Structure of the Male Gametophyte in Gymnosperms

Abstract

Summary Analysis of the morphological nature of the gymnospermous male gametophyte has been based on evidence from fossil gymnosperms, on a comparative survey of living vascular plants, and on ontogeny within the various families of the gymnosperms. Although fossil coniferous and taxad pollen is unknown, the fossil pollen of other gymnosperms is rather uniform in the presence of a layer of parietal cells (presumably an antheridial jacket) which surrounds a central, probably spermatogenous region. The same organization occurs in endosporal gametophytes of lower Tracheophyta of the present day. Reduction in the number of vegetative prothallial cells appears to have occurred early in gymnosperm evolution, so that the male gametophyte may be regarded essentially as a reduced antheridium. Between the fossil gymnosperms and the present forms there has occurred a reduction of the antheridial jacket and the corresponding production of a pollen tube. For various reasons, the balance of probability is in favour of a homology between the antheridial jacket of Palaeozoic gymnosperms and the tube cell of modern gymnosperms. In the lower tracheophytes and in Cordaimthus and the Recent gymnosperms, a polar organization of the endosporal male gametophyte is characteristic. On several grounds, it is shown that in this structure the presence of an antheridial stalk is precluded, and that therefore the use of the term ‘stalk cell’ is greatly in error. The cell which is often called ‘stalk cell’ is potentially–sometimes actually–spermatogenous and is sister to the virile spermatogenous cell. It is frequently sterile, however, and is therefore recognized here as the ‘sterile cell’. In the evolution of the Coniferales and the Taxales (as well as in the lower Tracheophyta) disappearance of the prothallial cells from the male gametophyte is a characteristic trend. Prothallial cells are lacking in the Taxodiaceae, Cupressaceae, Cephalotaxaceae and Taxaceae. (However, in two families, Araucariaceae and Podocarpaceae, there has developed a secondary proliferation of the prothallial cells). Recognition of the same trend in the Chlamydospermophyta and consideration of details of ontogeny indicate that prothallial cells must be absent from the gametophytes of Welevitschia and Gnetum. In these, the embryonal cell functions as an antheridial initial and produces a tube and a generative cell. The generative cell then divides into spermatogenous and sterile cells. Later, two male gametes result from division of the spermatogenous cell. Based on the morphological analyses indicated above, a terminology has been proposed which attempts to recognize morphological identities but does accept non‐committal terms of common usage, as long as they do not violate the morphological concepts. A representative synonymy is given, and some examples of the use of the suggested terminology are shown. Details of the ontogeny of the male gametophyte in the conifer and taxad families have been reviewed. Although many genera are still completely unknown, it appears c...

Development of male gametophyte of Larix leptolepis Gord. with emphasis on diffuse stage of meiosis

“…Most researchers have concluded that the prothallial cell disintegrates on the basis of external characters and structure, but there have been no detailed studies on the internal structure. In the present research, we provide evidence that the prothallial cells, usually two cells in Larix (Sterling 1963;Singh 1978), continue to divide in some cases, forming di-or multi-nucleate cells (Fig. 5q, u).…”

“…5n). Soon after this, the antheridial initial divided into the tube nucleus and the antheridial cell (generative cell; Sterling 1963) (Fig. 5o, p).…”

Ultrastructure, cytochemical, and histochemical studies on pollen and male gamete development in gymnosperms

“…Studies with the help of these techniques have not only added to our knowledge about the fine details of morphology and anatomy, but have also thrown light on the physiology and biochemistry of development of microspores. During the past two decades, some reviews have appeared on different aspects of gymnosperm embryology [Roychowdhury, 1962;Sterling, 1963;Maheshwari and Sanwal, 1963;Doyle, 1963;Dogra, 1964Dogra, , 1967Maheshwari and Singh, 1967;Konar and Oberoi, 1969a;Chesnoyand Thomas, 1971;Singh and Johri, 1972;Vasil, 1973, 19781. The book "Embryology of Gymnosperms" by Singh [1978] and the review "Ultrastructure, cyto-and histochemistry of female gametophyte of gymnosperms" by Konar and Moitra [1980] offer more recent information on the subject.…”

Microsporogenesis, Pollination, Pollen Germination and Male Gametophyte Development in Taxus brevifolia

“…Male gametophyte structure and development has been described in T. baccata, T. canadensis and T. cuspidata (Robertson, 1907;Dupler, 1917;Sterling, 1963;Pennell and Bell, 1986b). The terminology surrounding male gametophyte development in gymnosperms varies tremendously in the literature.…”

“…The terminology surrounding male gametophyte development in gymnosperms varies tremendously in the literature. This paper follows the terminology proposed by Sterling (1963) except sperm is used instead of male gamete. This change reduces unnecessary terminology dierentiating angiosperms and gymnosperms.…”