1
|
Sugi N, Izumi R, Tomomi S, Susaki D, Kinoshita T, Maruyama D. Removal of the endoplasma membrane upon sperm cell activation after pollen tube discharge. FRONTIERS IN PLANT SCIENCE 2023; 14:1116289. [PMID: 36778680 PMCID: PMC9909283 DOI: 10.3389/fpls.2023.1116289] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/05/2022] [Accepted: 01/17/2023] [Indexed: 06/18/2023]
Abstract
In pollen and pollen tubes, immotile sperm cells are enclosed by an inner vegetative plasma membrane (IVPM), a single endomembrane originating from the vegetative-cell plasma membrane. It is widely believed that sperm cells must be removed from the IVPM prior to gamete associations and fusions; however, details of the timing and morphological changes upon IVPM dissociation remain elusive. Here, we report a rapid IVPM breakdown immediately before double fertilization in Arabidopsis thaliana. The IVPM was stably observed in coiling pollen tubes when pollen tube discharge was prevented using lorelei mutant ovules. In contrast, a semi-in vivo fertilization assay in wild-type ovules demonstrated fragmented IVPM around sperm nuclei 1 min after pollen tube discharge. These observations revealed the dynamic alteration of released sperm cells and provided new insights into double fertilization in flowering plants. With a summary of recent findings on IVPM lipid composition, we discussed the possible physiological signals controlling IVPM breakdown.
Collapse
|
2
|
Schattner S, Schattner J, Munder F, Höppe E, Walter WJ. A Tug-of-War Model Explains the Saltatory Sperm Cell Movement in Arabidopsis thaliana Pollen Tubes by Kinesins With Calponin Homology Domain. FRONTIERS IN PLANT SCIENCE 2020; 11:601282. [PMID: 33664751 PMCID: PMC7921805 DOI: 10.3389/fpls.2020.601282] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/31/2020] [Accepted: 12/28/2020] [Indexed: 05/16/2023]
Abstract
Upon pollination, two sperm cells are transported inside the growing pollen tube toward the apex. One sperm cell fertilizes the egg cell to form the zygote, while the other fuses with the two polar nuclei to form the triploid endosperm. In Arabidopsis thaliana, the transport of the two sperm cells is characterized by sequential forward and backward movements with intermediate pauses. Until now, it is under debate which components of the plant cytoskeleton govern this mechanism. The sperm cells are interconnected and linked to the vegetative nucleus via a cytoplasmic projection, thus forming the male germ unit. This led to the common hypothesis that the vegetative nucleus is actively transported via myosin motors along actin cables while pulling along the sperm cells as passive cargo. In this study, however, we show that upon occasional germ unit disassembly, the sperm cells are transported independently and still follow the same bidirectional movement pattern. Moreover, we found that the net movement of sperm cells results from a combination of both longer and faster runs toward the pollen tube apex. We propose that the observed saltatory movement can be explained by the function of kinesins with calponin homology domain (KCH). This subgroup of the kinesin-14 family actively links actin filaments and microtubules. Based on KCH's specific properties derived from in vitro experiments, we built a tug-of-war model that could reproduce the characteristic sperm cell movement in pollen tubes.
Collapse
Affiliation(s)
- Saskia Schattner
- Department of Biology, Institute for Plant Science and Microbiology, University of Hamburg, Hamburg, Germany
| | - Jan Schattner
- Department of Biology, Institute for Plant Science and Microbiology, University of Hamburg, Hamburg, Germany
| | - Fabian Munder
- Department of Biology, Institute for Plant Science and Microbiology, University of Hamburg, Hamburg, Germany
| | - Eva Höppe
- Department of Biology, Institute for Plant Science and Microbiology, University of Hamburg, Hamburg, Germany
| | - Wilhelm J. Walter
- Department of Biology, Institute for Plant Science and Microbiology, University of Hamburg, Hamburg, Germany
- Department Medicine, Health and Medical University Potsdam, Potsdam, Germany
- *Correspondence: Wilhelm J. Walter
| |
Collapse
|
3
|
Abstract
The reproductive adaptations of land plants have played a key role in their terrestrial colonization and radiation. This encompasses mechanisms used for the production, dispersal and union of gametes to support sexual reproduction. The production of small motile male gametes and larger immotile female gametes (oogamy) in specialized multicellular gametangia evolved in the charophyte algae, the closest extant relatives of land plants. Reliance on water and motile male gametes for sexual reproduction was retained by bryophytes and basal vascular plants, but was overcome in seed plants by the dispersal of pollen and the guided delivery of non-motile sperm to the female gametes. Here we discuss the evolutionary history of male gametogenesis in streptophytes (green plants) and the underlying developmental biology, including recent advances in bryophyte and angiosperm models. We conclude with a perspective on research trends that promise to deliver a deeper understanding of the evolutionary and developmental mechanisms of male gametogenesis in plants.
Collapse
Affiliation(s)
- Dieter Hackenberg
- Department of Genetics and Genome Biology, University of Leicester, Leicester, United Kingdom.
| | - David Twell
- Department of Genetics and Genome Biology, University of Leicester, Leicester, United Kingdom.
| |
Collapse
|
4
|
Gotelli MM, Lattar EC, Zini LM, Galati BG. Style morphology and pollen tube pathway. PLANT REPRODUCTION 2017; 30:155-170. [PMID: 29116403 DOI: 10.1007/s00497-017-0312-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/20/2017] [Accepted: 10/31/2017] [Indexed: 06/07/2023]
Abstract
The style morphology and anatomy vary among different species. Three basic types are: open, closed, and semi-closed. Cells involved in the pollen tube pathway in the different types of styles present abundant endoplasmic reticulum, dictyosomes, mitochondria, and ribosomes. These secretory characteristics are related to the secretion where pollen tube grows. This secretion can be represented by the substances either in the canal or in the intercellular matrix or in the cell wall. Most studies suggest that pollen tubes only grow through the secretion of the canal in open styles. However, some species present pollen tubes that penetrate the epithelial cells of the canal, or grow through the middle lamella between these cells and subepithelial cells. In species with a closed style, a pathway is provided by the presence of an extracellular matrix, or by the thickened cell walls of the stylar transmitting tissue. There are reports in some species where pollen tubes can also penetrate the transmitting tissue cells and continue their growth through the cell lumen. In this review, we define subtypes of styles according to the path of the pollen tube. Style types were mapped on an angiosperm phylogenetic tree following the maximum parsimony principle. In line with this, it could be hypothesized that: the open style appeared in the early divergent angiosperms; the closed type of style originated in Asparagales, Poales, and Eudicots; and the semi-closed style appeared in Rosids, Ericales, and Gentianales. The open style seems to have been lost in core Eudicots, with reversions in some Rosids and Asterids.
Collapse
Affiliation(s)
- M M Gotelli
- Cátedra de Botánica General, Depto. de Recursos Naturales y Ambiente, Facultad de Agronomía, Universidad de Buenos Aires, Buenos Aires, Argentina.
- CONICET, Buenos Aires, Argentina.
| | - E C Lattar
- IBONE-UNNE-CONICET, Corrientes, Argentina
- Cátedra de Morfología de Plantas Vasculares, Facultad de Ciencias Agrarias, Universidad Nacional del Nordeste (FCA-UNNE), Corrientes, Argentina
| | - L M Zini
- IBONE-UNNE-CONICET, Corrientes, Argentina
| | - B G Galati
- Cátedra de Botánica General, Depto. de Recursos Naturales y Ambiente, Facultad de Agronomía, Universidad de Buenos Aires, Buenos Aires, Argentina
| |
Collapse
|
5
|
Intercellular communication in Arabidopsis thaliana pollen discovered via AHG3 transcript movement from the vegetative cell to sperm. Proc Natl Acad Sci U S A 2015; 112:13378-83. [PMID: 26466609 DOI: 10.1073/pnas.1510854112] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
An Arabidopsis pollen grain (male gametophyte) consists of three cells: the vegetative cell, which forms the pollen tube, and two sperm cells enclosed within the vegetative cell. It is still unclear if there is intercellular communication between the vegetative cell and the sperm cells. Here we show that ABA-hypersensitive germination3 (AHG3), encoding a protein phosphatase, is specifically transcribed in the vegetative cell but predominantly translated in sperm cells. We used a series of deletion constructs and promoter exchanges to document transport of AHG3 transcripts from the vegetative cell to sperm and showed that their transport requires sequences in both the 5' UTR and the coding region. Thus, in addition its known role in transporting sperm during pollen tube growth, the vegetative cell also contributes transcripts to the sperm cells.
Collapse
|
6
|
Cresti M, Van Went JL, Willemse MTM, Pacini E. FIBROUS MASSES AND CELL AND NUCLEUS MOVEMENT IN THE POLLEN TUBE OF PETUNIA HYBRIDA. ACTA ACUST UNITED AC 2015. [DOI: 10.1111/j.1438-8677.1976.tb01076.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Affiliation(s)
- M. Cresti
- Department of Botany; University of Siena; Italy
| | - J. L. Van Went
- Department of Botany; Agricultural University of Wageningen; The Netherlands
| | - M. T. M. Willemse
- Department of Botany; Agricultural University of Wageningen; The Netherlands
| | - E. Pacini
- Department of Botany; University of Siena; Italy
| |
Collapse
|
7
|
McCue AD, Cresti M, Feijó JA, Slotkin RK. Cytoplasmic connection of sperm cells to the pollen vegetative cell nucleus: potential roles of the male germ unit revisited. JOURNAL OF EXPERIMENTAL BOTANY 2011; 62:1621-31. [PMID: 21357775 DOI: 10.1093/jxb/err032] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
The male germ cells of angiosperm plants are neither free-living nor flagellated and therefore are dependent on the unique structure of the pollen grain for fertilization. During angiosperm male gametogenesis, an asymmetric mitotic division produces the generative cell, which is completely enclosed within the cytoplasm of the larger pollen grain vegetative cell. Mitotic division of the generative cell generates two sperm cells that remain connected by a common extracellular matrix with potential intercellular connections. In addition, one sperm cell has a cytoplasmic projection in contact with the vegetative cell nucleus. The shared extracellular matrix of the two sperm cells and the physical association of one sperm cell to the vegetative cell nucleus forms a linkage of all the genetic material in the pollen grain, termed the male germ unit. Found in species representing both the monocot and eudicot lineages, the cytoplasmic projection is formed by vesicle formation and microtubule elongation shortly after the formation of the generative cell and tethers the male germ unit until just prior to fertilization. The cytoplasmic projection plays a structural role in linking the male germ unit, but potentially plays other important roles. Recently, it has been speculated that the cytoplasmic projection and the male germ unit may facilitate communication between the somatic vegetative cell nucleus and the germinal sperm cells, via RNA and/or protein transport. This review focuses on the nature of the sperm cell cytoplasmic projection and the potential communicative function of the male germ unit.
Collapse
Affiliation(s)
- Andrea D McCue
- Department of Molecular Genetics, The Ohio State University, Columbus, OH 43210, USA
| | | | | | | |
Collapse
|
8
|
Cytoskeleton and Cytoplasmic Organization of Pollen and Pollen Tubes. INTERNATIONAL REVIEW OF CYTOLOGY 1992. [DOI: 10.1016/s0074-7696(08)61094-3] [Citation(s) in RCA: 109] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
|
9
|
Mogensen HL. The Male Germ Unit: Concept, Composition, and Significance. INTERNATIONAL REVIEW OF CYTOLOGY 1992. [DOI: 10.1016/s0074-7696(08)61095-5] [Citation(s) in RCA: 60] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
|
10
|
Kandasamy MK, Kappler R, Kristen U. Plasmatubules in the pollen tubes of Nicotiana sylvestris. PLANTA 1988; 173:35-41. [PMID: 24226176 DOI: 10.1007/bf00394484] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/1987] [Accepted: 08/06/1987] [Indexed: 06/02/2023]
Abstract
Ultrastructural studies of the pollen tubes of Nicotiana sylvestris grown in the pistil revealed an extensive development of plasmatubules formed by evaginations of the plasma membrane. The plasmatubules occurred as twisted tubular structures in the periplasmic space along the tube wall and, in cross section, exhibited circular profiles with an outer diameter of 28±4 nm. They were also seen in deep, pocket-like invaginations of the plasma membrane and in this case the profiles had an outer diameter of 34±8 nm. In the pocket-like invaginations they were partially branched and often closely packed to form groups with obvious patterns. The enlargement of the plasma-membrane area resulting from plasmatubules formed along the tube wall was about six-to tenfold. Pollen tubes grown in vitro exhibited poorly developed plasmatubules. It is suggested that the large extension of the plasma membrane could enhance the uptake of nutrients, and thus might be responsible for the comparatively fast growth of pollen tubes in the pistil. Moreover, it is also assumed that the turnover rate of the Golgi apparatus must be higher in pollen tubes growing in vivo than in vitro, in order to provide a sufficient amount of membrane for the formation of the plasma membrane with its tubular modifications.
Collapse
Affiliation(s)
- M K Kandasamy
- Institut für Allgemeine Botanik, Universität Hamburg, Ohnhorststrasse 18, D-2000, Hamburg 52, Federal Republic of Germany
| | | | | |
Collapse
|
11
|
Kroh M, Knuiman B. Exocytosis in non-plasmolyzed and plasmolyzed tobacco pollen tubes : A freeze-fracture study. PLANTA 1985; 166:287-299. [PMID: 24241509 DOI: 10.1007/bf00401164] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/1985] [Accepted: 04/17/1985] [Indexed: 06/02/2023]
Abstract
Exocytosis occurring during deposition of secondary wall material was studied by freeze-fracturing ultrarapidly frozen non-plasmolyzed and plasmolyzed tobacco pollen tubes. The secondary wall of tobacco pollen tubes shows a random orientation of microfibrils. This was observed directly on fractures through the tube wall and indirectly as imprints of microfibrils on fracture faces of the plasma membrane of non-plasmolyzed tubes. About half of the plasmatic fracture faces from non-plasmolyzed and plasmolyzed pollen tubes carried hexagonal arrays of intramembraneous particles in between randomly distributed particles. Deposition of secondary wall material was often accompanied by an undulated plasma membrane and the presence of membrane-bound vesicles in invaginations of the plasma membrane, between the plasma membrane and secondary wall and-especially in plasmolyzed tubes-within the secondary wall of tube flanks and wall cap. The findings are discussed in connection with published schemes of membrane behaviour during exocytosis.
Collapse
Affiliation(s)
- M Kroh
- Department of Botany, University of Nijmegen, Toernooiveld, NL-6525 ED, Nijmegen, The Netherlands
| | | |
Collapse
|
12
|
Zhou G, Weng J, Zeng Y, Huang J, Qian S, Liu G. Introduction of exogenous DNA into cotton embryos. Methods Enzymol 1983; 101:433-81. [PMID: 6577258 DOI: 10.1016/0076-6879(83)01032-0] [Citation(s) in RCA: 96] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
|
13
|
|
14
|
|
15
|
Kroh M, Knuiman B. Ultrastructure of cell wall and plugs of tobacco pollen tubes after chemical extraction of polysaccharides. PLANTA 1982; 154:241-250. [PMID: 24276067 DOI: 10.1007/bf00387870] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/21/1981] [Accepted: 12/17/1981] [Indexed: 06/02/2023]
Abstract
Tobacco pollen tubes grown in vitro and from pollinated tobacco styles were treated by chemical solvents to remove one or more of the following polysaccharides from the tube walls: pectin (ethylenediamine tetraacetic acid); hemicellulose (alkali); callose (alkali; potassium hypochlorite); cellulose (cuprammonium); and all polysaccharides with exception of cellulose (H2O2/glacial acetic acid). Both the inner tube wall, which we had regarded as the secondary wall, and the plugs contained, in addition to callose, microfibrils of cellulose and "non-cellulosic" microfibrils that had "pectin-like" properties. When using the expressions callosic or callose layer and callose plugs in reference to pollen tubes, one should realize that they do not imply the exclusive presence of callose in the inner tube wall layer and its localized thickenings.
Collapse
Affiliation(s)
- M Kroh
- Botanisch Laboratorium, Katholieke Universiteit, Toernooiveld, NL-6525 ED, Nijmegen, The Netherlands
| | | |
Collapse
|
16
|
Uwate WJ, Lin J. Cytological zonation of Prunus avium L. pollen tubes in vivo. JOURNAL OF ULTRASTRUCTURE RESEARCH 1980; 71:173-84. [PMID: 7381990 DOI: 10.1016/s0022-5320(80)90105-7] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
|
17
|
Cresti M, van Went JL. Callose deposition and plug formation in Petunia pollen tubes in situ. PLANTA 1976; 133:35-40. [PMID: 24425176 DOI: 10.1007/bf00386003] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/06/1976] [Accepted: 08/04/1976] [Indexed: 05/08/2023]
Abstract
In Petunia pollen tubes growing in the style there appear to be two ways of callose deposition. The first one is callose deposition outside the plasma membrane as a distinct layer closely appressed to the cell wall. The second one is callose deposition within the cytoplasm as distinct callose grains, leading to the formation of callose plugs. This second way is accompanied by a characteristic ultrastructure of the cytoplasm, namely strong electron-density of the plasma matrix, partial absence of the plasma membrane and the absence of plastids and dictyosomes. For both ways of callose deposition a mechanism is proposed and the function of callose plugs is discussed.
Collapse
Affiliation(s)
- M Cresti
- Department of Botany, Agricultural University, Wageningen, The Netherlands
| | | |
Collapse
|
18
|
Morré DJ, VanderWoude WJ. Origin and growth of cell surface components. THE ... SYMPOSIUM. SOCIETY FOR DEVELOPMENTAL BIOLOGY. SYMPOSIUM 1974; 30:81-111. [PMID: 4601201 DOI: 10.1016/b978-0-12-612973-1.50010-3] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
|
19
|
Fraser TW, Gunning BE. Ultrastructure of the hairs of the filamentous green alga Bulbochaete hiloensis (Nordst.) Tiffany: an apoplastidic plant cell with a well developed Golgi apparatus. PLANTA 1973; 113:1-19. [PMID: 24468841 DOI: 10.1007/bf00385184] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/1973] [Indexed: 06/03/2023]
Abstract
Bulbochaete hiloensis is a filamentous green alga in the Oedogoniales. It possesses colourless hair cells, the ultrastructure and development of which are unusual in several respects: (1) The initial wall of the hair cell is formed by eversion of a pre-formed pad of cell wall material (Cook, 1962). (2) The hair cells are apoplastidic, even lacking colourless remnants of plastid material. (3) A nucleolus is lacking from young and mature hair cell nuclei, though it is not known whether one is present in the earliest stages. (4) Despite the absence of chloroplasts, starch reserves, and a nucleolus, the ultrastructure of the cytoplasm is characteristic of intensive granulocrine secretory activity. Massed cisternae of rough endoplasmic reticulum and numerous dictyosomes, together with associated transitional and secretory vesicles, are present. Substrate for the biosyntheses in these systems must enter the hairs via plasmodesmata, which exist in the basal wall. The product is probably a mucilage, exported to the exterior through a system of pores which pierce the outer wall of the hair. (5) Microtubules lie in the hair, and in its bulbous base, where some may be interpreted as having a role in anchoring the nucleus. (6) The significance of the apoplastidic and anucleolate condition is discussed.
Collapse
Affiliation(s)
- T W Fraser
- Department of Botany, Queen's University, BT7 1NN, Belfast, N. Ireland
| | | |
Collapse
|
20
|
Contribution à l’Étude cyto-physiologique du stigmate: I. Les étapes observées durant les processus glandulaires chez une Oleaceae: Forsythia intermedia Zabel. ACTA ACUST UNITED AC 1973. [DOI: 10.1016/s0044-328x(73)80149-7] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
|
21
|
|
22
|
Parthasarathy MV, Mühlethaler K. Cytoplasmic microfilaments in plant cells. JOURNAL OF ULTRASTRUCTURE RESEARCH 1972; 38:46-62. [PMID: 4333275 DOI: 10.1016/s0022-5320(72)90083-4] [Citation(s) in RCA: 62] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
|
23
|
Jensen WA, Fisher DB. Cotton embryogenesis: The tissues of the stigma and style and their relation to the pollen tube. PLANTA 1968; 84:97-121. [PMID: 24515374 DOI: 10.1007/bf00398389] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/12/1968] [Indexed: 06/03/2023]
Abstract
The stigma of cotton (Gossypium hirsutum) is covered by unicellular hairs. The cytoplasm of these hairs degenerates before the stigma becomes receptive. The vacuole remains intact, but the hair cytoplasm becomes a mass of dark, amorphous material with only a few organelles still being visible. The rest of the stigma consists of thin-walled parenchyma cells with large vacuoles and large amounts of starch. The cells of the style are differentiated into a uniseriate epidermis, vascular tissue, a cortex of thin-walled, vacuolate parenchyma cells, and the transmitting tissue. This latter tissue occupies the center of the style and consists of thick-walled cells with few vacuoles. The cells are rich in starch, ribosomes, endoplasmic reticulum and dictyosomes. They also contain deposits of calcium salts in the form of druses. The pollen germinates on the stigmatic hairs, grows down the outside of the hair and between the cells of the stigma to the transmitting tissue of the style. There the tubes grow between the walls of the cells but do not enter the cells themselves. Some transmitting cells adjacent to the pollen tube degenerate after the tip of the pollen tube has grown past them. However, not all degenerate, and those that do show no fixed spatial relationship to one another. The cells which do degenerate follow a characteristic pattern of breakdown. No ultrastructural evidence was found for the secretion of hydrolytic enzymes by the pollen tube.
Collapse
Affiliation(s)
- W A Jensen
- Department of Botany, University of California, Berkeley
| | | |
Collapse
|
24
|
Fisher DB, Jensen WA. Cotton embryogenesis: The identification, as nuclei, of the X-bodies in the degenerated synergid. PLANTA 1968; 84:122-133. [PMID: 24515375 DOI: 10.1007/bf00398390] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/16/1968] [Indexed: 06/03/2023]
Abstract
The "x-bodies" present in the degenerated synergid of cotton were shown to contain DNA by specific staining with Azure B, the Feulgen procedure, and by labelling with (3)H-actinomycin D. They are identified on a morphological basis as the degenerated vegetative nucleus of the pollen tube which is always found in the degenerated synergid tip, and as the degenerated synergid nucleus, which is found about halfway up the degenerated synergid near the side towards the central cell. The positions of these nuclei and of some other structures have been used to construct a tentative description of some of the events occurring during pollen-tube discharge and movement of the sperm through the synergid. Some observations which may indicate some of the factors involved in interaction of the synergid and pollen tube cytoplasm are discussed.
Collapse
Affiliation(s)
- D B Fisher
- Department of Botany, University of California, Berkeley
| | | |
Collapse
|