Biology of the Male Generative Organs of the Species of the Genus Quercus L.

1989

135 S.

25 Abb., 1 Tab., zahlr. Lit. Ang.

Bandaufführung

83022

The monograph brings the first more complex view of the male generative organs of the species of the genus Quercus L. with an emphasis on the autochthonous taxa in Slovakia from several aspects: differentiation, morphogenesis, physiology and morphology of male gametophyte. Differentiation of the generative organis since their establishment up to the stage of male gametophyte is a long-lasting process. The male generative organs start developing in middle to late July. The development stops on the level of sporogeneous tissue in autumn and continues in the following year, depending on climatic conditions. Generally, the anther wall differentiates late in March and microsporocytes enter the stage of meiotic division approximately in early April. The anther wall is four-layered including tapetum. Tapetum of the species of the genus Quercus L. is secretoric in character. The course of meiotic divisin is asynchronous and relatively fast, taking 2-4 days. The asynchronism can also be observed within a given inflorescence. In the meiotic cycle, 12 bivalents arise at regular conjugation of chromosomes. Anomalies discovered in the process of microsporogenesis in control trees growin in relatively clean environment amounted to 15-20%. In urban environment, contaminated especially by car gas exhausts, the anomalies increased to 20-25%, which suggests certain increasing tendency, but does not prove significant influence of urban environment components on the given process. Abnormalities detected in the development of male gametophyte observable under both contaminated and non- contaminated conditions included disturbances in the regular production of bivalents, retarded chromosome movement or their dropping from the division spindle in metaphases I, II and anaphases I, II; as well as premature or retarded migration of chromosomes to the poles, etc. The occurrence of various deviations from the normal course of microsporogenesis becomes also manifest with the rise of dyads and polyads. Quercus species are characterized by simultaneous type of tetrad formation. Microspore arrangement is characterized by predominant isobilateralism and is typically tetraedic. The mature pollen grains of oaks are bicellular. Exceptionally, as a result of disturbances in the normal division of microspore nucleus, mononucleic or polynucleic grains appeared in the time of pollen shedding. Peculiar development of pollen grains observed only in contaminated environment included also the rise of gigantic pollen grains and of pollen grains with the changed number of apertures. The irregularities and abnormalities observed in the ontogenesis of male gametophyte may bring about reduced production of viable pollen, which has been proved by tests of pollen viability in vitro. Time differences in the onsel of reducing division, course of meiotic phases, rise of pollen grains and the ...