摘要:

Temporal and spatial patterns of specific leaf weight (SLW, g/m2) were determined for deciduous hardwood tree species in natural habitats in northern lower Michigan to evaluate the utility of SLW as an index of leaf photosynthetic capacity. No significant diurnal changes in SLW were found. Specific leaf weight decreased and then increased during leaf expansion in the spring. Most species, especially those located in the understory, then had relatively constant SLW for most of the growing season, followed by a decline in SLW during autumn. Specific leaf weight decreased exponentially down through the canopy with increasing cumulative leaf area index. Red oak (Quercus rubra), paper birch (Betula papyrifera), bigtooth aspen (Populus grandidentata), red maple (Acer rubrum), sugar maple (A. saccharum), and beech (Fagus grandifolia) generally had successively lower SLW, for leaves at any one level in the canopy. On a given site, comparisons between years and comparisons of leaves growing within 35 cm of each other showed that differences in SLW among species were not due solely to microenvironmental effects on SLW. Bigtooth aspen, red oak, and red maple on lower‐fertility sites had lower SLW than the same species on higher‐fertility sites. Maximum CO2exchange rate, measured at light‐saturation in ambient CO2and leaf temperatures of 20 to 25 C, increased with SLW. Photosynthetic capacities of species ranked by SLW in a shaded habitat suggest that red oak, red maple, sugar maple, and beech are successively better adapted to shady conditions.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1986.tb08555.x

出版商:Wiley    

年代:1986

数据来源: WILEY

摘要:

Guayule (Parthenium argentatum), a native shrub of the Chihuahuan desert, contains rubber. Guayule has been crossed with otherPartheniumspecies in an attempt to improve its agronomic characteristics. The resulting hybrids show intermediate morphologies. EachPartheniumspecies has a characteristic combination of leaf trichomes. In order to recognize the contribution of each parent in future studies of hybrids, characteristics of leaf trichomes of the followingPartheniumspecies were studied:P. tomentosum, P. fruticosum, P. SchottiiandP. rollinsianum.All species studied had two or more types of trichomes, and, in some species, trichomes of upper and lower epidermal surfaces were different. The prominent trichomes on upper epidermis ofP. tomentosumandP. fruticosumwere simple, uniseriate, conical trichomes, which also were observed on both epidermal surfaces ofP. Schottii.Extremely long, narrow, simple, whiplike, trichomes formed a dense cover on both surfaces ofP. rollinsianumand on the lower surfaces ofP. tomentosumandP. fruticosum.Simple, uniseriate, cylindrical trichomes, and biseriate, glandular trichomes were observed in all four species.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1986.tb08556.x

出版商:Wiley    

年代:1986

数据来源: WILEY

摘要:

The optical properties of the leaves of twelve tropical sun species and thirteen tropical extreme shade species were examined with an integrating sphere attached to a spectroradiometer. Measurements of diffuse reflectance and transmittance allowed calculations of absorptance, 350–1,100 nm. Although some shade species absorbed higher percentages of quantum flux densities for photosynthesis (400–700 nm, PPFD) than the mean for the sun species, the sun and shade species as groups were not significantly different from each other: 90.2, S.D. 3.6% for shade species and 88.6, S.D. 2.4% for the sun species. The groups of species did not differ in total absorptance of energy 350–1,100 nm. Furthermore, the sun and shade species were identical in their shift of absorptance at wavelengths between 650 and 750 nm. The anthocyanic coloration of the leaf undersurfaces of two species polymorphic for this characteristic (Trionela hirsutaandIschnosciphon pruinosus) is correlated with increased absorptance at the upper end of the action spectrum of photosynthesis. Although sun and shade species have similar optical properties, the energy investment (as documented by dry wt per unit area of leaf surface) is much less for the shade species.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1986.tb08557.x

出版商:Wiley    

年代:1986

数据来源: WILEY

摘要:

Nearly a century ago, Rosenvinge published a now‐classic paper reporting nuclear transfer between cells ofPolysiphoniaduring secondary pit connection (SPC) formation. While reinvestigating this phenomenon, we discovered that the uninucleate apical cell, which is the progenitor of all cells in the plant, has many times (ca. 64–128 ×) the level of nuclear DNA characteristic of nuclei of gametes or mature pericentral cells. Via a regular sequence of cell divisions, the polyploid apical cell gives rise to tiers of cells, each composed of a number of pericentral cells which surround a single central cell. A large proportion of the nuclear divisions are not accompanied by DNA replication. Thus, as the number of nuclei within elongating pericentral cells increases, the DNA level of nuclei in these cells “cascades” down to the DNA level expected for the particular life history generation (i.e., gametophyte or tetrasporophyte). In mature pericentral cells, the number of nuclei is proportional to the volume of the cell. The pattern of nuclear division, reduction in ploidy level and the timing of intercellular nuclear transfer via SPC formation is regular and characteristic of a species. Nuclei transferred from one cell to an adjacent cell participate in the further nuclear divisions of the recipient cell. The degree of polyploidy in apical cells may determine the number of cells in a “determinant” branch or even the number of cells in “indeterminant” axes. In addition, the highly polyploid state of the germinating spore and its pattern of development may provide for the rapid initial growth so characteristic of this taxon.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1986.tb08558.x

出版商:Wiley    

年代:1986

数据来源: WILEY

摘要:

Myristica fragransandM. malabaricaare dioecious. Both staminate and pistillate plants produce axillary flowering structures. Each pistillate flower is solitary, borne terminally on a short, second‐order shoot that bears a pair of ephemeral bracts. Each staminate inflorescence similarly produces a terminal flower and, usually, a third‐order, racemose axis in the axil of each pair of bracts. Each flower on these indeterminate axes is in the axil of a bract. On the abaxial side immediately below the perianth, each flower has a bracteole, which is produced by the floral apex. Three tepal primordia are initiated on the margins of the floral apex in an acyclic pattern. Subsequent intercalary growth produces a perianth tube. Alternate with the tepals, three anther primordia arise on the margins of a broadened floral apex in an acyclic or helical pattern. Usually two more anther primordia arise adjacent to each of the first three primordia, producing a total of nine primordia. At this stage the floral apex begins to lose its meristematic appearance, but the residuum persists. Intercalary growth below the floral apex produces a columnar receptacle. The anther primordia remain adnate to the receptacle and grow longitudinally as the receptacle elongates. Each primordium develops into an anther with two pairs of septate, elongate microsporangia. In pistillate flowers, a carpel primordium encircles the floral apex eventually producing an ascidiate carpel with a cleft on the oblique apex and upper adaxial wall. The floral ontogeny supports the morphological interpretation of myristicaceous flowers as trimerous with either four‐sporangiate anthers or monocarpellate pistils.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1986.tb08559.x

出版商:Wiley    

年代:1986

数据来源: WILEY

摘要:

Experimental hybridization data generally agree with patterns of morphological, ecogeographic, and chromosomal variation in support of current taxonomic hypotheses forGaurasectionStipogaura.Average rates of capsule‐set for intersectional crosses are significantly lower than for interspecific crosses withinStipogaura(14% vs. 63% respectively,P<0.001). Post‐mating reproductive isolation within the section is not well‐developed, as indicated by comparable averages of cross‐success for interspecific (19%) and intraspecific (17%) crosses. WithinStipogaura,lowered rates of capsule‐set (forG. filipescrosses) and germination (seed fromG. calcicola, G. filipes,andG. sinuatacrosses) segregate the five species into four fertility groups.Gaura calcicola(n =7) andG. sinuata(n= 14) differ by lower pollen staining in the hybrids ofG. sinuata,a result of odd‐ploid hybridity. The order of average, interspecific cross‐success isG. mckelveyae(35%),G. villosa(25%),G. calcicola(14%),G. sinuata(10%), andG. filipes(2%). Patterns of interspecific fertility do not precisely parallel phylogenetic hypotheses based upon morphology. Three diploid taxa that closely resemble one another in growth habit (G. mckelveyae, G. calcicola, G. filipes) differ widely in rates of crossing success.Gaura villosais relatively specialized morphologically but retains a high degree of interspecific fertility.Gaura sinuatais also specialized, but readily produces hybrids in crosses with three of the diploids.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1986.tb08560.x

出版商:Wiley    

年代:1986

数据来源: WILEY

摘要:

Three fragments of fascicles of a possible five‐needle pine are described from the Upper Cretaceous Yezo Group (Santonian/Senonian) of Hokkaido. Specimens from the Omakizawa, Oyubari, Yubari City, the Koyanozawa, Ikushumbetsu, Mikasa City, and the Sankebetsugawa, Haboro are preserved in calcium carbonate nodules containing abundant ammonites. Leaves borne in apparent fascicles of five measure 0.7–0.8 mm in radial and 0.8–1.0 mm in tangential diam and are represented by short fragments of isolated needles. Thick‐walled epidermal cells on these amphistomatic leaves resemble the underlying uniform hypodermis. Two external resin canals are situated near the lateral corners toward the adaxial surface. Only slightly plicate mesophyll cells in a layer one to two cells thick border on an elliptical endodermis with thickened outer cell walls. Two to three layers of transfusion tissue surround the double vascular strand. Two vascular bundles are separated by one cell layer of sclerenchyma fibers. Small patches of abaxial and adaxial sclerenchyma fibers have also been observed. Leaves most closely resemble those ofPinus leiophyllaSchl. et Cham. SubgenusPinus,SectionPinea,SubsectionLeiophyllaeandP. montezumaeLamb. SubgenusPinus,SectionPinus,SubsectionPonderosaeand are described as a new speciesP. hokkaidoensissp. nov. Stockey and Ueda. Close anatomical comparisons are made with this leaf and previously described permineralized Upper Cretaceous pine needles from Hokkaido and eastern North America.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1986.tb08561.x

出版商:Wiley    

年代:1986

数据来源: WILEY

摘要:

The halophyte,Salicornia pacificavar.utahensis(Tiderstorm) Munz produces seed under high salinity conditions, and deposits its seed on saline soil. Experiments were conducted to determine the effect of salinity, temperature and growth regulators on germination. Results indicate that the seeds can germinate at very high salt concentration (5% NaCl). Germination was sensitive to the changes in temperature regimes. At higher 30–20 C, light‐dark sequence, no germination occurred at 3, 4 and 5% NaCl treatments. On the other hand, 30% germination did occur at 5% NaCl treatment at a temperature regime of 15–5 C. These seeds required light for germination. Only 50% germination occurred in the non‐saline control in the dark and the addition of NaCl further reduced germination. The GA3partially alleviated the inhibitory effect of NaCl and darkness. Kinetin did not promote germination.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1986.tb08562.x

出版商:Wiley    

年代:1986

数据来源: WILEY

摘要:

We measured seed set and losses due to mammal and insect predation during 1983 in seven northern Maine populations of Furbish's Lousewort (Pedicularis furbishiaeS. Wats.; Scrophulariaceae), a perennial herb endemic to the banks of the St. John River. Only about a quarter of initiated flowers developed a capsule with a full complement (mean = 25) of seeds. Secondary (lateral) inflorescences matured a smaller proportion of capsules than primary (terminal) inflorescences. About 58% of the initiated flower primordia were aborted or did not develop mature seeds by early September; this was probably not due to pollinator limitation.Several agents could have reduced seed production. Although spittlebugs infested between 3 and 30% (average 20%) of developing flower scapes by population, they did not depress the number of inflorescences initiated or the number of capsules matured. In contrast, 74% of capsules containing a lepidopteran seed predator (the plume mothAmblyptilia pica[Walsingham], newly discovered as a seed predator onP. furbishiae) had no seeds (mean = 3 seeds). Seed predation affected 39% of the potentially maturable capsules. In 6–30% of all capsules preyed upon, the lepidopteran was parasitized by an ichneumonoid wasp larva; these capsules matured about 7 seeds. Herbivory by rabbits, rodents, and deer also reduced seed set, eliminating 98% of the scapes at one site, and averaging 40% for other populations. Mammals and insects together removed at least 62% of maturable seeds. Populations varied widely in predation and seed set. Predispersal seed loss inP. furbishiae,coupled with slow seedling growth and occasional catastrophic mortality from ice scour and erosion, could limit population growth in this rare endemic.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1986.tb08563.x

出版商:Wiley    

年代:1986

数据来源: WILEY

摘要:

The tribes Amorpheae and Psoraleeae of the Leguminosae (Papilionoidae) share the characteristics of one‐seeded fruits and gland‐dotted foliage. Because of this, they traditionally have been considered closely related (either a single tribe or two closely related tribes). However, Barneby (1977) has suggested that the Amorpheae and Psoraleeae are not close but previously had been combined on the basis of a superficial resemblance. This paper describes the structure of the secretory cavities responsible for the gland dots. Approximately 50% of the species of each tribe were surveyed for cavity structure with leaflet clearings. Eight species were then chosen for developmental studies of their glands. Several distinct kinds of secretory cavities are present in these plants. Trabeculate cavities (found only in the Psoraleeae) are traversed by many elongated cells. This type of cavity and nontrabeculate cavities of the Psoraleeae initiate with localized dorsiventral elongation of protodermal cells to form a hemispherical protuberance on the leaf primordium surface. Development proceeds with separation of the cells of a protuberance along their lateral walls facing the protuberance center. As the leaf expands, the protuberance sinks until its apex is flush with the leaf surface. The result is a cavity lined by an epithelium of modified epidermal cells. Trabeculate cavities have more cells in the initial protodermal bump than nontrabeculate “epidermal” cavities, and the central cells of the protuberance are not involved in epithelium formation, but become separated from other cells on all lateral sides, transversing the cavity as trabeculae. Cavities of the Amorpheae are all nontrabeculate and subepidermal. They initiate with periclinal divisions of protodermal cells that result in two cell layers. The exterior layer differentiates into epidermis, while the interior layer divides to produce a small spherical group of cells (“epithelial initials”). Schizogeny occurs in the center of these cells to produce an epithelium‐lined cavity. Previous studies of cavity development in the Amorpheae described lysigenous and schizo‐lysigenous cavities for most species. These early reports are reviewed, and the possible role of preparation artifacts in producing images of lysigenous development in general is discussed.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1986.tb08564.x

出版商:Wiley    

年代:1986

数据来源: WILEY