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.
Preliminary data on radiation-induced gamete sterility in M1 plants of Nicotiana tabacum
Abstract In order to study the sterility of male and female gametes of M1 plants arising from mutagenic treatments, 7 M1 plants of Nicotiana tabacum “purpurea” originating from irradiated zygotes (4 kR of γ-rays) were paired with 7 control plants. In each of the 7 pairs, self-pollinations of the control and M1 plants and both reciprocal crosses were performed 5 times. Data were obtained on pollen fertility (by a staining test), seed set, seed germination and number of seedlings per fruit. The female and the male gametes of an M1 plant were both found to produce sterility when crossed to a control plant. Comparison between the two reciprocal crosses showed that the average contribution of M1 egg cells to the total amount of sterility of the 7 M1 plants was no larger than that due to the corresponding pollen grains. The fact that the M1 pollen grains, despite their numerical superiority, determine a sterility effect no lower than that induced by the M1 egg cells, is explained by a greater ability of the female gametes to tolerate the genetic damage induced from the mutagenic treatment.
Cognitive Correlaretes of Physics Achievement of Some Nigeria Senior Secondary Students
Some cognitive correlates of physics achievement of some Nigeria senior secondary students were considered in the study. Specifically, the study examined the relationship between measures of student’s field independency. Cognitive tasks, formal reasoning and their achievement in physics. Purposive and stratified random sampling techniques were employed to obtain a sample of 524 senior secondary two students from six education zones in Kogi State of Nigeria. Three instruments were used. They are science Reasoning Tasks (SRTs). Group Embedded Figures Test (GEFT) and Physics Achievement Test (PAT). Data analysis using multiple regressions reveals that measures of students’ fields’ independency and cognitive tasks predicted student’s achievement in physics generally. However, only measure of field independency predicted students’ achievement in physics in the higher order cognitive demand questions. Measures of formal reasoning had no significant relationship with students’ achievements in physics generally or in higher order cognitive demand questions in physics. However, the overall relationships between measures of field independency, cognitive tasks, formal reasoning and students’ achievement in physics generally and in higher order cognitive demand questions in physics were both significant. Educational implications of these findings were discussed.