Seedling Growth Form of Oaks

Growth forms of recently-established oak seedlings were comparedamong five species from California and three species from Japan.Evergreen and deciduous species were included, native to a varietyof habitats. Each seedling was grown in a tall tube in orderto measure main root length and was harvested when leaf expansionhad ceased. The effects of light intensity reduced to 5% onseedling growth form were not strong enough to overcome theinnate differences between species. Shoot/root and leaf area/rootweight ratios were smaller in the species from drier environmentswithin each region, though all Californian oaks showed muchgreater root elongation than did the Japanese oaks. Extensiveroot systems combined with small leaf areas would help seedlingssurvival in xeric and open sites. Large leaf areas combinedwith small roots would be profitable for surviving in shadeunder canopy. In oaks of both regions, xeromorphic evergreengrowth forms are clearly distinguished from hygromorphic evergreengrowth forms. Seedling growth form, habitat moisture gradient, California oaks, Japanese oaks, shoot/root ratio     

Flow regulation affects temporal patterns of riverine plant seed dispersal: potential implications for plant recruitment

1. Changes to the natural flow regime of a river caused by flow regulation may affect waterborne seed dispersal (hydrochory), and this may be an important mechanism by which regulation affects riverine plant communities. We assessed the effect of altered timing of seasonal flow peaks on hydrochory and considered the potential implications for plant recruitment. 2. We sampled hydrochory within five lowland rivers of temperate Australia, three of which are regulated by large dams. These dams are operated to store winter and spring rains and release water in summer and autumn for agriculture. At three sites on each river, hydrochory was sampled monthly for 12 months using passive drift nets. The contents of the drift samples were determined using the seedling‐emergence method. 3. More than 33 000 seedlings from 142 taxa germinated from the samples. In general, more seeds and taxa were observed in the drift at higher flows. By altering the period of peak flows from winter–spring to summer–autumn, flow regulation similarly affected the period of peak seed dispersal. The effect of regulation on seed dispersal varied between taxa depending on their timing of seed release and whether or not they maintain a persistent soil seed bank. 4. Hydrochory in rivers is a product of flow regime and the life history of plants. By altering natural flow regimes and thus hydrochorous dispersal patterns, flow regulation is likely to affect adversely the recruitment of native plant species with dispersal phenologies adapted to natural flow regimes (such as many riparian trees and shrubs) and encourage the spread of non‐native (exotic) species. 5. Changes to hydrochorous dispersal patterns are an important mechanism by which altered flow timing affects riverine plant communities. Natural seasonal flow peaks (in this case spring) are likely to be important for the recruitment of many native riparian woody taxa.     

Application of Flow Microflorometry to the Study of Algal Cells and Isolated Chloroplasts

The applicability of flow microfluorometry (FMF) to the studyof chlorophyll-containing cells was investigated through theuse of the blue-green alga Agmenellum quadruplicatum, the greenalgae Trebouxia, Chlorella, and Euglena spp., and isolated spinachchloroplasts. When excited by laser radiation (488 nm), algalcells emitted fluorescence with intensity positively relatedto the chloro-phyll content. The chlorophyll fluorescent signalswere used further as a differential criterion in determiningrelative size based on light scattering logic and to sort mixturesof algal cells having different chlorophyll content The FMFalso was useful in estimating nucleic acid and protein contentin completely dechlorophyUized algal cells with the use of ethidiumbromide (EB) and fluoresceinisothiocyanate (FITC), respectively.     

Brain, Gut and Skin Peptide Hormones in Lower Vertebrates

Understanding of peptide hormone evolution rests primarily onstructural information, either direct or inferred. We summarizestudies of fishes and amphibians to provide initial informationwithin the vertebrate lineage for selected peptides which exhibitvarying structural heterogeneity. For these peptides, thyrotropin-releasinghormone, somatostatin, luteinizing hormone-releasing hormoneand cholecystokinin related peptides manifest increasing diversification.Members of these peptide families are found distributed amonga variety of tissues (e.g., brain, gut, skin, retina, sympatheticnervous system), yet the number of genes encoding for individualtypes of peptides is presently uncertain. We emphasize the needfor additional structural information, for a more thorough anddiverse taxonomic investigation within the vertebrate lineage,and for specification of those genetic elements which ultimatelydetermine evolutionary opportunities for peptide evolution.     

Light-induced Activation of Cytoplasmic Protein Synthesis in Verticillium agaricinum

The level of protein synthetic activity in dark-grown cultures of Verticillium agaricinum was significantly enhanced by light. As expected the enhancement of protein synthetic activity was accompanied by a transformation of cytoplasmic monoribosomes to polyribosomes. Amino acid incorporation studies utilizing the synthetic mRNA, poly (U), suggest that the transformation was preceded by an activation of pre-existing ribosomes. The change in ribosome activity related, at least in part, to an increase in the level of peptidyl-tRNA associated with the ribosomes. In this regard the response of V. agaricinum ribosomes was similar to ribosome activation in several higher plant systems. The initial response at the level of the ribosome remains to be elucidated.     

Fine Structure and Taxonomic Position of the Giant Amoeboid Flagellate Pelomyxa palustris1,2

ABSTRACT Specimens of Pelomyxa palustris from five collecting sites had numerous nonmotile flagella. The structures are called flagella because of morphological similarities to flagella and because P. palustris has affinities with amoeboid flagellates. Flagella were photographed on living cells and studied by transmission and scanning electron microscopy. From 64 to 742 flagella per cell were estimated from scanning electron microscopy of ten cells 204 to 1269 μm in length. The nonmotile flagella arise from basal granules which were, in one strain, surrounded by radiating electron-dense microtubules. This strain also had excess axonemal microtubules. Abundant cytoplasmic microtubules were arranged in several different patterns. In about half of the P. palustris cells in which nuclei were studied, microtubules were either apposed to the nuclear membrane in a parallel alignment (with some also radiating) or radiating from the nuclear membrane (with none parallel). Bacteria associated with nuclei were of three characteristic types: Gram-negative rods, Gram-positive rods, and large rods. All nuclei within a given trophozoite had similar perinuclear features. Recent proposals for separation of Pelomyxa to its own phylum (based on its proposed primitive, unique nature) can not be justified. Pelomyxa is a complex, highly specialized organism adapted to live in a specific fresh-water environment. Mastigamoebid amoeboid flagellates of the genera Mastigamoeba, Mastigella, Mastigina, and possibly Dinamoeba are placed with Pelomyxa within the order Pelobiontida Page, 1976, emend., containing two families. Pelomyxidae Schulze, 1877, and Mastigamoebidae Goldschmidt, 1907.     

Microsporidian Parasites of Trematode Larvae from Aquatic Snails in West Malaysia

In a survey of microsporidian parasites of trematode larvae of Malaysian fresh-water snails, species of Nose-matidae were found 7 times in rediae from 425 Lymnaea rubiginosa, 6 times in rediae from 97 Indoplanorbis exustus and not at all in other snails. There were 3 species of Microsporida in all: one, found in Echinoparyphium dunni, Echinostoma hystricosum and Echinostoma malayanum was identified as Nosema eurytremae Canning; another, which was found in E. dunni and Echinostoma audyi, had paired nuclei (diplokaryon form) in sporogony only and was named a new species, Nosema vasicola sp.n.; the 3rd, from E. hystricosum, lacked diplokaryon nuclei throughout development, was considered to belong to a new genus and was named Unikaryon piriformis gen.n., sp.n. Nosema eurytremae was transmitted experimentally to Fasciola hepatica rediae in Lymnaea truncatula.     

The Pathogenic Amoeboflagellate Naegleria fowleri: Environmental Isolations,Competitors, Ecologic Interactions,and the Flagellate-Empty Habitat Hypothesis1

From several surveys of environmental sites, the virulent human pathogen, Naegleria fowleri, was isolated from a pond in Georgia, a sewage treatment plant in Missouri, and from the Potomac and Anacostia rivers near and in Washington, D.C. Widely scattered, sparse populations seemed only a potential threat to human health at the time of sampling. The data support an estimate that the sites sampled contain 10,000 typical, low temperature, bactivorous amoebae for each heat tolerant amoeba able to grow at 45° C. Heat tolerant competitors were much more common than N. fowleri. Naegleria lovaniensis, which is heat tolerant but nonpathogenic, was isolated from and downstream from an open air thermal pollution temperature gradient. Hot piles of composting sewage sludge yielded no amoeboflagellates, many heat tolerant (45–49° C) amoebae, and one thermophilic (52° C) Acanthamoeba. Features of the methods used include two-stage incubation to increase isolation of sparse organisms and distinction of N. fowleri from almost all other amoebae on agar plates. The flagellate-empty habitat hypothesis postulates a general model in which human intervention and/ or natural events remove usual competitors and the ability to transform to a motile flagellate confers an advantage in recolonizing.     

Comparison of Isocitrate Dehydrogenase Activity, Pyruvate Kinase Activity, and Polyphenol Content in Physiologically Different Pine Callus Tissue

During the growth of callus tissue of slash pine (Pinus elliottil Engelm.) several physiologically different types of tissue can be observed, often within the same culture. Different tissues were selected, based on color appearance, and used to determine isocitrate dehydrogenase and pyruvate kinase activity, and total polyphenol content. Isocitrate dehydrogenase and pyruvate kinase activity in yellow tissue was 3- to 5-fold greater than in brown tissue, whereas the polyphenol content in yellow tissue was approximately 5-fold less than in brown tissue. Dark brown callus, which also contained large amounts of polyphenols, did not have detectable enzyme activity. The differences in optimal concentrations of substrate and cofactors for the isocitrate dehydrogenase and pyruvate kinase reactions in yellow and brown tissues were very minor and therefore cannot account for the 3- to 5-fold difference in enzyme activity between these tissues. Also, the addition of brown or dark-brown tissue extract to the yellow tissue extract did not inhibit isocitrate dehydrogenase or pyruvate kinase activity in the yellow tissue extract.