bluuebunny/crossref_metadata_2025 huggingface dataset:
Organization of microtubules in developing pea root nodule cells
Authors: Davidson A L , Newcomb W
Published: April 2011

Pisum sativum L. (pea) root nodule cells undergo many cellular changes in response to infection by Rhizobium leguminosarum bv. viciae. These include cell growth, organelle reorganization, and changes relating to the increase in the number of bacteria within the cell. The objective of this study was to characterize microtubule organization during nodule cell development. The organization of microtubules was examined in developing pea root nodules using fluorescence and electron microscopy techniques. Immunolabelling of microtubules in meristematic cells showed diffuse fluorescence in the cell cortex and adjacent to the nuclear envelope. Recently infected cells contained randomly oriented cortical microtubules and cytoplasmic microtubules that were fragmented with diffuse fluorescence. Infected cells contained an extensive network of long, randomly arranged cortical microtubules with some parallel bundles. Cytoplasmic microtubules in single optical sections of infected cells appeared as short undulating filaments; however, overlapping images from a Z-series of an infected cell showed that the microtubules are long and wavy, and generally radiate inward from the cell cortex.Key words: nodule, microtubules, Rhizobium, pea, symbiosis.
Vegetative compatibility groups within Fusarium oxysporum f.sp. lini from Linum usitatissimum (flax) wilt nurseries in western Canada
Authors: Mpofu S I , Rashid K Y
Published: April 2011

Following the discovery of substantial differences in the development and severity of Fusarium wilt in Linum usitatissimum L. (flax) wilt nurseries in western Canada, a study of the population structure of Fusarium oxysporum f.sp. lini (Bolley) Snyd. & Hans using vegetative compatibility analysis was initiated. Vegetative compatibility was determined using nitrate non-utilizing mutants. From a total of 105 isolates, 74 were assigned to 12 vegetative compatibility groups (VCG 0440-04411), 22 were not compatible with any other isolates and 9 did not produce mutants. The populations of F. oxysporum f.sp. lini in Fusarium wilt nurseries in western Canada were significantly different. There was a predominant VCG in each of the nurseries, which was either nonexistent or not common in other nurseries, VCG 0440 in Indian Head, 0441 in Treherne, 0442 in Morden-80, 0443 in Saskatoon, and 0444 in Morden-60. There were only three overlapping VCGs; VCG 0440 was common to Morden-60 and Indian Head and VCGs 0442 and 0444 were common to Morden-60 and Morden-80. The differences in disease development and severity observed previously may be due to the differences in the population structure of the pathogen. These findings have significant implications for the approaches to breeding for Fusarium wilt resistance in flax.Key words: Fusarium oxysporum f.sp. lini, flax, Fusarium wilt, genetic diversity, vegetative compatibility.
Morphological variation in Scandinavian populations of the diploidtetraploid species pair Anthericum ramosum and Anthericum liliago (Anthericaceae)
Authors: Rosquist Gabrielle , Prentice Honor C
Published: April 2011

Both members of the diploidtetraploid species pair Anthericum ramosum L. and Anthericum liliago L. occur as geographically disjunct isolates on the margins of their northern range in Scandinavia. Variation in floral morphology was studied in 33 populations of A. ramosum from four geographic regions and 25 populations of A. liliago from seven regions in Scandinavia. Tepal shape was characterized with the help of moment invariants, and intra- and inter-specific variation in style and filament length was investigated. There were significant between-region and between-population differences in tepal shape and style and filament length within both species. However, despite the geographic disjunction of both species' distributions, there was considerable overlap in tepal shape between populations from the different regions. The hierarchical partitioning of tepal shape diversity was similar in the two species. Most of the total diversity was explained by regional and interpopulation components of diversity (48% and 35%, respectively, in A. ramosum and 61% and 22%, respectively, in A. liliago). The two species were clearly discriminated on the basis of tepal shape and style and outer filament lengths. A southern Swedish population, containing triploid hybrids between A. ramosum and A. liliago, was indistinguishable from other Scandinavian populations of A. liliago on the basis of tepal shape. However, a (allegedly hybrid) Danish population of A. liliago was intermediate between the two species in tepal shape.Key words: polyploidy, geographic variation, tepal shape, hybridization, moment invariants.
Corticolous bryophytes in managed Douglas-fir forests: habitat differentiation and responses to thinning and fertilization
Authors: Thomas Sean C , Liguori Denise A , Halpern Charles B
Published: April 2011

Corticolous bryophytes, that is, mosses and liverworts that inhabit tree trunks, represent an important component of plant diversity in temperate ecosystems, but little is known of their ecology in managed forests. In this study, we quantified community composition and habitat differentiation of corticolous bryophytes in Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) plantations subjected to experimental thinning and fertilization treatments. Twenty-four bryophyte species were recorded in a sample of 480, 225 cm2 quadrats on 60 tree trunks. All moss species and obligately epiphytic liverworts (those with a primary habitat preference for tree trunks) showed highest cover values on south and west exposures. In contrast, facultatively epiphytic liverworts occurred only at the tree base, and mainly on north and west exposures. Pairwise correlations among species cover values were nearly always positive, and cover of the most abundant species, Isothecium myosuroides, was also positively correlated with local species richness of other bryophyte taxa. These patterns suggest that competitive interactions among bryophyte species are not strong in this community. There was little evidence for fertilization or thinning effects on total bryophyte cover or species richness. However, analyses of community composition and species-specific responses indicated significant negative effects of thinning on some bryophyte species. Observed patterns of habitat differentiation, interspecific associations, and treatment responses suggest that stand hydrology and microclimate are of primary importance in determining the distribution and abundance of corticolous bryophytes in managed forests.Key words: corticolous bryophytes, liverworts, mosses, nitrogen fertilization, plant diversity, silvicultural thinning.
Molecular polymorphism and virulence phenotypes of the wheat leaf rust fungus Puccinia triticina in Canada
Authors: Kolmer J A
Published: April 2011

Sixty-nine Puccinia triticina isolates from the eastern region of Ontario and Quebec, the prairie region of Manitoba and Saskatchewan, and Alberta were tested for virulence to 22 near-isogenic Thatcher wheat lines in seedling tests and the Thatcher line with Lr22b in adult plant tests. The isolates were also tested for amplified fragment length polymorphism (AFLP) using 10 specific amplification primer pairs. Thirty-seven distinct virulence phenotypes were identified using the Thatcher lines and 69 molecular phenotypes were identified with 164 AFLP markers. The correlation of isolate grouping based on virulence phenotypes and AFLP phenotypes was 0.53. Almost all isolates from Manitoba and Saskatchewan with virulence to Lr17 had AFLP phenotypes that differed significantly from isolates in the same region that were avirulent to Lr17. This indicated that isolates with virulence to Lr17 are most likely a recent introduction to the prairie region. The presence of distinct groups of isolates based on virulence and AFLP variation provides evidence that a number of different P. triticina phenotypes have been introduced to North America.Key words: Puccinia recondita f.sp. tritici, AFLP, specific virulence.
Entophlyctis apiculata, a chytrid parasite of Chlamydomonas sp. (Chlorophyceae)
Authors: Shin Woongghi , Boo Sung Min , Longcore Joyce E
Published: April 2011

A chytridialean fungus identified as Entophlyctis apiculata (Braun) Fischer parasitized cells of Chlamydomonas sp. that bloomed in an agricultural pond in Hongsung, Korea, during 1999 and 2000. This is one of the species for which Fischer described the genus Entophlyctis in 1892. Since the segregation of the Spizellomycetales from the Chytridiales confusion has existed as to whether Entophlyctis is a spizellomycetalean or a chytridialean genus. We examined the morphology and development of the Korean E. apiculata with light and transmission electron microscopy. The parasite develops exogenously and has a monocentric, inoperculate zoosporangium. Zoospores within the sporangium contain a single lipid globule associated with a microbody, a rumposome, and a nonflagellated centriole that is parallel and attached by fibers to the kinetosome. These features indicate that E. apiculata is a member of the Chytridiales; however, zoospores were still within the zoosporangium and did not provide sufficient characters to determine the zoospore subtype, which is important for identifying clades within this order.Key words: Chytridiales, pond, Spizellomycetales, ultrastructure, zoospore.
Male and hermaphrodite flowers in the alpine lily Lloydia serotina
Authors: Manicacci D , Després L
Published: April 2011

In perennial species that produce only one flower per individual each year, androdicy (coexistence of genetic male and hermaphrodite individuals) may be difficult to distinguish from andromoncy (male and hermaphrodite flowers on the same plant). We show that the alpine lily, Lloydia serotina Rchb., produces functionally male and hermaphroditic flowers. Mean male frequency in 11 populations in the French Alps was 48.5%, ranging from 15.5 to 67.5%. Male flowers do not produce more pollen nor sire more seeds per flower in controlled pollinations than hermaphrodite flowers. Male floral scapes were consistently shorter than those of hermaphrodites. Out of several thousand observed floral scapes, four had two flowers, all with a terminal hermaphroditic flower and an axillary male one. Among 107 bulbs transplanted in pots in 1996, eighteen expressed a different sexual phenotype in 1999 or 2000, and one hermaphrodite produced two flowers of different sexes in 2000. Together, these results suggest that L. serotina is andromoncious throughout its lifetime.Key words: Lloydia serotina, andromoncy, male reproductive success, Liliaceae.
Formation and germination of resting spores from different strains from the Entomophthora muscae complex produced in Musca domestica
Authors: Thomsen Lene , Bresciani José , Eilenberg Jørgen
Published: April 2011

Three species within the Entomophthora muscae (Cohn) Fresenius complex (Entomophthora schizophorae Keller & Wilding, E. muscae s.str., and E. muscae "group B") were investigated for resting spore formation in vivo in the house fly (Musca domestica L.). Resting spores of E. muscae group B were experimentally induced from August to the beginning of February, while no resting spores were ever observed in E. schizophorae infected M. domestica or in flies infected by E. muscae s.str. originating from M. domestica. When newly dead fly cadavers containing E. muscae group B resting spores were kept moist, cystidia emerged from the abdomen; this is the first report of cystidia in the genus Entomophthora. Resting spore production was significantly affected by both temperature and E. muscae group B strain. More infected flies formed resting spores when kept 1 week at 10°C compared with constant exposure at 22°C, but the tendency of the different E. muscae group B strains to form resting spores persisted with shifting temperatures. After 4 months of incubation under natural winter conditions in Denmark, E. muscae group B resting spores germinated on water agar at 20°C with a 16 h light : 8 h dark photoperiod within 1 week, but no germ conidia were observed.Key words: Entomophthorales, Entomophthora muscae complex, Diptera, Musca domestica, resting spore formation, resting spore germination.
Stem orientation is related to growth rate, leaf dimensions, and the deciduous habit in temperate forest saplings
Authors: King David A
Published: April 2011

The orientation of the central stem is a key component of tree architecture. Stem orientation was related to extension rate in saplings growing in light conditions ranging from forest understories to large openings in 11 deciduous angiosperms, 1 evergreen angiosperm, and 2 evergreen conifers in the Appalachian Mountains of the southeastern United States. Most of the deciduous species showed pronounced differences between arced, dorsiventrally symmetric forms in slow-growing, shaded saplings and erect, radially symmetric forms in fast growing, sunlit saplings. In contrast, the evergreen species showed little or no shift in stem orientation in relation to growth rate and tended to be more erect in shade than the deciduous species. Evergreen saplings studied at other sites were also more erect in shade than the deciduous species studied here. Within the deciduous species, the degree of arcing in shade declined with increasing leaf size and petiole length. These results, involving two congeneric pairs, suggest that stem orientation is related more to leaf dimensions and leaf habit than to taxonomic classification per se. The positioning of a single cohort of nonoverlapping leaves in shaded deciduous saplings may increase the efficiency of light interception in arced forms, as compared with evergreen saplings, where new leaves must be positioned in relation to older leaf cohorts.Key words: tree architecture, growth rate, stem orientation, morphological plasticity.
Comparative floral morphometrics of distyly and homostyly in three evolutionary lineages of Amsinckia (Boraginaceae)
Authors: Li Ping , Johnston Mark O
Published: April 2011

Using three ancestor-descendant lineages of Amsinckia (Boraginaceae), we studied changes in floral morphology associated with evolution of the breeding system. Each lineage comprised a distylous ancestor and a homostylous descendant: (i) Amsinckia furcata Suksd.  Amsinckia vernicosa Hook. & Arn.; (ii) Amsinckia douglasiana A. DC.  Amsinckia tessellata var. gloriosa (Suksd.) Hoover; and (iii) Amsinckia spectabilis Fischer & C. Meyer. Comparisons of 26 floral traits were made between pins and thrums within the distylous groups, between distyly (pins and thrums combined) and homostyly as well as among pins, thrums, and homostyles. Differences among the morphs were also compared across the three lineages. In distylous flowers, the six traits directly related to stamen height or pistil height varied as expected from their close relationship to the definition of pins and thrums, with the stamen-height-related characters greater in thrums and the pistil-height-related characters greater in pins. Thrums had larger pollen grains in all lineages. Pollen production was either similar in the two distylous morphs or lower in thrums than in pins, depending on species. Thrums also tended to have larger style cross-sectional area and style transmission tissue cross-sectional area. In two of three lineages, thrums had longer corollas, whereas pins exceeded thrums in functional antherstigma separation and in stigmatic papilla size. The size order of a trait in pins versus thrums was consistent in all lineages for 18 of 26 traits; in seven of the eight remaining traits, A. spectabilis was the unusual lineage. Sepal length, corolla width, and stigma size did not differ significantly between the two distylous morphs. In homostyles, traits related to anther height and pistil height were intermediate between pins and thrums in all lineages; for other traits, including antherstigma separation and overall size, homostyles generally had the smallest values. For most traits, lineages differed in the degree of differentiation among the three morphs as well as between distyly and homostyly. Thus, in Amsinckia, the evolution of homostyly involves a general reduction in flower size, but by an amount that varies both among traits and among lineages.Key words: Amsinckia, dimorphism, distyly, floral evolution, homostyly, mating system.
The effect of crown position and tree age on resin-canal density in Scots pine (Pinus sylvestris L.) needles
Authors: Lin Jinxing , Sampson D A , Ceulemans R
Published: April 2011

Resin canals are an important taxonomic characteristic in conifers. In this paper we examined within- and between-needle variation of the cross-sectional number of resin canals in Scots pine (Pinus sylvestris L.). Variation within needles was determined from 12 free-hand sections taken along the whole length of foliage collected from a common crown position. The effect of crown location and tree age on resin-canal density was also examined from the midpoint cross sections of 450 Scots pine needles collected from interior and exterior locations from the top, middle, and bottom of 25 crowns of trees ranging in age from 8 to 70 years. Within-needle resin-canal density varied with needle length. Two resin canals were typical for the basal and the terminal needle cross sections. There were 3.2 and 8.6 resin canals for cross sections taken from 10 and 30% of the needle length from the basal sheath, respectively. Resin-canal density was largest, and relatively constant, between 30 and 80% of the needle length. We found significant differences in the cross-sectional number of needle resin canals, as influenced by crown positions and tree age. Resin-canal density increased with foliage height. Foliage from the top one-third of crowns had significantly more resin canals than foliage from the bottom. Foliage collected from the crown interior (proximal to the stem) had fewer resin canals than samples from the crown edge. Resin-canal density increased from 7.1 to 10.3 as tree age increased from 8 to 70 years. These results suggest that crown position and tree age need to be incorporated into the sampling protocols used to establish species standards in resin-canal density, at least for Scots pine, if meaningful comparisons are to be made.Key words: resin canal, needle age, crown position, needle anatomy, Pinus sylvestris.
Shoot type demography and dry matter partitioning: a morphometric approach in apple (Malus ×domestica)
Authors: Lauri Pierre-Éric , Kelner Jean-Jacques
Published: April 2011

In a study of the apple (Malus ×domestica Borkh.) canopy structure, 5-year-old 'Fuji' and 'Braeburn' trees grafted on a low-vigour rootstock (M9) were compared at both fruiting branch and shoot levels. Percentages of short ([Formula: see text]5 cm) shoots and short shoot leaf area were significantly higher on 'Braeburn' than on 'Fuji', (76.8% vs. 72.6% and 46.9% vs. 42.9% for 'Braeburn' and 'Fuji', respectively). This high percentage of short shoots as compared with literature data was probably due to the training method, which reduced vigour. At shoot level, the ratio between dry masses of axis and leaf, called the axialization index, was determined to compare short and long shoots. Axialization values were higher for 'Braeburn' than for 'Fuji'. Although overall and individual leaf area was greater on long shoots, long shoot axialization (0.64 and 0.54 for 'Braeburn' and 'Fuji', respectively) was approximately twice that of short shoots (0.36 and 0.24, respectively). Therefore, for short shoots, the reduced carbon investment in supporting tissues may explain the significant role short shoots played in supporting early fruit development. For long shoots, the longer time required to reach the autotrophic and then exporting stage as well as the detrimental effect of early extension shoot development on fruit set might be explained by greater axialization.Key words: long shoot, short shoot, axialization index, apple, Malus ×domestica, biomass partitioning.
Assessing competition intensity along productivity gradients using a simple model
Authors: Arii Ken , Turkington Roy
Published: April 2011

One of the most highly debated issues in plant ecology has been the manner in which competition intensity changes along productivity gradients. We have used a simple model to attempt to demonstrate that in theory, competition intensity can vary quite considerably along productivity gradients. Our model incorporates three key components: (i) changes in resource availability along a productivity gradient, (ii) changes in resource availability when neighbours are removed, and (iii) growth characteristics of the target species and (or) individuals to varying resource levels (i.e., response surface). Variation and interactions among these three components can potentially give rise to various, and occasionally complex, changes in competition intensity along productivity gradients. This partly explains the divergent, and sometimes contradictory, results reported in previous studies.Key words: competition intensity, productivity gradient, nutrient, light, model.
α-Galactosidase is synthesized in tomato seeds during development and is localized in the protein storage vacuoles
Authors: Bassel George W , Mullen Robert T , Bewley J Derek
Published: April 2011

The localization of the enzyme α-galactosidase (EC 3.2.1.22) was investigated during its synthesis in developing tomato (Lycopersicon esculentum Mill.) cv. Trust seeds. This enzyme is also present in germinating seeds, where it is involved in the mobilization of carbohydrate reserves during and following seed germination. Subcellular fractionation of developing tomato seeds revealed that there is a cosedimentation between α-galactosidase activity and protein storage vacuoles in a density gradient, which is dependent upon the presence of membranes. A second approach to localizing this enzyme involved the transient transformation of protoplasts from developing tomato seeds. A reporter construct, coding for tomato α-galactosidase, fused N-terminally to the bacterial enzyme chloramphenicol acetyltransferase was used for transient expression. Immunofluorescence microscopy revealed a colocalization between the α-galactosidase - chloramphenicol acetyltransferase fusion protein and the α-tonoplast intrinsic protein, and a partial colocalization with the dark intrinsic protein (both vacuolar proteins). These data indicate that the protein storage vacuole is the intracellular location for α-galactosidase in developing tomato seeds.Key words: α-galactosidase, protein storage vacuole, seed development, seed protoplasts, tomato, tonoplast intrinsic protein.
Some preliminary cytological observations on a new basic number in Paspalum convexum (Gramineae)
Authors: Selva Steven B.
Published: April 2011

That Paspalum convexum Humb. and Bonpl. is a valid member of the Plicatula species complex has been substantiated morphologically and anatomically, but its chromosome complement of n = 16 is very different. Four of its 16 bivalent chromosomes are larger than the others and are not quadrivalent associations, as had been suspected previously. With evidence that 10 is the basic number for the group, as well as for the genus as a whole, several mechanisms are proposed that would increase or reduce x = 10 or its multiple to a basic complement of 16 through gain or loss of centromeres, respectively.
Basidiospore germ pore and wall structure in Coniophora (Basidiomycetes: Aphyllophorales)
Authors: Ginns J. , Kokko Eric
Published: April 2011

A germ pore is present in the basidiospores of Coniophora puteana (Fr.) Karst. and probably in the spores of 11 other species of Coniophora. This is only the second report of a germ pore in any species of the order Aphyllophorales. Furthermore, whereas the wall of Coniophora spp. traditionally has been described as two-layered, that of, at least, C. puteana is here shown to be composed of several layers.
Some characteristics of the thrip vector relationship of tomato spotted wilt virus in Canada
Authors: Paliwal Y. C.
Published: April 2011

Two isolates of tomato spotted wilt virus (TSWV) from British Columbia were transmitted by Frankliniella occidentalis, which is common in British Columbia but does not occur in eastern Canada. Frankliniella occidentalis from B.C. transmitted the virus to a smaller proportion of Emilia plants as compared with Frankliniella fusca, a known vector that occurs in eastern Canada, after a 48-h acquisition feeding as nymphs on infected Emilia leaves. Neither isolate of the virus was transmitted by Thrips tabaci, which is a vector of TSWV in some other countries. Males and females and macropterous and brachypterous forms of F. fusca did not differ significantly in their vector ability. TSWV was detected serologically in homogenates of 50 ‘exposed' F. fusca (first-generation adults reared on newly infected plants) but was difficult to detect in homogenates prepared from these thrips 2 weeks later. Thrip transmissibility of the virus declined considerably when propagated for long periods without passage through the thrip vector.
Conjugation and growth of Sirobasidium magnum in laboratory culture
Authors: Flegel T.W.
Published: April 2011

The life cycle of the heterobasidiomycete, Sirobasidium magnum Boedijn, is described in artificial media. The haploid yeast phase, which may propagate by ballistospores, shows a modified tetrapolar mating system similar to that of Tremella Dill, ex Fr. The possible relationship to the imperfect yeasts Bullera Derx and Cryptococcus Kutzing emend. Phaff et Spencer is discussed.
Growth and metabolism of cells and tissues of jack pine (Pinus banksiana). 1. The establishment and some characteristics of a proliferated callus from jack pine seedlings
Authors: Durzan D. J. , Chalupa V. , Mia A. J.
Published: April 2011

No more than 2% of the embryos from dry seeds of jack pine (Pinus banksiana Lamb.) produced callus on agar with a defined nutrient medium. When contact of the embryo with the nutritive female gametophyte was maintained during imbibition, callus production by excised seedlings on the medium increased to over 80%. Callus production was optimal with 5-day-old seedlings. Percentage callus formation was greater when the initial contents of the explant in dry weight, glutamate N, amide N, total nucleotides, RNA, adenylate energy charge, and oxygen uptake were also greater. Small initial increases in levels of these components over those found in dry embryos and resulting from imbibition substantially improved callus production. Subsequent increases, concomitant with germination and seedling development, gave only slightly more callus. By contrast, inverse or poor relations were observed with DNA, total soluble protein, and aminoacyl tRNA synthetase activity. In the initial explants the most conspicuous cytological events, leading to optimal callus production, were the onset of the first wave of mitosis and prominence of nucleoli. Seed reserves were nearly consumed and ribosome-like particles, which were associated with chromatin, appeared as new cytoplasm was being synthesized during the onset of proliferation of cells on the agar medium.
Growth and metabolism of cells and tissue of jack pine (Pinus banksiana). 3. Growth of cells in liquid suspension cultures in light and darkness
Authors: Durzan D. J. , Chalupa V.
Published: April 2011

Friable, jack pine (Pinus banksiana Lamb.) callus on agar plates with a defined nutrient medium was transferred to a liquid medium of the same composition to establish cell suspension cultures. Dry weights and patterns of growth for daughter cells were estimated in continuous light or darkness, with or without conditioned media and arginine supplement. In all treatments, growth was near-exponential. Greatest final size was obtained with basal medium under continuous light.The distribution of clump sizes at the later stages of growth fits a stochastic model reflecting two types of daughter cell behavior described by the probability of one type remaining with the clump as opposed to sloughing off into the medium. In light, cells contained many more chloroplasts, thicker cell walls, and more compacted clumps than in darkness: yet cellular clumping patterns both in light and darkness were largely similar. Nearly 20% of the clumps showed polarity and symmetry and contained actively streaming suspensor-like cells. The remaining clumps were spherical and produced unorganized growth patterns. The progress of growth was eventually dominated by the tendency of daughter cells to remain attached to clumps compared with the initial tendency for clumps to fragment and cells to be released into the medium.
Growth and metabolism of cells and tissue of jack pine (Pinus banksiana). 7. Observations on cytoplasmic streaming and effects of L-glutamine and its analogues on subcellular activities
Authors: Durzan D. J. , Bourgon G.
Published: April 2011

Cells from jack pine (Pinus banksiana Lamb.) callus and suspension cultures were observed by cinemicrography to evaluate cytoplasmic streaming, motion of organelles, and nuclear behaviour under glutamine stress. Streaming rates were greatest in the largest cells. Rates were reduced in smaller cells, where transvacuolar strands were not as prominent and displacements of organelles were not strongly affected by cyclosis. During increased rates of cytoplasmic streaming, chloroplasts tended to associate with each other and mitochondria often changed direction and shape.The addition of 400 ppm L-glutamine to a defined basal medium increased the linear velocity of organelles from 2-7 microns (μ)/s to 7–12 μ/s, whereas D-glutamine eventually stopped cytoplasmic streaming, with a concomitant increase in nucleolar size. While additions of low levels of α-N-acetyl-L-glutamine and isoglutamine stimulated streaming, this occurred usually without other significant morphological effects. Cytoplasmic movements that were induced by exposure of cells to L-glutamine were intimately involved with the fine strands and with nuclear and nucleolar behavior. Movements ceased when strands were disrupted under nutritional stress and by inhibitory responses to D-glutamine.
Morphological, anatomical, habit, and habitat differences among the goldenaster genera Chrysopsis, Heterotheca, and Pityopsis (Compositae–Astereae)
Authors: Semple John C. , Blok Vivian C. , Heiman Patricia
Published: April 2011

The leaf morphology and anatomy, fruit morphology, growth forms, and distribution patterns of species of the three goldenaster genera Chrysopsis, Heterotheca, and Pityopsis were analyzed and compared, with the conclusion that they should be treated as three distinct genera. The species of Chrysopsis were characterized by flexible flagelliform hairs. Heterotheca had stiff uniseriate, osteolate hairs. Pityopsis had long filamentous hairs that adhered to each other in a reticulate pattern. Chrysopsis and Heterotheca had similar leaf anatomy and compressed-obconic fruits (except for the epappose ray floret fruits of sect. Heterotheca). Pityopsis had distinctive leaf anatomy and morphology and had fusiform fruits. Chrysopsis included one annual plus biennial to weakly perennial and true perennial species distributed primarily in Florida. Pityopsis included only herbaceous perennials with fibrous roots distributed throughout the southeastern United States for the most part. Heterotheca included mostly herbaceous perennials with taproots distributed throughout western North America from Canada to Mexico. Some members of sect. Heterotheca were annuals occurring in the southern United States. A key to the genera and sections of the goldenasters has been included. The following new nomenclatural combinations have been made: Chrysopsis gossypina ssp. cruiseana, C. gossypina ssp. hyssopifolia, C. gossypina, f. trichophylla, Heterotheca camphorata, Pityopsis adenolepsis, and Pityopsis graminifolia var. microcephala.
Karyotype evolution and chromosome numbers in Chrysopsis (Nutt.) Ell. sensu Semple (Compositae–Astereae)
Authors: Semple J. C. , Chinnappa C. C.
Published: April 2011

The karyotypes of all species of Chrysopsis were analysed and four basic complements were recognised. The X = 5 karyotype was possessed by all seven n = 5 species and consisted of three submetacentric and two acrocentric chromosomes, one bearing the nucleolar organizer region medially on its short arm. Each X = 4 species had a distinct karyotype. The n = 4 karyotype of C. mariana had diverged less from the X = 5 karyotype than that of C. pilosa. The X2 = 9 karyotype shared by three n = 9 taxa was found to be little more than a combination of the X = 5 karyotype and the X = 4 mariana karyotype and was therefore of allopolyploid origin. Some shifting in the location of the nucleolar organizer region has occurred in each group.
Stability of methylmercury and inorganic mercury in aquatic plants (Elodea densa)
Authors: Czuba M. , Mortimer D. C.
Published: April 2011

Elodea densa plants containing either methylmercury or inorganic mercury-203 were transferred to a flowing water system along with untreated plants for a period of 6 months. Although little or no radioactivity was measurable in the water throughout the experimental period, untreated plants accumulated some methylmercury (MMC) and to a lesser extent inorganic mercury (MC) within the 1st month. Treated plants lost more MC than MMC within the 1st month. The two species of mercury move in opposite directions within the plant with time: MMC moves toward young tissue whereas MC moves toward older tissue. Methylmercury remains stable in younger plant tissues almost indefinitely, but converts partly to inorganic forms in old and decomposed tissue. Conversion of inorganic mercury to methylmercury was not detected.
Phytohormone changes in Bouteloua gracilis infected by vesicular–arbuscular mycorrhizae: I. Cytokinin increases in the host plant
Authors: Allen Michael F. , Moore Jr. Thomas S. , Christensen Martha
Published: April 2011

Bouteloua gracilis was grown in defined, axenic culture with and without vesicular–arbuscular (VA) mycorrhizae. Leaves and roots of mycorrhizal and nonmycorrhizal plants were harvested and assayed for cytokinin content using a soybean callus tissue bioassay. Total cytokinin activity was 57 and 111% greater in leaves and roots, respectively, in mycorrhizal over control plants. Cytokinin activities, separated using paper chromatography with water saturated n-butanol as a solvent, doubled in roots and leaves at Rf values of 0.3 and 0.9 and increased 9-fold in roots at an Rf value of 0.1 with infection. This appears to be the first demonstration of altered cytokinin levels in plants resulting from mycorrhizal infection.
Pollen fertility in Java × New Guinea Impatiens interspecific hybrids
Authors: Pasutti David W. , Weigle Jack L.
Published: April 2011

Viable pollen-producing hybrids were obtained from the crosses New Guinea Impatiens Plant Introductions (P.I.'s) (2n = 32) × Java Impatiens P.I. 349629(2n = 16). The hybrids were crossed with a 24-chromosome amphidiploid ‘Tangeglow,’ resulting in 2n = 34-chromosome hybrids. One of these 34-chromosome hybrids was crossed with P.I. 349692 (2n = 16), producing two offspring having chromosome counts of 2n = 24 and 2n = 30. Subsequent crosses using the 30-chromosome hybrid showed a continuing tendency for production of viable partly unreduced gametes.
Scanning electron microscopy of Ceratiomyxa fruticulosa
Authors: Scheetz Raymond W. , Nelson Rodney K. , Carlson Eric C.
Published: April 2011

The development of Ceratiomyxa fruticulosa var. flexuosa was followed from the motile stages through sporophore formation by scanning electron microscopy. Sporophore maturation was also depicted for C. fruticulosa var. porioides. Swarm cells were found to be uniflagellate when first formed, with a second flagellum evident within 4 h. Fructifications at the prespore stage in var. flexuosa consisted of several layers of prespore cells underlaid by a fibrous network. Spore elevation in both varieties appeared- subhypothallic. Granules were found at the base of the individual stalked spores. Energy dispersive X-ray spectroscopy indicated the presence of calcium in the granules.
Effect of ammonia, nitrite, glutamate, and inhibitors of N metabolism on photosynthetic carbon fixation in isolated spinach leaf cells
Authors: Woo K. C. , Canvin D. T.
Published: April 2011

Photosynthetic 14CO2 fixation in spinach leaf cells was stimulated by ammonia. CO2 fixation in the presence of NH3 was inhibited by glutamate, NO2−, methionine sulfoximine, azaserine, or aminooxyacetate. In all instances, though, the decrease in 14CO2 fixation was largely due to decreased 14C in the neutral fraction rather than to decreased 14C in the basic or acidic fractions which are those fractions specifically increased by ammonia addition. Ammonia appears to stimulate "dark" 14CO2 fixation in addition to photosynthetic 14CO2 fixation. The treatments mentioned above did not abolish this "dark" 14CO2 fixation but rather slightly inhibited photosynthetic 14CO2 fixation so that total 14CO2 fixation was reduced. It would seem that the mechanism by which nitrogen assimilation stimulates 14CO2 incorporation into the basic fraction is still unresolved.
Aerial strands of Phaeococcus exophialae
Authors: Harris James L. , Roth Ivan L.
Published: April 2011

Phaeococcus exophialae, a black yeast, is examined by electron microscopy. In addition to previously reported yeast and hyphal growth forms, the fungus is observed to produce sterile aerial strands. Presence of a dialysis membrane barrier on the culture medium surface appears to be conducive to the development of the strands. Other factors controlling the production of the erect structures are not known. The strands are compared and contrasted with synnemata.
Dormancy studies in seed of Avena fatua. 12. Influence of temperature on germination behavior of nondormant families
Authors: Sawhney Ramma , Naylor J. M.
Published: April 2011

Experiments are reported which clarify the influence of temperature on dormancy of seed of Avena fatua. Temperature treatments administered at two stages of the life cycle, during seed development (stage 1) and during the period immediately following seed maturation (stage 2), influence the duration of dormancy in all families (pure lines) so far investigated. There is evidence for induction of thermodormancy by relatively high incubation temperatures. This effect is most evident in seed which experienced relatively low temperatures during maturation. The significance of dormancy in the adaptation of "nondormant" (ND) families is discussed.
The ontogeny of the sclerotia of Colletotrichum coccodes
Authors: Tu J. C.
Published: April 2011

The ontogeny of the sclerotia of Colletotrichum coccodes was investigated by scanning electron microscopy. The sclerotium originated as an acervulus differentiated from a stroma, a mass of tightly interwoven thick-walled hyphal cells. Initially, hyphae at the surface of the stroma differentiated into conidiophores and conidia which resulted in a typical acervulus. Following sporulation, the stroma beneath the acervulus assumed the form of a sclerotium. This sclerotium expanded laterally by repeating the processes of acervulus development. As a result, a large aggregate composed of several small sclerotia was formed.Structurally, a mature sclerotium, regardless of its size and shape, consisted of three zones: the outermost, sclerotized, brown spongy layer; the middle, plectenchymatous layer; and the innermost, prosenchymatous core (medulla). The majority of cells in the spongy layer were empty. The plectenchyma consisted of living, tightly packed, thick-walled cells with little or no intercellular spaces. The prosenchyma consisted of loosely packed, living hyphal cells.
The relationships of hop cultivars and wild variants of Humulus lupulus
Authors: Small Ernest
Published: April 2011

European, Japanese, and North American hop cultivars were compared with each other and with wild plants by means of numerical taxonomic analyses of vegetative morphological characters. The cultivars originating from the three geographical areas tended to be distinguishable. European cultivars proved to be very similar to indigenous wild European Humulus lupulus and almost certainly are derived from the wild plants. Japanese cultivars seem to be imported European stocks which have been introgressed by indigenous wild Japanese H. lupulus. Similarly American cultivars appear to be of hybrid origin, apparently between European cultivars and one of the three major indigenous varieties of wild North American plants. All domesticates examined were notably dissimilar to the midwestern United States H. lupulus var. pubescens, suggesting that this taxon is a potential source of new breeding germ plasm.
Cytoplasmic streaming in characean cells: role of subcortical fibrils
Authors: Kamitsubo Eiji
Published: April 2011

Three or four parallel fibrils of ca. 0.1 μm in width attached to each file of chloroplasts in intact internodal cells generate the motive force for cytoplasmic streaming. Experimental evidence for this conclusion is drawn from experiments in which fibrillar motion and streaming are interrupted by centrifugation, microbeam irradiation, and electrical stimulation. The role of Pb2+ in preventing cessation of cytoplasmic streaming after electrical stimulation is interpreted in terms of localized changes in viscosity of the cytoplasm.
Leptostroma on pine needles
Authors: Minter D. W.
Published: April 2011

The eight species and one variety of Leptostroma Fr. ex Fr. hitherto described on needles of Pinus L. are examined and where possible related to anamorphs of species of Lophodermium Chev. and Meloderma Darker. Three groups of these conidiomata can be distinguished based on the depth to which they are embedded in the needles and how they open. Within each group conidiomata of individual species are often hard to identify. Each group is keyed out and illustrated. Lophodermium molitoris sp. nov. and Lophodermium baculiferum Mayr with their respective Leptostroma stages are described and illustrated and L. baculiferum and Leptostroma strobicola Hilitz. are neotypified. Three species of Leptostroma which cannot be related to anamorphs of Lophodermium and Meloderma are excluded from Leptostroma.
Host–parasite relationships and development of the ergot sclerotium in Claviceps purpurea
Authors: Luttrell E. S.
Published: April 2011

Conidia of Claviceps purpurea germinate on the stigmas of Secale cereale, and intercellular hyphae grow downward through the style and inner wall of the ovary to the tip of the rachilla. Across the tip of the rachilla, hyphae surrounding living host cells form a narrow interface that plunges downward into the central vascular bundle approximately to the level of origin of the lodicules. This biotrophic relationship is well established 5–6 days after infection at anthesis and persists unaltered through maturation of the ergot sclerotium at approximately the 28th day. Tissues in the base of the ovary above this interface are destroyed and replaced by fungus stroma. Xylem vessels in the tip of the rachilla are destroyed and replaced by a hyphal core extending downward from the stromatic foot of the fungus. Hyphae emerging between the epidermal cells of the ovary form an external matrix that contributes to further expansion of the stroma. A palisade of phialidic conidiophores develops over the surface of the stroma, which is involuted into labyrinthine chambers. Conidia ooze from the florets in drops of honeydew by the 6th or 7th day. The ovarian cap and the upper part of the ovule are pushed upward on the apex of the conidial stroma, and some of these isolated host cells remain alive until the 11th day. A layer of vertically arranged parallel hyphae across the base of the conidial stroma forms a generative zone that sharply delimits the basal stromatic foot seated in the floret and by apically directed intercalary growth produces the compact tissues of the ergot sclerotium. The sclerotium begins to protrude from the floret by the 11th day. The withered remnants of the conidial stroma and the ovarian cap are carried upward on the tip of the massive sclerotium. Beneath the dark rind the hyaline tissue of the sclerotium consists primarily of compacted, isodiametric storage cells. A loose hyphal conducting tissue forms a central strand from which narrow vanes radiate irregularly toward the periphery. Ergot of rye is a replacement disease in which the parasite disintegrates host tissues in areas required for development of its own structures while maintaining a compatible relationship with adjacent host cells as a source of water and nutrients.
Development of Rozella in Allomyces: a single zoospore produces numerous zoosporangia and resistant sporangia
Authors: Held Abraham A.
Published: April 2011

Single thalli of Allomyces arbuscula were inoculated with single zoospores of an intracellular parasite, Rozella allomycis. Infection caused segmentation of numerous host hyphae which usually comprised a sector emerging from one limb of the arbusculate thallus. Most segments contained Rozella zoosporangia (ZS), but some basal segments contained resistant sporangia (RS). The spread of Rozella appeared to be centrifugal–acropetal and to follow the host's branching. Ultrastructural observations indicated that Rozella grew inside its host as a mycelium which lacked cell walls and became segmented by host septa. In broth-grown hosts, secondary infection of previously uninfected hyphae by zoospores released from ZS produced mostly RS.Thus the "polysporangiate" growth of some Rozella species, in which numerous ZS occur in linearly conjoined series and which has been juxtaposed to "monosporangiate" growth of others, can arise from single zoospores. The discussion considers taxonomic changes in Rozella and emphasizes developmental similarities between R. allomycis and Allomyces, as well as environmental effects on formation of ZS versus RS. A report that R. allomycis is heterothallic and produces RS only through appropriate pairing of mating types has not been confirmed.
Endogenous hormones in afterripening wild oat (Avena fatua) seed
Authors: Taylor J. S. , Simpson G. M.
Published: April 2011

Levels of gibberellins and cytokinins in dormant Avena fatua L. seeds were measured by bioassay during the afterripening process. Little change in the level of either hormone was detected in the dry seed. Following imbibition of fully afterripened seed, however, gibberellin levels increased while cytokinin levels declined. Seed strains varying in their degree of dormancy were also analysed for hormone levels; a significantly higher level of cytokinin activity was found in the most dormant strain compared with the least dormant strain. Low levels of bound hormones, including cytokinin ribotides and gibberellin glucose conjugates, were detected following enzyme hydrolysis but neither class of compounds varied greatly in level during afterripening.The major cytokinins detected in Avena fatua seeds cochromatographed with zeatin-9-glucoside, zeatin riboside, and zeatin on both HPLC columns and chromatography paper. The major gibberellin activity cochromatographed with GA4/GA7 on silica gel partition columns and thin-layer plates.Germination studies demonstrated that GA4/7 is significantly more active than GA3 in promoting the germination of dormant Avena fatua seeds. External applications of cytokinins were not found to affect the germination of dormant seed, but did promote germination in partially afterripened material.