Cytochemical and ultrastructural peculiarities of embryogenic pollen grains and of young androgenic embryos in Datura innoxia

1978 ◽  
Vol 56 (7) ◽  
pp. 805-817 ◽  
Author(s):  
Brigitte S. Sangwan-Norreel
Keyword(s):  
Nuclear Organization ◽  
Pollen Grains ◽  
Datura Innoxia ◽  
Flower Bud ◽  
Ultrastructural Studies ◽  
Embryo Formation ◽  
Embryogenic Pollen ◽  
Pollen Cell ◽  
Androgenic Embryos ◽  
Generative Nuclei

Cytochemical and ultrastructural studies of androgenic embryogenesis in Datura innoxia Mill. have been performed on (a) uncultured pollen grains collected at the stage favourable to embryo formation, i.e., at the time just before and just after the first haploid mitosis of the microspore nucleus (flower bud length of 4–5 cm); and (b) pollen grains and young androgenic embryos picked from the medium after 5, 9, and 11 days in culture.Only features presumed to play a role in the induction of androgenic embryogenesis are described.The phase of pollen development favourable to embryogenesis is very short but it involves important changes in the cytochemical features and in the ultrastructure of pollen grains. The changes are particularly clear in RNA and nucleohistone stainabilities and in the number and activity of the cytoplasmic organelles.It is suggested that it is not one particular metabolic or ultrastructural state of the cell which is responsible for the embryogenesis competence but that it is the fact that the changes occur which is important. Pollen which is in an unstable ultrastructural and metabolic state will be more sensitive to external stimuli.The study of very young androgenic embryos shows several features which are presumed to be responsible for the induction of embryogenesis: (a) Changes in cytoplasmic distribution and in nuclear organization consecutive to the first haploid mitosis in the microspore. These modifications sometimes lead to the formation of two equal pollen nuclei instead of differing vegetative and generative nuclei. The two identical nuclei are located in two equal-sized cells or in a single pollen cell. (b) Variations in pollen RNA content and in the organization of the endoplasmic reticulum which are related to changes in the pollen metabolism. (c) Modifications of the plasmalemma within pollen grains and of the cell wall surrounding the pollen grains. Such modifications are presumed to cause variations in the intercellular exchanges as well as in the exchanges between pollen and medium.

scholarly journals Analysis of the reproduction mode in Psidium spp. using the pollen:ovule ratio

2020 ◽  
Vol 43 ◽  
pp. e44062
Author(s):  
Maria Lorraine Fonseca Oliveira ◽  
Telma Nair Santana Pereira ◽  
Rodrigo Miranda Barbosa ◽  
Alexandre Pio Viana
Keyword(s):  
Pollen Grains ◽  
Flower Bud ◽  
Reproduction Mode ◽  
Reproductive Characteristics ◽  
Reproduction Strategy ◽  
Pollen:Ovule Ratio ◽  
Floral Bud

This research aimed to explore the reproductive characteristics of three species of Psidium (P. guajava L., P. cattleyanum Sabine, and P. guineense Sw.) and estimate a probable reproduction strategy based on the pollen:ovule (P:O) methodology. The number of pollen grains per floral bud (NGPB), number of pollen grains per anther (NGPA), number of anthers per flower bud (NAB), number of ovules per flower bud (NOB), and the P:O ratio of each species were estimated. All species had a P:O ratio over 2,000 and were classified as xenogamous. P.guajava presented the highest values for all characteristics evaluated, with the NGPB at 3,777,519, the NOB at 584.50 and a P:O ratio of 6,462.82. Similarly, P. cattleyanum had a P:O ratio of 5,649.89 (NGPB 762,736 and NOB 135). However, P. guineense was considered facultative xenogamous, with P:O of 2,085.75, the NGPB at 741,484 and the NOB at 355.50. Thus, it was concluded that the studied species have a preference for allogamy and require many pollen grains to fertilize each ovule, demonstrating that the transfer of pollen to the stigma is not very specialized.

scholarly journals Anatomical Characteristics of Petalized Anther Abortion in Male Sterile Camellia oleifera Plants

2021 ◽  
pp. 1-13
Author(s):  
Yang Hu ◽  
Chao Gao ◽  
Quanen Deng ◽  
Jie Qiu ◽  
Hongli Wei ◽  
...  
Keyword(s):  
Germination Rate ◽  
Pollen Grains ◽  
Relative Activity ◽  
Control Group ◽  
Camellia Oleifera ◽  
Male Sterile ◽  
Flower Bud ◽  
Triphenyltetrazolium Chloride ◽  
Pollen Sacs

Petalized anther abortion is an important characteristic of male sterility in plants. The male sterile plants (HB-21) evincing petalized anther abortion previously discovered in a clone population of the Camellia oleifera cultivar Huashuo by our research group were selected as the experimental material in this study. Using plant microscopy and anatomic methods and given the correspondence between external morphology and internal structure, we studied the anatomic characteristics of petalized anther abortion (with a fertile plant as the control group) in various stages, from flower bud differentiation to anther maturity, in hopes of providing a theoretical basis for research on and applications of male sterile C. oleifera plants, a new method for the selection of male sterile C. oleifera cultivars, and improvements in the yield and quality of C. oleifera. In this study, the development of anthers in C. oleifera was divided into 14 stages. Petalized anther abortion in male sterile plants was mainly initiated in the second stage (the stage of sporogenous cells). Either the petalized upper anther parts did not form pollen sacs, or the entire anthers did not form pollen sacs. The lower parts of some anthers could form deformed pollen sacs and develop, and these anthers could be roughly divided into two types: fully and partially petalized anthers. Abnormal callose and the premature degradation of the tapetum occurred in the pollen sacs formed by partially petalized anthers during the development process, resulting in the absence of inclusions in the pollen grains formed. Small quantities of mature pollen grains withered inward from the germinal furrows, exhibiting obvious abortion characteristics. The relative in vitro germination rate of the pollen produced by the partially petalized anthers of sterile plants was 11.20%, and the relative activity of triphenyltetrazolium chloride was 3.24%, while the fully petalized anthers did not generate pollen grains. Either the petalized anthers in male sterile plants did not produce pollen, or the vitality of the small amounts of pollen produced by sterile plants was very low compared with that of fertile plants. Such male sterile plants could be used to select correct clones and have good prospects for application in production.

Studies on heteromorphic self-incompatibility systems: the cytochemistry and ultrastructure of the tapetum of Primula obconica

1981 ◽  
Vol 50 (1) ◽  
pp. 419-431
Author(s):  
V.A. Stevens ◽  
B.G. Murray
Keyword(s):  
Tapetal Cell ◽  
Pollen Grains ◽  
Anther Wall ◽  
Cell Periphery ◽  
Self Incompatibility ◽  
Fibrous Layer ◽  
Ultrastructural Studies ◽  
Incompatibility System ◽  
Secretory Type ◽  
Main Components

This paper describes the cytochemistry and ultrastructure of the developing tapetum in Primula obconica, a plant with a heteromorphic, sporophytic self-incompatibility system. The tapetum is of the secretory type and cytochemical tests have shown that when it breaks down proteinaceous (esterase) and lipidic components are deposited on the developing pollen grains. Acid phosphatase, a marker of gametophytic enzyme activity, is confined to the cytoplasm and intine of the developing pollen. Ultrastructural studies show that prior to its dissolution the tapetum undergoes a number of changes. In the early stages of development the tapetum is rich in ribosomes and rough endoplasmic reticulum, but following the breakdown of the tapetal cell wall the main components of the cytoplasm are densely staining spherical bodies surrounded by ribosomes and orbicular bodies, which appear to be confined to the cell periphery. As the cells break down, rod-like fibrils can be seen amongst the degenerate organelles and within the bacular cavities of the pollen. On dehiscence the pollen has a lipidic coating in addition to the fibrillar material in the pollen wall and the remnants of the tapetum can be seen adhering to the fibrous layer of the anther wall. Thus the mature, binucleate pollen of P. obconica is demonstrated to carry wall materials of sporophytic origin.

scholarly journals Preferential reproduction mode of hermaphrodite papaya plant (Carica papaya L; Caricaceae)

2009 ◽  
Vol 31 (1) ◽  
pp. 182-189 ◽  
Author(s):  
Pedro Corrêa Damasceno junior ◽  
Telma Nair Santana Pereira ◽  
Messias Gonzaga Pereira ◽  
Francisco Filho da Silva ◽  
Margarete de Magalhães Souza ◽  
...  
Keyword(s):  
Reproductive System ◽  
Pollen Grains ◽  
Pollen Grain ◽  
Acetate Solution ◽  
Flower Bud ◽  
Stigma Receptivity ◽  
Flower Opening ◽  
Reproduction Mode ◽  
Pollen:Ovule Ratio

This research was done to study the reproductive system of papaya hermaphrodite plant based on the histochemical nature of pollen grain, stigma receptivity, in vivo pollen grain germination and pollen:ovule ratio. In the histochemical analysis, pollen grains were stained by using Sudan IV and I2KI solution ; the stigma receptivity was assessed by alpha-naphthtyl acetate solution in closed and opened flowers. Pollen germination and pollen tube growing were examined in flower buds near anthesis with 0.1% aniline blue. To estimate the pollen:ovule ratio , anthers from each flower bud were dissected and all pollen grains were counted; ovules were dissected from ovaries and were counted under stereomicroscope. The results indicated that papaya pollen grains are of lipidic nature; the stigmas were receptive before the opening and until 48 hours after opening; the pollen grains germinated and emitted polinic tube before flower opening and the pollen:ovule ratio indicated the predominance of autogamous reproductive system. These results indicate that hermaphrodite papaya trees is preferentially of optional autogamous with cleistogamy.

scholarly journals Gametogenesis and pollination processes in Ornithopus pinnatus (Mili.) Druce in reference to flower bud development

2015 ◽  
Vol 44 (2) ◽  
pp. 203-215 ◽  
Author(s):  
Wanda Wojciechowska
Keyword(s):  
Pollen Grains ◽  
Germination Capacity ◽  
Flower Bud ◽  
Bud Development ◽  
Flower Bud Development

It was found, that in <i>Ornithopus pinnatus</i> the development of microspores and pollen grains is not simultaneous in the two stamen whorls and it precedes the development of the embryo sacs. The pollen grains attain the highest germination capacity before the bud is open, when the embryo sacs arę mature.

scholarly journals Morbid mitosis and the activity of inert chromosomes in sorghum

1941 ◽  
Vol 130 (859) ◽  
pp. 127-150 ◽  
Keyword(s):  
Structural Changes ◽  
Wild Population ◽  
Specific Effect ◽  
Pollen Grains ◽  
Variable Number ◽  
Pollen Grain ◽  
Vegetative Nucleus ◽  
In The Wild ◽  
Primary Division ◽  
Generative Nuclei

Sorghum purpureo-sericeum has five paris of active, A , chromosomes and a variable number of extra, B , chromosomes in equilibrium in the wild population (Janaki-Ammal 1940; and table 7). The B -chromosomes vary in structure within and between plants owing to frequent spontaneous changes, including misdivision of the centromere. One is an iso-chromosome. The B 's are sex-limited so far as that is possible in a plant: they are confined to the germ track owing to loss by lagging elsewhere. They are lost in the radicle before seed ripening and in the shoot tissues as they reach maturity. Only in the anthers and ovaries are they regularly maintained. B -chromosomes pair with one another at meiosis when homologous, and the two arms of the iso-chromosome form chiasmata with one another. Pollen grains of plus plants (with extra B 's) have extra divisions of the vegetative nucleus rapidly following the primary division. The first pollen grain division is delayed by the presence of B -chromosomes. Its course is always normal. At the second division the B 's always pass to the generative pole undivided and so double its dose. When only two generative nuclei are formed, one or both may produce sperm. Three, four or five generative nuclei, however, kill the pollen grain. The extra divisions are thus malignant. The B -chromosomes as usual are heterochromatic. They have an abnormal nucleic acid cycle. Their action on the cells, containing them is non-specific and cumulative, and their apparently specific effect in stimulating mitosis in the pollen grains is possibly due to these being the only cells that contain them whose mitosis and growth are normally limited. Spontaneous structural changes in heterochromatic chromosomes are frequent at mitosis in plants and animals. Such changes could evidently establish malignant propensities in somatic cells by stimulating recurrent mitosis.

Absence of microspore polarity, symmetric divisions and pollen cell fate in Brachiaria decumbens (Gramineae)

Genome ◽  
2003 ◽  
Vol 46 (1) ◽  
pp. 83-88 ◽  
Author(s):  
Roberto Gargione Junqueira Filho ◽  
Andréa Beatriz Mendes-Bonato ◽  
Maria Suely Pagliarini ◽  
Nilton Cesar Pires Bione ◽  
Cacilda Borges do Valle ◽  
...  
Keyword(s):  
Cell Fate ◽  
Nuclear Polarization ◽  
Male Gametophyte ◽  
Chromatin Condensation ◽  
Generative Cell ◽  
Pollen Grains ◽  
Pollen Mitosis ◽  
Male Sterile ◽  
Brachiaria Decumbens ◽  
Pollen Cell

Meiotic division and male gametophyte development were analyzed in one tetraploid (2n = 4x = 36) accession of Brachiaria decumbens cv. Basilisk that showed some pollen sterility. Meiotic process was typical of polyploids in that it consisted of multiple chromosome associations. Precocious chromosome migration to the poles, laggards, and micronucleus formation were abundant in both meiosis I and II and resulted in tetrads with micronuclei. After callose dissolution, microspores were released into the anther locule and had the semblance of being normal. Although each microspore initiated its differentiation by pollen mitosis, in 43.24% of the microspores, nuclear polarization was not observed and the typical hemispherical cell plate was not detected. Division was symmetric and microspores lacked differentiation between the vegetative and the generative cell. Both nuclei were of equal size, presented equal chromatin condensation, and had a spherical shape. After the first pollen mitosis and cytokinesis, each cell underwent a new symmetric mitosis without nuclear polarization. At the end of the second pollen mitosis, four equal nuclei were observed in each pollen grain. After the second cytokinesis, the cells gave rise to four equal-sized pollen grains with a similar tetrad configuration that initially remained together. Sterile pollen grains resulted from abnormal pollen mitosis. This anomaly may be explained by a mutation, probably affecting microtubule cytoskeleton formation. The importance of this male-sterile mutation for Brachiaria breeding programs is discussed.Key words: Brachiaria decumbens, male sterility, pollen mitosis, microspore polarity, symmetric division, pollen cell fate, grasses.

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