Showing papers in "Botany in 1978"
TL;DR: The rate of flow of a dilute KCl solution through sections of stem, branches, and twigs was measured and expressed in microlitres per hour, under conditions of gravity flow, to measure leaf-specific conductivity (LSC), which is not uniform throughout the tree, LSC of the stem being higher than that of branches.
Abstract: The rate of flow of a dilute KCl solution through sections of stem, branches, and twigs was measured and expressed in microlitres per hour, under conditions of gravity flow, per gram fresh weight o...
503 citations
TL;DR: The observed patterns of species dominance and diversity suggest that the true population of endophytes has been inadequately sampled in the present study and that an order of magnitude more intensive sampling might be required for real patterns of dominance and Diversity to emerge.
Abstract: The incidence of internal fungal infections has been scored in coniferous needles from 19 hosts sampled in over 200 sites dispersed throughout western Oregon and southern Washington. Abies grandis, A. magnifica, Picea sitchensis, Pseudotsuga menziesii, and Sequoia sempervirens have proved congenial hosts for needle blade endophytes; petiole fungi are common in all species of Picea and Tsuga sampled. An undescribed taxon in the Hemiphacidiaceae, Chloroscypha spp., Cryptocline spp., Leptostroma spp., Naemacyclus spp., Phomopsis spp., Phyllosticta sp., and several unidentified Coelomycetes with Phoma-like spores were the dominant fungal taxa in the coniferous hosts sampled. The observed patterns of species dominance and diversity suggest that the true population of endophytes has been inadequately sampled in the present study and that an order of magnitude more intensive sampling might be required for real patterns of dominance and diversity to emerge. Many endophytes are restricted to a single coniferous ho...
339 citations
TL;DR: It is proposed that the chloroplasts of Euglena have arisen from the progressive reduction of endosymbiotic green algae and may be derived from the plasmalemma of the original symbiont.
Abstract: It is proposed that the chloroplasts of Euglena have arisen from the progressive reduction of endosymbiotic green algae. The theory is supported by the presence of a third membrane around the chlor...
330 citations
TL;DR: In these experiments, a sparse vesicular (chlamydospore) infection by Glomus fasciculatus was found in four species of Chenopodiaceae and two species of Cruciferae but only when grown in the presence of a mycorrhizal companion plant, citrus or onion.
Abstract: Members of the Chenopodiaceae and Cruciferae were reported to be nonmycorrhizal by early investigators; more recently, some species in these families have been reported to have low or in some cases...
193 citations
TL;DR: A decrease in weight was noted for N, P, K, Ca, Mg, and Zn during decomposition while an increase was found for Fe, Mn, Cu, and Na.
Abstract: Chemical element change in decomposing aspen and balsam poplar leaves was followed for 60 months in an aspen woodland site in southwestern Alberta, Canada. The changes in concentration and weights of the various elements and in several C:element and element:element ratios are discussed and compared with literature findings and with the concentrations, weights, and ratios encountered in the soil layers.The initial concentrations of all elements, except K and Na, were similar in both aspen and balsam leaf litter; K was higher initially in balsam leaf litter and Na was higher initially in aspen leaf litter. In the decomposing leaf litter, the concentrations of N, Ca, Zn, Mg, Fe, Mn, Cu, and Na generally increased with time while the concentrations of P and K decreased. A decrease in weight was noted for N, P, K, Ca, Mg, and Zn during decomposition while an increase was found for Fe, Mn, Cu, and Na. The order of mobility of elements after 60 months in decomposing aspen and balsam leaf litter was K > Na > P > ...
150 citations
TL;DR: The Scholander–Hammel pressure bomb has been used to measure ontogenetic and seasonal changes in π0 (the osmotic pressure of the symplasm at zero water potential), πp (the Osmotic Pressure of the s...
Abstract: The Scholander–Hammel pressure bomb has been used to measure ontogenetic and seasonal changes in π0 (the osmotic pressure of the symplasm at zero water potential), πp (the osmotic pressure of the s...
148 citations
TL;DR: Tree species developmental pathways, as indicated by 'succession vectors' on the ordination models are, for the most part, short and circular with the exception of Abies balsamea (balsam fir), which reflects the reestablishment of similar, relatively monospecific for boreal tree species.
Abstract: Ordination models of approximate environmental and dynamic relationship between eight boreal tree species were constructed based upon principal components analysis and Kruskal's nonmetric multidime...
133 citations
TL;DR: Changes in dry weight and N, P, K, Na, Ca, Mg, Al, and Fe content were studied over a 525-day period in decomposing Typha glauca and Scirpus fluviatilis shoots.
Abstract: Changes in dry weight and N, P, K, Na, Ca, Mg, Al, and Fe content were studied over a 525-day period in decomposing Typha glauca and Scirpus fluviatilis shoots. Submerged Typha litter decomposed more rapidly than submerged Scirpus litter, losing 50% of its original dry weight in 325 days while Scirpus litter still retained 62% of its original dry weight after 525 days. Major pathways of mineral flow from standing litter were (1) leaching during the first few weeks after shoot death and (2) fragmentation and litter fall during the rest of the study. Mineral losses from fallen litter were mainly due to leaching or to excretion by microbial populations associated with the litter. Microbial uptake (N, P) and adsorption (Ca, Al, Fe) were important processes in the fallen litter. After 525 days, as a result of the combined action of mineral uptake and release, Typha litter had net releases of N (71 kg/ha), P(10 kg/ha), K (123 kg/ha), Na (94 kg/ha), Ca (41 kg/ha), and Mg (25 kg/ha) and net accumulations of Al (2...
125 citations
TL;DR: A significant positive correspondence between peak charcoal influxes and peak influxes of aluminum and vanadium, indicating that increased soil erosion is responsible for their deposition, and fire has been a frequent, natural phenomenon affecting the landscape during this period.
Abstract: Laminated sediment (presumed varved) from Greenleaf Lake was examined for evidence of forest fires. A 500-year section dating approximately 770–1270 A.D. was analysed for influx of pollen, charcoal, aluminum, and vanadium using decadal samples. Intervals showing concurrent peaks in charcoal, aluminum, and vanadium influx, varve thickness, and charcoal:pollen ratio were interpreted as representing major fires within the drainage basin of Greenleaf Lake. By these criteria, six fires occurred within 500 years, or one fire approximately every 80 years. The pollen diagram indicates a stable forest composition for the past 1200 years. This, coupled with abundant charcoal fragments in all sediment samples, suggests that fire has been a frequent, natural phenomenon affecting the landscape during this period. There is a significant positive correspondence between peak charcoal influxes and peak influxes of aluminum and vanadium, indicating that increased soil erosion is responsible for their deposition.
120 citations
TL;DR: Hemlock is sensitive at all stages of its life cycle to disturbances that were intensified after European settlement as well as to the kinds of animal consumption that increase with disturbance, which may best explain the rarity of hemlock-dominated stands on richer sites.
Abstract: Along a transect of mature forests from Wisconsin to Nova Scotia, hemlock attains dominance most frequently where soil is thin or low in stored nutrients. Very probably, soil is also dependably moistened either by climate or seepage. The inability of shade-tolerant competitors to survive suppression on thin or infertile soil may explain hemlock's success, even though hemlock maintains understory populations at very low densities. Hemlock also grows well on moist uplands with richer soil but does not often attain dominance or form large aggregates in a continuously varying mixed forest. This is in contrast to hemlock's codominance on a wide variety of upland sites in the presettlement forest. Recent history, then, may best explain the rarity of hemlock-dominated stands on richer sites: (1) hemlock is sensitive at all stages of its life cycle to disturbances that were intensified after European settlement as well as to the kinds of animal consumption that increase with disturbance; (2) disturbance has been ...
109 citations
TL;DR: Weight loss and nutrient changes with decomposition were examined over a 2-year period for a variety of kinds of litter on five forest sites, with understory and leaf litter significantly faster on the hardwood stands than on the pine stands.
Abstract: Weight loss and nutrient (N, P, K, Ca, Mg) changes with decomposition were examined over a 2-year period fora variety of kinds of litter on five forest sites. Litter types included pine needles, leaves of four deciduous species (red maple, pin cherry, trembling aspen, and white birch), branches of pine and four deciduous species, understory vegetation, and partially decomposed forest floor material, while the study sites consisted of jack pine stands aged 16, 29, and 57 years and mixed hardwood stands aged 7 and 29 years. Statistically significant differences in rate of weight loss were found to occur, with understory and leaf litter significantly faster on the hardwood stands than on the pine stands, understory litter faster on the 7-year-old hardwood stand than on the 29-year-old stand, and forest floor material faster on the 29-year-old pine stand than on the 57-year-old pine stand. Among the four deciduous species examined, significant differences in leaf weight loss also occurred, but differences amo...
TL;DR: With progressive decrease in water content the gradual disappearance of the characteristic fluorescence transients was observed in both tolerant and sensitive algae, and rehydration in tolerant plants resulted in rapid recovery from severe desiccation; there was no such recovery in sensitive plants when water content was decreased below a critical value.
Abstract: Algae of higher intertidal regions tend to be tolerant of extended periods of desiccation, while many lower tidal or subtidal species do not withstand even mild water loss. (Tidal regions can be characterized as high (regularly immersed at high tide and exposed at low tide), low (emergence only during minus tides (lower than mean low tide)), or subtidal (never exposed at low tide and extending to the maximum depth at which net photosynthesis can occur).) The ecological necessity for tolerance in frequently emerged species is obvious, but the physiological basisof it is not well understood. Changes of photosynthetic partial reactions upon desiccation and rehydl-ation of tolerant and sensitive algae were studied by measurements of chlorophyll fluorescence induction kinetics (Kautsky effect). With progressive decrease in water content the gradual disappearance of the characteristic fluorescence transients was observed in both tolerant and sensitive species. The water content ranges where typical changes occurred were species dependent. Rehydration in tolerant plants resulted in rapid recovery from severe desiccation; there was no such recovery in sensitive plants when water content was decreased below a critical value. Analysis of the fluorescence changes upon desiccation and rehydration suggests: (I) electron transport between photosystem 11 and photosystem I. 21s well as H20 splitting are the partial reactions sensitive to desiccation; (2) in the resistant Porpl~yrn sn~ljlin~~e~lsis , intersystem electron transport is blocked at around 25% water content; (3) further desiccation leads to loss of water-splitting activity and eventually to the complete loss of variable fluorescence photosystem 11 reaction centers; and (4) on rehydration intersystem electron transport begins almost immediately while recovery of H20 splitting requires several minutes.
TL;DR: The total numbers of seeds found were small and the correspondence with species in the vegetation was poor, consistent with reports from other old- growth forests and may be accounted for by a combination of low seed input and rapid loss of viable seeds from the soil reservoir for old-growth forest species.
Abstract: Species of buried, germinating seeds and species occurring in the vegetation are compared for two Colorado subalpine forest stands, one dry and one mesic, both over 325 years old. The total numbers of seeds found were small and the correspondence with species in the vegetation was poor. This is consistent with reports from other old-growth forests and may be accounted for by a combination of low seed input and rapid loss of viable seeds from the soil reservoir for old-growth forest species.
TL;DR: Basidiocarps of 39 epigeous species of proven or potential mycorrhizal fungi were found in three fertilized Pinus taeda plantation s during 1972 and 1973.
Abstract: Basidiocarps of 39 epigeous species of proven or potential mycorrhizal fungi were found in three fertilized Pinus taeda plantation s during 1972 and 1973. The largest numbers of basidiocarps on all three plantations were found on nonfertilized plots or plots fertilized with P only. Fewest basidiocarps were found on plots fertilized with N. Numbers of basidiocarps of Suillus hirtellus were decreased by N fertilization. Numbers of basidiocarps of some other potential mycorrhizal fungi were not altered substantially by fertilization treatments. The average numbers of total living mycorrhizal tips were correlated well with average numbers of epigeous basidiocarps of proven or potential mycorrhizal fungi on fertilized plots. However, if mycorrhizal tips formed by Cenococcum geophilum, which do not form visible basidiocarps, were ignored, the remaining mycorrhizal tips were not well correlated with numbers of basidiocarps of proven or potential mycorrhizal fungi.
TL;DR: Water contents near equilibrium over distilled water (water potential near zero) were 10–20% of saturation water contents, which suggested that after saturation by rainfall, considerable water loss can take place before water stress is experienced.
Abstract: Relationships between water content and water potential for Hylocomium splendens (Hedw.) B.S.G., Pleurozium schreberi (Brid.) Mitt., Ptilium crista-castrensis (Hedw.) De Not., and Tomenthypnnm nitens (Hedw.) Loeske, the last occurring in a distinctly different habitat from the first three, showed no hysteresis effect between wetting and drying curves and no appreciable differences among the species.Water contents near equilibrium over distilled water (water potential near zero) were 10–20% of saturation water contents, which suggested that after saturation by rainfall, considerable water loss can take place before water stress is experienced.The capacity for net assimilation decreased with depth in the moss canopy in all species, and the species showed similar decreases in net assimilation rates with decreasing water contents, from maximum rates at 3 to 6 g H2O g−1 dry weight to near or below zero rates around 0.4 g H2O g−1 dry weight.
TL;DR: Individual leaves of three bog ericads, leatherleaf, bog laurel, and Labrador tea, were retained for a maximum of two growing seasons in a peat bog in southern Ontario, but net photosynthetic rates decreased with leafage, but in terms of leaf nitrogen content, new and old leaves fixed equal amounts of carbon.
Abstract: Individual leaves of three bog ericads, leatherleaf (Chamaedaphne calyculata), bog laurel (Kalmia polifolia), and Labrador tea (Ledum groenlandicum), were retained for a maximum of two growing seasons in a peat bog in southern Ontario. The premature loss of mature leaves, resulting from artificial defoliation, significantly reduced the growth of new shoots of L. groenlandicum and K. polifolia but not of C. calyculata. Defoliation effects were directly proportional to the normal retention time for overwintering leaves. Mature leaves probably translocate photosynthate, nitrogen, and phosphorus to other plant parts. This would explain why leaf dry weights were greatest at the start, rather than at the end, of the leaves' second growing season. Net photosynthetic rates decreased with leafage, but in terms of leaf nitrogen content, new and old leaves fixed equal amounts of carbon.
TL;DR: A variety of numerical taxonomic procedures was employed to assess variation of 437 diverse populations of Daucus carota sensu lato, grown under controlled conditions, and of 100 herbarium sheets, finding the domesticated plants to be sharply discontinuous from the wild plants.
Abstract: A variety of numerical taxonomic procedures was employed to assess variation of 437 diverse populations of Daucus carota sensu lato, grown under controlled conditions, and of 100 herbarium sheets. ...
TL;DR: Objective analyses by Bray–Curtis ordination and reciprocal averaging ordination were used to analyse the vegetation data and proved useful in the data reduction and interpretation of results.
Abstract: Picea mariana – Vaccinium uliginosum vegetation was sampled in a north–south transect near Inuvik, N.W.T., Canada. Four stages in the postfire recovery sequence were described. Little qualitative change in vascular plants was found in the transect or with time since burning, although quantitative changes were found to exist. Contrary to vascular plant development, an orderly postfire succession of cryptogamic species was found. The postfire recovery sequence by comparison with other open boreal forest studies has a persistent shrub-dominated stage. Burning, with few exceptions, occurred within 100 years of examination along the transect. Objective analyses by Bray–Curtis ordination and reciprocal averaging ordination were used to analyse the vegetation data and proved useful in the data reduction and interpretation of results.
TL;DR: A freshwater isolate of Stichococcus bacillaris Naeg was evaluated for its ability to grow, photosynthesize, and osmoregulate over a wide range of salinity, indicating that it is a euryhaline organism.
Abstract: A freshwater isolate of Stichococcus bacillaris Naeg. (strain UTEX 314) was evaluated for its ability to grow, photosynthesize, and osmoregulate over a wide range of salinity. The growth and photosynthetic measurements indicate that it is a euryhaline organism. Studies of the soluble organic metabolite pools showed that the steady-state levels of two solutes varied with salinity; sorbitol (a polyol) and proline (an amino acid). Intracellular proline levels increased from 0.002 to 0.28 M over the salinity range of 0 to40%c whereas the sorbitol level increased from 0.10 to 0.52 M. The level of total amino acids (excepting proline) remained relatively constant. No single amino acid of this group exceeded an intracellular concentration of 0.04 M. The changes in the concentrations of these solutes accounted for at least 75% of the required increase in intracellular osmolality in cells following adaptation to high salinity media. Sorbitol and proline are very soluble, nontoxic, and are efficient osmotic solutes...
TL;DR: The effectiveness of excess cadmium, cobalt, nickel, and zinc in eliciting similar early responses was studied in white beans, finding that each caused the appearance of a red–brown discoloration first in the veins of unifoliate leaves and later in petioles and stems.
Abstract: The effectiveness of excess cadmium, cobalt, nickel, and zinc in eliciting similar early responses was studied in white beans. Each metal caused the appearance of a red–brown discoloration first in the veins of unifoliate leaves and later in petioles and stems. Cadmium, nickel, and zinc did so within 1 day, cobalt within 4 days. The effectiveness of the metals in inducing visual symptoms and in decreasing dry matter production were in the order . Within 1 day of adding excess metal, each caused the unifoliate leaves to orient themselves towards the vertical from the normal horizontal. Each metal caused premature leaf closure within the normal nyctinastic cycle.Excess cobalt, nickel, and zinc all caused abnormal starch accumulations in unifoliate leaves within 2–3 days. These metals also caused a major shift towards relatively apolar soluble phenolic components in leaves but not in roots. Cadmium, besides being most toxic, did not cause starch accumulation or a shift in the complement of soluble phenolics.
TL;DR: The evergreen characteristic of Lobelia dortmanna L. involves biomass and nutrient conservation, and reproductive failure as a controlling factor at the margin of the population is suggested.
Abstract: The evergreen characteristic of Lobelia dortmanna L. involves biomass and nutrient conservation. Although 60% of the maximum, midsummer biomass overwinters, little or no new tissue is produced between October and early May. Annual net production, estimated from the rate of leaf turnover, is less than the maximum biomass (P/B = 0.69 per year). Nitrogen and P concentrations are lowest in mid-August, when the amount of each analyzed element per square metre is near its maximum (N, P, Ca, Mg, Na, K). Autumnal uptake of N may contribute 25% of the next season's growth requirements, but P uptake is largely offset by losses during the winter. Fruiting and sterile plants have similar contents of N, P, and K in late July, but the fruiting plants are richer in Ca, Mg, Na, Fe, Mn, and Zn. At the maximum depth limit of the population in Mirror Lake, New Hampshire (2.3 m), flowering is absent and seedlings are sparse, suggesting reproductive failure as a controlling factor at the margin of the population.
TL;DR: It can be shown that the total flux in a stem, calculated as the sum of the flux in single vessels, agrees quite well with the data reported in literature.
Abstract: We measured water flow in simple xylem vessels of Sechium edule at various pressures. We found a disagreement with Poiseuille's law, which changes from vessel to vessel and becomes abruptly pronounced in some cases. We discuss our data in terms of an 'impediment coefficient,' K. It can be shown that the total flux in a stem, calculated as the sum of the flux in single vessels, agrees quite well with the data reported in literature.
TL;DR: Seasonal changes in the ultrastructure of the mesophyll of needles of Norway spruce are described and the shape of chloroplasts changes.
Abstract: Seasonal changes in the ultrastructure of the mesophyll of needles of Norway spruce are described. During the growing season, the tannin is in the form of a ribbon along the margin of the vacuole o...
TL;DR: In one population of Nemophila menziesii var.
Abstract: Nemophila menziesii typically bears perfect, protandrous. self-compatible but predominantly outcrossed flowers. In one population of Nemophila menziesii var. intermedia at Point Reyes, California, approximately 25% of the plants are completely male sterile. The flowers of these pistillate plants possess only small rudiments of stamens and lack anthers entirely. This phenotype is constant in nature as well as under cultivation. Male sterility appears to be inherited cytoplasmically, but there is at least one nuclear fertility-restoring allele in the population. The fertility-restoring allele may be at a single multiallelic locus, recessive to one nonfertility-restoring allele and dominant to another nonfertility-restoring allele, or there may be fertility-restoring alleles present at two or more loci. The population carries a significant load of deleterious recessive alleles at other loci, as evidenced by floral abnormalities and partial pollen abortion in some of the progeny from selfed hermaphrodites. Ma...
TL;DR: A consistent pattern of variation of the primary xylem has been documented for most levels of the shoot system of Archaeopteris and for smaller pieces of Callixylon (Archaeopteridales), and there is a decrease in diameter of primaryxylem from major to minor units of branching.
Abstract: A consistent pattern of variation of the primary xylem has been documented for most levels of the shoot system of Archaeopteris and for smaller pieces of Callixylon (Archaeopteridales). In general,...
TL;DR: Turnera ulmifolia (Turneraceae) is a polymorphic complex native to the New World tropics which is composed of heterostylous and homOSTylous forms and Varieties angustifolia, elegans, and intermedia are also used as garden ornamentals, and man has played a major role in the expansion of their ranges.
Abstract: Turnera ulmifolia (Turneraceae) is a polymorphic complex native to the New World tropics which is composed of heterostylous and homostylous forms. The distylous varieties elegans, intermedia, and s...
TL;DR: Morphology of the genus matches that of Alpinia in the Zingiberaceae except for greater irregularity of the parallel vein set at and near their origin on the costa and the lack of any evidence of a ligule on the petiole as in Alpinsia.
Abstract: Zingiberopsis attenuata Hickey and Peterson is a new species of monocotyledon from the Paleocene Paskapoo Formation of Alberta. Leaves of this species with their parallel veins grouped into three s...
TL;DR: A period of 1 to 3 days imbibition followed by drying altered the subsequent germination responses of seeds of Rumex crispas, explaining why seedlings of R. crispas appear rapidly each summer following a droug...
Abstract: A period of 1 to 3 days imbibition followed by drying altered the subsequent germination responses of seeds of Rumex crispus L. When the imbibition took place under alternating light and temperature conditions subsequent germination was faster and more complete. In contrast, when the seeds imbibed at a constant temperature and in nearly continuous darkness subsequent germination was delayed and less complete. Subsidiary tests demonstrated that (a) within a 24-h drying period, the seeds lost virtually all water imbibed over 1 to 3 days; (b) a 3-day imbibition pretreatment was followed by faster, more complete germination in a 0.25 M mannitol solution; (c) the duration of the drying period (up to 29 days) had little effect on the outcome; and (d) seeds pretreated for 1 to 3 days under an alternating light and temperature regime germinated more rapidly than untreated seeds when sown in soil in a greenhouse. These results help to explain why seedlings of R. crispas appear rapidly each summer following a droug...
TL;DR: Gliocladium catenulatum parasitizes Sclerotinia sclerotiorum and Fusarium spp.
Abstract: Gliocladium catenulatum parasitizes Sclerotinia sclerotiorum and Fusarium spp. It kills the host by direct hyphal contact causing the affected cells to collapse or disintegrate. Pseudoappressoria are formed by the hyperparasite but hyphae derived from them do not penetrate the host cell walls. Vegetative hyphae of all species tested and macroconidia of Fusarium spp. are susceptible to this hyperparasite but chlamydospores of Fusarium equiseti are resistant.
TL;DR: Various Lower Tertiary epiphyllous microfungi are described from southern Australia, including the monotypic new genus Cribrites aurea and the new species Callimothallus australis.
Abstract: Various Lower Tertiary epiphyllous microfungi are described from southern Australia, including the monotypic new genus Cribrites aurea and the new species Callimothallus australis. Modern equivalents were searched for in 72 leaf-litter samples from Australasia. The habitat indicator value of the fossils is assessed by comparison with the geographic, climatic, and vegetational relationships of the modern forms.