[en] Male pupae of the domesticated silkmoth, P. ricini were irradiated with 600 - 6000 R of ⁶⁰Co gamma ray and studied for the nature and frequency of visible chiasmata in the meiotic spermatocytes. Significant increase in lower doses (600, 1200 R) and decrease in higher dose (6000 R) were observed. More interstitial chiasmata were induced in the medium bivalents; and low frequency of terminals restricted to the smaller bivalents. The minimum chiasma per bivalent was one and never zero. Nature of monocentric versus holocentric chromosomes with regard to the gamma induced chiasmata were, however, discussed. (author)

[en] Turn over of meiotic irregularities, pollen, capsule and seed sterility in M₁ and M₂ generations, derived from x-ray treated dry seeds of Linum usitatissimum L.(CV. B-67, Mukta and Neelum) were compared. Total percentage of meiotic abnormalities was highest in B-67 amongst the control population. But in comparison with respective controls, the turn over of meiotic irregularities was high in the M₁ populations of Mukta and Neelum. The extent of irregularities in meiosis of M₂ was less than that of M₁ generation. The pollen sterility percentage in the two generations remained almost unchanged, while capsule and seed sterility were reduced in M₂ generation. (author)

[en] Estimation of DNA amounts (in arbitrary units) in two genera, two species, and three cultivars of one species, permits comparison between them and indicates that the biggest difference is between the two genera, Lactuca and Cichorium; but that the difference between the cultivars of Lactuca sativa is greater than the difference between Lactuca serriola and the mean for Lactuca sativa. Lactuca serriola is a presumed ancestor of Lactuca sativa. The most radiosensitive species, L. serriola, has slightly less DNA and smaller nuclear volume than the next most sensitive, L. sativa cult. Cos. This is discussed. (author)

[en] After gamma irradiation (30 Kr) of seeds of Capsicum annuum cultivar cerasiformis (2 n = 24) two plants were recorded each carrying two interchanges. The nucleolus organiser chromosome appeared not to be involved. The interchange heterozygotes were weak and meiosis was irregular. At least one multivalent association per PMC was recorded. At metaphase I the predominant orientation was adjacent. The probable reasons for anaphase I and other meiotic irregularities and the incidence of high pollen sterility are discussed. (author)

[en] Healthy dry seeds of pusa ruby variety of Lycopersicon esculentum Mill. were irradiated with gamma rays at 10 KR, 20 KR, 30 KR, 40 KR and 50 KR dose levels. Meiotic studies were made in treated plants as well as in control plants. At metaphase I, meiotic abnormalities like clumping and stickiness of chromosomes, univalents, multivalents, fragments and irregular grouping of chromosomes were observed. At anaphase I, there were laggards and unequal grouping of chromosomes at poles. Germination percentage and pollen fertility were also studied. Pollen sterility seems to be the cumulative result of various abnormal meiotic stages as well as of physiological and genetic damages induced probably by breakage of chromosomes. The frequency of meiotic abnormalities with reference to the effect of radiation doses is discussed. (author)

[en] Modification of induced genetic damage after exposure to LD₅₀ and LD₉₀ doses of ⁶⁰Co gamma-irradiation on dormant seeds of Solanum incanum L. by pre- and post-treatments of thiourea was investigated. Thiourea pre-treatment reduced cellular lesions, growth injury and the death of seedlings, while post-treatment increased lethality. Incorporation of ³H-tymidine into DNA fraction gradually increased with 10^-4 to 10^-2 M thiourea treatment when applied before irradiation. Post-treatment of the thiourea, on the other hand, not only showed poor labelling of DNA but also delayed its synthesis. (author)

[en] Gamma irradiation of seeds (100 to 1000 Gy) or inflorescences (3000 Gy) of Nicotiana tabacum L. var. xanthi Dulieu mainly induced chromatoclastic effects affecting the microspore mother cells (MMCs) during meiosis: chromosome fragmentation, chromosome stickiness promoting the formation of chiasmas even between non-homologous chromosomes, single or multiple chromosomal bridges during anaphases and telophases I and II and irregular chromosomal disjunction. In plants raised from irradiated seeds, the frequency of abnormal meiotic figures and the rate of pollen sterility were directly related to the gamma ray dose. Gamma irradiation also induced the early dysfunction of the tapetum (tapetal degeneration was already visible at pachytene) with nuclear pycnosis or an expanded and sticky chromatin network and this no doubt contributed to pollen sterility. (author)

[en] The volume of pollen, total number of pollen/flower, the percent of pollen germination and tube growth of long-styled flower were higher than the short-styled flowers in S. torvum. In addition, the pollination studies were conducted among the four selected sets for optimum fruit set investigation. Fruit set was not seen in both the first and second sets (female shorts-short male and female short-long male). However, the maximum fruit set was obtained in the fourth set (female long-male long). Pollen grains of long-styled flowers irradiated with 1-800 krad were germinated in the basal medium. The percent of pollen germination and the tube growth was stimulated over the control with 1 and 50 krad dose exposures, but increasing dose rates inhibited both the above processes. Utilization of insoluble polysaccharides, and the synthesis of RNA and protein were enhanced over the control with the effect of 50 krad. The higher (800 krad) dose exposures inhibited all the above cytochemical constituents. Various dose-treated pollens were used to pollinate the stigma surface of the long-styled flowers. The fruit set, fruit volume, fresh and dry weight of fruits, and the number of seed set/fruit, were enhanced over the control by 1 and 50 krad, while the higher doses caused inhibitory effect. Interestingly, the fruit set was not caused by radiation doses 400 krad and above. (author)

[en] A rapid quantitative technique of nuclear track autoradiography is described which is reproducible and minimizes artifacts. The method is applied to human breast cancer cell cultures. (author)

[en] The effect of different mutagens on the induction of mitotic aberrations in diploid and tetraploid solanum nigrum L. has been studied. All the mutagens were found to be effective in inducting mitotic chromosomal aberrations in case of both the diploid and tetraploid. The percentage of cells showing mitotic abnormalities was found to be more in the tetraploid S. nigrum as compared to the diploid. (author)