ANEUSOMATY IN ANEUPLOID POPULATIONS OF CLAYTONIA VIRGINICA

Lewis Walter H. (Stephen F. Austin State Coll., Nacogdoches, Texas.) Aneusomaty in aneuploid populations of Claytonia virginica. Amer. Jour. Bot. 49(9): 918–928. Illus. 1962.—From 2 central east Texas populations of Claytonia virginica, 15 chromosome numbers, 2n = 14, 15, 16, 18, 25, 26, 27, 28, 29 30, 31, 32, 33, 36, and 58, were found among a sample of 181 plants. The most frequently encountered numbers were 2n = 14, 28, and 29. Among an additional 14 plants the pollen mother cells in the same bud differed from one another in chromosome number, as well as the pollen and premeiotic cells from the same plant. The chromosomes of the most unstable plant varied from 2n = 14–36. Numerous meiotic abnormalities, including inversions, dicentrics, bridges, fragments, non-disjunctions, univalents, and multivalents, were observed for the aneusomatic and trisomic plants. It is suggested that the origin of the aneusomatics is related to the numerical disparity of the gametic chromosomes composing them. Since the species is perennial in habit, thereby allowing the unstable plants to produce gametes with varying chromosome numbers year after year, it is further proposed that the wide range of aneuploid known for C. virginica resulted, at least in part from the presence of aneusomatic individuals.     

SPONTANEOUS AND INDUCED CHROMOSOME BREAKAGE IN CLAYTONIA VIRGINICA

Meiocytes in three morphologically similar but cytologically different wild populations of Claytonia virginica L. were examined. Over a three-year period levels of spontaneous chromosome breakage were consistent for each population but differed between populations. Random samples of inflorescences from two of the populations were treated with 0.005 % aqueous solutions of nucleic acid precursors: adenine, adenosine, thymine, thymidine, guanosine 5'-monophosphate (GMP), and cytosine 5'-monophosphate (CMP). Statistically significant increases in chromosome breakage were observed in the population with little background breakage when inflorescences were treated with adenosine, thymine, thymidine, GMP, and CMP. In the population with moderate spontaneous breakage, a significant increase was observed only in plants treated with adenosine. Breakage induced with nucleic acid precursors was similar to that which occurred spontaneously; the predominant aberration was the single bridge.     

ANEUPLOIDY IN CLAYTONIA VIRGINICA

Rothwell , Norman V. (Long Island U., Brooklyn, N. Y.) Aneuploidy in Claytonia virginica. Amer. Jour. Bot. 46(5): 353–360. Illus. 1959.—Within the taxon, Claytonia virginica L., an extensive aneuploid series has been found including the following chromosome numbers: 2n = 12, 14, 16, 17, 18, 19, 20, 22, 24, 26, 28, 30, 32, 34, 36, 48, and 72. Studies revealed that a population could be composed of individuals differing in chromosome number. Pollen fertility appears to be high in natural populations and in plants showing meiotic irregularities. Different karyotypes were found within the taxon; plants having the same chromosome number may have different karyotypes. Hybrids have been obtained as the result of crossing plants differing both in number and karyotype. From all the evidence, C. virginica appears to be able to tolerate transitions from one cytological type to another. The hypothesis is proposed that most of the various numbers have been derived from a haploid complement of 8 chromosomes possessing median centromeres. The following factors are suggested to account for the origin of the different numbers: nondisjunction, univalent lagging, misdivision of univalents, polyploidy, and fertile triploids.     

GEOGRAPHY OF CLAYTONIA VIRGINICA CYTOTYPES

Three widespread ploidy levels have evolved in Claytonia virginica, a diploid represented by n = 8, 7, and 6 races, a triploid primarily by n = 12 and 11, and a tetraploid by n = 16, 15, 14, and other aneutetraploids. In addition, sporadic higher polyploids (5x–24x) occur throughout eastern North America. These data are considered briefly in relation to meiotic behavior, to coexistence of major cytotypes, and to speciation.     

我国扁桃属植物的染色体数

本文观察了我国扁桃属(Amygdalus)植物的染色体数。其结果:1.普通扁桃A. communis L. 2n=16;2.榆叶梅A. triloba(Lindl.)Ricker 2n=64;3.长柄扁桃A. pedunculata Pall. 2n=96;4.蒙古扁桃A. mongolica(Maxim.)Yü2n=16;5.西康扁桃A. tangutica Korsh. 2n=16;6.矮扁桃A. ledehouriana Schlecht 2n=16。以上这些结果表明,在我国丰富的扁桃种质资源中,多倍体的潜力还相当大,这对我国今后培育扁桃新品种无疑是特别值得注意的。     

CHROMOSOME NUMBERS FROM THE FLORA OF THE JUAN FERNANDEZ ISLANDS

Forty-one chromosome counts are reported for 29 species of the flora of the Juan Fernandez Islands, Chile. Counts are provided for the first time for Azara (Flacourtiaceae), Cuminia (Lamiaceae), Dysopsis (Euphorbiaceae), Raphithamnus (Verbenaceae), Robinsonia (Asteraceae) and Ugni (Myrtaceae). New species counts are in Dendroseris and Erigeron (Asteraceae), Eryngium (Apiaceae), Escallonia (Saxifragaceae), Haloragis (Haloragaceae), Libertia (Iridaceae), Myrceugenia (Myrtaceae), Pernettya (Ericaceae), Peperomia (Piperaceae), Spergularia (Caryophyllaceae), and Wahlenbergia (Campanulaceae). The level of recent polyploidy and aneuploidy in the chromosomally known flora is each estimated conservatively at 6%. Almost all of the endemic lineages appear to have evolved at the same ploidy level from their polyploid mainland relatives. Furthermore, there is no evidence for chromosomal evolution by euploidy or aneuploidy within endemic genera. The level of ancient polyploidy in the endemic Juan Fernandez flora is estimated to be 66%. This high level correlates with the idea that many of the woody endemics (comprising nearly one-half of the woody species in our chromosomal sample) have been derived paedomorphically from herbaceous perennial mainland ancestors in temperate, orogenetically active, Andean regions, in which high levels of polyploidy would be expected.     

CHROMOSOME NUMBERS IN THE GENUS ANTHURIUM

Chromosome numbers were determined for 63 Anthurium species. Thirty-eight of these were newly determined. Generally the present work confirmed existing chromosome counts when these were available for comparison. The most common somatic chromosome number found was 30, but counts ranged from 2n = 20 to 90. In a few instances conflicting counts were obtained. B chromosomes were found frequently in Sect. Cardiolonchium and varied in number from one to three. Four polyploid series were evident from all available counts: 20-40, 24-30-48-84, 28-56 and 30-60-90-ca 124. Most species were part of the polyploid complex based on 30. Although species were not observed with n = 5, 6 or 7, movement among the basic numbers was considered to have occurred at this level. The relationship among these basic numbers and n = 15 (x₂) is still obscure.     

FLAVONOID RACES OF CLAYTONIA VIRGINICA (PORTULACACEAE)

Four flavonoid races have been found in the Claytonia virginica aneuploid complex, differing from one another in the accumulation of 12 kaempferol and quercetin 3-glycosides. Each of these races has a distinctive geographical distribution within the overall range of the species. The three major diploid cytotypes of C. virginica each belong to different races, two of which also include polyploids; a fourth race consists entirely of polyploids. An examination of biosynthetic pathways indicates that a small number of genetic changes are responsible for the observed variation; polyploidy per se does not appear to have contributed significantly to the production of novel compounds. Flavonoid data also suggest strongly that polyploidy within rather than between modern chemical races has been responsible for the bulk of chromosome number variation in the species.     

中国苹果属植物染色体数目报告

本文观察了中国苹果属植物17个种22个材料的染色体数目。观察结果指出,多倍体在全部研究材料中占44.6%,其中有些种因材料来源不同,其倍数性各异。本结果可供我国苹果遗传育种参考。     

秦岭六种提灯藓的染色体研究

本文以藓类植物的幼嫩孢蒴及茎尖为材料,对产于中国秦岭的六种提灯藓的染色体进行了观察计数。首次报道了M．pseudolycopodioides的染色体数目为n＝6;M．marginatum和M．lycopoidioides的染色体数分别为n=12及n＝6,与前人报道的结果一致;M．Laevinerve、M．heterophyllum以及M．thomsoii的染色体数目均为n＝6,与前人的报道不完全相同。本文旨在为本属的研究提供一定的细胞学资料。     

东北产20种植物染色体数目

东北产２０种植物染色体数目沙伟,王丽华,杨晓杰,戚晓丽,马革红,赵大勇（齐齐哈尔师范学院生物系齐齐哈尔１６１００６）关键词染色体数目,毛茛属,蒲公英属,鸢尾属,白屈菜属ＣＨＲＯＭＯＳＯＭＥＮＵＭＢＥＲＳＯＦ２０ＳＰＥＣＩＥＳＦＲＯＭＮＯＲＴＨＥＡＳＴ...     

上海地区若干种栽培植物的染色体数目

本文报道了上海地区栽培的11属12种植物的染色体数目,并就有关的细胞学和分类学问题略作了讨论。凭证标本藏于复旦大学生物系植物标本室。     

四种猕猴桃属植物的染色体数目观察

本文报道了四种猕猴桃植物的染色体数目。结合其他作者的有关报道,讨论了猕猴桃属的染色体基数,性染色体,倍性,及其与地理分布之间的关系。     

菝葜属13个种的染色体数目

获英属（Silmax）常常放在广义的百合科（Liliaceaes．1．）,是一个多为木本、攀援的（少为草本、直立）雌雄异株属"'。近几十年来人们根据它的某些独特性状已单立1科：获葵科（Smilaeaceae）,一般含茨基属、肖获卖属（Heterosmilax）和RIPogonum等3个属'·'。本研究旨在以     

CHROMOSOME RACES IN CLAYTONIA LANCEOLATA (PORTULACACEAE)

Chromosome numbers of n = 8, 12, and 16 were determined for 11 populations of Claytonia lanceolata occurring in the southwestern Rocky Mountains of Utah. No evidence of the wide infra-populational variation of chromosome numbers known in the related eastern species, C. virginica, was observed. The chromosome numbers in C. lanceolata probably evolved from a base number of x = 8. Diploids(n = 8) apparently produced tetraploids (n = 16) of putative autoploid origin. Pairing relationships, including the presence of univalents, bivalents, and trivalents, suggest the chromosome numbers of n = 12 are triploids derived from natural hybridization between diploids and tetraploids. Higher chromosome numbers previously reported in C. lanceolata from Colorado, and presumably based on x = 12, can be explained by subsequent polyploid increases in the triploids. The diploid and tetraploid populations analyzed in this study occupy different ecological habitats. The diploids occur at lower elevations along the foothills, whereas the tetraploids are restricted to higher montane and sub-alpine elevations. The triploids were discovered at intermediate elevations.     

NEW BASIC CHROMOSOME NUMBERS FOR GENERA OF NEOTROPICAL FERNS

Chromosome numbers for eight genera of Costa Rican ferns are reported here for the first time. These are: Neurocallis, n = 58; Marginariopsis, n = 35; Dicranoglossum, n = 36; Glyphotaenium, n = 37; Cochlidium, n = 33; Ormoloma, n = 42; Peltapteris, n = 40; and Loxsomopsis, n = 46. Chromosome observations involving several other genera are included: Solanopteris, n = 37; Xiphopteris, n = 32; Hemidictyum, n = 31: Pleuroderris, 2n = 80; Dictyoxiphium, 2n = 80; and Polystichum, n = 41. These numbers are compared to those of genera of presumed taxonomic affinity.