摘要:

The hypothesis was tested that the well‐known maximal sensitivity to a light break at or near the middle of the dark period of short‐day plantXanthiumis correlated with a specific stage of leaf initiation. Samples were collected at various hours before and during noninductive 6‐hr dark periods. Lengths of leaf primordia were calculated from serial transverse sections. The reproducible results confirmed that leaf initiation occurred at or near middark under the 18:6 hr light: dark growing conditions. The author suggests the working hypothesis that for a light break to be effective in nullifying the effect of a “long” night in photoperiodically sensitive plants, the light must react with a specific early stage of leaf initiation.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1992.tb13626.x

出版商:Wiley    

年代:1992

数据来源: WILEY

摘要:

Differentiation in the anther ofLilium longiflorumoccurs in discrete stages that correlate well with flower bud length. Using both sodium dodecyl sulfate and two‐dimensional polyacrylamide gel electrophoresis, detectable proteins that accumulated during the development of lily anthers were documented. In terms of histology and protein patterns, anther ontogeny was divided into three major phases. Phase I encompassed early proliferative stages as well as the differentiation of the locules. Phase II extended from the onset of meiosis through to mature microspores. Phase III began after microspore mitosis occurred to form pollen. Ten floral organ‐enriched and 17 floral organ‐specific polypeptides were detected during development. The appearance and disappearance of these polypeptides correlated well with the transitions between phases. Two groups of floral organ‐specific proteins in Phase II were chosen for further analysis. Both groups of polypeptides were stamen‐specific. The 15.0 kD proteins were anther‐specific and were the most abundant floral proteins detected; the 75.0 kD proteins were detected in both the anther and filament.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1992.tb13627.x

出版商:Wiley    

年代:1992

数据来源: WILEY

摘要:

The effects of different watering regimes on vegetative growth, histological properties of wood, and the derived values relevant to paper and pulp production ofGmelina arboreaRoxb. were investigated. Soil moisture stress significantly retarded vegetative growth as analyzed by leaf area ratio, root shoot ratio, net assimilation rate, and relative growth rate. Moisture stress also adversely affected specific gravity of the wood, fiber length, diameter, lumen size, and fiber wall thickness, but enhanced flexibility coefficient, lowered slenderness ratio, and runkel ratio. Although water stress reduces the volume of wood produced and changes wood fiber properties, it does not significantly affect the quality of paper produced fromGmelinawood.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1992.tb13628.x

出版商:Wiley    

年代:1992

数据来源: WILEY

摘要:

Although the dispersal of seeds around individual plants (the seed shadow) has frequently been characterized, the dispersion of seedlings around plants (the seedling shadow) has rarely been examined. We mapped 101 and 149 seedlings of the prairie compass plant (Silphium laciniatum) that appeared in our study area in 1987 and 1990 following mass flowering in 1986 and 1989. We also mapped the locations of flowering stems which appeared in 1986 and 1989 and recorded the number of flowerheads at each stem location. The frequency distributions of distance between a seedling and the nearest flowering stem were identical in the 2 years, with a median distance of 1.0 m. The large size and lack of wind‐dispersal structures of compass plant seeds (achenes) are responsible for their limited dispersal. From estimates of the total seed production in the study area in 1986 and 1989, we calculated that about 1% of seeds became seedlings in each year. Flowering stem locations with a higher number of flowerheads had a significantly higher density of seedlings around them. This indicates that recruitment to compass plant populations is not a “lottery”; individual plants that produce more seeds produce, on average, more seedlings.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1992.tb13629.x

出版商:Wiley    

年代:1992

数据来源: WILEY

摘要:

Pollen accumulation rates and their relationship to stigma morphology and pollinator visitation behavior were compared between female and hermaphrodite sex morphs of the alpine plantSilene acaulisvar.subacaulescens(Caryophyllaceae). Although stigmas of female and perfect flowers collected comparable pollen loads, stigmas of female flowers became receptive earlier in anthesis and therefore recruited a larger number of pollen tubes. Together with early receptivity young female flowers had a larger stigmatic area with longer papillae than did perfect flowers. Pollinator behavior also differed between morphs, with bumble bees spending more time probing female than perfect flowers. Differences in stigma receptivity schedules of female and perfect flowers have consequences for different opportunities for sexual selection in the two sex morphs. Female flowers, by providing a more effective gametophytic screen, have the potential to produce higher quality offspring. This is proposed as a further compensatory advantage maintaining females, with a single fitness function, in populations containing hermaphrodites which have both male and female fitness functions.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1992.tb13630.x

出版商:Wiley    

年代:1992

数据来源: WILEY

摘要:

Studies ofLilium philadelphicumon Isle Royale National Park, Lake Superior, show that thecae (pollen‐containing sacs) of dehisced anthers close in the rain, thus protecting the pollen and prolonging the pollen donor phase of the flower. To our knowledge, this is the first report of anthers with longitudinal dehiscence reclosing after opening. Individual flowers ofL. philadelphicumare long lived (8–11 d), do not shorten their flowering period in response to successful fertilization of the ovules, and are primarily pollinated by butterflies. Butterflies do not forage in the rain and may first visit a flower several days after anthesis. Under such circumstances, strong selection may exist to protect pollen during unfavorable weather conditions in order to prolong the pollen donor phase. Flowers with long pollen donor phases are likely to contribute more offspring to the next generation than flowers with short pollen donor phases.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1992.tb13631.x

出版商:Wiley    

年代:1992

数据来源: WILEY

摘要:

Fertilized stands ofPseudotsuga menziesiiwere found to have glaucous needles. We investigated the morphological and quantitative characteristics of the epicuticular waxes of needles of fertilized and control trees. Glaucousness was caused by ornate tubular epicuticular wax. Dipping needles in chloroform, which dissolves waxes, eliminated the glaucous appearance. Based on cryostage scanning electron microscopic observations, the epicuticular waxes in the nonstomatal region were much more ornate on the needles of the fertilized trees (experimental needles) than in unfertilized trees (control needles). The stomatal region in both experimental and control needles showed similarly ornate waxes. Quantities of waxes were similar in experimental and control needles. The glaucousness was not the result of greater quantities of wax; rather, fertilization altered wax morphology in the nonstomatal regions.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1992.tb13632.x

出版商:Wiley    

年代:1992

数据来源: WILEY

摘要:

The pinnately compound, indeterminate leaves ofG. glabraandG. guidoniawere air layered, detached from their original shoots, and grown on their own adventitious root systems for up to 58 mo and 26 mo, respectively. The detached leaves grew in the same indeterminate manner and reached sizes similar to attached leaves. Although detached leaves grew autonomously, they never produced shoot buds. Leaves of both species were grafted onto their own stems and cut free of their original leaf bases. Leaf scions survived and grew for up to 29 mo and 20 mo, respectively, similar to ungrafted leaves. Axillary branches were grafted onto subtending leaves. Branch scions grew on their leaf stocks for over 30 mo and 24 mo, respectively, after being cut free from the branch bases. Secondary growth of the leaf axis (petiole) was promoted, and vascular tissues of leaf and branch axes were continuous. However, the unlignified basal region of the leaf, including the abscission zone, remained unchanged after grafting. The results indicate that proximity of roots and bypassing the abscission zone did not enhance leaf longevity or pinna production. The presence of a growing branch on a leaf did not modify the structure of the abscission zone, which suggests that the zone is strongly committed or developmentally fixed.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1992.tb13633.x

出版商:Wiley    

年代:1992

数据来源: WILEY

摘要:

Formation of secretory vesicles in the noncellular secretory cavity of glandular trichomes ofCannabis salivaL. was examined by transmission electron microscopy. Two patterns of vesicle formation occurred during gland morphogenesis. 1) During initial phases of cavity formation small hyaline areas arose in the wall near the plasma membrane of the disc cell. Hyaline areas of elongated shape and different sizes were distributed throughout the wall and adjacent to the secretory cavity. Hyaline areas increased in size, some possibly fusing with others. These hyaline areas, possessing a membrane, moved into the cavity where they formed vesicles. As membraned vesicles they developed a more or less round shape and their contents became electron‐dense. 2) During development of the secretory cavity and when abundant secretions were present in the disc cells, these secretions passed through the wall to accumulate as membraned vesicles of different sizes in the cavity. As secretions emerged from the wall, a membrane of wall origin delimited the secretory material from cavity contents. Vesicles released from the wall migrated in the secretory cavity and contacted the sheath where their contents permeated into the subcuticular wall as large or diffused quantities of secretions. In the subcuticular wall these secretions migrated to the wall–cuticle interface where they contributed to structural thickening of the cuticle. This study demonstrates that the secretory process in glands ofCannabisinvolves not only secretion of materials from the disc cell, but that the disc cell somehow packages these secretions into membraned vesicles outside the cell wall prior to deposition into the secretory cavity for subsequent structural development of the sheath.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1992.tb13634.x

出版商:Wiley    

年代:1992

数据来源: WILEY

摘要:

InHevea, currently described culture conditions allow the induction of two modes of embryogenesis in callus formed on excised portions of the internal integument of immature seeds. One mode is of unicellular origin and is transitory, only resulting in the production of globular proembryos. The other is of multicellular origin and produces embryos. Specific culture conditions appear to favor one or the other mode of development in a given genotype. The ontogenesis of embryos of multicellular origin bypasses the classical stages of zygotic embryogenesis. The structural abnormalities observed in most somatic embryos are probably responsible for the low germination rates obtained.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1992.tb13635.x

出版商:Wiley    

年代:1992

数据来源: WILEY