摘要:

Shields, LoraMangum, and FrancisDrouet.(New Mexico Highlands U., Las Vegas.)Distribution of terrestrial algae within the Nevada Test Site.Amer. Jour. Bot. 49(6): 547–554. Illus. 1962.—Twelve terrestrial algal species, other than diatoms, were identified by microscopic examination of natural soil growths from the Nevada Test Site. Four soil species appeared in culture only. Fifteen taxa occurred only in the vicinity of the one aquatic habitat. Colloidal sheaths ofMicrocoleus vaginatus, Schizothrix californicaandSchizothrix aculissimastabilize soil particles, forming a surface crust.Nostoc commune, Scytonema hofmanniiandProtosiphon cinnamomeusare commonly associated with lichens. With one exception, no natural algal growths were found within 0.6 mile of nuclear detonation points during the 2 years following an event. Since at least one species,Microcoleus vaginatus, survives acute gamma exposures of 2,560 kr, blast and thermal damage, rather than radiation, appear to account for the removal of soil algae. The slow recovery can be explained largely in terms of aridity. Soil texture, which influences cohesiveness and moisture levels, strongly affects the composition of terrestrial algal populations in relation to major shrub types within the test site.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1962.tb14979.x

出版商:Wiley    

年代:1962

数据来源: WILEY

摘要:

Panicker, Radha K., and E. R. B. Shanmugasundaram. (U. Madras, India.)Temperature‐independent riboflavineless mutants of Aspergillus nidulans.Amer. Jour. Bot. 49(6): 555–559. Illus. 1962.—Studies on the biosynthesis of riboflavine using 5 non‐allelic, riboflavineless mutants ofAspergillus nidulansshow that: (1) all of them are temperature‐independent; (2) optimal amounts of the vitamin required for maximal growth vary from one mutant to the other; (3) the riboflavine activity of purines and pyrimidines on the mutants are none too different from the earlier observations onNeurospora crassa, Eremothecium ashbyiiandAshbya gossypii; and (4) the isoalloxazine and alloxazine derivatives are not only devoid of vitamin activity but also slightly inhibit the growth of the mutants in presence of the vitamin.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1962.tb14980.x

出版商:Wiley    

年代:1962

数据来源: WILEY

摘要:

Morretes, Berta Lange de. (U. Sao Paulo, Brazil.)Terminal phloem in vascular bundles of leaves of Capsicum annuum and Phaseolus vulgaris.Amer. Jour. Bot. 49(6): 560–567. Illus. 1962.—The terminations of vascular bundles in the mesophyll ofCapsicum annuumandPhaseolus vulgariswere studied in mature leaves. InCapsicum, both the principal and the lateral vein endings contain phloem and, generally, the xylem and the phloem end together; in some bundles, however, the last xylem element extends slightly beyond the last sieve element. InPhaseolus, main and lateral vein endings may terminate with both xylem and phloem, or xylem only. Some lateral endings contain no sieve elements; in such endings, parenchyma may occupy the position of the phloem. The sieve elements of the vein endings contain slime bodies. In both species the companion cells of terminal phloem are wider than the sieve elements, have dense cytoplasm, and rich granulation.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1962.tb14981.x

出版商:Wiley    

年代:1962

数据来源: WILEY

摘要:

Belkengren, R. O. (Oregon State U., Corvallis.)Growth and sexual reproduction of the moss Amblystegium riparium under sterile conditions.Amer. Jour. Bot. 49(6): 567–571. Illus. 1962.—Growth ofAmblystegium ripariumas primary or secondary protonemata, or as a leafy gametophyte under aseptic conditions, is reported. Yeast extract appears to be inhibitory for shoot growth but not for protonemal growth; it appears to cause the death of shoot buds on protonemata before they differentiate into leafy shoots, so that the organism grows as protonema only. Sexual reproduction of this organism in continuously illuminated cultures was induced by a CO2‐free period followed by addition of CO2or sugar. Senescence in a culture may also induce sporophyte formation presumably by interfering with photosynthesis or some other function.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1962.tb14982.x

出版商:Wiley    

年代:1962

数据来源: WILEY

摘要:

Edwardson, J. R., and M. K. Corbett. (Florida Agric. Expt. Sta., Gainesville.)A virus‐like syndrome in tomato caused by a mutation.Amer. Jour. Bot. 49(6): 571–575. Illus. 1962.—A mutation in the ‘Marglobe’ tomato variety, similar in appearance to tomatoes infected with strains of cucumber mosaic virus or tobacco mosaic virus, was found in 1959. The ‘Marglobe’ mutant also closely resembles the phenotypes of thewiryseries of tomato mutants in possessing narrow cotyledons, abnormal “wiry” leaves, reduced laminae of leaflets, divided sepals and petals, apocarpous ovaries and a high degree of female sterility. The appearance of the mutant is not attributable to virus infection because none of the mutant characters appeared in stock or scions of reciprocally grafted mutant and normal plants Segregation of the “wiry” phenotype in F2and backcross populations indicates that the mutant phenotype is controlled by a single pair of recessive genes exhibiting marked pleiotropic effects.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1962.tb14983.x

出版商:Wiley    

年代:1962

数据来源: WILEY

摘要:

Thompson, MaxineM. (U. California, Davis.)Cytogenetics of Rubus. III. Meiotic instability in some higher polyploids.Amer. Jour. Bot. 49(6): 575–582. Illus. 1962.—Meiotic instability occurred in low frequency in polyploidRubusvarieties, ‘Young,’ ‘Boysen,’ and ‘Mayes.’ Subdivision of the chromosome complement into 2 or more groups that function independently within the cell, nondisjunction of chromosomes, and unequal distribution of the chromosomes to the polar regions at anaphase were noted at either or both meiotic divisions in the pollen mother cells. The termcomplement fractionationis suggested for the phenomenon of independently operating groups of chromosomes of variable numbers within meiotic as well as mitotic cells. The presence of PMC's with unusual chromosome numbers indicates a pre‐meiotic instability similar to that observed in meiotic cells. With such a cytological mechanism a polyploid organism can produce gametes with extremely variable chromosome numbers. Some of these gametes will be functional due to a tendency for the formation of balanced genomes. The significance of complement fractionation is considered in relation to unusual breeding results, its value as a tool for plant breeders and its role as an evolutionary mechanism. Polyploids are considered as a storehouse of variability which occasionally, by means of the cytological mechanism described, can be released in the form of distinct, new segregants at different levels of ploidy.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1962.tb14984.x

出版商:Wiley    

年代:1962

数据来源: WILEY

摘要:

Haber, Alan H. (Oak Ridge Natl. Lab., Oak Ridge, Tenn.)Nonessentiality of concurrent cell divisions for degree of polarization of leaf growth. I. Studies with radiation‐induced mitotic inhibition.Amer. Jour. Bot. 49(6): 583–589. Illus. 1962.—During germination and seedling growth, the first foliage leaf of wheat shows polarized growth with striking changes in shape. During this polarized growth, most of the new cell plates are formed perpendicular to the axis of greatest elongation (longitudinal axis). The relation between leaf length and leaf width is the same in leaves normally growing with cell division as in leaves growing with negligible cell division after gamma‐irradiation (800 kr) of the unsown grain. Although cell division is necessary for continued growth and normal development, concurrent cell divisions play no role in determining the degree of polarization, i.e., the ratio of the rates of linear extension in length per mm length to linear extension in width per mm width. The majority of the new cell plates formedbeforethe growth period studied were parallel to the axis of greatest absolute and relative elongation during the growth period studied. Irradiated and unirradiated wheat having the same leaf size, and thus the same leaf shape, have quite different cell sizes, shapes, and numbers in both the leaf epidermis and the chlorenchymatous mesophyll. It is concluded that: (1) the orientations of cell divisions, whether concurrent with or prior to the growth period studied, play no role in the basic mechanism which determines the manner in which leaves change shape; and (2) genetic information specifies leaf form independently of genetic influences on sizes and shapes of cells and on the extents and orientations of cell divisions.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1962.tb14985.x

出版商:Wiley    

年代:1962

数据来源: WILEY

摘要:

Paolillo, D. J., Jr. (U. Illinois, Urbana.)The plastids of Isoetes. howellii.Amer. Jour. Bot. 49(6): 590–598. Illus. 1962.—The plastids of various tissues of the sporophyte ofIsoetes howelliihave been investigated with the light and electron microscopes. The plastid in all observed stages of development is bounded by an envelope composed of 2 closely placed membranes. The proplastid in meristematic tissues is a flattened, often circular, structure, which is differentiated into a peripheral portion (plastonema) that stains deeply, and an internal portion (plastosome) that stains very lightly with dyes that color protein. Tubules and lamellae, as well as starch, occur in the plastonema before they are found in the plastosome. In the mature photosynthetic tissues of the leaf, chloroplasts with lamellated grana resembling those of the higher plants are found. Amyloplasts are found near the vascular bundle of the leaf. In addition to plastids and other organelles, the cells of the ligule contain highly organized portions of endoplasmic reticulum. Long, tortuous amyloplasts are found in the parenchyma of the stem. The plastids of the root cortex also mature as amyloplasts. The structure of the chloroplast is similar to that reported forPsilotumbut different from that reported in some accounts onSelaginella.An examination of various accounts of the chloroplast ofSelaginellaindicates that environmental effects must be considered in a comparison of the structure of chloroplasts of different species.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1962.tb14986.x

出版商:Wiley    

年代:1962

数据来源: WILEY

摘要:

Ellison, W. L., R. E. Alston, and B. L. Turner. (U. Texas, Austin.)Methods of presentation of crude biochemical data for systematic purposes, with particular reference to the genus Bahia (Compositae).Amer. Jour. Bot. 49(6): 599–604. Illus. 1962. — A partial biochemical “profile” (as determined chromatographically for selected constituents) of a given species is compared with that of other species in the genera concerned. The chemical affinities of each of these pairings are expressed in percentages along the radii of a circle. The points are then connected so that these affinities are shown in the form of polygons. Such graphs can be looked upon as pattern configurations purporting to show biochemical similarities or differences between and among species. Graphic information of this nature can be used to supplement those data obtained from morphological studies. In addition to affinity values and polygonal diagrams, chromatographic data can be presented in the form of synthetic numerical indices which permit quantitative expression of systematic relationships among taxa of any taxonomic rank. This relationship is expressed in a fashion that presumably gives equal weight to both similarities and differences. These techniques were applied to a systematic evaluation of relationships inBahiaand related genera. Several taxonomic dispositions were suggested, the most striking being the treatment ofBahiaas composing 2 phyletic series, the Alternifoliae and the Oppositifoliae, and the suggestion thatBahia oppositifoliabe treated as a separate genus,Picradeniopsis.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1962.tb14987.x

出版商:Wiley    

年代:1962

数据来源: WILEY

摘要:

Menzel, MargaretY. (Florida State U., Tallahassee.)Pachytene chromosomes of the intergeneric hybrid Lycopersicon esculentum X Solanum lycopersicoides.Amer. Jour. Bot. 49(6): 605–615. Illus. 1962.—Pachytene bivalents of the hybrid were compared with those of the parents to determine whether the chromosome differentiation assumed to underlie chiasma failure and sterility of the F1and preferential pairing in the corresponding amphidiploid was reflected in visible differences or failure of synapsis between homeologues. The total pachytene complement length ofS. lycopersicoidesDun. was nearly 1.5 times that of the ‘Pearson’ tomato parent; the complement of the hybrid was of intermediate length. Pairing in the hybrid showed that the chromosomes of the parents were visually similar and completely synapsed in 43 of the 47 identifiable regions into which the pachytene complement may be divided. The similar regions included all 23 distal, achromatic segments in which chiasmata were localized, and 20 of the proximal, chromatic segments. The other 4 chromatic segments differed in length and hence exhibited a “deficiency” configuration. According to Barton's system of numbering, these were the short (nucleolar) arm of chromosome 2, the proximal segments of the long arms of chromosomes 4 and 9, and the proximal segments of the short arm of chromosome 10. Sporadic inversion, deletion and translocation configurations found in about 1–5% of pachytene nuclei of the hybrid probably represented newly‐arisen spontaneous aberrations rather than constant differences between the parental genomes. No evidence was found that the chromosomes of the parents differed by small structural rearrangements. Either the rearrangements were below the resolving power of the methods employed, or differentiation has affected some property or properties of the chromosomes other than linear order. Evidence from metaphase I suggested that inequalities in chromatic regions of hybrid bivalents inhibited chiasma formation in adjacent achromatic segments but enhanced it in achromatic segments of the opposite arm. The mean number of bivalent arms having chiasmata at metaphase I was nearly as high in the hybrid as in the ‘Pearson’ parent Univalents at metaphase I in the hybrid result not from failure of synapsis or lowered chiasma frequency but from an unbalanced distribution of chiasmata among the chromosome arms.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1962.tb14988.x

出版商:Wiley    

年代:1962

数据来源: WILEY