Microspore Cytoplasm Research Articles

The Effects of Sodium 2,3-Dichloroisobutyrate on Microsporogenesis and Fruit Set inLycopersicon esculentumMill

Histological and histochemical examinations of sodium 2,3-dichloroisobutyrate (DCB) treated tomato floral buds at various stages of development showed that I)CB affected the development of microspores and tapetal cells. DCB at 0-075 and 0-15% resulted in the formation of uninucleate microspores, absence of microspore starch, retardation of exine formation, degeneration of microspore cytoplasm, and a delay in the breakdown of the tapetum. Embryo sac development was unaffected by DCB. The interference of carbohydrate metabolism by DCB was indicated. Reduction of fruit set by DCB was caused by abnormal or lack of pollen formation.

A Cytochemical Study of Anther Development in <i>Iphigenia pallida</i> Bak

Microsporogenesis and anther development in Iphigenia pallida Bak. were investigated using the cytochemical staining methods for the demonstration of insoluble polysaccharides, RNA, proteins and DNA. The insoluble polysaccharides and proteins are at low level in sporogenous tissue and PMCs. Both of them gradually increase in dyads, tetrads and microspores. Large number of starch grains appearing in the-vegetative cell of the young 2-celled pollen grain disintegrate and form densely PAS positive cytoplasm in the shedding pollen grain. A protein and PAS positive layer deposited internally around the PMCs at the beginning of meiosis, disappears prior to the separation of microspores from the tetrads. The cytoplasm of PMCs, dyads, tetrads, microspores and pollen grains is rich in RNA. The nucleus of the generative cell is more Feulgen positive than that of the vegetative cell. The tapetal cells have rich RNA and considerable concentration of proteins as well as polysaccharides. The fibrous endothecial thickenings are lignified.

Nucleo-Cytoplasmic Interaction following Meiosis in the Young Microspores of Lilium Longiflorum; Events at the Nuclear Envelope

Abstract Interaction between the nucleus and the cytoplasm of young microspores of Lilium longiflorum has been investigated during the tetrad and prevacuolate stages of microsporogenesis. Two types of membrane-bound inclusions become associated with the nucleus over this period, small vesicles invested by a single unit membrane profile and larger bodies, about 0.5 μm in diameter, with a double bounding membrane. The small vesicles contain an evenly staining matrix and are probably released from the perinuclear space into the cytoplasm, but the nature and fate of the larger bodies, which contain a granular matrix resembling nucleoprotein, is not evident. Their content suggests that they are formed in the nucleus but their strong similarity to double membraned inclusions, present in the cells since the mid-prophase stage, calls for an alternative interpretation. Ribbons or sheets of membrane, resembling elements of the ‘annulate lamellae’ characteristic of certain animal cells, are formed at the nuclear env...

Ultrastructure of the postmeiotic nuclear envelope in microspores of Podocarpus macrophyllus

Nuclei of haploid microspore tetrads of Podocarpus macrophyllus show extensive invaginations of the nuclear envelope. Evaginations of the outer nuclear membrane form vesicles as well as direct channels to the plasmalemma through the microspore cytoplasm. Such activity of the nuclear envelope and its outer membrane coincide with the deposition of exine layers of the microspore wall. It is suggested that the greatly increased surface area of the nuclear envelope formed by the invaginations, the formation and blebbing off of vesicles from the outer nuclear membrane, the presence of channels connecting the nuclear envelope to the plasmalemma, and the association of chromatin-like material within the nucleus with the nuclear envelope invaginations are related to the synthesis and transport of exine precursor substances and ribonucleoproteins.

POLLEN EXINE DEPOSITION: A CLUE TO ITS CONTROL

The development of Linum microspores with very incomplete chromosome complements into miniature pollen grains with essentially normal exine and germ pores indicates that genetic control for exine deposition rests, not with the haploid genome, but with the spore cytoplasm. A close correlation between the amount of exine laid down with amount of cytoplasm in the spore also suggests that control of exine deposition is more closely related to the microspore cytoplasm rather than to the enclosed genome.

The ultrastructure and ontogeny of pollen in Helleborus foetidus L. 3. The formation of the pollen grain wall.

ABSTRACT The first recognizable elements of the pollen grain wall of Helleborus foetidus are initiated in the cellulosic primexine which is formed immediately outside the microspore cytoplasm while the pollen grains are still in the tetrad configuration and enveloped in a thick layer of callose. Elements of the primexine give rise to the precursors of the rod-like bacula of the mature exine. The bacula increase in electron density due to the rapid deposition of sporopollenin, and begin to expand laterally at the outer side to form the tectum. There follows a lateral expansion on the inner side to form the foot-layer. Further deposition of sporopollenin is continued and all elements of the pollen grain wall expand outwards and laterally as the pollen grain enlarges. The enveloping callose disappears and the pollen grains are free in the thecal cavity. A secondary exine is deposited below the primary exine, particularly around the furrows. Initially this process involves a number of thin electron-transparent lines or lamellae about 4 nm thick that appear to arise from the cytoplasm and provide a locus around which sporopollenin is deposited. As the deposition proceeds, the lamellae thicken and finally merge with each other to form the secondary exine. No sign of the lamellae can be seen in the mature pollen grain wall. Towards the end of secondary exine formation the deposition of sporopollenin does not appear to be centred on thin lamellae, but appears as small granules which gradually coalesce. The secondary exine remains discontinuous in the region of the furrow, but becomes consolidated in the inter-furrow regions. As the pollen grain matures the sporopollenin, which is electron-dense when initially deposited, becomes progressively less so. The final stage in development is the deposition of the cellulosic intine, which forms inside the secondary exine and is associated with increased dictyosome activity and randomly oriented microtubules.

Cyto-histological studies on the male sterility of Satsuma orange (Citrus unshiu MARC.)

In order to determine the cause of pollen abortion in male-sterile Satsuma orange, certain morphological and cyto-histological studies with anthers were undertaken as compared with the male-fertile Buntan and Natsudaidai. Cyto-histological observations on Satsuma orange treated with temperature and IAA were also carried out.1. In the early stage of anther development, meiosis and microspore formation were quite similar in fertile and sterile species of Citrus.2. Tapetum in fertile species started to degenerate soon after the liberation of microspores from the wall of tetrads and almost completely degenerated during the disappearance of vacuoles from the cytoplasm of microspore.3. Tapetum in sterile Satsuma orange occassionally showed an extraordinary development of large vacuole at the vacuole appearing stage and completely disintegrated at the vacuole enlarging stage of microspore. However, tapetum which remained cellular without large vacuoles persisted unusually long and degenerated at the vacuole enlarging stage of microspore. So it may be suggested that the tapetum in sterile Satsuma orange can not play normal nutritive role and supplies less nutrients to the developing pollens.4. Abnormal behavior of tapetum in Satsuma orange could be recovered partially and the pollen fertility could be increased by temperature (at 20°C minimum temperature) and IAA treatments (500 ppm) to those plants growing under unfavorable temperature condition.

Cell Growth and Nucleic Acids in the Pollen of Rhoeo Discolor

1. A cytoplasmic basophily, which is removed when cells are treated with a ribonuclease enzyme, has been used as a means of identifying ribose nucleic acids and of following their distribution in the cells of the anthers of Rhoeo, and to a lesser extent in the pistil of the flower. Rapid cell growth is invariably accompanied by large amounts of ribonucleic acid in the cytoplasm and heavy deposits of chromatin in nuclei. 2. In young anthers the cytoplasm of both tapetal and sporogenous tissues is extremely rich in ribonucleic acid. As the pollen mother cells prepare for the meiotic divisions, the ribonucleic acid disappears from the cytoplasm, presumably being passed into the nucleus and changed into desoxyribose nucleic acid (chromatin). Initially the cytoplasm of microspores is devoid of basophilic material, but as they grow into mature pollen grains large amounts of ribonucleic acids accumulate in the cytoplasm. 3. The growth of tapetal cells is accompanied by one or more endomitotic nuclear division cycles. The tapetal cells, which are rich in cytoplasmic nucleic acid at the time of cytolysis, are the source of the ribonucleic acid which accumulates in the maturing pollen grains. 4. There is a similarity between microspore growth at the expense of tapetal cells and growth of oocytes in animals through the agency of nurse cells. Large amounts of ribonucleic acid are stored in mature pollen grains and used in the extremely rapid synthesis of new materials which accompanies pollen tube growth.