I.K. Vasil

Bio: I.K. Vasil is an academic researcher from University of Florida. The author has an hindex of 1, co-authored 1 publications receiving 123 citations.

Physiology and cytology of anther developmeent

Abstract: An understanding of the morphology and physiology of the angiosperm flower and its component parts is of considerable importance in programmes for the development of new agricultural and horticultural varieties, in the elucidation of various hereditary processes and their control, and for an insight into various problems of cell biology, cell division and the physiology and control of reproduction. A great deal of work has been produced since the days of Amici (1824) and Hofmeister (I 848) regarding the developmental aspects of reproductive parts of the angiosperm flower, fertilization and the development of endosperm and embryo leading to the formation of a mature seed. Much of this work is summarized in the books by Schnarf (1929, 1931), and Maheshwari (1950, 1963). Unfortunately, very little effort, if any, has been made to understand the physiology of the reproductive organs of the angiosperm flower, particularly the chemical and cytochemical changes involved in the initiation and control of these processes (Vasil, 1965). The ultrastructural studies made by Rosen, Gawlik, Dashek & Siegesmung (1964) and by Sassen (1964) of the pollen tubes, by Heslop-Harrison (1962, 1963b, 1964) of the developing anther, and by Jensen (1963) of the embryo sac, fertilization and embryogenesis are, therefore, especially welcome. Some work has also been done recently on the histochemical and biochemical aspects of reproduction in higher plants (Linskens, 1 9 6 4 ~ ) . In order to limit the field of discussion and because of my own interest and familiarity with the angiosperm anther, this article is restricted to a summary, discussion and evaluation of our knowledge of the physiology and cytology of anther development, particularly the role of tapetum and the development of pollen grains." Discussion of the various aspects of the physiology of pollen grains after dehiscence is excluded as

Different Temporal and Spatial Gene Expression Patterns Occur during Anther Development.

Abstract: We studied the temporal and spatial regulation of three mRNA sequence sets that are present exclusively, or at elevated levels, in the tobacco anther. One mRNA set accumulates in the tapetum and decays as the tapetum degenerates later in anther development. The second mRNA set accumulates after the tapetal-specific mRNAs, is localized within the stomium and connective, and also decays as these cell types degenerate during anther maturation. The third mRNA sequence set persists throughout anther development and is localized within most anther tissues. A tapetal-specific gene, designated as TA29, was isolated from a tobacco genome library. Runoff transcription studies and experiments with chimeric [beta]-glucuronidase and diphtheria toxin A-chain genes showed that the TA29 gene is regulated primarily at the transcriptional level and that a 122-base pair 5[prime] region can program the tapetal-specific expression pattern. Destruction of the tapetum by the cytotoxic gene had no effect on the differentiation and/or function of surrounding sporophytic tissues but led to the production of male-sterile plants. Together, our studies show that several independent gene expression programs occur during anther development and that these programs correlate with the differentiated state of specific anther cell types.

Anatomy and cytology of microsporogenesis in cytoplasmic male sterile angiosperms

Abstract: The studies reviewed date from 1925 to 1972 and contain extensive anatomical and cytological information all too often incomplete or vague. The terminology for microsporogenesis used is also often sketchy or inaccurate. An attempt therefore has been made to establish some consistency in microsporogenesis terminology via Fig. 1 and the tables. We have given, in convenient tabular form, CMS taxa, investigators, and the morphological and cytological events reported. By referring to a few keys, the reader can gain further insight into specific CMS taxa and can easily compare studies The work of Laser (1972) is only part of a more extensive investigation of the anatomy, cytology, and histochemistry of N and CMSSorghum bicolor (Laser, unpub.). To date, only a small part is published (Christensen, Horner & Lersten, 1972), but when completed it probably will be the most complete study to date of these aspects of CMS. Hoefert (1969a, 1969b, 1971) has investigated only normal microsporogenesis so far, but her intention also is to make a detailed descriptive comparison of N and CMS development. Such comparative electron microscope studies will be needed to help answer questions raised in the Introduction of this review. Concerning the events within microspores at the beginning of abortion, for example, there is complete ignorance of what organelle shows the first sign of disintegration or whether there is a definite sequence or simply a simultaneous collapse. The answer to this question could yield valuable clues to the direct cause of abortion Looking at the existing published studies and taking into account numerous examples of questionable technique and interpretation, we conclude that abortion has been shown to occur at almost every point in development, and that probably more than one mechanism is involved

Anther culture for haploid and doubled haploid production

Abstract: Haploids are plants with a gametophytic chromosome number and doubled haploids are haploids that have undergone chromosome duplication. The production of haploids and doubled haploids (DHs) through gametic embryogenesis allows a single-step development of complete homozygous lines from heterozygous parents, shortening the time required to produce homozygous plants in comparison with the conventional breeding methods that employ several generations of selfing. The production of haploids and DHs provides a particularly attractive biotechnological tool, and the development of haploidy technology and protocols to produce homozygous plants has had a significant impact on agricultural systems. Nowadays, these biotechnologies represent an integral part of the breeding programmes of many agronomically important crops. There are several available methods to obtain haploids and DHs, of which in vitro anther or isolated microspore culture are the most effective and widely used. This review article deals with the current status of knowledge on the production of haploids and DHs through pollen embryogenesis and, in particular, anther culture.