摘要:

Within‐tree and seasonal variation in quantitative characters of oak leaves were evaluated by factorial analysis of variance. All linear and areal measurements illustrate marked within‐tree and seasonal variation. Numbers of lobes and bristle tips and primary vein angle appear relatively stable within trees and among seasons. In many instances, size‐correction reduces both within‐tree and seasonal variance to nonsignificant levels. However, all characters do not illustrate the same trends either within trees or across the seasons. The results have important implications for those attempting to evaluate among‐tree and among‐population variation.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1988.tb08798.x

出版商:Wiley    

年代:1988

数据来源: WILEY

摘要:

Numerous megafossils of Lauraceae have been reported from the early Tertiary of North America, but the subfamilial affinities are usually not well understood due to the great morphological variability found in extant taxa. The flowers ofAndroglandula tennessensisgen. et sp. nov. Taylor, from the Middle Eocene Claiborne Formation, are six‐parted, pedicellate, bracteate, and have stamens with paired basal staminal glands. The flowers have ethereal oil cells and paracytic stomates throughout. The fossil species has affinities with the subtribe Cinnamomineae, and this supports suggestions that the Middle Eocene climate of the southeastern U.S. was subtropical. The existence of this fossil, and reports of the subtribe from the Eocene of Europe, indicate a South American‐North American‐European‐southeast Asian paleodistribution suggesting that extinction in North America and Europe was the cause of the tribe's current disjunct distribution.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1988.tb08799.x

出版商:Wiley    

年代:1988

数据来源: WILEY

摘要:

The reproductive ecology of a dioecious Caribbean seagrass,Thalassia testudinumwas studied in St. Croix, U.S. Virgin Islands. Flowering inThalassiacoincided with spring tides with anthesis and anther dehiscence in staminate plants occurring at night. As predicted by search theory, pollen is dispersed in negatively buoyant rafts of pollen grains (that superficially resemble strings of frog spawn) which are bound by a slime of apparent thecal origin. Dispersal of pollen is submarine and approximately two‐dimensional along the plane of the substratum. The stigmas on pistillate plants are linear, stiff, and densely papillate; they protrude from the mouth of the subtending leaf. Floral ratios of staminate to pistillate flowers were 60 to 1 with an average distance of 4.0 cm from pistillate flower to the closest staminate flowers. Populations included a high proportion of short shoots with numerous (>100) leaf scars indicating ages for these axes of up to 3–4 years. Nonflowering shoots can be sexed and frequency of flowering can be assessed from scars of old inflorescences. Preliminary results suggest that there is no regular pattern of flowering, since the interval between flowering events is variable.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1988.tb08800.x

出版商:Wiley    

年代:1988

数据来源: WILEY

摘要:

In vitro bioassays on seven species of ectomycorrhizal fungi associated with black spruce (Picea mariana(Mill.) BSP) were tested under allelopathic action of raspberry (Rubus idaeusL.). Radial growth inhibitions were observed when fungi were confronted with increasing concentrations (0%–0.1%–0.5%–2.5%) of foliar leachates made from May, July, and September material (1986). For the 2.5% treatment, speciesPaxillus involutus, Laccaria proximo, Laccaria bicolor, Thelephora terrestris, andCortinarius pseudonapusgrew only 6, 8, 32, 42, and 46% of their control, whereasHebeloma cylindrosporumandCenococcum geophilumwere stimulated. Tree seedlings from raspberry invaded plantation showed mycorrhizal infection rate over 75%, with fine roots mainly colonized byC. geophilum.In combination with efforts of tree improvement and based on the results of this study, it seems important to select a well‐adapted my‐corrhizae, when interference by raspberry is involved.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1988.tb08801.x

出版商:Wiley    

年代:1988

数据来源: WILEY

摘要:

The floral nectar sugar compositions of 20 New World species from 10 genera and of five interspecific hybrids in tribe Antirrhineae have been analyzed using high‐performance liquid chromatography. Species are pollinated by short‐tongued bees, long‐tongued bees, and hummingbirds. Ornithophily represents the derived condition in the tribe and has arisen independently in subtribes Maurandyinae and Gambeliinae. All nectars analyzed are sucrose‐dominant or ‐rich, except for the hexose‐rich nectar ofMohavea breviflora.Despite the predominance of sucrose, floral nectar sugars from species pollinated by different pollen vectors have characteristic constituents. Nectar sugars from flowers visited by hummingbirds average 76.2% sucrose and have compositions remarkably similar to hummingbird nectars analyzed in previous studies of unrelated species. Long‐tongued bee nectars average 87% sucrose and differ from shorttongued bee nectars which have the lowest mean sucrose percentage (40.2%). The association of sugar constituent types and principal pollinators is concordant with previous data and supports hypotheses concerning pollinator preferences and the adaptive significance of certain nectar sugar compositions. Within this adaptive framework, phylogenetic constraint is also operative and may explain the predominance of sucrose in nectar sugars, similarities in sugar composition among hummingbird nectars in subtribes Maurandyinae and Gambeliinae, and the similarity of nectar fromGalvezia leucantha(long‐tongued bee‐pollinated) to hummingbird‐pollinated species also in subtribe Gambeliinae.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1988.tb08802.x

出版商:Wiley    

年代:1988

数据来源: WILEY

摘要:

The tissue ofCystoseira osmundacea(Turn.) C. Ag. (Fucales, Phaeophyta) undergoes pronounced developmental changes when in association with the fungusHaloguignardia irritans(Setchell et Estee) Cribb et Cribb (Sphaeriales, Ascomycotina). Nonmeristematic cortical cells are induced to divide and ultimately form a structure composed of tightly packed club‐shaped projections. Each projection contains a single fungal ascocarp or spermogonium. A protective multilayered algal tissue surrounds the fungal reproductive structures. This association significantly alters algal morphology to the apparent protective advantage of the fungus.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1988.tb08803.x

出版商:Wiley    

年代:1988

数据来源: WILEY

摘要:

Periclinal chloroplast chimeras are genetic mosaics which possess shoot apices composed of one or more chlorophyll‐deficient histogens and can exist as a series of arrangements of normal and mutant layers (A‐B‐B, A‐B‐A, etc.). Three periclinal chimeral cultivars ofSansevieria trifasciataL., each of which possesses normal green cell layer(s) but a genetically different chlorophyll‐deficient cell layer(s), were utilized to study the effect of genotype on the ability of the cell layers of leaf cuttings and of cultured leaf tissue to regenerate shoots. The epidermis and LI derivatives were apparently incapable of shoot regeneration via leaf cutting, yet in two cultivars produced some shoots in vitro. In two of the cultivars, the chlorophyll‐deficient cells never produced shoots. In the third, the capability of chlorophyll‐deficient cell layers to produce shoots was less in vitro than in vivo, indicating that when determining morphogenic potential, direct comparisons between in vitro and in vivo systems may not be valid. Results also demonstrate that because genetically different albino cell layers can differ in their morphogenic response, utilizing a series of periclinal chimeras is useful only if the series is composed of the same two genotypes.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1988.tb08804.x

出版商:Wiley    

年代:1988

数据来源: WILEY

摘要:

Bending experiments were performed to analyze mechanical properties within the apical 15 mm of the primary root of corn,Zea mays.Force required to maintain a root in a bent shape declined with the logarithm of time, indicating significant stress relaxation. Spatial distributions of local curvature, strain due to bending, and geometrical moment of inertia were calculated from digitized photographs of mechanically bent roots during and after imposition of a bending moment. When roots were bent to nonuniform curvature (maximum K = 3 cm–1at the location 8 mm from the root tip), “irreversible” curvature (residual curvature 4 hr after release of the bending moment) was approximately 44% of initial curvature. This percentage of irreversible curvature (and associated bending strain) was uniform throughout the growth zone. When roots were bent to uniform curvature of either 1 cm–1or 1.67 cm–1, “springback” curvature (residual curvature after two minutes of bending) varied from 60% of initial curvature in the apical regions (at 4 mm) to 85% of initial curvature at the base of the growth zone. The results are consistent with a model in which total strain is proportional to stress, and irreversible strain at a particular location is proportional to total strain at the same location.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1988.tb08805.x

出版商:Wiley    

年代:1988

数据来源: WILEY

摘要:

A bending technique was used to infer the spatial distributions of rheological properties within the growth zone of the root of corn,Zea mays.“Bending modulus” (ratio of stress to strain, calculated from engineering theory of bending) falls from 20 MPa near the root tip (3 mm from the tip) to 6 MPa at the location 6 mm from the tip and then remains uniform through the basal region of the growth zone. Where growth stops, at 11–12 mm, there is a sharp rise in bending modulus. The profile of bending moduli is not changed by root incubation temperature during the growth period prior to bending, but it is shifted to the left in roots growing more slowly than the average at either of two temperatures (19 and 29 C). The spatial distribution of “compliance” (reciprocal of bending modulus and a measure of tissue extensibility) resembles the distribution of swelling in response to osmotic perturbation. The distribution of compliance does not parallel that of growth rate. Attempts to explain the discrepancy between compliance and growth rate lead us to examine the theoretical basis for the calculations and to suggest that the dependence of compliance on rate of stretching is physiologically important.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1988.tb08806.x

出版商:Wiley    

年代:1988

数据来源: WILEY

摘要:

A new plant cohort starts with the formation of zygotes at ovule fertilization. This paper presents an ecological study of the effects of resource limitation and pollen donor on the survivorship and size of plant embryos in maturing fruits of the common bean,Phaseolus vulgarisL. For naturally selfed flowers of domesticated and wild beans, embryos in basal ovular positions were more likely to abort or, if they survived, become lighter seeds than stylar embryos. Embryo survivorship was higher for the cultivar when maternal plants grew in larger pots. Early seed abortion in the cultivar was random with respect to ovular position. In late abortion basal embryos had a higher mortality than stylar ones. The basal embryos lacked gross genetic defects since they developed adult organs in embryo culture. In more outbred crosses with the cultivar the position effect in embryo survivorship and size disappeared. This difference among paternal parents implicates a genetic component to the observed position effects. The variation in mature seed size may affect adult characteristics since large seeds produced larger juvenile plants than small seeds.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1988.tb08807.x

出版商:Wiley    

年代:1988

数据来源: WILEY