Morphological and embryological studies in Nymphaeaceae. II. Brasenia schreberei Gmel. and Nelumbo nucifera Gaertn

1965 ◽  
Vol 13 (3) ◽  
pp. 379 ◽  
Author(s):  
P Khanna
Keyword(s):  
Embryo Sac ◽  
Pollen Grains ◽  
Pollen Sterility ◽  
Nelumbo Nucifera ◽  
Primary Endosperm Nucleus ◽  
Polygonum Type ◽  
Globular Stage ◽  
Compound Pollen ◽  
Mother Cells ◽  
Antipodal Cells

The stamens are whorled in Brasenia schreberei and spirally arranged in Nelumbo nucifera. The anther is tetrasporangiate. Parietal layers are five-celled in thickness in B. schreberei and six-celled in N. nucifera. Endothecial cells contain a tannin-like substance and develop fibrous thickenings in N. nucifera. The middle layers are persistent in N. nucifera and ephemeral in B. schreberei. The tapetal cells become multinucleate and the layer develops cutinization on its inner walls in N. nucifera. It is secretory. Micronuclei are formed at the meiosis in the microspore mother cells. These degenerate in B. schreberei and form micropollen grains in N. nucifera. Polysporads and compound pollen grains occur frequently in the latter. Pollen sterility is common. In B. schreberei the carpel is horseshoe-shaped, unites with its margins, and bears two to three pendulous ovules with lamina1 placentation. The carpel in N. nucifera, however, remains open in its early development, unites by the growth of the interlocking hairs, and contains a single ovule. A single parietal layer is present in B. schreberei, and four to five such layers in N. nucifera. A hypostase is formed in B. schreberei. The nucellus functions as perisperm in the latter and is consumed early in N. nucifera. A linear megaspore tetrad is formed in which the chalazal megaspore is functional. The embryo sac is of the Polygonum type. The antipodal cells are ephemeral in B. Schreberei and persistent with secondary multiplication in N. nucifera. In post-fertilized ovules one of the synergids is persistent. Fertilization is non-synchronous in N. nucifera and simultaneous in B. schreberei. In N. nucifera the antipodal cells become enlarged and multinucleate, and occupy the elongated tube formed by the downward penetration of the embryo sac. They degenerate at the early globular stage of the embryo and are not persistent when the embryo is pear-shaped. In B. schreberei a transverse cytokinesis follows division of the primary endosperm nucleus and two unequal cells are formed. The small chalazal endosperm cell penetrates the nucellus below and forms a long tube-like haustorium occupying three-quarters of the length of the nucellus. Its nucleus subsequently hypertrophies and degenerates completely at the globular stage of the embryo. Endosperm is ab initio cellular in B. schreberei and free nuclear in N. nucifera.

The embryology of Kunzea capitata Reichb

1969 ◽  
Vol 17 (1) ◽  
pp. 97 ◽  
Author(s):  
N Prakash
Keyword(s):  
Outer Integument ◽  
Cell Formation ◽  
Embryo Sac ◽  
Pollen Grains ◽  
Basic Type ◽  
Ring Stage ◽  
Polygonum Type ◽  
Signet Ring ◽  
Mother Cells ◽  
Antipodal Cells

The anther is tetrasporangiate and the development of its wall is of the Basic type. Ubisch granules are formed on the surface of the tapetum at the signet-ring stage of the pollen grains. The anther dehisces by longitudinal slits, and pollen grains are shed at the two-celled stage. The female archesporium is subepidermal and cuts off the primary parietal cell. A six-layered parietal tissue is formed below the nucellar epidermis by the time megasporogenesis is completed. The flowers are protandrous, and in any given bud meiosis in megaspore mother cells follows that in microspore mother cells. Embryo sac development is of the Polygonum type and the antipodal cells are ephemeral. Cell formation in the nuclear endosperm commences at the micropylar end and proceeds towards the chalaza. Embryogeny corresponds to the Onagrad type and no evidence of polyembryony was found. Both the integuments take part in the formation of the seed coat, in which the cells of the outer layer of the outer integument are conspicuously elongated. A comparison is made with the embryological findings in other myrtaceous plants.

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.

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.

A contribution to the life history of Angophora floribunda (Sm.) Sweet (Myrtaceae)

1969 ◽  
Vol 17 (3) ◽  
pp. 457 ◽  
Author(s):  
N Prakash
Keyword(s):  
Floral Development ◽  
Outer Integument ◽  
Embryo Sac ◽  
Pollen Grains ◽  
Flower Buds ◽  
Polygonum Type ◽  
Mature Embryos ◽  
History Of ◽  
Sterile Pollen ◽  
Mother Cells

The flower buds of Angophora floribunda appear in the last week of November and anthesis occurs in the middle of January the following year. There is no prolonged resting phase at any stage during embryology and the seeds are shed during late February to early March. In floral development, the petals are the last structures to be formed. Early anther development precedes corresponding stages in the ovules of the same flower, but events in the ovules proceed more rapidly and meiosis occurs simultaneously in the spore mother cells of both organs. The mature two-celled pollen grains are shed when the ovules contain four-or eight-nucleate embryo sacs. Many flowers bear anthers containing only sterile pollen grains, which occur either singly or as tetrads. Various abnormalities in the development of the pollen are reported, and the anthers containing sterile pollen neither develop fibrous bands in the endothecium nor do they dehisce. The ovules are bitegminal, crassinucellar, and hemianatropous. Occasional bifurcation of the inner integument was observed and a hypostase differentiates at the four-nucleate stage of the embryo sac. The embryo sac follows the Polygonum type of development and is five-nucleate and four-celled when mature. The endosperm is Nuclear in origin, and in about half the seeds examined a granular unidentified substance accumulates in the embryo sac. The development of the embryo is irregular and the seedlings bear a collar-like structure at the junction of the hypocotyl and the radicle. The mature embryos are usually dicotyledonous but rarely tricotyledonous. The seed coat is formed exclusively by the outer integument; in the ripe seed it consists of an outer epidermis of large, palisade-like, thin-walled, tanniniferous cells and an inner crystalliferous layer.

Embryological studies in the compositae. IV. Sporogenesis, gametogenesis, and embryogeny in Brachycome ciliaris (Labill.) Less

1964 ◽  
Vol 12 (2) ◽  
pp. 142 ◽  
Author(s):  
GL Davis
Keyword(s):  
New South ◽  
Embryo Sac ◽  
Pollen Grains ◽  
Egg Cell ◽  
Male Sterile ◽  
Morphological Variations ◽  
Secondary Nucleus ◽  
South Wales ◽  
Mother Cells ◽  
Antipodal Cells

Material of two varieties of Brachycome ciliaris was obtained from several localities in southern Queensland and western New South Wales, and no embryological differences were found between populations in spite of considerable morphological variations. The plant was highly male-sterile, and although development of the anthers was normal up to the formation of microspore mother cells, presumed meiotic abnormalities resulted in failure to form microspore tetrads except in one instance. The formation of plasmodial microspore mother cells and unreduced pollen grains is described and the occurrence of normal pollen grains in two capitula is recorded. In the ovule, meiosis is suppressed and the megaspore mother cell becomes vacuolate and functions directly as the uninucleate embryo sac. Three nuclear divisions precede the formation of an eight-nucleate embryo sac in which the antipodal cells undergo secondary multiplication. There is circumstantial evidence that the polar nuclei divide simultaneously to form the fist four endosperm nuclei and do not first fuse to form a secondary nucleus. The egg cell develops parthenogenetically and cleavages follow the asterad type of development. The eariy stages of embryogeny are completed before the opening of the florets.

Floral morphology, embryology, and relationships of the Berberidaceae.

1969 ◽  
Vol 17 (1) ◽  
pp. 69 ◽  
Author(s):  
RLN Sastri
Keyword(s):  
Floral Morphology ◽  
Embryo Sac ◽  
Pollen Grains ◽  
Wall Layer ◽  
Vascular Supply ◽  
Anther Wall ◽  
Polygonum Type ◽  
Innermost Layer ◽  
Secretory Type ◽  
Mother Cells

The floral morphology and development of the gametophytes in Berberis umbellata and Mahonia leschenaultii have been studied. All the perianth members have three traces each in B. umbellata while in M. leschenaultii the members of the outer three whorls have five veins each and those of the fourth three veins each. The vascular supply for the inner two whorls of perianth and the stamens arises as conjoint traces. The wall of the gynoecium is traversed by numerous bundles with some concentrated in the placental region. The dorsal and ventral bundles are differentiated in M. leschenaultii but not in B. umbellata. The tricarpellary interpretation of the gynoecium is shown to be unconvincing. The gynoecium is regarded as monocarpellary. The mature anther wall is five-layered including the epidermis, of which the innermost layer forms the tapetum of secretory type. The tapetal cells are four to eight-nucleate. The hypodermal wall layer develops into a fibrous endothecium in M. leschenaultii. In B. urnbellata, the endothecium develops U-shaped thickenings. Division of pollen mother cells is successive. Pollen tetrads are usually isobilateral. Mature pollen grains are three-colpate and two-celled. The ovule is anatropous, bitegmic, and crassinucellate. In B. umbellata, a rudimentary aril is formed as an outgrowth of the funiculus. The single hypodermal archesporial cell in the young ovule cuts off a parietal cell. Development of the embryo sac is of the Polygonum type. The synergids show filiform apparatus and are persistent. The antipodals are large and persistent in M. leschenaultii and ephemeral in B. umbellata. The relationships of the Berberidaceae (sensu Hutchinson 1959) to the Menispermaceae, Lardizabalaceae, and the Ranunculaceae (sensu lato) are discussed.

Life history of Tetragonia tetragonioides (Pall.) O. Kuntze

1967 ◽  
Vol 15 (3) ◽  
pp. 413 ◽  
Author(s):  
N Prakash
Keyword(s):  
Cell Formation ◽  
Embryo Sac ◽  
Pollen Grains ◽  
Mature Embryo ◽  
Polygonum Type ◽  
Innermost Layer ◽  
Glandular Cells ◽  
History Of ◽  
Mother Cells ◽  
Tetragonia Tetragonioides

Accessory flowers arise from the surface of inferior ovaries in 25 % of the flowers of Tetragonia, suggesting an axial nature of the inferior ovary. The ovary is six to nine-loculed, with a single pendulous ovule in each locule. The anther is tetrasporangiate. The innermost layer of the four-layered wall constitutes a secretory tapetum with multinucleate cells. Cytokinesis in microspore mother cells is simultaneous and results in tetrahedral or decussate tetrads. The pollen grains are shed at the three-celled stage. The ovules are bitegminal, crassinucellar, and anacampylotropus. The funiculus is long and bears an obturator of glandular cells. The inner integument forms the micropyle and forms a collar at the distal end. A nucellar cap is present. The nucellus persists in the seed as perisperm. The archesporium is multicelled, although only a single cell develops. Following meiosis the megaspore mother cell gives rise to a linear row of three or four megaspores, of which only the chalaza1 functions to form an embryo sac of the Polygonum type. The endosperm is of the Nuclear type and eventually assumes a horseshoe shape. Cell formation is restricted to the micropylar region, the rest remaining nuclear until consumed by the embryo. The embryogeny is of the Solanad type, and the mature embryo is curved and dicotyledonous.

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.

Apomixis and abnormal anther development in Calotis lappulacea Benth. (Compositae)

1968 ◽  
Vol 16 (1) ◽  
pp. 1 ◽  
Author(s):  
GL Davis
Keyword(s):  
New South ◽  
Embryo Sac ◽  
Pollen Grains ◽  
Anther Wall ◽  
Male Gametes ◽  
Globular Stage ◽  
South Wales ◽  
Vertical Division ◽  
Endosperm Formation ◽  
Embryo Sac Formation

A comparative study was made of material collected from four localities in New South Wales and Queensland and a number of embryological aberrations were found to be common to all districts. During microsporogenesis, certain tapetal cells not only failed to contribute to the tapetal periplasmodium but, after increasing in size, they separated from the anther wall and resembled one-, two-, or four-nucleate embryo sacs developing among the microspores. In one anther a structure was present which was very similar to a fully differentiated embryo sac. Although the pollen grains of some anthers contained male gametes, most anthers dehisced when the pollen was two-celled and some shrivelled soon after meiosis. Megasporogenesis was followed by the formation of linear tetrads of megaspores, but embryo sac formation was the result of somatic apospory and C. lappulacea appears to be an obligate apomict. The enlarging somatic cell usually invades the nucellar lobe and replaces the megaspores but one or more such celis commonly develop also in the chalaza, and up to eight embryo sacs were found in one ovule. Enlargement of a chalazal embryo sac sometimes resulted in penetration of the ovular epidermis and its invasion of the loculus as a haustorium-like structure. Extrusion of a developing embryo sac through the micropyle was common. Embryogeny is of the Asterad type, but vertical division of the terminal cell ca was delayed until after the basal cell cb had given rise to superposed cells m and ci. Polyembryony was common but only one embryo in each ovule reached maturity. Endosperm formation was independent of embryogeny but unless it was initiated before the globular stage of the embryo, the embryo sac collapsed and the embryo degenerated.

The development of the embryo sac of sunflower Helianthus annuus after fertilization

1973 ◽  
Vol 51 (5) ◽  
pp. 879-890 ◽  
Author(s):  
William Newcomb
Keyword(s):  
Helianthus Annuus ◽  
Mitotic Spindle ◽  
Embryo Sac ◽  
Endosperm Development ◽  
Primary Endosperm Nucleus ◽  
Single Row ◽  
Wall Formation ◽  
Globular Stage ◽  
Spindle Apparatus ◽  
Single Fertilization

The degeneration of one synergid denotes the initiation of embryo and endosperm development in the embryo sac of sunflower Helianthus annuus L. The other synergid, the persistent synergid, is present until the late globular stage of embryogenesis. The primary endosperm nucleus divides before the zygote nucleus forming a coenocytic nuclear endosperm. When about eight endosperm nuclei are present during the early globular stage of embryogenesis, endosperm wall formation starts at the micropylar end of the embryo sac. The walls continue to grow toward the chalazal end of the embryo sac apparently as a result of the activity of Golgi located at the tips of the growing walls. Most endosperm wall formation is not associated with a mitotic spindle apparatus in sunflower. The suspensor of the embryo consists of a large basal cell during the proembryo stages, a single row of cells during the early globular stages, and at the late globular stage a double tier of cells near the radicle end of the embryo and a single row at the micropylar end of the embryo sac. Occasionally embryo development occurs in the absence of endosperm when only single fertilization has taken place. The development and nutritional implications of post-fertilization events in the sunflower embryo sac are discussed.

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