摘要:

Nuclear 1C DNA content in haploid megagametophyte tissue of 18 North American and one exoticPinusspecies was determined using scanning microspectrophotometry. The nuclear DNA content in root meristematic cells ofZea maysL. ssp.mays, inbred line Va35 (4C = 10.31 pg) was used as a standard. DNA content measured by microspectrophotometry was verified using laser flow cytometry with two additional standards,Hordeum vulgarecv. Sultan (2C = 11.12 pg) andP. eldarica(2C = 47.30 pg). DNA values obtained by both methods were significantly correlated(r= 0.987). The 1C nuclear DNA content ranged from 21 pg to 31 pg. The ratio of DNA content in embryo tissue ofP. eldaricato that in megagametophyte tissue was 1.72 by scanning microspectrophotometry and 1.74 by laser flow cytometry. To date, this is the most comprehensive data set available for North AmericanPinusspecies. Relationships between genome size of 18 North AmericanPinusspecies and climatic factors and indices of growth were investigated using regression and correlation analyses. Positive correlations were observed between nuclear DNA content and growth indices, minimum seed‐bearing age, and seed dimensions. Strong negative correlations were observed between nuclear DNA content and two climatic factors, the lowest mean annual and monthly precipitation (excluding January) and the highest mean monthly spring air temperature. These correlations suggest that the large genome size and its variation inPinusare adapted responses to the habitats of these species.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1993.tb15360.x

出版商:Wiley    

年代:1993

数据来源: WILEY

摘要:

Interannual variations in cone and seed production ofPinus banksianaLamb, were studied at the species northern limit of distribution in Québec (Canada). Cone number per cone‐bearing branch, potential number of seeds per cone, number of formed, filled, and viable seeds per cone, and seed viability, germination rate, and mass were determined for two populations of the species, over a 9‐year series. There were significant differences among years, but not between populations, in all the variables considered. The populations were well synchronized with each other, suggesting that climatic influence on the variables considered might be significant. Apparent periodicity in reproductive output also suggests the existence of some internal cycle, possibly in relation to tree reserves. Annual viable seed production is the result of a combination of events in the reproductive cycle of an individual (i.e., cone initiation, pollination, fertilization, and embryo maturation), each one specifically affected by climate. There are no apparent trade‐offs between seed mass and number of filled seeds per cone over time; moreover, there seems to be a positive relationship between seed mass and number of viable seeds per cone. Climate conditions during fertilization and embryo maturation (both of which occur during the same season) appear to significantly influence the species reproductive output. We present regression models based on meteorological variables to estimate cone and viable seed production, and seed mass.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1993.tb15361.x

出版商:Wiley    

年代:1993

数据来源: WILEY

摘要:

We compared genetic variability and clonal diversity in the closely related sedgesCarex lasiocarpaandC. pellitausing allozyme markers at 12 loci. Both species produce spreading rhizomes, occur in open habitats, and can form large clones; C.lasiocarpaprimarily along lakeshores, or in bogs, fens, or marshes, andC. pellitamore commonly along riverbanks and ditches or in wet meadows. Polymorphism was high in both species, similar to that of other rhizomatousCarexand to other species with comparable growth forms and life histories. Total gene diversity was higher forC. lasiocarpa(HT= 0.266) than forC. pellita(HT= 0.248), but the coefficient of differentiation among populations was lower. Rare alleles usually occurred as heterozygotes rather than homozygotes, and significant deviations from Hardy‐Weinberg equilibrium were found at few loci, suggesting that both species are predominantly outcrossing. Mean clone size, diversity, and evenness were not significantly different between the two species, although populations varied from monoclonal to those where nearly every sampled shoot belonged to a different clone. No significant differences in genetic variation or clone size ofC. pellitawere found when comparisons were made between groups based on climate (warmer vs. cooler) or successional stage (pioneer vs. established). However, within C.lasiocarpa, genetic variability decreased and clone size increased in cooler climates and at established sites.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1993.tb15362.x

出版商:Wiley    

年代:1993

数据来源: WILEY

摘要:

Fossil seeds ofEnsete, a genus presently native to Asia and Africa, have been recovered from the middle Eocene of Oregon, confirming the presence of Musaceae in the North American Tertiary. The seed ofEnsete oregonensesp. nov. is operculate, with a well‐defined micropylar collar, a pronounced chalazal chamber, and a wide hilar cavity. A survey of seed morphology in extant Zingiberales provides characters for distinguishing Musaceae from other families of the order, furnishes criteria for distinguishing the three extant genera of Musaceae (Musa, EnseteandMusella), and facilitates critical assessment of fossil seed remains. “Musa”cardiospermaJain from the Cretaceous/Tertiary boundary Deccan Series of India is excluded from Musaceae (although retained in Zingiberales) on the basis of fruit and seed characters, including the lack of laticifers and absence of a chalazal chamber. We reexamined the musaceous seeds from Colombia that previously were described as Tertiary fossils (Musa enseteformisBerry, 1925) and now believe that they are recent, nonfossil remains, evidently fromEnsete ventricosum, which is grown in the region where the specimens were originally obtained. In addition, a reputed fossil banana fruit from the Cretaceous of Colombia was reexamined and determined to be a concretion of nonbiological origin.Ensete oregonenseis significant therefore, as the first unequivocal fossil record ofEnseteand of Musaceae. Although the Musaceae are currently native only to the Old World tropics, this discovery establishes that the family was present in North America about 43 million years ago.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1993.tb15363.x

出版商:Wiley    

年代:1993

数据来源: WILEY

摘要:

Previous investigations reported that the marine algaCaulerpa prolifera, a giant coenocyte, had a fast morphogenetic response to a change in position with regard to gravity: the next rhizoid formed approximately 1 day later on the new underside of the inverted rhizome (Jacobs and Olson, 1980,American Journal of Botany67: 141–146). Preceding the change in site of rhizoid development was a striking accumulation of amyloplasts at the new prospective rhizoid‐initiation site in the rhizome tip. Detailed monitoring with video equipment of invertedCaulerpaplants, growing under controlled conditions, now reveals that after the amyloplast accumulation, but before the gravimorphogenetic effect on rhizoid development, the inverted rhizome tip shows a negative gravitropism that restores it to its normally upturned position. Because the experiments were performed with two‐sided illumination, this was clearly not a phototropic response.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1993.tb15364.x

出版商:Wiley    

年代:1993

数据来源: WILEY

摘要:

Using stereological procedures, a detailed analysis was made from thin section electron micrographs of secreting and nonsecreting salt glands ofFrankenia grandifolia(Cham. and Schlecht) andAvicennia germinans(L.) Stem. InF. grandifoliasecretory cells, vacuolar volume significantly decreased, while the volume of endoplasmic reticulum increased in secreting glands. Numerous minivacuoles were predominantly located along the periphery of secreting secretory cells, some in apparent fusion with the plasma membrane. No difference was found in mitochondrial volume in the secretory cells between secreting and nonsecreting glands. InA. germinans, there was a significant decrease in vacuolar volume in secreting secretory cells. The volume of the endoplasmic reticulum and mitochondria also increased in these cells. However, no evidence of mini‐vacuolar fusion with the plasma membrane was observed. These results indicate that the physical process of secretion may differ betweenF. grandifoliaandA. germinans; in both, however, the ultrastructural observations support the contention that specific structural parameters are correlated with the process of secretion.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1993.tb15365.x

出版商:Wiley    

年代:1993

数据来源: WILEY

摘要:

A carrot cell culture line was shown to be highly embryogenic, but plantlet recovery (conversion) was low (about 14%). The majority of somatic embryos that did not convert showed pronounced vacuolation in the apical notch, leading to their inability to form primary leaves and thereby convert. Comparisons of developing meristems in the shoot apical notch of converting somatic and zygotic embryos revealed similarities in cytoplasmic density and meristem organization between the two populations. Abscisic acid (ABA) was shown to significantly increase conversion in somatic embryos of globular, torpedo, and preplantlet stages (62%, 62.5% and 40%, respectively). Somatic embryos that were treated with 50μMABA showed retention of the highly cytoplasmic cells in the apical notch. Histological analysis showed a resemblance between shoot apices of converting somatic embryos and ABA‐treated somatic embryos. ABA may be an induction agent for meristematic organization, or perhaps may cause cells of the apical notch to extend competence for determination as meristematic cells.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1993.tb15366.x

出版商:Wiley    

年代:1993

数据来源: WILEY

摘要:

Photosynthesis, stomatal conductance, and water use efficiency were compared betweenLonicera japonica(Japanese honeysuckle), an invasive species in the southeastern United States, and its native congener,Lonicera sempervirens(coral honeysuckle), to determine the role of seasonal patterns of water loss and carbon gain in the invasive ability of the exotic. Diurnal measurements were taken monthly for 1 year under a closed forest canopy and in an open field. There were few significant differences in photosynthetic rates between the two species in either environment. However, at both sites,Lonicera japonicaretained its old leaves over winter while old leaves ofL. sempervirenssenesced. Also, new leaves ofL. japonicahad significantly higher photosynthetic rates than the emerging leaves ofL. sempervirens(6.2 vs. 4.4μmol m2sec‐1under the canopy; 4.4 vs. 3.0μmol m‐2sec‐1in the open). Although differences in conductance and water use efficiency between species were seldom significant,L. japonicatended to have higher maximum values thanL. sempervirens.Retention of old leaves byL. japonicaduring new leaf formation (January–March) as well as higher photosynthetic rates in new leaves contribute to greater annual carbon gain and help explain the invasive ability of Japanese honeysuckle.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1993.tb15367.x

出版商:Wiley    

年代:1993

数据来源: WILEY

摘要:

Flowering phenology, fruit set, and pollinator frequency of the ericaceous alpine dwarf shrub,Rhododendron aureum, were compared among three quadrats arranged along a snowmelt gradient on a slope. Bagging and self‐pollination experiments showed thatR. aureumwas physiologically self‐compatible, but pollinator visitation highly enhanced fruit set. Depending on the lateness of snowmelt, flowering time varied from mid‐June to late July among quadrats. Pollinator visitation increased as the flowering season progressed, and fruit set was significantly higher in the quadrat with latest snowmelt. Emasculation experiments suggested that later flowering might promote cross‐pollination. Thus, later flowering was advantageous for effective pollination. On the other hand, later‐flowering plants often failed to set fruits because of the onset of autumn frost and snow before fruit maturation.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1993.tb15368.x

出版商:Wiley    

年代:1993

数据来源: WILEY

摘要:

Various mutually compatible hypotheses have been proposed to explain the low levels of fruit set observed in many hermaphrodite plants. I carried out trials to determine which of these hypotheses best explains the low fruit set occurring inPrunus mahalebL. (Rosaceae). The results of insect exclusion, supplementary pollination, and flower removal experiments indicate that the ovary reserve hypothesis and the selective abortion hypothesis seem to be the most likely explanations for the production of excess flowers inP. mahaleb.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1993.tb15369.x

出版商:Wiley    

年代:1993

数据来源: WILEY