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Volume 31, Issue 2
Displaying 1-3 of 3 articles from this issue
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1. RANDOM GENETIC DRIFT IN NATURAL POPULATIONS OF TRILLIUM KAMTSCHATICUM PALLYuichiro HIRAIZUMI1956 Volume 31 Issue 2 Pages 33-48
Published: 1956
Released on J-STAGE: May 21, 2007
JOURNAL FREE ACCESS1. Random genetic drift which is a factor in evolution was studied by means of considering the chromosomal variation in natural populations of Trillium kamtschaticum.
2. Homogeneity of chromosome constitution was expressed by the “Number of types per chromosome”. abbreviated as N.T.C., and the rate of decrease of N.T.C. in relation to population size was calculated.
3. Actual values of N.T.C. in various populations of T. kamtschaticum were calculated. It seems adequate to conclude, with reference to ecological, geological and historical background, that the values of N.T.C. indicate the effectiveness of random genetic drift in determining the genetic constitution of natural populations.View full abstractDownload PDF (7431K) -
Toyohiko KAWATANI, Tadaro OHNO, Kozo KINOSHITA1956 Volume 31 Issue 2 Pages 49-53
Published: 1956
Released on J-STAGE: May 21, 2007
JOURNAL FREE ACCESSThe writers successfully brought up tetraploid plants (n=18) of Insect Flower (Chrysanthemum cinerariaefolium Bocc.) by the treatment with colchicine in 1947, and these were cultivated during 1947 to 1953 in comparison with the diploid. The results of morphological investigations and chemical analyses (content of pyrethrin) are summarized as follows:-
1) The results of morphological investigations are shown in Tables 1, 2, 3 and 4. The dimensions of stomata were larger in the tetraploid than the diploid and there was a stochastically significant difference. The number of stomata per field of vision was smaller in the tetraploid than in the diploid, there being also a significant difference.
2) The size of flowers was larger and the number of ray flowers was more numerous in the tetraploid than the diploid, there also being a significant difference.
3) The results of chemical analyses (content of pyrethrin) are shown in Table 5. The content of pyrethrin in the air-dried flowers was also larger in the tetaploid than the diploid, there also being a significant difference. This fact shows the possibility of increasing the content of effective principles in medicinal plants by the artificial chromosome doubling and thereby breeding superior varieties.
4) No significant difference was observed in the content of pyrethrin I and II between the tetraploid and diploid plants.
5) It was stochastically confirmed that the pyrethrin content of dried flowers decreased by storage.View full abstractDownload PDF (483K) -
Hisao HIRAI1956 Volume 31 Issue 2 Pages 54-64
Published: 1956
Released on J-STAGE: May 21, 2007
JOURNAL FREE ACCESSThis paper constitutes the first report of the chromosome survey undertaken by the author in the Japanese Neuroptera and describes the chromosomes of nine species covering three families of the Osmyloidea, with some considerations on the relationship to taxonomy. The species under study and their chromosome numbers are given in the following table:
All the species herein studied showed that the males possessed the sex-determining mechanism of an ordinary X-Y type, with an exception of Plethosmylus decoratus which was characterized by the formula of an X1X2-Y mechanism in the male. The X and Y usually exhibit remarkable precocious separation in the first meiotic metaphase in eight species under and Y is less remarkable than that in the other species. Probably, this unusual behavior of the X and Y seems to be characteristic to the Sisyridae, because some other species of this family was found also to show a similar condition.
The behavior of the X- and Y-elements was traced in the meiotic nucleus through the growing stages of the first spermatocyte. In the stages ranging from the leptotene to pachytene the X and Y appear as a heteropycnotic chromatic body with a tripartite structure, in close association with a nucleolus. The body shows a weak affinity to stain in the diplotene nucleus. The diakinetic nucleus shows the X- and Y-elements which have separated far apart. It is then apparent that the precocious separation of the X- and Y-elements has taken place in the stage of diakinesis.View full abstractDownload PDF (1398K)
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