Calcium Distribution and Accumulation in Ovules of Plumbago Zeylanica

2000 ◽  
Vol 6 (S2) ◽  
pp. 696-697
Author(s):  
Hua Zhu ◽  
Scott D. Russell
Keyword(s):  
Pollen Tube ◽  
Apoptotic Cell ◽  
Embryo Sac ◽  
Flowering Plants ◽  
Cell Type ◽  
Mobile Form ◽  
Plumbago Zeylanica ◽  
Male Gametes ◽  
High Concentrations ◽  
Potassium Pyroantimonate

The embryo sac (ES) of Plumbago zeylanica, unlike most other flowering plants, lacks synergidsthe cell type that usually receives the pollen tube and the male gametes. Normally, synergids store copious amounts of calcium, estimated to exceed 15% by weight; this is believed to attract pollen tubes, which penetrate the ES, and may trigger the release of the sperm cells within one of the two synergids. If high concentrations of calcium are truly required for fertilization, the ES of Plumbago should also contain significant quantities. Synergids in normal flowering plants are preprogrammed for cell death, receiving the contents of the pollen tube directly in their cells, whereas synergid-lacking angiosperms apparently do not have such an apoptotic cell in the ES. Potassium pyroantimonate labeling was used to localize principally loosely-bound calcium, because it is a relatively mobile form of the Ca2+ ion that is available for redistribution during fertilization events.

Cytoskeletal organisation and modification during pollen tube arrival, gamete delivery and fertilisation in Plumbago zeylanica

Zygote ◽  
1993 ◽  
Vol 1 (2) ◽  
pp. 143-154 ◽  
Author(s):  
Bing-Quan Huang ◽  
Elisabeth S. Pierson ◽  
Scott D. Russell ◽  
Antonio Tiezzi ◽  
Mauro Cresti
Keyword(s):  
Pollen Tube ◽  
Embryo Sac ◽  
Central Cell ◽  
Egg Cell ◽  
Target Cells ◽  
Sperm Cells ◽  
Plumbago Zeylanica ◽  
Rhodamine Phalloidin ◽  
Male Gametes ◽  
Pollen Tube Penetration

The cytoskeletal organisation of the isolated embryo sac and egg cells of Plumbago zeylanica was examined before, during and after pollen tube penetration into the embryo sac to determine the potential involvement of microtubules and actin filaments in fertilisation. Material was singly and triply stained using Hoechst 33258 to localise DNA, fluorescein isothiocyanate (FITC)-labelled anti- α-tubulin to detect microtubules and rhodamine-phalloidin to visualise F-actin. Microtubules in the unfertilised egg cell are longitudinally aligned in the micropylar and mid-lateral areas, aggregating into bundles near the filiform apparatus. In the perinuclear cytoplasm of the egg cell, microtubules become more or less randomly aligned. F-actin bundles form a longitudinally aligned mesh in the chalazal cytoplasm of the egg cell. In the central cell, microtubules and F-actin are distributed along transvacuolar strands and are also evident in the perinuclear region and at the periphery of the cell. During pollen tube penetration, sparse microtubule bundles near the pathway of the pollen tube may form an apparent microtubular ‘conduit’ surrounding the male gametes at the delivery site. Actin aggregates become organised near the pathway of the pollen tube and at the delivery site of the sperm cells. Subsequently, actin aggregates form a ‘corona’ structure in the intercellular region between the egg and central cell where gametic fusion occurs. The corona may have a role in maintaining the close proximity of the egg and central cell and helping the two sperm cells move and bind to their target cells. The cytoskeleton may also be involved in causing the two nuclei of the egg and central cell to approach one another at the site of gametic fusion and transporting the two sperm nuclei into alignment with their respective female nucleus. The cytoskeleton is reorganised during early embryogenesis.

Fertilization in Plumbago zeylanica: entry and discharge of the pollen tube in the embryo sac

1982 ◽  
Vol 60 (11) ◽  
pp. 2219-2230 ◽  
Author(s):  
Scott D. Russell
Keyword(s):  
Cell Wall ◽  
Pollen Tube ◽  
Female Gametophyte ◽  
Embryo Sac ◽  
Central Cell ◽  
Vegetative Nucleus ◽  
Egg Cell ◽  
Ultrastructural Organization ◽  
Plumbago Zeylanica ◽  
Male Gametes

The ultrastructural organization of the megagametophyte of Plumbago zeylanica, which lacks synergids, was examined in chemically and physically fixed ovules after entry of the pollen tube. Similar to angiosperms with conventionally organized megagametophytes, the pollen tube enters the ovule through a micropyle, formed by the inner integument, and approaches the female gametophyte by growing between nucellar cells. Unlike other described female gametophytes, however, continued pollen tube growth results in direct penetration of the base of the egg through cell wall projections forming a filiform apparatus and is completed between the egg and central cell without disrupting either of these cells' plasma membranes. A terminal pollen tube aperture forms when the pollen tube reaches an area of strong curvature near the summit of the egg; this results in the release of two sperm cells, the vegetative nucleus, and a limited amount of pollen cytoplasm. The formerly continuous chalazal egg cell wall is locally disrupted near the tip of the pollen tube and apparently is thus modified for reception of male gametes. Discharged pollen cytoplasm rapidly degenerates between the egg and central cell, but unlike pollen tube discharge in conventionally organized megagametophytes, it is unassociated with the degeneraton of any receptor cell within the female gametophyte. Sperm nuclei are transmitted, one to the egg and the other to the central cell, to effect double fertilization by nuclear fusion with their respective female reproductive nuclei. The vegetative nucleus and discharged pollen cytoplasm degenerate between the developing embryo and endosperm during early embryogenesis. The emerging concept that the egg of Plumbago possesses combined egg and synergid functions is supported by the present study and suggests that the megagametophyte of this plant displays a highly specialized egg apparatus composed exclusively of a single, modified egg cell.

scholarly journals Ultrastructure of fertilization in Plumbago zeylanica

2014 ◽  
Vol 50 (1-2) ◽  
pp. 185-189 ◽  
Author(s):  
Scott D. Russell ◽  
David D. Cass
Keyword(s):  
Cell Wall ◽  
Pollen Tube ◽  
Female Gametophyte ◽  
Tube Growth ◽  
Vegetative Nucleus ◽  
Plumbago Zeylanica ◽  
Specialized Cell ◽  
Wall Ingrowths ◽  
Male Gametes ◽  
Cell Wall Ingrowths

The synergidless female gametophyte of <em>Plumbago zeylanica</em> receives the pollen tube through specialized cell wall ingrowths at the base of the egg; tube growth continues between egg and central cells. Pollen tube discharge occurs between egg and central cell and results in release of two male gametes, vegetative nucleus, and some pollen cytoplasm. Except for the location of gamete discharge, details of transmission and fusion of gametic nuclei appear to conform to reports of these processes in taxa possessing conventional embryo sacs.

Flora’s Secret Gardens

2018 ◽  
Author(s):  
Lincoln Taiz ◽  
Lee Taiz
Keyword(s):  
Pollen Tube ◽  
Embryo Sac ◽  
Flowering Plants ◽  
Sexual Stage ◽  
Male And Female ◽  
Plant Kingdom ◽  
Asexual Spore ◽  
The Rose ◽  
Plant Sex ◽  
Alternation Of Generations

Wilhelm Hofmeister established the unity of the Plant Kingdom through the discovery of Alternation of Generations. In both cryptogams and flowering plants a diploid asexual stage, or sporophyte, alternates with a haploid sexual stage. Thus the flower is not the true sexual stage, but rather the asexual spore-producing stage. The main difference between ferns and roses is that the spores of the fern are visible on the undersides of the leaves, while the spores of the rose are concealed within the anthers and ovaries. These spores develop into the actual sexual stage of the spermatophyte, the male and female gametophytes, i.e. the pollen tube and the embryo sac. Hofmeister’s discovery solved of the age-old quandary over plant sex. The sexualists and the asexualists can both claim to have been correct, but it was the sexualists who freed their minds from cultural biases and glimpsed the true sexual nature of plants.

scholarly journals Developmental biology of dispersed pollen grains

2020 ◽  
Vol 64 (1-2-3) ◽  
pp. 7-19
Author(s):  
Kundaranahalli R. Shivanna ◽  
Rajesh Tandon
Keyword(s):  
Developmental Biology ◽  
Pollen Tube ◽  
Pollen Germination ◽  
Pollen Viability ◽  
Pollen Dispersal ◽  
Embryo Sac ◽  
Pollen Grains ◽  
Male Gametes ◽  
Functional Aspects ◽  
Structural Details

Professor Panchanan Maheshwari served as Professor and Head of the Department of Botany, University of Delhi, from 1950 to 1966 and built an internationally reputed School of integrated plant embryology. Studies carried out during and after Maheshwari’s period from this School have enormously advanced our knowledge of the structural, developmental and functional aspects of embryological processes. This review covers studies carried out at the Delhi School on the developmental biology of dispersed pollen grains which operate from pollen dispersal from the anthers until pollen tubes discharge the male gametes in the embryo sac for fertilization. These events include pollen viability and vigour, pollen germination and pollen tube growth, structural details of the pistil relevant to pollen function, pollination and pollen-pistil interaction.

scholarly journals Live-cell imaging of early events following pollen perception in self-incompatible Arabidopsis thaliana

2019 ◽  
Author(s):  
Frédérique Rozier ◽  
Lucie Riglet ◽  
Chie Kodera ◽  
Vincent Bayle ◽  
Eléonore Durand ◽  
...  
Keyword(s):  
Pollen Tube ◽  
Imaging System ◽  
Initial Period ◽  
Embryo Sac ◽  
Live Imaging ◽  
Mechanical Pressure ◽  
Pollen Hydration ◽  
Male Gametes ◽  
Incompatible Pollen ◽  
Compatible Pollen

AbstractEarly events occurring at the surface of the female organ are critical for plant reproduction, especially in species with a dry stigma. Following landing on the stigmatic papilla cells, the pollen hydrates and germinates a tube, which penetrates the cell wall and grows towards the ovules to convey the male gametes to the embryo sac. In self-incompatible (SI) species within the Brassicaceae, these processes are blocked when the stigma encounters an incompatible pollen. Here, based on the generation of SI-Arabidopsis lines and by setting up a live imaging system, we showed that control of pollen hydration has a central role in pollen selectivity. The faster pollen pumps water from the papilla during an initial period of 10 minutes, the faster it germinates. Furthermore, we found that the SI barriers act to block the proper hydration of incompatible pollen and when hydration is promoted by high humidity, an additional control prevents pollen tube penetration into the stigmatic wall. In papilla cells, actin bundles focalize at the contact site with the compatible pollen but not with the incompatible one, raising the possibility that stigmatic cells react to the mechanical pressure applied by the invading growing tube.HighlightA live imaging system coupled with self-incompatible Arabidopsis lines highlight the role of stigmatic cells in controlling pollen hydration and in reacting to pollen tube intrusion by remodeling actin cytoskeleton.

scholarly journals Paving the Way for Fertilization: The Role of the Transmitting Tract

2021 ◽  
Vol 22 (5) ◽  
pp. 2603
Author(s):  
Ana Marta Pereira ◽  
Diana Moreira ◽  
Sílvia Coimbra ◽  
Simona Masiero
Keyword(s):  
Pollen Tube ◽  
Pollen Tube Growth ◽  
Current Knowledge ◽  
Embryo Sac ◽  
Tube Growth ◽  
Signaling Cascades ◽  
Secretory Cells ◽  
Transmitting Tract ◽  
Specialized Tissue

Angiosperm reproduction relies on the precise growth of the pollen tube through different pistil tissues carrying two sperm cells into the ovules’ embryo sac, where they fuse with the egg and the central cell to accomplish double fertilization and ultimately initiate seed development. A network of intrinsic and tightly regulated communication and signaling cascades, which mediate continuous interactions between the pollen tube and the sporophytic and gametophytic female tissues, ensures the fast and meticulous growth of pollen tubes along the pistil, until it reaches the ovule embryo sac. Most of the pollen tube growth occurs in a specialized tissue—the transmitting tract—connecting the stigma, the style, and the ovary. This tissue is composed of highly secretory cells responsible for producing an extensive extracellular matrix. This multifaceted matrix is proposed to support and provide nutrition and adhesion for pollen tube growth and guidance. Insights pertaining to the mechanisms that underlie these processes remain sparse due to the difficulty of accessing and manipulating the female sporophytic tissues enclosed in the pistil. Here, we summarize the current knowledge on this key step of reproduction in flowering plants with special emphasis on the female transmitting tract tissue.

scholarly journals The mac1 Gene: Controlling the Commitment to the Meiotic Pathway in Maize

Genetics ◽  
1996 ◽  
Vol 142 (3) ◽  
pp. 1009-1020 ◽  
Author(s):  
William F Sheridan ◽  
Nadezhda A Avalkina ◽  
Ivan I Shamrov ◽  
Tatyana B Batyea ◽  
Inna N Golubovskaya
Keyword(s):  
Female Gametophyte ◽  
Embryo Sac ◽  
Flowering Plants ◽  
Normal Female ◽  
Ovule Development ◽  
Partial Sterility ◽  
Embryo Sac Formation ◽  
Female Gametophyte Development ◽  
Normal Meiosis ◽  
Pleiotropic Mutation

Abstract The switch from the vegetative to the reproductive pathway of development in flowering plants requires the commitment of the subepidermal cells of the ovules and anthers to enter the meiotic pathway. These cells, the hypodermal cells, either directly or indirectly form the archesporial cells that, in turn, differentiate into the megasporocytes and microsporocytes. We have isolated a recessive pleiotropic mutation that we have termed multiple archesporial cells1 (macl) and located it to the short arm of chromosome 10. Its cytological phenotype suggests that this locus plays an important role in the switch of the hypodermal cells from the vegetative to the meiotic (sporogenous) pathway in maize ovules. During normal ovule development in maize, only a single hypodermal cell develops into an archesporial cell and this differentiates into the single megasporocyte. In macl mutant ovules several hypodermal cells develop into archesporial cells, and the resulting megasporocytes undergo a normal meiosis. More than one megaspore survives in the tetrad and more than one embryo sac is formed in each ovule. Ears on mutant plants show partial sterility resulting from abnormalities in megaspore differentiation and embryo sac formation. The sporophytic expression of this gene is therefore also important for normal female gametophyte development.

Overgrowth of Pollen Tubes in Embryo Sacs of Rhododendron Following Interspecific Pollinations

1986 ◽  
Vol 34 (4) ◽  
pp. 413 ◽  
Author(s):  
EG Williams ◽  
V Kaul ◽  
JL Rouse ◽  
BF Palser
Keyword(s):  
Pollen Tube ◽  
Embryo Sac ◽  
Pollen Tubes ◽  
Egg Cell ◽  
Interspecific Crosses ◽  
Main Body

Frequent overgrowths of pollen tubes within the embryo sac are characteristic of a number of interspecific crosses in the genus Rhododendron (Ericaceae). The combined techniques of sectioning, squashing and whole-ovule clearing have confirmed that in ovules showing this phenomenon the pollen tube fails to terminate growth and release sperms on entry into a synergid; instead it continues to grow beyond the synergid and egg cell, often filling the main body of the embryo sac with a coiled and distorted mass. Such ovules fail to develop further. The occurrence and possible causes of this error syndrome are discussed.

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