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.

Fruit and Seed Structure of Thryptomene calycina (Myrtaceae)

1993 ◽  
Vol 41 (2) ◽  
pp. 183 ◽  
Author(s):  
DV Beardsell ◽  
RB Knox ◽  
EG Williams
Keyword(s):  
Seed Coat ◽  
Embryo Sac ◽  
Small Cells ◽  
Seed Structure ◽  
Polygonum Type ◽  
Developing Seed ◽  
Nucellar Tissue ◽  
Auramine O ◽  
Hydrophobic Lipid ◽  
Thin Band

At anthesis the receptacle of flowers of T. calycina (Lindl.) Stapf is enclosed by a layer of small cells with a thick cuticle. The hypodermis consists mostly of large oil-containing cells interspersed with much smaller cells. The tissue surrounding the ovary consists mostly of spongy parenchyma. The micropyle of the ovule is formed only by the inner integument which is double-layered. The embryo sac at anthesis is typical of the Myrtaceae, and appears to follow the monosporic polygonum type, with considerable nucellar tissue surrounding it. In a mature fruit the parenchyma is compressed into a thin band surrounding the seed. The integuments form a two-layered seed coat within the fruit. The aborted ovule is displaced below and to one side of the developing seed. In fruit weathered for several years there is an accumulation of phenolic material giving the fruit a black appearance. The two layers of the seed coat within freshly shed fruit lie closely together and stain strongly with the lipid stain auramine O. In fruit weathered for at least 2 years the two layers of the seed coat become separated for at least part of their length and staining from auramine O is less intense. The breakdown in seed dormancy in weathered fruits is probably due to a less complete barrier to water uptake provided by the separation of the two layers. This would increase lateral and radial movement of water. The observed reduction in the hydrophobic lipid content of the testa layers probably also aids water entry into the seed in a weathered fruit.

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.

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.

Floral Morphology of the family compositae, III. Embryology of Siegesbeckia orientalis L

1965 ◽  
Vol 13 (1) ◽  
pp. 1 ◽  
Author(s):  
S Misra
Keyword(s):  
Vascular Bundle ◽  
Floral Morphology ◽  
Embryo Sac ◽  
Cell Plate ◽  
Pollen Grain ◽  
Polygonum Type ◽  
Outermost Layer ◽  
The Family ◽  
Siegesbeckia Orientalis ◽  
Ray Florets

The capitulum is heterogamous and globose with a biseriate involucre, the outer most bracts being radiating and glandular wuhile the inner are boat-shaped, enclosing the ray florets. The disc florets are also subtended by bracts, although one or two central bracts do not bear florets. The corolla of the ray florets is bilabiate in material collected from Mussoorie, India, while posterior lip is suppressed in that form Mt.Abu. The stamen and the style correspond to types 2 and V11 respectively of Small (1919). Occasional staminodes in the ray florets represent a reversionary feature. The development and structure of the microsporangium is described. An ephemeral cell plate is formed after meiosis 1 of the sporocytes. The mature pollen grain is tricellular; the male garnets are elongated and laxly spiral. The ovule develops slightly to one side of the base of the loculus, and a funicular vascular bundle branches in the integument. The endothelium is uniseriate, later becoming multiseriate at the two ends of the embryo sac, and it develops a cuticle on its inner face which persists in the seed after the endothelium degenerates. The development of the embryo sac is of the Polygonum type. The antipodals and one synergid become haustorial after fertilization. Supernumery pollen tubes were noted. Failure of fertilization in exceptional cases results in unusaul behaviour of the endothelium, degeneration of the embryo sacs, and seed sterility. The endosperm is nuclear, later becoming cellular, and is outermost layer persists in the seed. Embryogeny is of the asterad type.

scholarly journals Development of generative structures of polar Caryophyllaceae plants: the Arctic Cerastium alpinum and Silene involucrata, and the Antarctic Colobanthus quitensis

2017 ◽  
Vol 38 (1) ◽  
pp. 83-104 ◽  
Author(s):  
Wioleta Kellmann-Sopyła ◽  
Justyna Koc ◽  
Ryszard J. Górecki ◽  
Marcin Domaciuk ◽  
Irena Giełwanowska
Keyword(s):  
Embryo Sac ◽  
Single Layer ◽  
Pollen Grains ◽  
The Arctic ◽  
Egg Cell ◽  
Colobanthus Quitensis ◽  
West Antarctic ◽  
The Family ◽  
Electron Microscopes ◽  
Species Specific

AbstractThe embryology of three polar flowering plants of the family Caryophyllaceae was studied using the methods and techniques of the light, normal and fluorescence microscopes, and the electron microscopes, scanning and transmission. The analyzed species wereColobanthus quitensisof West Antarctic (King George Island, South Shetlands Islands) as well asCerastium alpinumandSilene involucrataof the Arctic (Spitsbergen, Svalbard). In all evaluated species, flowering responses were adapted to the short Arctic and Australian summer, and adaptations to autogamy and anemogamy were also observed. The microsporangia of the analyzed plants produced small numbers of microspore mother cells that were differentiated into a dozen or dozens of trinucleate pollen grains. The majority of mature pollen grains remained inside microsporangia and germinated in the thecae. The monosporous Polygonum type (the most common type in angiosperms) of embryo sac development was observed in the studied species. The egg apparatus had an egg cell and two synergids with typical polarization. A well-developed filiform apparatus was differentiated in the micropylar end of the synergids. In mature diaspores of the analyzed plants of the family Caryophyllaceae, a large and peripherally located embryo was, in most part, adjacent to perisperm cells filled with reserve substances, whereas the radicle was surrounded by micropylar endosperm composed of a single layer of cells with thick, intensely stained cytoplasm, organelles and reserve substances. The testae of the analyzed plants were characterized by species-specific primary and secondary sculpture, and they contained large amounts of osmophilic material with varied density. Seeds ofC. quitensis,C. alpinumandS. involucrataare very small, light and compact shaped.

Gametogenesis in Galbulimima belgraveana (Himantandraceae)

1984 ◽  
Vol 32 (6) ◽  
pp. 605 ◽  
Author(s):  
N Prakash ◽  
DB Foreman ◽  
SJ Griffith
Keyword(s):  
Close Relationships ◽  
Embryo Sac ◽  
Pollen Grains ◽  
Mature Pollen ◽  
Ovule Development ◽  
Abaxial Side ◽  
Polygonum Type ◽  
Early Stages

The flowers of Galbulimima belgraveana (F. Muell.) Sprague are bisexual, calyptrate and protogynous. The numerous free stamens are laminar and arranged spirally on an elongated receptacle; only the middle stamens are fertile. There are four microsporangia embedded on the abaxial side of the microsporophyll. The tapetum is secretory and often double. A variety of spore tetrad types is produced. The mature pollen grains are single, monosulcate, scabrate, atectate, spheroidal and 2-celled. The carpels of a flower are initially free but later become concrescent so that a single fruit is formed. The ovules are anatropous, crassinucellar and bitegminal, and show an elongated embryo sac that conforms to the polygonum type of development. There is a massive parietal tissue in early stages of ovule development. In its embryological features, the species shows close relationships to the families Annonaceae and Degeneriaceae and, to a slightly lesser extent, the Magnoliaceae and Eupomatiaceae.

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