摘要:

Alcohol dehydrogenase activity can be readily localized within bean seeds using the tetrazolium method. In the seed coat, prior to the cotyledon stage of embryo development, staining was seen throughout, especially in the branched parenchyma cells and the integumentary tapetum. As the embryo entered the maturation stage, a gradual decrease in the staining intensity was observed throughout the seed coat. Embryos stained well at all stages of development. In the course of this investigation, a high activity of “nothing dehydrogenase” was observed. Since its activity could be inhibited by methylpyrazole, an ADH inhibitor, it is concluded that the nothing dehydrogenase activity is caused by alcohol dehydrogenase.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1987.tb12137.x

出版商:Wiley    

年代:1987

数据来源: WILEY

摘要:

The effect of pretreatment on zinc‐ and copper‐enriched media on subsequent tolerance ofF. hygrometricato these metals was tested in three individuals each from a tolerant and a nontolerant population. Some individuals showed a significant response to pretreatment and some did not, and those that did varied in both intensity and direction. In general, pretreatment affected protonemal growth more than stem production. Although pretreatment effects were demonstrated, genetic differences between individuals and populations were more important determinants of the level of tolerance.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1987.tb12138.x

出版商:Wiley    

年代:1987

数据来源: WILEY

摘要:

The relative contributions of genetic and maternal factors to phenotypic variation were studied in seedlings of the clonal herbSolidago altissimaL. Pairwise crosses were made to establish 19 full‐sibships. Because crosses were reciprocal, each parent served as seed parent to half its offspring and as pollen parent to the other half. For 18 characters, genetic variation was estimated from the between sibship variance and maternal variation from the variance between maternal groups within sibships. Early in the growing season, maternal effects exerted strong influence over variation in leaf and stem dimensions, while genetic influences were weak or absent. At the end of the season genetic influences on leaf and stem dimensions, relative biomass allocation between stem and leaves, and the propensity to flower were significant but maternal effects were not. However, both genetic and maternal influences were found on the number and lengths of new rhizomes.Phenotypic, genetic, and maternal correlation matrices were examined through principal component analysis for trade‐offs among vegetative growth, clonal expansion and floral reproduction which could constrain the evolution of life history patterns. At the phenotypic level, seedlings with strong vegetative growth produced more and longer rhizomes, and were more likely to flower. Genetically, correlations among these functions were weak or absent. Strong maternal contributions to seedling vegetative growth correlated positively with the number and length of rhizomes. Thus, no trade‐offs acting during the seedling stage were found. However, there were indications of a genetically influenced trade‐off between the number of rhizomes produced in the seedling year with the size of the ramets produced in the second year.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1987.tb12139.x

出版商:Wiley    

年代:1987

数据来源: WILEY

摘要:

To investigate differences in leaf structure, chlorophyll and nutrients on terminal branches of the understory treeAsimina triloba, the first (proximal) and the last (distal) leaves to develop in the spring were compared. Proximal leaf expansion was completed before the overstory canopy was fully closed but distal leaf expansion occurred during and after the development of the overstory canopy. Fully expanded proximal leaves were 76% smaller in area, were 18% thicker and had 36% more stomates per m of leaf area when compared to distal leaves. In addition, maximum stomatal conductance to water vapor was greater (150 vs. 120 mmol m−‐2s−‐1) and the minimum PPFD required for maximum conductance was higher (200 vs. 150 μmol m−‐2s−‐1) for the proximal leaves. Chlorophyll content was also greater for proximal leaves, but nitrogen and phosphorus contents were lower throughout the entire summer. Seasonal measurements indicated an increase in chlorophyllacontent and reductions in nitrogen content throughout the summer growth period for leaves from both positions. The results suggest that distal and proximal leaves differed physiologically and that the measured differences were related to the changing irradiance environment during leaf development. The time of leaf expansion, as indicated by leaf position on the branch, may be an important consideration when examining the water and photosynthetic relations of understory trees.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1987.tb12140.x

出版商:Wiley    

年代:1987

数据来源: WILEY

摘要:

Shoot apices ofSaraca indicaproduce adult leaves that have 4 to 6 pairs of leaflets, whereas those ofS. bijugausually have only 2 pairs. In both species one leaflet pair is found during the juvenile phase. Juvenility lasts many plastochrons inS. bijugabut is restricted to a few inS. indica.The shoot apical meristems of these two taxa are similar in structure, cell number, and cell size; however, the shoot apex ofSaraca bijugais slightly more stratified, having 2–3 tunica layers as opposed to 1–2 inS. indica.For most of the plastochron the apical meristem in both species is situated laterally at the base of the most recently formed leaf. A newly forming primordium and its internode shift the apical meristem upward unilaterally; the meristem passes through a brief apical dome stage and becomes positioned 180° from its origin at the beginning of the plastochron. Hence, there is a true pendulum meristem in both species. InS. bijugathe maximum length of the youngest leaf primordium, just prior to the formation of its successor, is twice that ofS. indica.The internodes immediately below the shoot apex and the axillary buds develop more rapidly inS. bijugathan inS. indica.It is suggested that the bijugate leaf ofS. bijugarepresents a case of neoteny in plants.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1987.tb12141.x

出版商:Wiley    

年代:1987

数据来源: WILEY

摘要:

Fossil palynomorphs representing 40 taxa have been recovered from lower(?) Miocene (Uscari sequence) deposits in southern Costa Rica. Three paleocommunities are suggested for the vicinity of the depositional basin—coastal mangrove (Rhizophora); some form of the lowland wet forest (Phaeoceros, Cnemideria, Bombacaceae,Alchornea, cf.Glycydendrum, cf.Banisteriopsis, Hiraea, Myrtaceae (Eugenia/Myrciatype), and Melastomataceae); and especially the midaltitude (1,000–2,000 m) cloud forest (Lycopodium, Selaginella, cf.Hymenophyllum, Lophosoria, Pityrogramma, Pteris, Podocarpus(common),Ilex, Ericaceae (Cavendishiatype), andLisiantehus). Absent are members of higher altitude communities, and vegetation of drier to arid aspect. Savannahs, important in the interchange of mammalian faunas between North and South America, remain undetected in Gulf/Caribbean Tertiary floras. Paleoenvironments are estimated as wet tropical, similar to present‐day conditions, with a less diverse and insular paleophysiography accounting principally for differences between the early Miocene and modern life zones. This is in contrast to the Paraje Solo assemblage from Veracruz, Mexico, which reflects distinctly cooler climates in the late Miocene. These results are consistent with plate tectonic models for the Gulf/Caribbean region, and emerging global paleotemperature patterns derived from18O studies of marine invertebrates.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1987.tb12142.x

出版商:Wiley    

年代:1987

数据来源: WILEY

摘要:

Three Tertiary microfossil floras from northern Latin America are considered with reference to paleoenvironments and paleoenvironmental trends, especially paleotemperatures: Gatuncillo (middle (?) to late Eocene, Panama), Uscari (early Miocene, Costa Rica), and Paraje Solo (late Miocene, Veracruz, Mexico). The composition of the floras reflect lower temperatures in the late Miocene for terrestrial environments at ca. 18°N latitude, and temperatures comparable to the present for the middle (?) to late Eocene and early Miocene at ca. 9°N latitude. These values are consistent with Tertiary paleotemperature curves derived from18O and13C isotope studies of marine invertebrates, and show that the global drop in temperature at the end of the Miocene affected terrestrial biotas at least as far south as 18°N latitude. Comparison of the paleobotanical data with paleotemperature curves further reveals that the late Miocene was not only a likely time for the introduction of northern temperate elements into the Latin American biota (viz., establishment of the floristic and faunal relationship between eastern United States and eastern Mexico), but that earlier times were progressively less favorable because of generally rising temperatures and more tropical conditions. Information on the Tertiary history of vegetation in the Gulf/Caribbean region is also being monitored with reference to the effect of global sea level changes, although the specific influence of these fluctuations cannot as yet be detected.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1987.tb12143.x

出版商:Wiley    

年代:1987

数据来源: WILEY

摘要:

Four different kinds of leaf hairs occur inEnceliaspecies. These are unicellular‐based and multicellular‐based uniseriate hairs, moniliform hairs, and biseriate glandular hairs. The unicellular‐based uniseriate hairs appear responsible for increased leaf spectral reflectance by species within the genus. In particular, it appears that elongation of the distal cell of the uniseriate hair is necessary for increased leaf reflectance.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1987.tb12144.x

出版商:Wiley    

年代:1987

数据来源: WILEY

摘要:

A greenhouse experiment was conducted onAcer rubrumseedlings to evaluate the effects of flood frequency on production and allocation of biomass and to test the effects of N and P fertilization on production and allocation. Seedlings from the Dismal Swamp were subjected to three flood treatments (no flooding, intermittent flooding, and continuous flooding) and four enrichment treatments (no enrichment, N additions, P additions, and N + P additions). More continuous flooding resulted in less biomass production. Biomass increased during the study in all treatments except for root mass in the continuously flooded treatment. However, production of abundant adventitious roots compensated for the lack of normal root growth. Root/shoot ratios exhibited the greatest decreases in the continuously flooded plants. Plants with N + P added had significantly more leaf, stem, and total mass than the nonenriched plants four months into the study. The N + P additions had apparently compensated for the effects of flood stress in the continuously flooded plants by the end of the study. The fertilized seedlings accumulated higher concentrations of N and P, but their nutrient use efficiency (biomass production per unit nutrient absorbed) was lower than in the nonenriched plants.Acer rubrumseedlings survive flooded conditions through several adaptations; however, theirgrowth is slowed by continuous flooding.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1987.tb12145.x

出版商:Wiley    

年代:1987

数据来源: WILEY

摘要:

High starch concentrations in the sporophylls of male cones of five species of cycad and their depletion during their heat‐producing phase of development suggest that starch is a major fuel source for thermogenesis in these plants. Carbon‐13/carbon‐12 ratio analyses of respired CO2, starch, and lipids in a male cone of one of these species,Macrozamia mooreiF. Muell., indicate that although starch is a major contributor to respiration, lipids are also an important respiratory substrate.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1987.tb12146.x

出版商:Wiley    

年代:1987

数据来源: WILEY