(s):  
Seed Development ◽  
Early Development ◽  
Mother Cell ◽  
Megaspore Mother Cell ◽  
Embryo Sac ◽  
Tagetes Patula ◽  
Polygonum Type ◽  
Chalazal Megaspore ◽  
The Family ◽  
Apomictic Reproduction

The genus Tagetes reproduces sexually by seed, but recent morphological and hybridization studies in Tagetes patula suggest an apomictic type of reproduction (seed development without fertilization). In order to determine the sexual or apomictic origen of the embryo, we have studied megasporogenesis, megagametogenesis and the early development of the embryo. Tagetes patula L. has a typical ovule for the family Asteraceae: anatropous, unitegmic, tenuinucellate and with basal placentation. A single hypodermal archesporial cell develops directly as the megaspore mother cell. Megaspogenesis is normal and embryo sac develops from the chalazal megaspore. The embryo sac is of the Polygonum type. Female ray flowers show irregularities in megagametophyte development such as formation of more than eight nuclei, inverted polarity and incomplete differentiation of the megagametophyte cells in mature flowers. These irregularities do not necessarily prove apomictic reproduction in Tagetes patula.

Reproductive development in two species of Darwinia Rudge (Myrtaceae)

1969 ◽  
Vol 17 (2) ◽  
pp. 215 ◽  
Author(s):  
N Prakash
Keyword(s):  
Embryo Sac ◽  
Pollen Grains ◽  
Reproductive Development ◽  
Outer Zone ◽  
Mature Embryo ◽  
Globular Embryo ◽  
Primary Endosperm Nucleus ◽  
Oil Glands ◽  
Polygonum Type ◽  
History Of

In Darwinia the floral parts are differentiated in a "calyx-orolla-gynoeciumandroecium" sequence. In individual buds stages of microsporogenesis markedly precede corresponding stages of megasporogenesis. The anther is tetrasporangiate with all sporangia lying in one plane. The secretory tapetum is one- to three-layered within the same microsporangium and a large number of Ubisch bodies are formed. The anthers dehisce by minute lateral pores and an ingenious mechanism helps disperse the twocelled pollen grains. A basal placenta in the single loculus of the ovary bears four ovules in D. micropetala and two in D. fascicularis. In both species, however, only one ovule is functional after fertilization. The fully grown ovules are anatropous, crassinucellar, and bitegmic; the inner integument forms the micropyle. The parietal tissue is most massive at the completion of megasporogenesis but is progressively destroyed later. The embryo sac follows the Polygonum type of developnlent and when mature is five-nucleate, the three antipodals being ephemeral. Following fertilization, the primary endosperm nucleus divides before the zygote. Subsequent nuclear divisions in the endosperm mother cell are synchronous and lead to a free-nuclear endosperm which becomes secondarily cellular, starting from the micropylar end at the time the globular embryo assumes an elongated shape. Embryogeny is irregular and the mature embryo is straight with a massive radicle and a hypocotyl which terminates in two barely recognizable cotyledons. Sometimes the minute cotyledons are borne on a narrow neck-like extension of the hypocotyl. A suspensor is absent. Both integuments are represented in the seed coat and only the outer layer of the outer and the inner layer of the inner integuments, with their thick-walled tanniniferous cells, remain in the fully grown seed. The ovary wall is demarcated into an outer zone containing oil glands surrounded by cells containing a tannin-like substance and an inner zone of spongy parenchyma. In the fruit this spongy zone breaks down completely but the outer zone is retained. The two species of Darwinia, while closely resembling each other in their embryology, differ significantly from other Myrtaceae. However, no taxonomic conclusions are drawn at this stage, pending enquiry into the life history of other members of the tribe Chamaelaucieae.

Embryological studies in the compositae, I. Sporogenesis, Gametogenesis, and Embryogeny in Cotula australis (Less.) Hook. F

1962 ◽  
Vol 10 (1) ◽  
pp. 1 ◽  
Author(s):  
GL Davis
Keyword(s):  
Mother Cell ◽  
Megaspore Mother Cell ◽  
Embryo Sac ◽  
Subsequent Development ◽  
Pollen Grains ◽  
Archesporial Cell ◽  
Polygonum Type ◽  
Wall Formation ◽  
Chalazal Megaspore

Cotula australis has a discoid heterogamous capitulum in which the outermost three whorls of florets are female and naked. The bisexual disk florets are fully fertile and have a four-lobed corolla with four shortly epipetalous stamens. The anthers contain only two microsporangia. Wall formation and microsporogenesis are described and the pollen grains are shed at the three-celled condition. The ovule is teguinucellate and the hypodermal archesporial cell develops directly as the megaspore mother cell. Megasporogenesis is normal and the monosporio embryo sac develops from the chalazal megaspore. Breakdown of the nucellar epidermis takes place when the embryo sac is binucleate and its subsequent development follows the Polygonum type. The synergids extend deeply into the micropyle and one persists until late in embryogeny as a haustorium. The development of the embryo is of the Asterad type, and the endosperm is cellular. C. coronopifolia agrees with C. australis in the presence of only two microsporangia in each anther and the development of a synergid haustorium.

Embryo sac development in some representatives of the tribe Cynodonteae (Poaceae)

Bothalia ◽  
1994 ◽  
Vol 24 (1) ◽  
pp. 101-105 ◽  
Author(s):  
A. Strydom ◽  
J. J. Spies
Keyword(s):  
Cynodon Dactylon ◽  
Embryo Sac ◽  
Polygonum Type ◽  
Embryo Sac Development ◽  
Obligate Apomixis ◽  
Chloris Virgata

Chloris virgata Sw., Cynodon dactylon (L.) Pers., Harpochloa falx (L. f.) Kuntze, and Tragus berteronianus Schult. have a Polygonum type of embryo sac development. Unreduced embryo sacs were found in Eustachys paspaloides (Vahl) Lanza Mattei,  Harpochloa falx, and  Rendlia altera (Rendle) Chiov. Both facultative and obligate apomixis were observed. The Hieracium type of embryo sac development was observed in the aposporic specimens.

Ovule and seed structure in Scolopia zeyheri (Scolopieae), with notes on the embryology of Salicaceae

Bothalia ◽  
2005 ◽  
Vol 35 (2) ◽  
pp. 175-183 ◽  
Author(s):  
E. M. A. Steyn ◽  
A. E. Van Wyk ◽  
G. F. Smith
Keyword(s):  
Microscopic Study ◽  
Seed Coat ◽  
Embryo Sac ◽  
Single Layer ◽  
Relevant Information ◽  
Seed Structure ◽  
Globular Embryo ◽  
Polygonum Type ◽  
Old World ◽  
Seed Characters

Scolopia zeyheri (Nees) Harv. is a widespread African tree and a member of the largest genus of the tropical Old World tribe Scolopieae (Salicaceae sensu lato). This light microscopic study is the first report on ovule and seed structure in the genus and the tribe. Ovules vary from four to six per ovary, are anatropous. crassinucellate. bitegmic and occur in an epitropous (rarely pleurotropous). median-parietal position in the unilocular, usually bicarpellate ovary. A very extensive nucellus cap. comprising nucellus epidermal derivatives and parietal tissue, characterizes the young ovule during mega- sporogenesis and megagametogenesis, but the chalazal nucellus is poorly developed. During meiosis. the micropvlar dyad cell degenerates early. The functional dyad cell forms two megaspores of which the chalazal one usually develops into a Polygonum-type embryo sac. At maturity, the micropylar end of the embryo sac is covered by the remnants of the nucellus epidermis, the parietal tissue having degenerated. The globular embryo has a short suspensor and lies in nuclear endosperm becoming cellular. The seed coat develops from both integuments, is tannimferous. has a glabrous surface with stomata and a single layer of exotegmic, longitudinal fibres.Results are compared with relevant information previously reported for genera in the tribes Flacourtieae. Samvdeae. Saliceae, Scyphostegiae and for Oncoha Forssk. (Salicaceae sensu lato). Embryologically Scolopia shows a number of ple- siomorphic features compared to other Salicaceae. For example, it lacks an extranucellar embryo sac. an apomorphic fea­ture in many Salicaceae. A summary of ovule and seed characters in Salicaceae sensu lato is given and contrasted with data available for Achariaceae  sensu lato. Embryological data broadly supports the reclassification of genera, traditionally referred to Flacourtiaceae. amongst Salicaceae sensu lato and Achariaceae sensu lato.

The floral morphology and embryology of Themeda australis (R. Br.) Stapf

1964 ◽  
Vol 12 (2) ◽  
pp. 157 ◽  
Author(s):  
PS Woodland
Keyword(s):  
Embryo Sac ◽  
Pollen Grains ◽  
Low Fertility ◽  
Linear Tetrad ◽  
Polygonum Type ◽  
Morphological Variations ◽  
Endosperm Formation ◽  
Secretory Type ◽  
Successive Cytokinesis ◽  
Mother Cells

A comparative study was carried out between diploid and tetraploid races of Themeda australis from Armidale and Cobar, respectively. Some morphological variations occur in both populations, but sporogenesis and gametogenesis are identical. The anther is tetrasporangiate and the development of its four-layered wall is described. The tapetum is of the secretory type and its cells become binucleate at the initiation of meiosis in the adjacent microspore mother cells which undergo successive cytokinesis. Microspore tetrads are usually isobilateral and the pollen grains are three-celled at dehiscence, which takes place by lateral longitudinal slits. The ovule is of a modified anatropous form and bitegmic, the broad micropyle being formed of both integuments. The single hypodermal archesporial cell develops directly into the megaspore mother cell and the nucellar epidermis undergoes periclinal and anticlinal divisions to form a conspicuous epistase. The chalaza1 megaspore of the linear tetrad gives rise to a Polygonum-type embryo sac. Material from the Armidale population showed one embryo sac per ovule, but two to five embryo sacs were present in that from Cobar. Embryogeny is typically graminaceous and endosperm formation is at first free-nuclear, later becoming cellular. Polyembryony follows fertilization of several embryo sacs within the same ovule. The reasons for low fertility of T. australis and poor germination of seeds are discussed.

Embryology of Isotoma petraea

1970 ◽  
Vol 18 (2) ◽  
pp. 213 ◽  
Author(s):  
IC Beltran
Keyword(s):  
Mother Cell ◽  
Embryo Sac ◽  
Endosperm Development ◽  
Ovule Development ◽  
Polygonum Type ◽  
Development Patterns ◽  
Embryo Formation ◽  
Ring Bivalents ◽  
Form Ring ◽  
Embryo Sac Formation

Ovule development, embryo sac formation, and embryogeny of I. Petraea are described. The ovules are anatropous, unitegmic, and tenuinucellar. Meiosis in the megaspore mother cell is regular and the chromosomes with terminalized chiasmata form ring bivalents at metaphase 1. The Polygonum type embryo sac, Scutellaria type endosperm development, and Solanad embryo formation correspond with development patterns in other members of the Lobeliaceae.

THE DEVELOPMENT OF THE BLUEBERRY SEED

1957 ◽  
Vol 35 (2) ◽  
pp. 139-153 ◽  
Author(s):  
Hugh P. Bell
Keyword(s):  
Seed Development ◽  
Seed Coat ◽  
Embryo Sac ◽  
Pollen Tubes ◽  
Homogeneous Plasma ◽  
Stage Of Development ◽  
Micropylar Endosperm ◽  
Mature Seeds ◽  
Number Of Seeds

Seed development was followed from fertilization to maturity. Pollen tubes required about 4 days to grow from stigma to ovule. In some plants, particularly bagged ones, nucellar cells remained alive and contents of the embryo sac degenerated. Many ovules did not develop. Seeds were counted and sorted in a random representative collection of 1075 berries. The average number of seeds per berry was 64.2. Of these 49.9 (or 77.7%) were imperfect. More complete pollination increased the percentage of normally developing ovules. Development of perfect seeds followed a familiar pattern. Unfamiliar features were noted as follows: 1. Degeneration of cells at both micropylar and chalazal ends resulted in a homogeneous plasma. This plasma formed strands across haustoria and almost completely surrounded the zygote. 2. Micropylar endosperm cells formed a dense plug. Developing embryos may have had difficulty in penetrating this plug. 3. Many embryos had died at some stage of development. 4. A conspicuous integumentary tapetum was present until the endosperm was about half its final size.Embryo development was the "soland" type. Mature seeds were "axile linear". Imperfect seeds were chiefly of two types: (a) medium sized and solid with middle integumentary layers lignified, or (b) small and collapsed with all tissues inside seed coat disintegrated. No imperfect seed had an embryo.

scholarly journals Interaction Between Maternal Effect and Zygotic Effect Mutations During Maize Seed Development

Genetics ◽  
2001 ◽  
Vol 159 (1) ◽  
pp. 303-315 ◽  
Author(s):  
Matthew M S Evans ◽  
Jerry L Kermicle
Keyword(s):  
Seed Development ◽  
Maternal Effects ◽  
Maternal Effect ◽  
Male Gametophyte ◽  
Embryo Sac ◽  
Chromosome 2 ◽  
Maize Seed ◽  
Mutant Female ◽  
Two Stages ◽  
The Relationship

Abstract Double fertilization of the embryo sac by the two sperm cells of a pollen grain initiates seed development. Proper development of the seed depends not only on the action of genes from the resulting embryo and endosperm, but also on maternal genes acting at two stages. Mutations with both sporophytic maternal effects and gametophytic maternal effects have been identified. A new maternal effect mutation in maize, maternal effect lethal1 (mel1), causes the production of defective seed from mutant female gametophytes. It shows reduced pollen transmission, suggesting a requirement in the male gametophyte, but has no paternal effect on seed development. Interestingly, the defective kernel phenotype of mel1 is conditioned only in seeds that inherit mel1 maternally and are homozygous for the recessive allele (endogenous to the W22 inbred line) of either of two genes, sporophyte enhancer of mel1 (snm1) or snm2, suggesting redundancy between maternally and zygotically required genes. Both mel1 and snm1 map to the short arm of chromosome 2, and snm2 maps to the long arm of chromosome 10. The mode of action of mel1 and the relationship between mel1 and snm1 and snm2 are discussed.

Female gametophyte and seed development in Musella lasiocarpa (Musaceae), a monotypic genus endemic to Southwestern China

2007 ◽  
Vol 85 (10) ◽  
pp. 964-975 ◽  
Author(s):  
Chun-Ying Xue ◽  
Hong Wang ◽  
De-Zhu Li
Keyword(s):  
Seed Development ◽  
Female Gametophyte ◽  
Wild Population ◽  
Embryo Sac ◽  
Single Species ◽  
Ex Situ ◽  
Southwestern China ◽  
Conservation Strategies ◽  
Female Sterility ◽  
Monotypic Genus

Musella is a monotypic genus composed of a single species, Musella lasiocarpa (Franch.) C.Y. Wu ex H.W. Li, endemic to Southwestern China. The genus status of Musella remains controversial. Musella had been placed first in Musa , then in Ensete , and back to Musa before its monotypic status was recognized. Musella was reported to be extinct in the wild and maintained through cultivation only via vegetative propagation through sprouting of rhizomes. In this study, female gametophyte and seed development of Musella are described to assess its systematic position and possible reasons why the wild population is now extinct. The ovules are anatropous, bitegmic, and crassinucellar. The micropyle is formed by both integuments. The megaspore mother cell undergoes meiotic division and forms a linear megaspore triad or more rarely, a T-shaped megaspore tetrad. The chalazal megaspore develops into a Polygonum type embryo sac. A nucellar pad forms, and a hypostase differentiates. Fertilization is porogamous. Endosperm formation is of the nuclear type. The zygote degenerates and so the process by which the embryo develops, if it does, remains unclear. An operculum, micropylar collar, and chalazal chamber form in mature seeds. The storage tissue is mainly endosperm containing large, compound starch grains and some perisperm. The seed coat has lignified exotestal cells, 25–30 cell layers of sclerotic mesotestal cells, and unspecialized endotesta cells; the tegment consists of two layers of longitudinally elongated cells. The seed is inviable. After comparison with the other Musaceae s. str. taxa using embryological and botanical features, we conclude that Musella should be a distinct genus. Female sterility in Musella may be the main reason why the wild population is extinct. Based on these findings, we propose conservation strategies for this endemic species, including habitat protection as well as ex-situ conservation.

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