摘要:

Six primary monosomes of the amphidiploid speciesGossypium hirsutumhave been identified as separate chromosomes of the complement. On the basis of cytogenetic tests involving translocations, a diploid species of the D genome group, and genetic markers, 4 of the 6 monosomes were designated chromosomes 1, 2, 4 and 6 of the A subgenome and 2 were designated chromosomes 17 and 18 of the D subgenome. Fourteen other monosomes were identified as duplicates of 3 of the above 6 primaries.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1964.tb06608.x

出版商:Wiley    

年代:1964

数据来源: WILEY

摘要:

Examination of 140 collections ofChara zeylanicafrom 3 southwestern states shows that a strong dichotomy exists in the collections. Some produce 4‐plated antheridia while others produce 8‐plated antheridia. Absolute separation of the study material is possible on the basis of plate number. In addition, 3 other characters (length/width ratio of oospores; fertility of first branchlet node; and number of distal ecorticate branchlet internodes) show strong correlation with the antheridial type. Preliminary chromosomal work indicates that a segregation at this level may also be possible. In 4‐plated collections examined,n= 28; 8‐plated collections are usuallyn= 56; however, a few 8‐plated collections aren= 42. No conclusion has been reached regarding the status of the latter collections.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1964.tb06609.x

出版商:Wiley    

年代:1964

数据来源: WILEY

摘要:

The plasma membrane bounding the cytoplasm immediately inside the hyphal wall ofStreptomyces cinnamonensismay not retract from the hyphal wall. When it does retract from the wall, it appears as a single dark line in some sections and as 2 dark lines separated by a light zone in others. The membrane system consists of mesosomes and endomembrane structures. The mesosomes are those membrane structures whose derivatives appear to be the plasma membrane. The endomembrane structures, in the present report, are those that appear to have been derived from either the cytoplasm or the limiting membranes of the pre‐existing membrane structures. All membranes seem capable of proliferation, a mechanism obviously responsible for the growth of the individual membrane structures and for the origin of many new ones. The mesosomes, according to their limits, are of 2 distinct types, the open mesosomes and the closed mesosomes. The open mesosomes are partially enclosed by limiting membranes, leaving the unenclosed sides limited by the wall. These mesosomes, when old, usually in aerial hyphae, may become attached to the wall and somewhat deleted from their limiting membranes. The individual membranes in their interior may appear disfigured. The closed mesosomes are completely surrounded by the limiting membranes. These mesosomes, as well as endomembrane structures, retain their original positions in the cytoplasm even in the older aerial hyphae, and the membranes in their interior usually remain practically as distinct in the aerial hyphae as they are in the substratal hyphae. New mesosomes and endomembrane structures are being formed continuously as the mycelium develops. The mesosomes, as a rule, occupy more or less the peripheral regions of the cytoplasm, while the endomembrane structures distribute themselves widely in the cytoplasm and also in the nucleoids. The appearance of the unit membranes, being double‐layered (2 dark lines separated by a light line), is not consistent. The membranes as a whole are more resistant to degeneration than the cytoplasm and the nucleoids.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1964.tb06610.x

出版商:Wiley    

年代:1964

数据来源: WILEY

摘要:

The present data indicate internuclear selection in dikaryotic‐homokaryotic matings is not due to differential rates of migration of the 2 types of migrant nuclei or to differential rates of saturation of the homokaryon. The advancing fronts of the 2 types of migrating nuclei are separated by essentially the same distance shortly after migration has been initiated and during later periods in the migration process. Internuclear selection, controlled by the incompatibility factors, must occur during the initiation of migration or earlier. Migration of both types of nuclei from the dikaryon has been demonstrated in hemicompatible and incompatible matings.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1964.tb06611.x

出版商:Wiley    

年代:1964

数据来源: WILEY

摘要:

'Sideshootless,’ a mutant strain of tomato which does not produce axillary buds during vegetative growth, was compared with normally branching plants in order to study the nature of development particularly with regard to axillary buds. Sectioned material revealed no indication of axillary bud initiation in the sideshootless plant at any time during the vegetative phase of growth. In the normal plants, buds were noted to arise in the axil of the fifth youngest leaf. The buds take their origin in tissue which is in direct continuity with the apical meristem. The bud primordia later become set apart from the apex as vacuolation takes place in the surrounding tissue. At the time of floral initiation, the mutant and normal strains behave similarly. Axillary buds appear in the axils of the 2 leaves immediately below the floral apex. One of the buds elongates to overtop the existing plant axis; the other develops as a typical sidebranch. The inflorescence is pushed aside in the process. This pattern is repeated with each inflorescence; thus an axis composed of several superimposed laterals results.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1964.tb06612.x

出版商:Wiley    

年代:1964

数据来源: WILEY

摘要:

This is the second of 2 articles (Nos. III and IV) dealing with the formal taxonomy ofAriocarpus.A description of the genus and a key to the subgenera and species appeared in the third article of the series. This article includes a description, illustrations, a map of authenticated collection sites, citation of common names, a discussion of synonymy and types, and a list of specimens examined of each species in the subgenusAriocarpus.The accepted species which are discussed areAriocarpus retusus, A. agavoides, A. trigonus,andA. scapharostrus.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1964.tb06613.x

出版商:Wiley    

年代:1964

数据来源: WILEY

摘要:

After gamma irradiation of wheat grain, embryos can germinate and grow without detectable mitotic figures and without increases in tissue‐cell numbers. Roots growing without DNA synthesis after irradiation show the 2 striking examples of normal nuclear behavior on the anatomic level that occur in unirradiated roots: (1) trichoblast nuclei migrate into the root hairs and change shape; and (2) nuclei in sieve‐tube elements and vessel elements disappear. Nuclei that do not synthesize DNA do synthesize RNA, some of which moves into the cytoplasm. Therefore, the irradiation that prevents DNA synthesis and mitosis has not completely inactivated all nuclear functions. On a purely descriptive level, the irradiation that prevents cell division seems to prevent the initiation at the apical “meristem” of immature vascular elements but does not prevent maturation in those vascular elements detectable before irradiation. Although the ultimate extent of growth is reduced in those structures which suffer radiation‐induced mitotic inhibition, it is not reduced in those structures (epiblast, coleorhiza, root hairs) which develop without cell division in unirradiated controls and, therefore, have no mitosis for the radiation to inhibit. This established generalization leads to the inference that the smaller sizes attained by gamma‐plantlet roots and leaves may be attributed largely or almost entirely to the radiation‐induced mitotic inhibition rather than to other actions of radiation. Irrespective of the validity of this last inference, the extent of growth theoretically possible without cell division is at least as great as the observed growth of gamma‐plantlets under given experimental conditions. Also reported are variations in radiation sensitivity among different batches of grain, among different organs within the same embryo, and among different cell types within the same organ. These variations are discussed with reference to suggestions and precautions concerning the use of radiation‐induced mitotic inhibition for developmental studies.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1964.tb06614.x

出版商:Wiley    

年代:1964

数据来源: WILEY

摘要:

Clarkia arcuataandC. lassenensisare the 2 members of the subsection Flexicaules. Although closely related morphologically, they show very different patterns of chromosomal variability in nature. About 25% of the plants grown from wild seed ofC. arcuata,a predominantly cross‐pollinating species, were heterozygous for 1 or 2 translocations; such heterozygotes were found in 5 of the 9 populations sampled. An analysis of the chromosome pairing in intraspecific crosses indicated that at least 5 different translocations giving a ring of 4 with the “standard” strain, 2 giving a ring of 6, and 2 giving a ring of 8 are present in nature. No arrangement was found with widespread distribution, and it is impossible to say at present what might be the primitive arrangement of this species. One population was found to contain an inversion, a rearrangement which is very rare inClarkiaat the intraspecific level. InC. lassenensis,a predominantly self‐pollinating species, only 6% (3 plants) of a sample of 53 were translocation heterozygotes, and these heterozygotes were found in only 2 of 13 populations. Intraspecific crosses indicated that one chromosome arrangement, the “standard,” was present throughout the species range.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1964.tb06615.x

出版商:Wiley    

年代:1964

数据来源: WILEY

摘要:

Pollen size statistics are presented for 10 closely related species ofBoutelouaand relationships between pollen size and chromosome numbers are presented for 13 populations of 5 species and 3 varieties. With 1 exception, all populations of all taxa conformed to a general pattern of pollen size dependent upon chromosome number. Chromosome numbers varied from 2n= 20 to 2n= ca. 103, with several independent aneuploid series. Statistical analyses were made of pollen size as related to chromosome number in the 3 varieties ofB. curtipendula.These data showed that tetraploids (2n =40) of var.tenuishad significantly greater pollen size and coefficient of variation than diploids (2n =20) of the same variety. Similarly, aneuploids of var.curtipendulawith 2n= 45 to 2n =64 chromosomes had significantly larger and more variable pollen than tetraploids (2n= 40) of the same variety. Highly significant positive regression coefficients were obtained from analyses of chromosome numbers and mean pollen size, and chromosome numbers and coefficient of variation, for var.curtipendula.Regression coefficients for var.caespitosapopulations with chromosome numbers over the hexaploid (2n= 60) level were not significant.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1964.tb06616.x

出版商:Wiley    

年代:1964

数据来源: WILEY

摘要:

Root tips of the festucoid grass,Festuca arundinacea,and 2 panicoid species,Chloris gayanaandPanicum virgatum,were processed using 2 different staining techniques. Measurements of nucleolar size were taken on epidermal and cortical cells. Trichoblasts and hair cells ofFestucawere found to contain much larger nucleoli than those in hairless initials or hairless cells. Significant nucleolar size differences between hair and hairless cells were also found in the 2 panicoid species. In contrast toFestuca,this difference between the 2 cell types was not as pronounced, and overlapping in nucleolar size occurred between adjacent hair and hairless cells. The cortex was composed of rows of cells in which nucleolar size simply decreased with cell distance from the apex. The significance of the observed nucleolar differences among cell types of the root tip is discussed briefly in relation to systematics, enzyme activity patterns, and differentiation.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1964.tb06617.x

出版商:Wiley    

年代:1964

数据来源: WILEY