Efficiency of induced mutagenesis at early stages (gametes, zygotes, proembryos) of ontogenesis in Nigella damascena L.
SummaryAn original technique has been developed of treating gametes, zygotes and early embryos of Nigella damascena L. with chemical and physical mutagens. A delay in fertilization and a decrease in the rate of cell division of the embryo and the endosperm after mutagen treatment have been found. Our method of treating gametes, zygotes and proembryos with chemical and physical mutagens is, by all criteria, superior to that of treating dry seeds. Treatment applied at early stages of ontogenesis not only induced a much higher mutation ratio compared with dry seeds, but also gave a broader mutation spectrum. The 55 types of hereditary change obtained affect the structure of vegetative and reproductive organs. Mutations which change the structure of the reproductive organs of flowers are of specific interest.The optimum dose for this object and the method of treatment which induces high mutation ratio (up to 96 % of families with changes) is 0.003p (16 hrs) for ethylenimine and 0.005p or 0.008p (16 hrs) for nitrosomethylurea. Treatment of dry seeds turned out to be much less effective.
Fertilité Pollinique de Nicotiana Tabacum L. Après Irradiation Gamma Aux Stades Gamètes, Zygote et Proembryon
RESUMELes plantes de Nicotiana tabacum examinees proviennent de graines obtenues apres divers traitements des fleurs par les radiotions gamma. Les stades irradies furent les gametes, le zygote et le proembryon; les doses totales furent de 1000, 2000 et 4000 r appliquees en 16 heures; pour le zygote, les trois doses totales furent egalement appliquees en 4 heures (intensites quatre fois plus fortes).L'analyse de la fertilite pollinique, qui fut effectuee sur toutes les plantes de la R1, montre que la fertilite diminue avec la dose dans les quatre series experimentales, et que parmi les stades irradies, les gametes sont les plus sensibles et les proembryons les moins sensibles. Les deux series d'irradiations sur le zygote montrent que les plus fortes intensites induisent moins de sterilite pollinique que les intensites faibles.
Abortion of male and female gametes in the tomato determined by allelic interaction.
NGIOSPERM gametogenesis, particularly on the male side, is highly susA ceptible to disturbance by either environment o r genotype. Exemplary of environmental agents, sodium a,P-dichloroisobutyrate disrupts pollen development, the effect being sufficiently specific and complete to warrant use of this chemical for purposes of emasculation (EATON 1957). Instances of genetic control are commonplace; at least 30 genes are known in Datura stramonium that condition abortion of the microspores to which they segregate (AVERY, SATINA, and RIETSEMA 1959). In the presence of certain other genes, viable pollen grains may develop, but they fare poorly in competition with grains of other genotypes. Whatever the detrimental effect, segregation of linked genes can be distorted, the degree of distortion depending on the intensity of linkage. Genes affecting gametophyte development are often discovered, in fact, as a result of such distortion. Interest in the present case intensified and the material was investigated in detail when it became apparent that it is exceptional in the following three respects: (1) male and female gametes are equally affected; (2) gametes abort only in certain hybrid combinations; and ( 3 ) the abortion factor behaves as if it were not completely penetrant.