摘要:

Study of seed banks, field seedling emergence, and survival of macrophytes in four zones (steep bank—SB; gentle bank—GB; midbank—MB; high marsh —HM) along transects perpendicular to a stream channel in a freshwater tidal wetland showed that many species are widely distributed. Of the 35 species in the seed bank, 50% were common to all zones; of the 20 species emerging in the field, 77% were observed in all zones. Density of seeds, seedlings, and mature plants of most species, however, varied significantly with habitat. The seed bank of each zone reflected the dominant vegetation of that zone. Most species, even those with high potential for water dispersal, were not evenly distributed. Reciprocal transplants and survival persistence data of dominants corresponded with their habitat preferences. Seed bank densities differed from zone to zone (SB 1,717 m‐2; GB 1,645; MB 2,730; HM 3,620). In all zones the maximum field seedling density was less than the comparable seed bank one (SB 38% less; GB 33%; MB 46%; and HM 10%). These data, coupled with the higher proportion of the total seed bank and total field seedlings occurring in the HM, suggest that the stream channel sites were more stressful early in the growing season than the HM. Because of differential establishment and survival, importance of a species relative to the rest of the vegetation may change with time and occurrence of a species in the vegetation may greatly outweigh its importance in the seed bank or even the seedling stage. Although seeds of annual species were numerous with seven species making up 85% of the seed bank, annual species comprised only about half of the species recorded in the seed bank of each zone. It is not possible at our present level of understanding of seed banks in the freshwater tidal marsh to predict vegetation change. Various combinations of species attributes contribute to the zonation patterns observed in the freshwater tidal wetland.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1985.tb08280.x

出版商:Wiley    

年代:1985

数据来源: WILEY

摘要:

Icacinoxylon pittiense, a new species of angiospermous wood from the Lower Cretaceous Cedar Mountain Formation of Utah is described and compared with similar fossil and modem woods. It is distinguished from other species ofIcacinoxylonby its thick‐walled fiber‐tracheids with their walls making up at least 50% of the total diameter of the cells, conspicuous bordered pits with obliquely crossing extended apertures on both the tangential and radial walls of its fiber‐tracheids, scalariform perforation plates with as few as four or greater than 30 bars, transitional opposite to scalariform pitting on its vessel walls, thick‐walled ray cells, and distinct sheath or border cells in its rays.Icacinoxylon pittienseis the first species of this genus to be reported from Cretaceous sediments. This wood is of special interest because very few angiosperm woods have been reported from lower Cretaceous strata.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1985.tb08281.x

出版商:Wiley    

年代:1985

数据来源: WILEY

摘要:

This report summarizes a 6‐yr study of male and female cone production in a population of 216 ponderosa pines whose ages, diameters, and genotypes at 7 protein polymorphisms are known. There are different schedules of male and female reproduction. The majority of cones are produced by the same few trees each year. There is a tradeoff between growth rate and female cone production but not pollen production. Differential female (but not male) cone production is associated with protein genotype. The variance of female reproductive effort declines with increasing protein heterozygosity.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1985.tb08282.x

出版商:Wiley    

年代:1985

数据来源: WILEY

摘要:

In north central Kentucky, seeds of the mesic forest biennialHydrophyllum appendiculatumMichx., are innately dormant at maturity in June. Under natural and simulated seasonal temperature changes, dormancy break occurred in two stages. Root dormancy was broken by high summer temperatures, and shoot dormancy was broken by low winter temperatures. Consequently, roots emerged from seeds during autumn, and cotyledons emerged the following spring. A 90‐day warm (30/15 C) stratification treatment broke root dormancy, but the roots emerged only after transfer to lower temperatures. After the warm stratification treatment, roots emerged from 93, 73, 6 and 9% of the seeds incubated at 5, 15/6, 20/10 and 30/15 C (12/12 hr), respectively. Zero, 28, 56 and 84 days of cold (5 C) stratification of seeds with emerged roots resulted in 9, 21, 49 and 82% cotyledon emergence, respectively, at 20/10 C. Thus,H. appendiculatumexhibits a type of morpho‐physiological dormancy known as epicotyl dormancy. Although many seeds germinate the first year, others remain dormant and germinate in successive years until the fourth season after ripening.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1985.tb08283.x

出版商:Wiley    

年代:1985

数据来源: WILEY

摘要:

Phloem histology in the petioles of two genera of Pennsylvanian ferns is detailed from coal balls collected at various localities in North America. BothAnkyropterisandAnachoropterishave primary phloem that completely surrounds the central xylem trace and is separated from it by a parenchymatous sheath.Ankyropteriscontains very narrow (about 13.5μm diam) sieve elements and a few strands of phloem parenchyma. End walls are either horizontal or slightly oblique and sieve areas as well as scattered individual pores have been observed.Anachoropterisphloem contains two different sizes of sieve elements. Small sieve elements that surround the C‐shaped trace are similar to those seen inAnkyropteris.Larger elements (approximately 50–120μm in diam) are present only within the C‐shaped trace, and are elongate (up to 2.5 mm) with very oblique end walls. Sieve areas on these large cells are conspicuous, 5–8.5μm in diam and aggregated into groups. The cell wall within each sieve area appears to be composed of criss‐crossed fibrillar material. Phloem anatomy in these two ferns is compared to that previously described in other Carboniferous vascular cryptogams, as well as that known from extant plants.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1985.tb08284.x

出版商:Wiley    

年代:1985

数据来源: WILEY

摘要:

The concentrations of 15 heavy metals in aquatic plants on Charity Island was compared to those in plants on the shoreline of Saginaw Bay, Lake Huron, U.S.A. Heavy metal concentrations were measured by neutron activation analysis. Charity Island was found to have significantly higher levels of nine of fifteen metals investigated. This indicates that distance from known pollution source was not the only factor affecting the heavy metal accumulation of the aquatic plants.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1985.tb08285.x

出版商:Wiley    

年代:1985

数据来源: WILEY

摘要:

The cycadZamia pumilaL. was examined for differences in leaflet morphology between sun and shade plants and between males and females within a single population in northern Puerto Rico. Sun leaflets are significantly smaller than shade leaflets in length, width, and surface area; and sun leaflets have a higher length: width ratio than shade leaflets. Also, average densitythickness is greater for sun leaflets than for shade leaflets. Males and females are similar in leaflet size; but the females had a larger number of leaflets per leaf than males.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1985.tb08286.x

出版商:Wiley    

年代:1985

数据来源: WILEY

摘要:

Kyllinga nervosaandThemeda triandraplants were subjected to different clipping and nitrogen availability regimes. Following an extended period of growth under these conditions, total biomass, gas exchange and several morphological parameters were measured.Kyllinga nervosashowed compensatory growth to moderate levels of clipping whereas any clipping reduced the total biomass ofT. triandra.Unclipped plants of either species were unable to respond to increased levels of nitrogen. Clipped plants responded in an ambiguous fashion, with increased allocation to offtake (material removed by clipping) in both species. Total biomass ofK. nervosawas highest at 15 mM nitrogen levels which are equivalent to field levels. Both photosynthesis and respiration rates were unaffected by nitrogen treatments. Photosynthesis was significantly reduced by the most severe clipping regime ofK. nervosa, but was unaffected by clipping ofT. triandra.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1985.tb08287.x

出版商:Wiley    

年代:1985

数据来源: WILEY

摘要:

The classification of specialized floral syndromes has imposed a bias in the interpretation of pollination systems which may be either more generalized, or more specialized, than we have universally acknowledged. An analysis of floral biology in two umbellifer genera,ThaspiumandZizia, was undertaken in order to determine the extent to which cryptic floral or inflorescence variations determine pollination specialization despite a broad visitor spectrum and open reward system. Separate analyses were made of the primary attractants, nectar and pollen, and the secondary attractants, floral color and floral and inflorescence structure in conjunction with analyses of pollinator movements, stigmatic pollen loads and fruit set. All data support the conclusion that cryptic variation in floral and inflorescence characters enhance specialization for pollination by solitary bees or syrphid flies. In addition, evidence is presented for the importance of the oligolectic relationship between taxa ofThaspiumandZiziaand the solitary bee,Andrena ziziae.The need for more experimental work both to further define the oligolectic relationship and to understand how floral and inflorescence color and structure affect insect movements is especially revealed by this study. The degree of pollination specialization inThaspiumandZiziais not uncommon in Apiaceae and has important implications for floral evolution in this family and other plant groups with pollination systems categorized as “promiscuous.”

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1985.tb08288.x

出版商:Wiley    

年代:1985

数据来源: WILEY

摘要:

The anatomical basis for the shrunken endosperm phenotype of eight recessive maternal effect mutants (seg1‐seg8) of barley (Hordeum vulgareL.) is described. Plants which are homozygous recessive for these nuclear genes produce only shrunken seeds regardless of pollen source. Light microscopy revealed that four of the mutants,seg1, seg3, seg6, andseg7, exhibited premature termination of grain filling because of the necrosis and crushing of the chalaza and nucellar projection of the pericarp early in the grain‐filling period, resulting in thin, wrinkled seed. Endosperm growth of these mutants before the occurrence of chalazal necrosis seemed normal. The other four mutants exhibited characteristic abnormalities in the endosperm growth pattern but normal development of matemal‐origin tissues. Endosperm size was severely reduced inseg2, in which two flat columns of tissue were present with no central endosperm.Seg4 andseg5 developed distorted, disorganized endosperms of variable size. Endosperms ofseg8 developed as two well‐filled lobes with no central endosperm, resulting in a distinct dorsal crease. We suggest that the mutants are useful as probes to study maternal effects on endosperm development.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1985.tb08289.x

出版商:Wiley    

年代:1985

数据来源: WILEY