摘要:

Morphological data, chromosome behavior, and occurrence strongly suggest that the Florida fern known asAsplenium plenumarose as a cross (AAB1B2) between a sexual 2xspecies,A. abscissum(AA), and a “sterile” 3xhybrid,A. curtissii(AB1B2). A mechanism is described whereby such an origin is possible:A. curtissii, among other so‐called “sterile” hybrids, has the ability to produce unreduced spore mother cells capable of becoming spores directly. Such spores are able to form gametophytes with viable sperms and have the potential of producing sporophytes apogamously. It is highly probable that this heretofore overlooked process has operated in the origin of the hybrid fern,A. plenum, and is the first to be reported in the literature.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1967.tb10734.x

出版商:Wiley    

年代:1967

数据来源: WILEY

摘要:

Studies of the cytology of angiosperm pollen which extend our knowledge of the distribution of binucleate and trinucleate pollen to almost 2,000 species of flowering plants are summarized. Approximately 70% of the species studied release pollen in a binucleate stage, and none of them shed both types of pollen as a constant varietal trait. All phylogenetically primitive taxa are binucleate. The trinucleate trait evidently has originated independently at many times during angiosperm evolution. In no instance must one infer the origin of binucleate taxa from trinucleate ancestors. Most genera are monotypic with respect to pollen cytology, and only 10 genera are known to include both binucleate and trinucleate species. Among the 265 families studied, 179 include only binucleate genera and 54 include only trinucleate genera, while 32 include both types. Nearly all aquatic species with submersed flowers shed pollen in a trinucleate stage. A group of physiological differences which distinguish binucleate and trinucleate pollen is reviewed in relation to the survival and possible selective advantage of trinucleate mutants, and the significance of the binucleate pollen grain in the origin and evolution of flowering plants is discussed.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1967.tb10735.x

出版商:Wiley    

年代:1967

数据来源: WILEY

摘要:

Pollination of 40 emasculatedE. canadensisflorets withA. dasystachyumpollen gave rise to 12 shriveled seeds, one of which was viable. The hybrid seedling developed into a vigorous plant whose vegetative and spike characteristics were for the most part intermediate between those of the parents. Both parents behaved cytologically as allotetraploids, 2n= 28, and formed 14 bivalents regularly at metaphase I. Chromosome associations in the hybrid, 2n= 28, averaged 0.42 I, 13.70 II, 0.02 III, and 0.03 IV in 142 metaphase‐I cells interpreted. The hybrid produced 165 seeds under open‐pollination during its second year in the field.E. canadensisandA. dasystachyumapparently contain closely homologous genomes whose major structural differences consist of several inverted segments and possibly a small reciprocal translocation. The close homology between theE. canadensisandA. dasystachyumgenomes was unexpected in view of the wide morphological, ecological, and reproductive differences that separate the two species.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1967.tb10736.x

出版商:Wiley    

年代:1967

数据来源: WILEY

摘要:

Protein spectra from 4nand 6nspecies ofTriticumwere obtained by electrophoresis of seed extracts on polyacrylamide gels. Homologies among the species with regard to protein bands were tested by comparing each species with the standardT. dicoccumin a protein mixture spectrum. By reference to two pairs of homologous bands, each spectrum was then adjusted to the migration velocity of the standard by photographic enlargement. The homologies were found to be consistent with evidence from conventional methods regarding genome relationships among theTriticumpolyploids.T. dicoccoidesand other known AABB tetraploids showed nine fast‐moving albumin homologues, whileT. timopheeviand other known AAGG tetraploids showed seven. The two genomic groups had five albumin bands in common. The hexaploid (AABBDD) subspecies showed 12 albumin homologues, 9 of which were also homologous with the 9 of the AABB tetraploids and 3 of which were attributed to the D‐genome donor. Differences among species within each of the tetraploid genomic groups and among the hexaploid subspecies were largely confined to the slow‐moving bands of the gliadin series.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1967.tb10737.x

出版商:Wiley    

年代:1967

数据来源: WILEY

摘要:

A comparative study was made of the effectiveness of various hormone and metabolite mixtures in inducing vascular cambium initiation and secondary vascular tissue formation in isolated first‐transfer roots of the radish,Raphanus sativusL. ‘White Icicle,‘ when provided to the cut basal end of the root grown in sterile culture. An auxin, such as indoleacetic acid (IAA) at 10–5m, a cytokinin, such as 6‐benzylamino purine at 5 × 10–6m, a cyclitol, such asmyo‐inositol at 5 × 10–4M and sucrose at 8% were all required for maximum response. Requirements for auxin and cytokinin were absolute; in their absence no cambium was formed. The addition of cyclitol, while not an absolute requirement for cambium initiation, increased the magnitude of the response markedly. Alternative auxins such asα‐naphthaleneaeetic acid and 2,4‐dichlorophenoxyacetic acid were equally as effective as IAA. Alternative effective cytokinins included 6‐furfurylaminopurine, 6‐phenylaminopurine and 6‐(γ,γ‐dimethylallylamino)purine. Alternative cyclitols equivalent tomyo‐inositol were seyllitol and pinitol. Other related cyclitols tested were much less effective or totally inactive.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1967.tb10738.x

出版商:Wiley    

年代:1967

数据来源: WILEY

摘要:

Seedling trees were grown in complete nutrient solution and in one without added boron for a period of 5 years. Roots and shoots of boron‐deficient plants showed a variety of symptoms which were involved in the disruption of normal cellular differentiation. Abnormalities in structure, cell shape, wall conformation and rigidity are described for both primary and secondary tissues. The persistence of the trees in spite of the death of apical meristems and local or seasonal variations are discussed.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1967.tb10739.x

出版商:Wiley    

年代:1967

数据来源: WILEY

摘要:

Extracts of uninduced thalli, induced thalli, stalks, antheridiophore and archegoniophore disks ofMarchantia polymorphawere subjected to starch‐gel zone electrophoresis. Developed gels were treated with appropriate reaction mixtures to detect sites of activity for 12 enzyme systems; only phosphatases, esterases, and peroxidases were observed. Although common sites of phosphatase, peroxidase, and esterase activity were detected in all tested extracts, additional sites of peroxidase and esterase activity were found in extracts from antheridiophore disks. The antheridia provided the additional esterases as determined by the electrophoresis of antheridial extracts and by a histochemical test for esterases in sections of antheridiophores.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1967.tb10740.x

出版商:Wiley    

年代:1967

数据来源: WILEY

摘要:

Phytochrome reversion from the Pfr form to the Pr form inPastinaca sativaL. tissue occurs very rapidly during the first 1½ hr after exposure to red light and then more slowly; some Pfr is still present after 12 hr at 26 C. Phytochrome destruction, on the other hand, is initially very slow and does not become evident until after the period of rapid reversion. The rate of reversion is reduced by low temperatures but not by low levels of oxygen. Phytochrome destruction in parsnip tissue briefly exposed to red light is also unaffected by low levels of oxygen, suggesting that it may differ in mechanism from destruction in etiolated seedlings. However, reduced oxygen levels inhibit phytochrome loss in tissues held in darkness. Phytochrome in cauliflower tissue proved to be fully light‐stable, confirming earlier observations.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1967.tb10741.x

出版商:Wiley    

年代:1967

数据来源: WILEY

摘要:

Phlox cuspidata(n= 7) andP. drummondiisubsp.drummondii(n= 7) are closely related annuals which are indigenous to eastern and central Texas. The species typically occupy different ecological niches but may form contiguous or confluent populations in disturbed habitats and hybridize therein. On the basis of correlative interpretations of exomorphic, chromatographic and fertility information, hybridizing populations can be segregated into three distinct classes: (1) highly fertile plants with the morphological and phenolic attributes ofP. drummondii; (2) highly fertile plants with the morphological and chemical attributes ofP. cuspidata; (3) sterile plants with manifestly intermediate morphology and complementary chromatographic patterns. These data strongly suggest that hybridizing populations ofP. drummondiiandP. cuspidataare tritypic, being composed of “pure” or essentially “pure” parental species and a group of plants which has all of the attributes characteristic of an F1hybrid.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1967.tb10742.x

出版商:Wiley    

年代:1967

数据来源: WILEY

摘要:

Cleavage of the multinucleate sporangial cytoplasm begins by a rearrangement and subsequent fusion of randomly dispersed cleavage vesicles. The vesicles line up in planes equidistant from neighboring nuclei and along the sporangial wall. In addition, they contribute to the enlargement of the central vacuole. Fusion of these vesicles with themselves and with the central vacuole cleaves the cytoplasm into uninucleate zoospores, each with two flagella. The sporangial wall consists of two layers, an outer thin one which is continuous over the plug of the discharge pore and an inner thick one which tapers off near the plug. The plug consists of fibrillar material and is ejected upon release of the zoospores. A plug‐like structure separating the forming sporangium from the hypha has a homogeneous matrix pervaded with an anastomosing network of fine electron‐dense channels. In addition, glycogen‐like granules occur within mitochondria and paired structures are interpreted as procentrioles.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1967.tb10743.x

出版商:Wiley    

年代:1967

数据来源: WILEY