摘要:

Seed‐coat morphology of 14 species ofCollomia(Polemoniaceae) was examined with light microscopy and scanning electron microscopy. Two seed types were observed based on surface sulpturing: Type 1—hexagonal epidermal cells forming a shallow reticulum with well‐defined cell boundaries; Type 2—longitudinally ridged and irregularly arranged crater‐like depressions with inconspicuous cell boundaries. Only two species,C. debilisandC. larseniiof sect.Collomiastrumhave seed‐coat Type 1. Seed‐coat Type 2 is characteristic of all species of sect.Collomia, sect.Courtoisia, andC. mazama, C. rawsonianaof sect.Collomiastrum. The present investigation reveals a fairly homogeneous seed‐coat pattern in the genus and does not offer significant information for realignment of infrageneric classification. Anatomical studies with light microscopy show that a mucilaginous seed coat develops from the outermost layer of integument in which each epidermal cell develops spiral secondary wall thickenings. Mucilaginous seeds of mostCollomiaspecies probably provide adaptive significance in that adherence of seeds to ground prohibits further dispersal to unfavorable habitats, or epizoochoric dispersal.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1981.tb07821.x

出版商:Wiley    

年代:1981

数据来源: WILEY

摘要:

The stigmatic papillae of sweet cherry were examined to determine developmental characteristics of the wet‐stigma surface. Early stages of secretion are detectable 1 wk prior to anthesis by using a 1% crystal violet solution. The number of stainable cells and the amount of interstitial staining subsequently increase, although secretions are not visible on unstained specimens until anthesis. Auto‐fluorescence above 500 nm (excited by 335–480 nm) becomes microscopically detectable at floral maturity and grows more intense after anther dehiscence. Light microscopy of plastic sections shows that papillae degenerate in peripheral regions of unpollinated mature stigmas, and that this is even more pronounced in pollinated ones. The distal portions of the papillae are covered with a homogeneous cuticular cap, which when viewed with electron microscopy encloses a subcutaneous secretion prior to cuticle exfoliation. Other exudates observed with electron microscopy prior to anthesis are interstitial electron‐translucent globules and surrounding matrix, and assorted vesicles, lipid globules, and starch grains which are present at floral maturity. Flowers observed under field conditions in the terminal secretion stage accumulate trichomatous structures. Our observations indicate that the stigma ofPrunus aviumL. is characterized by several phases of secretion which appear to be facilitated by mechanical abrasion. A model for the primary pollen‐receptive area is proposed and suggestions are made concerning the origin of the secretions.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1981.tb07822.x

出版商:Wiley    

年代:1981

数据来源: WILEY

摘要:

In germinating spores ofOnoclea sensibilis, the nucleus migrates to one end prior to an asymmetric cell division that partitions each spore into two daughter cells of unequal size. The larger cell develops into a protonema, whereas the smaller cell immediately differentiates into a rhizoid. When spores were germinated in the presence of methanol, nuclear migration was inhibited and most nuclei moved only to the raphe on the proximal side of the spores. Subsequent cell division partitioned each spore into daughter cells of equal size of which both developed into a protonema and neither into a rhizoid. Spores became sensitive to methanol at a time just prior to or coincident with nuclear migration and the effects of the alcohol were rapidly reversible as long as the spores were removed from methanol prior to the completion of cell division. Exposure to methanol prior to, but not during, nuclear migration or after mitosis had no effect upon rhizoid differentiation. The alcohol disrupted the formation of crosswalls after mitosis and they were often convoluted and irregularly branched. These results are consistent with the interpretation that methanol may disrupt a membrane site that plays an essential role in nuclear movement and rhizoid differentiation.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1981.tb07823.x

出版商:Wiley    

年代:1981

数据来源: WILEY

摘要:

The effects of age from seed, out‐of‐phase dormancy, and gibberellin treatment with water stress on the reproductive and vegetative development of the long shoot terminal bud were observed. Scions of different ages were grafted onto 1‐yr‐old rootstocks, and the younger scions grew more and produced fewer strobili than older ones. Out‐of‐phase dormancy promoted both male and female flowering at all ages, but the older scions responded better. Gibberellin4/7plus water stress promoted development of female strobili only. Treatments that promote flowering also increase the size of the resting bud. It is proposed that treatment effects promoting flowering appear to fall into two categories: 1) Those which promote the formation of a resting bud, and 2) those which affect the subsequent development of resting buds which have the potential to develop strobili.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1981.tb07824.x

出版商:Wiley    

年代:1981

数据来源: WILEY

摘要:

Somatic incompatibility in two strains of the myxomyceteDidymium iridisis controlled by at least 13 loci: seven fusion loci and six clear‐zone loci. Details on correlating loci of the Hon 1 strain with Pan 1 loci are given and a unified nomenclature, applicable to both strains, has been developed from data presented in this paper. Although fusion loci generally prevent fusion between different plasmodial incompatibility phenotypes, studies on individual loci have shown that a limited transient fusion may occasionally take place. Thus, the differences between the fusion and clear‐zone loci are not as distinct as once thought. However, the 13 somatic incompatibility loci are still easily designated as either fusion or clear‐zone loci, and no locus has thus far been found with true intermediate function. Studies on individual locus function are also discussed.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1981.tb07825.x

出版商:Wiley    

年代:1981

数据来源: WILEY

摘要:

Taquari is the common name of a bamboo that occurs in the cerrado biome of central Brazil where it is subjected to long dry seasons and periodic fires. The buds of the culm are covered by hard scales that protect them during the dry season. The pachymorph rhizomes with short necks form a dense underground system that also aids in carrying the plant through this hostile period. The buds of the upper nodes of the culm begin growing during the wet season and produce horizontal subequal branches that do not rebranch. Those of the lowermost nodes, which occur at ground level or just below, are apparently specialized to break into growth only after fire. Although homologous to the buds of the upper nodes, those at the base of the plant produce tall, erect branches that rebranch and take on the appearance and function of the culms that were destroyed by fire. The spikelet, type of inflorescence, and fruit (achene) indicate that taquari should not be retained inArundinaria, where originally described, or inRhipidocladum, where recently transferred, but deserves recognition as a distinct genus, which is here given the name,Actinocladum. Included are complete descriptions of the new genus and its sole species:A. verticillatum(Nees in Martius) McClure ex Soderstrom.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1981.tb07826.x

出版商:Wiley    

年代:1981

数据来源: WILEY

摘要:

Formica schaufussi, a medium‐sized ant common throughout the Piedmont and Coastal Plain of the southeastern United States, has been observed in association withDiamorpha smallii, a self‐incompatible annual endemic to granite outcrops in the Southeast, over a 6‐yr period. Observations of ants collected on the flowers show large numbers of the sticky pollen grains adhering to hairs and indentations primarily on the thoraces of the ants. Though small native bees and flies are frequent and sometimes effective pollinators, it is highly unlikely that the monotypic genusDiamorphacoevolved with the introduced honeybee, as has been suggested. Characteristics indicative of an “ant‐pollination syndrome” include occurrence in hot, dry habitats, a high density of very small plants bearing overlapping inflorescences at a uniform height, and low seed number, pollen volume, and nectar quantity.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1981.tb07827.x

出版商:Wiley    

年代:1981

数据来源: WILEY

摘要:

Chromosome counts are reported for 33 species from all four sections of the genusHaplopappusin South America. These include first reports for 28 species and two putative hybrids. All chromosome numbers reported herein are 2n= 5II, with the exception ofH. prunelloideswith 2n= 6II. Unlike the North American species, the morphological diversity of South American taxa is not concomitant with chromosomal variation.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1981.tb07828.x

出版商:Wiley    

年代:1981

数据来源: WILEY

摘要:

This paper describes an attempt to present living stem tissue with defined mechanical stress in a spatial configuration which can be easily interpreted in section. We have applied compressive stress to a growingColeusinternode in vivo, using stainless‐steel spring‐clips which act through a double‐edged glass interface of known area.We have found that cambial activity consisting of cell division and enlargement continues even under applied compressive stress ranging up to 20 atm. Tissue reactions to applied stress are discussed in terms of the equilibration of forces propagating through the tissue before, during, and after the presentation of externally applied stress.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1981.tb07829.x

出版商:Wiley    

年代:1981

数据来源: WILEY

摘要:

Vallitheca valentiagen. et sp. nov. is a permineralized, synangiate fructification of probable seed fern affinities from the Wewoka Formation (Desmoinesian) near Ada, Oklahoma. Synangia are oblong to pyriform, average 1 cm long, and contain 32 to 48 tubular sporangia embedded proximally in ground tissue. The sporangia are arranged within the synangia in a unique pattern: a ring of peripheral sporangia dehisces toward the center of the synangium and a central group of sporangia dehisces outward. This unique arrangement is unlike that of any currently recognized group.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1981.tb07830.x

出版商:Wiley    

年代:1981

数据来源: WILEY