Showing papers in "Botany in 1984"
TL;DR: A new procedure using chlorazol black E has been developed for staining vesicular–arbuscular mycorrhizal fungi in cleared roots, and it was found to be much superior to previously used stains for showing details of internal hyphae and particularly arbuscules.
Abstract: A new procedure using chlorazol black E has been developed for staining vesicular–arbuscular mycorrhizal fungi in cleared roots. In a comparative study, chlorazol black E was found to be much super...
492 citations
TL;DR: Natural and wound periderms and a variety of internal barrier layers contain a somewhat analogous polymer called suberin, which is probably composed of aromatic domains somewhat similar to those found in lignin and aliphatic polyester domains somewhatSimilar to cutin.
Abstract: Cutin, the structural component of plant cuticle, is a biopolyester composed of hydroxy- and hydroxyepoxy-fatty acids The major monomers are a 16-hydroxy C16 acid, a 10,16-dihydroxy C16 acid toget
296 citations
TL;DR: Two new species are described in the section: Trichoderma citrinoviride Bissett has relatively large, ellipsoidal conidia and a very sparse branching system with curved or sinuous conidiophores, branches, and phialides.
Abstract: Variation in strains assignable to the Trichoderma longibrachiatum Rifai and T. pseudokoningii Rifai species aggregates was studied. Morphological similarities allow their assignment to one section...
223 citations
TL;DR: Both the initiation and maturation of Rhizobium infections were found to be governed by the acropetal development of host root hairs, and regions of the root where mature root hairs were present at the time of inoculation were not susceptible to RhZobium infection.
Abstract: Roots of young soybean (Glycine max (L.) Merr.) seedlings inoculated with Rhizobium japonicum Kirchner USDA 110 ARS were examined in serial sections by light microscopy to ascertain the extent of i...
210 citations
TL;DR: Salsola kali, a colonizing annual which does not form vesicular–arbuscular mycorrhizae (nonmycotrophic), was grown in pure culture and in mixtures with two mycotrophic grasses which are late successional dominants, Agropyron smithii and Bouteloua gracilis.
Abstract: Salsola kali, a colonizing annual which does not form vesicular–arbuscular mycorrhizae (nonmycotrophic), was grown in pure culture and in mixtures with two mycotrophic grasses which are late successional dominants, Agropyron smithii and Bouteloua gracilis. Soils were either left sterile or inoculated with mycorrhizal fungi. In pure culture mycorrhizae caused no significant increase in dry mass of either grass, but in mixed culture with S. kali, mycorrhizal infection was significantly related to increased mass of grasses. Mycorrhizal infection was related to increased stomatal conductance of the grasses in both pure and mixed culture. Salsola kali had lower stomatal conductance but not a significantly reduced mass with mycorrhizal fungi. Hyphae of mycorrhizal fungi, but not vesicles or arbuscules, were observed in the rhizosphere and occasionally the cortex of S. kali. Where competition between colonizing nonmycorrhizal species and later successional mycorrhizal species is a mechanism which drives successi...
187 citations
TL;DR: Ectomycorrhizae of jack pine occurring in mature stands, on bare roadsides, and in a recently burned area were compared.
Abstract: Ectomycorrhizae of jack pine occurring in mature stands, on bare roadsides, and in a recently burned area were compared. Fifty-six fungus associates were identified from sporocarp collections. Species of Elaphomyces, Suillus, Cortinarius, Cantharellus, and hydnums were almost exclusively limited to mature stands. Laccaria proxima, Rhizopogon rubescens. Scleroderma macrorhizon, and Astraeus hygrometricus were typically found on disturbed sites. Visual observations and direct isolations from ectomycorrhizae further indicated that the symbionts differed between the burn site and mature jack pine – lichen woodlands. A majority of the ectomycorrhizae in all sites were nondescript and could not be identified by culturing. Unlike the vascular plants, ectomycorrhizal symbionts were very numerous without any single species or small group of species dominating jack pine root systems. Pure culture syntheses confirmed that Tricholoma flavovirens, T. pessundatum, T. zelleri, Suillus flavovirens, S. albidipes, Cenococc...
173 citations
TL;DR: In tobacco mosaic virus infected hypersensitive Nicotiana species, the pathogenesis-related or b proteins were found with other proteins in the intercellular fluid of leaf tissue.
Abstract: In tobacco mosaic virus infected hypersensitive Nicotiana species, the pathogenesis-related (PR) or b proteins were found with other proteins in the intercellular fluid of leaf tissue. Analysis of leaves from mock-inoculated plants did not reveal the presence of detectable amounts of proteins in the intercellular fluid. The presence of proteins in the intercellular fluid seems to be widespread since 10 proteins were detected in tobacco mosaic virus infected Chenopodium quinoa Willd. These proteins were found not only in inoculated tissue but also in the intercellular fluid of uninoculated upper leaves. A two-dimensional gel electrophoretic analysis of intercellular fluid proteins from N. tabacum L. cv. Xanthi-nc infected leaves showed that the relative molecular weight of protein b2 is larger (14 700) than the one of b1 and b3 (14 200). Other proteins, ranging in molecular weights from 12 500 to 36 300, could also be detected. We postulate that the presence of rather large amounts of proteins, including t...
162 citations
TL;DR: It is found that the fraction of holocellulose in the total ligno cellulose during decomposition approached an asymptotic value at which the disappearance of both the chemical components proceeded at the same rate.
Abstract: We investigated the relative changes in celluloses and lignin during decomposition of leaf and needle litters and wood in field experiments. The litter came from two different forest systems: one i...
160 citations
TL;DR: In both morphs, increasing amounts of pollen generally resulted in increased levels of seed set, although considerable variance was observed at all pollination intensities, which failed to detect a difference in the response of the floral morphs to pollination intensity.
Abstract: Controlled pollination experiments were performed on the self-incompatible distylous herb Turnera ulmifolia L. to investigate the effects of pollination intensity and large amounts of incompatible pollen on seed set. In the first experiment, known numbers of compatible pollen grains ranging from 1 to 100 were applied to stigmas of the floral morphs. In both morphs, increasing amounts of pollen generally resulted in increased levels of seed set, although considerable variance was observed at all pollination intensities. Approximately two to seven pollen grains are required to produce a single seed and more than 95 grains are required to achieve maximum seed set in T. ulmifolia. Regression analysis of the seed set data failed to detect a difference in the response of the floral morphs to pollination intensity. In the second experiment, known proportions of compatible and incompatible pollen were applied to stigmas at various time intervals. Most treatments involving mixtures of compatible and incompatible p...
152 citations
TL;DR: The occurrence of forest fires in the Muddus National Park (area), just north of the Arctic Circle in northern Sweden, was investigated on 75 separate sample plots and forest fires were shown to have occurred in the five different types of forest investigated.
Abstract: The occurrence of forest fires in the Muddus National Park (area, 50 000 ha), just north of the Arctic Circle in northern Sweden, was investigated on 75 separate sample plots. Between 1413 and the present, evidence of 47 fire years was obtained by dating the fire scars on living Scots pines (Pinus sylvestris), the oldest of which had germinated in 1274. The fire traces found on the sample plots were fire scars on living or dead trees or charcoal fragments in the humus layer. Plots lacking all traces of former forest fires were mainly those situated on sites surrounded by extensive mires. Forest fires were shown to have occurred in the five different types of forest investigated. The commonest frequencies of fires in the pine forests occurred with the interval 81–90 years, while the mean frequency was 110 years. The mean interval of time elapsed since the last forest fire occurred in the pine forests was 144 years. Some of the major fire years in the Muddus area coincide with forest fires in other parts of...
138 citations
TL;DR: The peatlands sampled in this study are located in northern Minnesota and include 32 stands positioned in seven sites in the Red Lake peatland and Lake Itasca areas, and calculations of niche breadth and niche overlap for four microhabitat axes suggest independent species utilization of the gradients.
Abstract: The peatlands sampled in this study are located in northern Minnesota and include 32 stands positioned in seven sites in the Red Lake peatland and Lake Itasca areas. Surface water chemistry ranges ...
TL;DR: Five of six possible hybrid combinations of the two native North American species of Populus sect.
Abstract: Five of six possible hybrid combinations of the two native North American species of Populus sect. Aigeiros Duby with the three native species of sect. Tacamahaca Spach have been found in nature. Putative hybrids occur wherever species of the two sections are sympatric and sometimes even beyond the range of one or both parents. Parents of the sixth possible combination are not, however, sympatric and this explains the apparent absence of the corresponding hybrid. Although the five hybrids can easily be recognized as a group, each parentage yields hybrids of unique morphology, all of which have previously been provided with binomials. Variability within each hybrid reflects variation in its parents. These hybrids are morphologically intermediate between their putative parents and have an additive chromatographic profile combining leaf flavonoids of each pair. Trees of P. × generosa (P. deltoides × P. trichocarpa) and P. × jackii (P. deltoides × P. balsamifera) from natural populations closely resemble arti...
TL;DR: LSCs, which indicate the relative water supply to different plant parts, decrease acropetally but are higher in the trunk than in branches and are particularly low in second-order branches and at branch insertions.
Abstract: Leaf specific conductivities (LSCs, hydraulic conductivity per gram dry weight of supplied leaves), Huber values (transverse xylem area per gram dry weight of supplied leaves), specific conductivities (hydraulic conductivity per unit transverse xylem area), and tracheid diameters were measured throughout the trunk and erown of 9- to 96-year-old trees of Tsuga canadensis (L.) Carr. By definition, LSC = Huber value × specific conductivity. Specific conductivity is controlled by wood anatomical features, especially tracheid diameter. LSCs, which indicate the relative water supply to different plant parts, decrease acropetally but are higher in the trunk than in branches and are particularly low in second-order branches and at branch insertions. The differential water supply is due to larger Huber values in the leader and to particularly narrow tracheids at branch junctions. In addition, as trunks enlarge they produce wider tracheids, resulting in greater specific conductivity than in supported branches. Base...
TL;DR: The greatest effects of water stress on growth were seen following the recovery period and were most severe for sweetgum seedlings grown at the lowest CO2 concentration.
Abstract: Mathematical growth analysis techniques were used to assess the possible interactive effects of atmospheric carbon dioxide enrichment and water stress on growth and biomass partitioning of Liquidambar styraciflua L. (sweetgum) and Pinus taeda L. (loblolly pine) seedlings. Plants were grown from seed under 1000 μmol∙m−2∙s−1 photosynthetic photon flux density at CO2 concentrations of 350, 675, and 1000 μL∙L−1 for 56 days. At this time, half the seedlings in each CO2 treatment had water withheld until plant water potentials reached about −2.5 MPa in the most stressed plants, while the remaining plants were well watered. At the end of the drying cycle, stressed plants were returned to well-watered conditions for a 14-day recovery period. The greatest effects of water stress on growth were seen following the recovery period and were most severe for sweetgum seedlings grown at the lowest CO2 concentration. For sweetgum seedlings in particular, the reduction of early seedling growth following exposure to a perio...
TL;DR: The gel strengths of alkali-modified agar showed a strong inverse relationship with increasing temperature of growth in each of the three clones examined, and the increase in 4-O-methyl-L-galactose content of the agars as the growth temperature increased was especially marked.
Abstract: Agars were prepared from a wild type and two morphological mutants of Gracilaria tikvahiae grown at 17, 22, and 27 °C, and from apical segments, main axis segments, and lateral branches of the wild type clone MP-2 grown at 17 and 27 °C. The yield of native agar was 9–11% from the young parts and 19–23% from the most mature parts of the MP-2 thallus. The gel strengths of alkali-modified agars showed a strong inverse relationship with increasing temperature of growth in each of the three clones examined. The modified agar produced from plants grown at high temperature contained more sulfate and less 3,6-anhydro-L-galactose than agars produced at lower temperatures. The increase in 4-O-methyl-L-galactose content of the agars as the growth temperature increased was especially marked. Dissection experiments on clone MP-2 showed that agar with the maximum gel strength and 3,6-anhydro-L-galactose content and the minimum sulfate and 4-O-methyl-L-galactose content was produced at low temperature by apical segments...
TL;DR: The early developmental stages of maize caryopses were studied at a fine structural level and it was found that the placentochalazal region of the endosperm contains cells showing ultrastructural features of transfer cells, including wall ingrowths, indicating an important function of these cells in the transport of nutrients supplying the developing embryo.
Abstract: The early developmental stages of maize caryopses were studied at a fine structural level. Emphasis was placed on the interactions between the developing embryo and the surrounding endosperm. It wa...
TL;DR: Patatin, the major protein of potato tubers, was copurified with lipid acyl hydrolase (LAH) and the common identity of patatin and LAH was demonstrated by sodium dodecyl sulfate denaturation studies, isoelectric focusing, and the inhibition of LAH activity by patatin antiserum.
Abstract: Patatin, the major protein of potato tubers, was copurified with lipid acyl hydrolase (LAH). The common identity of LAH and patatin was demonstrated by sodium dodecyl sulfate denaturation studies, ...
TL;DR: Variation in substrate chemistry and plant community composition of hollow and low-hummock communities varied considerably along the strongly minerotrophic to weakly Minerotrophic peatland gradient, while the chemistry of the upper peat layers of the hummocks and hummock plantcommunity composition were similar in all of the peatlands studied.
Abstract: A broad range of water chemistry (pH 3.5–8.2; Ca, 2–120 mg L−1) and substrate chemistry (pH 3.3–7.8; Ca, 4–138 mequiv. 100 g−1) exists among peatlands present in central Alberta. The six peatlands ...
TL;DR: Evergreen and winter-green habits, as well as heteroptosis, were also assumed to be adaptive to life in the understory of deciduous broad-leaved forests in Hokkaido, northern Japan.
Abstract: Leaf survival of 29 species of small trees and shrubs was described in and around deciduous broad-leaved forests in Hokkaido, northern Japan. Twenty-four species had green leaves in the summer (sum...
TL;DR: Four small oligotrophic basin mires on the Precambrian Shield were quantitatively analyzed for vegetation patterns and surface water and groundwater chemistry and abundance patterns of the dominant Carex species can be correlated with pH of the surface water of the mire.
Abstract: Four small oligotrophic basin mires on the Precambrian Shield were quantitatively analyzed for vegetation patterns and surface water and groundwater chemistry. Mean concentrations of ions in the surface waters of all vegetation stands indicate these mires to be characterized by low calcium content (0.6–1.9 mg Ca L−1), low corrected conductivity (12–31 μmho cm−1 (1 mho = 1 S)), and relatively high pH (4.0–5.7). Mire 224 is dominated by Chamaedaphne calyculata, Scheuchzeria palustris, and Carex oligosperma. The surface water mean determinations are Ca, 1.10 ± 0.51 mg L−1; Mg, 0.57 ± 0.2 mg L−1; corrected conductivity, 16.7 ± 4.2 μmho cm−1; and pH 4.37. Abundance patterns of the dominant Carex species can be correlated with pH of the surface water of the mire. Mire 239 is characterized by Smilacina trifolia, Ledum groenlandicum, and Carex trisperma. The mean surface water determinations are Ca, 1.53 ± 0.36 mg L−1; Mg, 0.59 mg L−1; corrected conductivity, 21.2 ± 2.0 μmho cm−1; and pH 4.0. Significant differen...
TL;DR: First-year needles and stems of Abies balsamea were collected at the end of the growing season along an elevational gradient on Mt. Moosilauke, NH.
Abstract: First-year needles and stems of Abies balsamea were collected at the end of the growing season along an elevational gradient on Mt. Moosilauke, NH. Tissue was sampled from the base (732 m), midslop...
TL;DR: The A1 and A2 mating types can be distinguished isozymically suggesting that they are genetically isolated and that sexual reproduction involving both mating types does not occur in the field.
Abstract: Genetic variation in 183 isolates of Phytophthora cinnamomi from a wide range of hosts and locations in Australia and Papua New Guinea (PNG) was assessed at 20 isozyme loci Low levels of isozyme variation were found in both the A, and A2 mating types within Australia Only two A2 multilocus genotypes were detected among Australian and PNG isolates, the more common one being found throughout the range Fourteen of the 15 A1 isolates from 12 locations in Australia were identical at all 20 isozyme loci In contrast there was much higher variability in the eight PNG A1 isolates compared with the Australian Ai isolates and all A2 isolates The A1 and A2 mating types can be distinguished isozymically suggesting that they are genetically isolated and that sexual reproduction involving both mating types does not occur in the field
TL;DR: It is argued that the dismantling of the chloroplast is a highly organized process and that the concept of loss of chloroplasts by digestion in a lytic vacuole is not tenable.
Abstract: The biochemical events in chloroplast breakdown are described. Special attention is given to the regulation of RNA, lipid, chlorophyll, and protein degradation. A new hypothesis is presented concerning the relationship between proteolysis and the initial steps in chlorophyll breakdown. It is argued that the dismantling of the chloroplast is a highly organized process and that the concept of loss of chloroplasts by digestion in a lytic vacuole is not tenable.
TL;DR: An increasing number of phytochemicals, including phenols, terpenoids, polyketides, and alkaloids, are being recognized as photochemically active substances or photosensitizers, unlike the photosynthetic pigments or the phytochromes, which do not have any known functions in the plant species in which they occur.
Abstract: An increasing number of phytochemicals, including phenols, terpenoids, polyketides, and alkaloids, are being recognized as photochemically active substances or photosensitizers. These compounds, unlike the photosynthetic pigments or the phytochromes, do not have any known functions in the plant species in which they occur. However, when introduced into other biological systems, e.g., cells or complex organisms, many of them arc extremely toxic in light. The cellular targets and the photochemical processes for some of them have been defined. In one type of process there is cycloaddition of the photosensitizer with a nucleic acid base, e.g., the formation of a photoadduct of a furanocoumarin such as 8-methoxypsoralen with thymine in a nucleic acid. Certain alkaloids including furanoquinolines. β-carbolines, canthinones, and certain furanochromones and chromenes appear to be of this type; they are photogenotoxic, giving rise to gross chromosomal aberrations in light. A second type of photoreaction, inherentl...
TL;DR: The general decrease in growth potential and sink strength for nutrients in leaves of nitrogen-limited plants suggested that factors other than simply availability of nitrogen likely were involved in the restriction of growth in the leaf canopy and the associated increase in carbon allocation to the roots.
Abstract: Alterations in internal partitioning of carbon were evaluated in plants exposed to limited nitrogen supply. Vegetative, nonnodulated soybean plants (Glycine max (L.) Merrill, 'Ransom') were grown for 21 days with 1.0 mM NO3- and then exposed to solutions containing 1.0, 0.1, or 0.0 mM NO3- for a 25-day treatment period. In nitrogen-limited plants, there were decreases in emergence of new leaves and in the expansion rate and final area at full expansion of individual leaves. As indicated by alterations in accumulation of dry weight, a larger proportion of available carbon in the plant was partitioned to the roots with decreased availability of nitrogen. Partitioning of reduced nitrogen to the root also was increased and, in plants devoid of an external supply, considerable redistribution of reduced nitrogen from leaves to the root occurred. The general decrease in growth potential and sink strength for nutrients in leaves of nitrogen-limited plants suggested that factors other than simply availability of nitrogen likely were involved in the restriction of growth in the leaf canopy and the associated increase in carbon allocation to the roots.
TL;DR: Perennial plants of 19 families were surveyed for colonization by vesicular–arbuscular mycorrhizal (VAM) fungi at four sites in the Anza–Borrego Desert State Park, California, an area characterized as arid to extremely arid.
Abstract: Perennial plants of 19 families were surveyed for colonization by vesicular–arbuscular mycorrhizal (VAM) fungi at four sites in the Anza–Borrego Desert State Park, California, an area characterized as arid to extremely arid. Soils at all sites were very low in phosphorus and nitrogen and had a coarse sandy texture. The sites were distinct in the floristic composition of their vegetation. All plants (38 species) were colonized by VAM fungi (six species). The distribution of the VAM mycoflora was not random. Site preference by VAM-fungal species was ascribed to an interaction of factors pertaining to the host plants and to edaphic and climatic conditions.
TL;DR: Sedimentologic and biologic evidence indicates soil instability and relatively high soil erosion rates from the watersheds during the late-glacial period accounts for the abundance of Glomus in late- glacial sediments, and the reduced abundance of the fungus in Holocene sediments is attributed to a decrease in the rate of soil erosion after the est...
Abstract: Specimens of the vesicular–arbuscular mycorrhizal fungal Glomus fasciculatum complex have been identified from lake sediment cores from Gould Pond (central Maine) and Upper South Branch Pond (north central Maine). The fungus became established with tundra vegetation on newly developing soils soon after the melting of Wisconsin ice. This is the first record of such an occurrence for North America. The earliest specimens from Gould Pond were deposited in sediment dated at about 13 000 years old and those at Upper South Branch Pond between about 12 500 and 11 000 years old. This is at least 1000 years prior to the arrival of trees in those areas. Sedimentologic and biologic evidence indicates soil instability and relatively high soil erosion rates from the watersheds during the late-glacial period. Thus erosion probably accounts for the abundance of Glomus in late-glacial sediments. The reduced abundance of the fungus in Holocene sediments is attributed to a decrease in the rate of soil erosion after the est...
TL;DR: Although total leaf dry weight and total number of leaves per plant did not differ between nonhardened and cold-hardened plants at maximum growth, total...
Abstract: The accurate interpretation of physiological and biochemical alterations observed in plants grown under contrasting environmental conditions requires knowledge of their relative physiological ages. For this purpose, we compared the growth kinetics of winter rye (Secale cereale L. cv. Puma) at nonhardening and cold-hardening temperatures. Growth at nonhardening temperatures was characterized by a 10-day lag phase with the attainment of maximum growth after about 28 days. Growth at cold-hardening temperatures resulted in an extension of the lag phase to about 21 days with maximum growth being attained after 56 days. The calculated growth coefficient at cold-hardening temperatures was 35–40% of that at nonhardening temperatures. This relationship was consistent with growth parameters such as leaf dry weight, fresh weight, and area, but not with plant height. Although total leaf dry weight and total number of leaves per plant did not differ between nonhardened and cold-hardened plants at maximum growth, total...
TL;DR: Many of the large columnar cacti Trichocereus chilensis near Santiago are infected by Tristerix aphyllus, one of the most highly reduced seed plants known: as it is an endoparasite, inflorescence are the only parts of the plant ever to emerge from the host, all the rest exists as an endophytic haustorial system.
Abstract: Many of the large columnar cacti Trichocereus chilensis near Santiago are infected by Tristerix aphyllus. This is one of the most highly reduced seed plants known: as it is an endoparasite, inflorescences are the only parts of the plant ever to emerge from the host, all the rest exists as an endophytic haustorial system; roots, vegetative stems, and leaves are not produced. After infection, the parasite spreads through the thick cortex of the host, reaching the vascular cambium and conducting tissues. It continues to grow intrusively throughout all tissues of the host shoot. In its invasive stage it occurs as a "myceliumlike" mass of uniseriate filaments that grow between host cells but only rarely enter them. Later growth is by longitudinal cell division that produces irregular parenchymatous strands. Eventually, xylem and phloem differentiate in the endophytic strands; the phloem is like that of other seed plants, but the xylem is almost pure parenchyma, with only occasional, idioblastic tracheary eleme...
TL;DR: A mathematical model is formulated for the course of mass loss as a system consisting of two fractions, a readily decomposable (labile) one and a refractory one and shows that the decay rate decreases with time as the chemical composition changes.
Abstract: Scots pine needles were collected and field incubations were begun in the autumn of 6 consecutive years. The incubated needles were sampled three times a year and analysed for mass loss and chemical composition. The longest incubation time obtained was 1825 days. Four series of needles from a nutrition experiment (three levels of nutrient application and one control) sampled at one occasion were followed in the same way for 1448 days. The logarithm of remaining mass versus time of the pooled samples fits a linear regression well (average rate constant = 0.286 year−1, r2 = 0.963, n = 75). A higher resolution shows, however, that the decay rate decreases with time as the chemical composition changes. To better understand the decomposition process we have formulated a mathematical model for the course of mass loss as a system consisting of two fractions, a readily decomposable (labile) one and a refractory one. The mass loss from the two fractions can be direct or mass can be transferred from the refractory ...