摘要:

Brown, Claud L. (U. Georgia, Athens), and Karl Sax.The influence of pressure on the differentiation of secondary tissues.Amer. Jour. Bot. 49(7): 683–691. Illus. 1962.—When longitudinal bark strips ofPopulus trichocarpaandPinus strobusare separated from the bole wood during early spring and maintained in a humid environment while attached to the parent tree, the cambial zone along the inner surface of the segments rapidly proliferates producing an extensive parenchymatous callus. Subsequently, a new phellogen and cambium differentiate and extend tangentially around the outer periphery of the callus pad, this resulting in the formation of a new stem‐like structure. Whenever bark strips are separated from the bole wood by a layer of polyethylene plastic film and held firmly against the tree by externally applied pressure, the cambium continues to function normally, setting aside derivatives which differentiate and mature into normal, elongate xylary and phloic elements. The importance of mutual pressures and spatial relationships in controlling patterns of differentiation in secondary tissues is clearly demonstrated.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1962.tb14997.x

出版商:Wiley    

年代:1962

数据来源: WILEY

摘要:

Prakash, U., E. S. Barghoorn, and R. A. Scott. (Harvard U., Cambridge, Mass.)Fossil wood of Robinia and Gleditsia from the Tertiary of Montana. Amer. Jour. Bot. 49(7): 692–696. Illus. 1962.—Fossil woods representing 2 genera of the Leguminosae,RobiniaLinnaeus andGleditsiaClayton, have been identified from Tertiary beds in southern Montana. These woods are noteworthy owing to their exceptionally fine structural preservation and from the standpoint of their paleogeographical distribution. Neither genus now lives in the region of Montana.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1962.tb14998.x

出版商:Wiley    

年代:1962

数据来源: WILEY

摘要:

Kitani, Y., L. S. Olive, and ArifS. El‐Ani. (Columbia U., New York City.)Genetics of Sordaria fimicola. V. Aberrant segregation at the g locus.Amer. Jour. Bot. 49(7): 697–706. Illus. 1962.—Aberrant segregation of thegray‐sporecolor locus inSordaria fimicolawas studied with the aid of closely linked markers. It was found that 6:2 and 5:3 asci occur with about the same frequency, but asci with an excess of wild‐type spores occur with a frequency 5.5 times that of asci with an excess of gray spores. Also, the frequency of related crossing over (occurring close to the miscopied loeus and involving the miscopying strand) was much higher than the expected value, and in 5:3 asci it appears to be at least twice that found in 6:2 asci. Nine aberrant 4:4 asci, each with 2 spore pairs heterogeneous for color, were found. These are believed to have resulted from reciprocal double transreplication. The rarest aberrant type was represented by a single 7:1 ascus, which is difficult to explain on the basis of a single meiotic process. Miscopying is discussed with relation to an 8‐strand model of paired homologues and the occurrence of localized chromosome pairing during prezygotene DNA synthesis. Several possible explanations for the occurrence of aberrant tetrads are considered. Miscopying has also been found to involve several spore‐color loci not previously studied; whereas, several other such mutant loci fail to show evidence of it. One locus (m) shows abnormal segregation of the 6:2 but not the 5:3 type.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1962.tb14999.x

出版商:Wiley    

年代:1962

数据来源: WILEY

摘要:

Gifford, ErnestM., Jr., and HerbertB. Tepper. (U. California, Davis.)Histochemical and autoradiographic studies of floral induction in Chenopodium album.Amer. Jour. Bot. 49(7): 706–714. Illus. 1962.—Chenopodium albumwas induced to flower using short‐day photoperiods. Changes in the chondriome, starch, total protein, ribonucleic acid (RNA), deoxyribonucleic acid (DNA), and histone distribution in cells of vegetative and inflorescence shoot apices were studied. The distal cells of the vegetative apex (especially the axial tunica cells) possess larger nucleoli and vacuoles, less granular mitochondria, and more differentiated plastids than do other cells of the apex; the distal cells stain lightly with dyes that indicate the presence of DNA and histone. RNA is distributed relatively uniformly in the shoot apex; the cells at sites of leaf initiation and young leaf primordia contain slightly higher concentrations of RNA than the axial cells of the shoot apex. Protein is uniformly distributed throughout the vegetative as well as the inflorescence apex. Upon induction, the chemical and morphological differences between cells in the shoot apex gradually disappear. RNA concentration of cells in the apex increases, reaching a maximum after 4 inductive cycles. Protein concentration of cells also increases, but this increase lags behind that of RNA.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1962.tb15000.x

出版商:Wiley    

年代:1962

数据来源: WILEY

摘要:

Hoff, VictorJ. (U. Arkansas, Fayetteville.)An analysis of outcrossing in certain complex‐heterozygous Euoenotheras. I. Frequency of outcrossing.Amer. Jour. Bot. 49(7): 715–721. 1962.—Eleven complex‐heterozygous races ofEuoenotherawere used for study. The races were grown in the midst of the experimental garden in which plants from approximately 150 races and hybrid combinations were growing together in close proximity so as to afford the maximum opportunity for outcrossing. Many capsules (126) resulting from unguarded flowers were collected from the chosen races and the seed grown to determine the number of hybrid plants resulting from outcrossing within each fruit. Among the various capsules, the number of outcrosses ranged from 0% to over 50% of the plants grown, while the total amount of outcrossing ranged from 0.7 to 7.8% among 5 different collections of capsules. A relationship between the amount of pollen produced by a flower or normally deposited on its stigma and the degree of outcrossing was noted. It is concluded that outcrossing probably occurs with sufficient frequency to account for the large number of complex‐combinations found in nature.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1962.tb15001.x

出版商:Wiley    

年代:1962

数据来源: WILEY

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1962.tb15002.x

出版商:Wiley    

年代:1962

数据来源: WILEY

摘要:

TuckerShirleyC. (Northwestern U., Evanston, Ill.)Ontogeny and phyllotaxis of the terminal vegetative shoots of Michelia fuscata.Amer. Jour. Bot. 49(7): 722–737. Illus. 1962.—Two patterns of symmetry occur inMichelia fuscataIn the lead shoots, leaves arise in a 2/5 spiral arrangement which may be either clockwise or counterclockwise. Other shoots are dorsiventrally organized; these shoots produce leaves in a modified ½ phyllotaxis in which the angle between the 2 files of leaves lies between 100° and 150°, according to the particular branch. Both types of shoot have a zonate apical meristem with a biseriate tunica a central initial zone, and a peripheral zone. The apical configuration of cells does not change appreciably during the plastochron. The flat to low‐convex outline of the shoot apex is maintained by initiation of the leaves close to the summit of the apex; the diameter of the meristem diminishes greatly after such an initiation. Leaf inception in the subsurface tunica layer is followed by precocious activity of the marginal meristems which extend the stipular flanges completely around the base of the apical meristem. The stipular margins then fuse laterally and form a hood over the apex. A subapical initial meanwhile is active in the leaf blade, where it persists up to the time the leaf is 2 mm high. The most recent primordium is 300 μ high before another leaf is initiated. The vascular system of the stem is a cylindrical network of leaf traces, with 6–12 traces per leaf. The procambium develops acropetally from preexisting vascular strands in the stem below. Elements of the diverse sclereid system differ in shape in different tissues, according to the availability of intercellular space. Goebel's term “Pendelsymmetrie” is discussed with reference to apical activity inMichelia.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1962.tb15003.x

出版商:Wiley    

年代:1962

数据来源: WILEY

摘要:

Kamemoto, H., and K. Shindo. (U. Hawaii, Honolulu.)Genome relationships in interspecific and intergeneric hybrids of Renanthera.Amer. Jour. Bot. 49(7): 737–748. Illus. 1962.—Chromosome numbers and meiotic behavior of species and hybrids ofRenanthera(Orchidaceae) were investigated.Renanthera elongata, R. histrionica, R. matutina, R. monachica, andR. storieiwere diploid (2n= 38). The race ofR. coccineacommonly grown in Hawaii was found to be hexaploid (2n= 114), while a recently introduced clone from Thailand was diploid (2n= 38). Diploid interspecific hybrids formed about 18 bivalents at M‐I, indicating a relatively strong homology of parental chromosomes. The tetraploid hybrid of diploidR. monachicaand hexaploidR. coccineashowed predominantly 37 or 38 bivalents, indicating good homology of genomes of the 2 parental species, and autosyndetic pairing in the 2 additional genomes ofR. coccinea.Intergeneric hybrids involvingRenantheraspp. could be classified into 2 distinct groups: those with 14–11 bivalents that are generally oriented at the metaphase plate and eventually lead to a preponderance of tetrads or tetrads with microcytes, and those with fewer bivalents (9–5) many of which are unoriented pseudobivalents and which ultimately give rise to dyads and dyads with microcytes. Relationships of parental species on a taxonomic basis are closer in the former than the latter group.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1962.tb15004.x

出版商:Wiley    

年代:1962

数据来源: WILEY

摘要:

Takats, StephenT. (Brookhaven Natl. Lab., Upton, N. Y.)An attempt to detect utilization of DNA breakdown products from the tapetum for DNA synthesis in the microspores of Lilium longiflorum.Amer. Jour. Bot. 49(7): 748–758. Illus. 1962.—The tapetum in anthers ofLilium longiflorumencloses the developing microspores and when it degenerates is a possible source of precursor material for DNA4synthesis in the microspores. To check this, time‐course experiments were carried out tracing the fate of label introduced into the tapetal DNA. H3‐thymidine was given in vivo to anthers during late pachytene of meiosis, when the tapetum can be selectively labelled. Growth was then followed by sampling anthers until the tapetum degenerated and the microspores synthesized DNA and divided. Autoradiographs indicated that the label in tapetal nuclei was lost shortly before DNA synthesis in the microspores. The microspore walls were transiently labelled, but the microspore nuclei did not incorporate a detectable amount of label. The results are discussed in the light of related biochemical findings, and are explained on the basis of: (1) complete catabolism of tapetal DNA (or tapetal thymine); and (2) the existence of a non‐tapetal pool of precursors.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1962.tb15005.x

出版商:Wiley    

年代:1962

数据来源: WILEY

摘要:

Wall, J. R., and C. F. Andrus. (U.S.D.A., U. S. Vegetable Breeding Laboratory, Charleston, S. C.)The inheritance and physiology of boron response in the tomato.Amer. Jour. Bot. 49(7): 758–762. Illus. 1962.—Brittle stem (btl), an abnormal sublethal phenotype in the tomato caused by boron deficiency, was found to be controlled by a single recessive gene. The threshold of boron concentration forbrittle‐stemexpression is not constant but fluctuates and is intimately associated with a number of interrelated environmental factors. Light duration and intensity are especially significant, while temperature and nitrogen, phosphorus, and calcium availability probably contribute tobtlexpression. It is suggested that when boron supply is limiting,brittle‐stem(boron deficiency) symptoms are intensified by any environmental factor or factors which enhance plant growth. Plants ofbtl/btlgenotype contain much less boron in their leaves than do those of the control variety ‘Rutgers’; conversely, these plants contain more boron in their roots when grown in nutrient cultures of high boron content. This finding is discussed in relation to possible modes of gene action.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1962.tb15006.x

出版商:Wiley    

年代:1962

数据来源: WILEY