bluuebunny/crossref_metadata_2025 huggingface dataset:
Actinomycetes in discolored wood of living silver maple
Authors: Blanchette Robert A. , Sutherland John B. , Crawford Don L.
Published: October 2008

The greenish-brown margin of discolored wood in three living silver maple trees, Acer saccharinum L., was examined by scanning electron microscopy and microbiological culture techniques. Micrographs of xylem vessels revealed filamentous structures; some of them appeared to be actinomycetous hyphae. Actinomycetes identified as Streptomyces parvullus Waksman & Gregory, S. sparsogenes Owen, Dietz & Camiener, and a third Streptomyces strain were isolated repeatedly from discolored wood of each tree. These isolates grew in liquid media in the presence of 0.1% (w/v) concentrations of several phenols. Although other phenols included in the test were not substantially degraded, p-hydroxybenzoic acid was utilized as a carbon source by S. parvullus. All three actinomycetes inhibited growth of selected wood-inhabiting fungi when paired on malt agar. When inoculated on sterilized sapwood and discolored wood from silver maple, the actinomycetes colonized vessel walls and occlusions, but were not observed to decay cell walls.
Effects of position and age on leaf photosynthesis in corn (Zea mays)
Authors: Thiagarajah M. R. , Hunt L. A. , Mahon J. D.
Published: October 2008

The effects of position and age of leaves on CO2 exchange rate (CER) are described for a single-cross corn (Zea mays L.) hybrid ('Harrow 691') grown at 10-h and 20-h photoperiods. The effect of leaf age is also described for barren plants grown at a 10-h photoperiod.CER of newly matured leaves increased from leaf 3 to leaf 6 (10 h) or 8 (20 h). The rates were not significantly different for leaves 6 to 13, but were lower for leaf 14, at 10 h; while the rate for leaf 10 was lower than for leaf 8 but not different from that for leaves 11–15, at 20 h.CER declined with leaf age, but the rate of decline was reduced after pollination at both 10 h and 20 h. The stomatal resistance changed little for a period of 4 to 5 weeks following silking. The decline in CER of all leaves studied for barren plants was smooth, with the rate being unaffected in the postsilking period; in these plants changes in stomatal resistance closely reflected the decrease in photosynthetic rates.The results emphasize that the CER of newly matured leaves was lower for leaves produced in the early stages of ontogeny than for those maturing later, and that the pattern of decline with age in photosynthetic activity varied considerably amongst those leaves that would have been contributing assimilates to the developing ear.
Tripartite associations in snowbrush (Ceanothus velutinus): effect of vesicular–arbuscular mycorrhizae on growth, nodulation, and nitrogen fixation
Authors: Rose S. L. , Youngberg C. T.
Published: October 2008

Symbiotic associations were established between nitrogen-fixing nonleguminous (actinorrhizal) snowbrush (Ceanothus velutinus Dougl.) seedlings and two categories of microorganisms: vesicular–arbuscular (VA) mycorrhizal fungi and a filamentous actinomycete capable of inducing nodule formation. The actinomycete is housed in nodules where fixation of atmospheric dinitrogen occurs and is made available to the host plant; the mycorrhizal fungus is both inter- and intra-cellular within the root tissue and may be found within the nodules. The two major nutrients, N and P, are made available and can be supplied to the host plant by these two symbiotic microorganisms. The root system of snowbrush seedlings was dually colonized by VA mycorrhizal fungi and a nitrogen-fixing actinomycete and the possibility of a direct interaction between the endophytes in the symbioses was investigated. Dually infected plants showed increases in total dry weight of shoots and roots, number of nodules, weight of nodular tissue, as well as higher levels of N, Ca2+, and P, and an increase in nitrogenase activity as measured by acetylene reduction.
In vitro initiation of adventitious buds and its modification by high concentration of benzyladenine in leaf tissues of mulberry (Morus alba)
Authors: Oka S. , Ohyama K.
Published: October 2008

Leaf explants of mulberry (Mortis alba L.) derived from aseptically grown shoots and seedlings were cultured on Murashige and Skoog's medium. Normal and abnormal leaves were grown by varying the concentration of benzyladenine. They differed in the way of forming adventitious buds. In normal leaves bud initiation occurred exclusively at the cut ends of midribs after removing petioles, while in abnormal ones buds formed at any region on midribs and petioles. Histological observations were made to study different patterns of bud initiation.
Gigaspora margarita inoculation of Nicotiana tabacum: responses to fertilization
Authors: Csinos Alexanders
Published: October 2008

Gigaspora margarita was increased in pot culture using Sorghum vulgare ('Shallu'). Soil was treated with methyl bromide (102 mg/L) for 24 h or heat treated at 82 °C for 6 h and mixed with vermiculite. Tobacco (Nicotiana tabacum) NC 2326 was inoculated at transplating with 500 (in 1978) or 4050 (in 1979) azygospores per plant and fertilized at three levels. Positive responses in growth to inoculation and significantly greater numbers of spores were observed both years at only the lowest fertilization levels. In the 1978 test, frenching of tobacco occurred in only the low fertilization level. Significantly less frenching occurred in the mycorrhizal inoculated treatment than in the control.
The effect of drying on Spirodela polyrhiza turion germination
Authors: Malek Lada
Published: October 2008

Mild drying in air or exposure to the osmoticum polyethylene glycol 6000 at 5, 10, or 20% (w/w) concentration stimulated germination rate of Spirodela polyrhiza (duckweed) turions. Treatment of the turions for several days in polyethylene glycol 6000 induced rapid germination of the turions. This germination response provides a model system for the study of metabolic changes prior to and during turion germination.
Pollen morphology of the Rosaceae of western Canada. II. Dryas, Fragaria, Holodiscus
Authors: Hebda R. J. , Chinnappa C. C. , Smith B. M.
Published: October 2008

Morphology and geographic variation of pollen grains of three genera of the Rosaceae (Dryas, Fragaria, Holodiscus) of western Canada were studied using the light microscope and scanning electron microscope. Dryas spp. pollen is tricolporate with a weakly developed fusiform aperture in the colpus, which upon expansion of the grain becomes a large rectangular opening. Sculpturing consists of ridges and valleys (striate or rugulate), the latter containing perforations, which grades to a network of ridges and perforations (reticulate) at colpus margins. Ridges are parallel to the colpus or form looping patterns. Dryas integrifolia and Dryas octopetala pollen in silicone oil usually are larger than those of Dryas drummondii. Fragaria spp. pollen is tricolporate with a well-developed complex equatorial aperture. Fragaria chiloensis and F. vesca exhibit a lobed and equatorially extended endoaperture, which is overarched by sexine. Fragaria virginiana usually has a less distinct endoaperture. Fragaria species have a fusiform colpus operculum. Sculpturing consists of nonasastomosing ridges parallel to the colpus and valleys containing obscure microperforations. Holodiscus discolor pollen is tricolporate. Sculpturing is striate to reticulostriate, consisting of ridges and valleys with perforations. A distinct zone, either lacking ridges or of densely packed ridges, borders the colpus.
A comparison of the death induced by fungal invasion or toxic chemicals in cowpea epidermal cells. I. Cell death induced by heavy metal salts
Authors: Meyer Susan L. F. , Heath Michèle C.
Published: October 2008

Death was induced in cowpea leaf epidermal cells by the application of the metal salts CuCl2, CuSO4, and HgCl2. When unfixed, salt-treated cells were observed by light microscopy, their degeneration and death were seen to follow a series of stages: (1) cessation of cytoplasmic streaming, (2) morphological changes in the cytoplasm such as the formation of large vesicles and the appearance of particles in the vacuole, and (3) protoplast collapse. The relative timing of these stages after salt application was affected by the nature and concentration of the chemical used. The application of fluorescein diacetate and plasmolysing sucrose solutions before or after the addition of the copper salts suggested that the semipermeability of the tonoplast was lost during stage 2 and that of the protoplast boundary at stage 3. Following the cessation of cytoplasmic streaming, the changes observed in unfixed cells occurred rapidly and correlated well with the ultrastructural changes observed in the same cells after fixation. First, microtubules appeared to decrease in abundance. Then coiled polyribosomes, endoplasmic reticulum, and Golgi bodies rapidly became undetectable, mitochondrial cristae became dilated, and the cytoplasm consisted of aggregates of ribosome-containing material interspersed with vesicles. However, the study also showed that the first observable sign of degeneration seen in unfixed cells (i.e., the cessation of cytoplasmic streaming) appears to have no clearly diagnostic feature detectable by electron microscopy.
Factors influencing root formation in dicots by Agrobacterium rhizogenes
Authors: Him Karen Whiteman Runs , Scheffer Rudy J. , Strobel Gary A.
Published: October 2008

Agrobacterium rhizogenes (Riker et al.) Conn genetically transforms the roots of many dicotyledonous plants, causing them to produce numerous functional secondary roots. The intentional inoculation of forest, nursery, or vegetable transplants with A. rhizogenes may have some value in promoting rapid establishment after transplanting. We examined some factors that may influence the development of roots in plants inoculated with A. rhizogenes (by the carrot disc assay). A pH near neutrality, a temperature of ca. 25 °C, and a freshly cut root surface serving as the inoculation site favoured root development. Roots that were inoculated and then stored at 10 °C did not produce secondary roots at that temperature. However, upon placement at 23 °C for 2 days new roots began to form. Octopine at 10 mM stimulated root production. Carrot roots stored for 9 months produced few if any roots upon inoculation with A. rhizogenes, suggesting the importance of tissue age in genetic transformation.
Role of chromosome 5A in wheat in control of some traits associated with cold hardiness of winter wheat
Authors: Roberts D. W. A. , MacDonald M. D.
Published: October 2008

Chromosome 5A in the hardy winter wheats 'Winalta' and 'Kharkov 22 MC (Triticum aestivum L.) carries at least one of the several loci controlling the expression of cold hardiness, low temperature induced reduction in leaf length, percent dry matter in leaves, prostrate growth habit, and proportion of peak I to peak II invertase in leaves.
Curled root hairs are a site of entry for Bradyrhizobium infecting hydroponically grown soybean plants with mature root systems
Authors: Selker Jeanne M. L. , Imsande John , Newcomb Eldon H.
Published: October 2008

Early emergent nodules on roots of hydroponically grown soybean plants (Glycine max (L.) Merr.) were sectioned serially to locate the site of infection by Bradyrhizobium japonicum. The plants had been inoculated only after their root systems had produced numerous higher order branches. The hydroponic solutions contained all required nutrients, including either a suboptimal concentration of nitrate (0.5 mM) or an excess of nitrate (4.0 mM). In all six nodules examined, three with suboptimal nitrate and three with excess nitrate, we found a centrally located root hair containing an infection thread. We conclude that mature root systems of soybean grown in aqueous culture can undergo infection through root hairs in the way that is typical of young seedlings grown either in pots of vermiculite or pouches.
Mechanisms of aluminum tolerance in Triticum aestivum (wheat). V. Nitrogen nutrition, plant-induced pH, and tolerance to aluminum; correlation without causality?
Authors: Taylor Gregory J.
Published: October 2008

An aluminum-tolerant cultivar ('Atlas-66') and an aluminum-sensitive cultivar ('Scout-66') of Triticum aestivum L. were grown in solution culture under conditions of varying [Formula: see text] and [Formula: see text] supply with or without 75 μM aluminum. Plants grown with a low [Formula: see text] ratio in solution maintained a higher solution pH than plants grown with a high [Formula: see text] ratio. Although root growth of 'Scout-66' was greater under high [Formula: see text], high solution pH conditions, the relative tolerance of the cultivars to Al was unaffected by the [Formula: see text] ratio and by solution pH. The superior Al tolerance of 'Atlas-66' could not be explained solely by its ability to maintain a high solution pH in mixed nitrogen solutions.
The effect of ethylene on root growth of Zea mays seedlings
Authors: Whalen Maureen C. , Feldman Lewis J.
Published: October 2008

The control of primary root growth in Zea mays cv. Merit by ethylene was examined. At applied concentrations of ethylene equal to or greater than 0.1 μL L−1, root elongation during 24 h was inhibited. The half-maximal response occurred at 0.6 μL L−1 and the response saturated at 6 μL L−1. Inhibition of elongation took place within 20 min. However, after ethylene was removed, elongation recovered to control values within 15 min. Root elongation was also inhibited by green light. The inhibition caused by a 24-h exposure to ethylene was restricted to the elongating region just behind the apex, with inhibition of cortical cell elongation being the primary contributor to the effect. Based on use of 2,5-norbornadiene, a gaseous competitive inhibitor of ethylene, it was concluded that endogenous ethylene normally inhibits root elongation.
Haustorial mother cell development by Uromyces vignae on collodion membranes
Authors: Heath Michèle C. , Perumalla C. J.
Published: October 2008

The development of infection structures by the rust fungus Uromyces vignae was observed on oil-containing collodion membranes. About 40% of infection hyphae formed a haustorial mother cell, but this structure commonly senesced and died more rapidly than the infection hypha to which it was attached. These data suggest that the continued development of the haustorial mother cell requires some component normally provided by the host plant. Before they died, many haustorial mother cells apparently formed the thickened region of the wall which normally is traversed by the penetration peg during haustorium formation. Such a peg was observed in the centre of up to 40% of these thickened regions. However, no pegs protruded beyond the haustorial mother cell far enough to be called a haustorial neck. The thickened region of the haustorial mother cell wall could be differentiated from the rest of the wall by its lack of fluorescence under ultraviolet irradiation when mounted in Calcofluor or SITS (4-acetomido-4′-iso-thiocyanatostilbene-2,2′-disulphonic acid). Treatment with alkali, acid, chloroform–methanol, protease, and laminarinase did not affect this differential fluorescence, and the haustorial mother cell wall stained uniformly for proteins, carbohydrates, and chitin. Since Calcofluor normally binds to chitin, these data suggest that the thickened region of the haustorial mother cell wall may physically exclude the dye or may contain potential binding sites that are masked by other wall components.
The role of photosynthetic activity in the response of isolated Glycine max mesophyll cells to ozone
Authors: Omielan J. A. , Pell E. J.
Published: October 2008

The hypothesis that active photosynthesis results in a more severe cellular response to ozone (O3) was tested. Using suspensions of isolated soybean (Glycine max (L.) Merr. cv. Chippewa 64) mesophyll cells, we measured photosynthetic carbon fixation rates and cell viability, as determined by fluorescein diacetate staining, before and after treatment with O3 in the light and dark in the presence or absence of NaHCO3. Ozone reduced the photosynthesis rates of isolated mesophyll cells to a greater degree than cell viability, suggesting greater sensitivity of photosynthesis. Posttreatment photosynthesis rates were higher in cells that were fumigated in media containing NaHCO3 than in cells fumigated in its absence. The only interaction detected was between the gaseous treatments and light, in which relative cell viability was reduced more by O3 in the light than in the dark, in the second experiment. The interaction was, at least in part, a reflection of experimental error. Of greater significance was the observation that the photosynthetic function could be affected equally by O3 in the dark and in the light.
Effects of soil moisture and soil sterilization on vesicular–arbuscular mycorrhizal colonization and growth of little bluestem (Schizachyrium scoparium)
Authors: Cerligione Lisa J. , Liberta Anthony E. , Anderson Roger C.
Published: October 2008

Nonmycorrhizal little-bluestem plants grown in sterile soil and mycorrhizal plants grown in unsterilized soil were experimentally subjected to varied soil moisture conditions that ranged from saturation for 12 h followed by drainage for 48 h to allowing soil to dry to permanent wilting point and returning it to field capacity 72 h later. Nonmycorrhizal plants produced significantly (p < 0.05) greater root and shoot biomass, had lower root/shoot ratios, and produced more flowering culms than mycorrhizal plants. However, mycorrhizal plants had significantly higher tissue concentrations of phosphorus, calcium, zinc, iron, copper, aluminum, and sodium and lower concentrations of potassium amd manganese. There was a decrease in percent colonization as soil water availability decreased.
Ultrastructural observations on Helvellaceae (Pezizales). Ascosporogenesis of selected species of Helvetia
Authors: Gibson Jack L. , Kimbrough James W.
Published: October 2008

The ultrastructure of ascosporogenesis including observations on spore delimitation, primary wall deposition, and formation of the secondary wall is examined in three species of the genus Helvella. The double membranes delimiting the spores and the ascus plasmalemma stain identically with silver proteinate poststain. Primary wall formation is similar in all species examined, although very early development was observed only for H. macropus. Secondary wall formation, which results in the characteristic spore ornamentation, appears to be quite similar for the three species. In addition, observations are made on the structure and origin of the epispore and on cytological details of the epiplasm and sporoplasm relating to spore ontogeny.
Responses related to lignification and intravascular periderm formation in carnations resistant to Fusarium wilt
Authors: Baayen R. P.
Published: October 2008

Stem inoculation of resistant 'Novada' carnations with Fusarium oxysporum Schlecht. f.sp. dianthi (Prill. & Del.) Snyder & Hansen, races 1, 2, and 4 or F. oxysporum Schlecht. f.sp. lycopersici (Sacc.) Snyder & Hansen did not induce visible disease symptoms. The plants showed a similar localization response to all fungal isolates. The response consisted of the occlusion of xylem vessels with brown gums, and browning and death of some xylem parenchyma cells, as well as the occurrence of various wall modifications in other xylem parenchyma cells. The wall modifications comprised the deposition of additional wall layers, formation of various appositions, and infusion with phenolic-containing material. The brown gums and infused walls eventually contained phenolic polymers related to lignin. The occluded zone was surrounded by hyperplastic xylem parenchyma tissue, of which the inner cell layers differentiated into suberized phellem tissue, whereas vascular regeneration occurred in the outer layers. The significance of the various wall modifications and of the formation of intravascular wound periderm for resistance of carnations to Fusarium wilt is discussed.
La végétation forestière du secteur nord-ouest de la vallée du Saint-Laurent, Québec
Authors: St-Jacques Claude , Gagnon Daniel
Published: October 2008

The forest vegetation of the north-west section of the St. Lawrence Valley in Quebec was sampled within 68 quadrats. The location of the quadrats was selected by means of a stratified random sampling plan. Ordination (detrended correspondence analysis) and cluster analysis (TWINSPAN) allowed the identification of 11 forest community types. The ecological factors most closely associated with the distribution of these communities are soil drainage and richness. These two factors are strongly related to the types of surface deposits. Communities dominated by Acer saccharum are found on well drained and nutrient-rich moraines. On the contrary, communities dominated by Acer rubrum and the majority of coniferous forests are found on poorly drained and nutrient-poor soils. Two floristically distinct community types, the Fraxinus – Tilia americana forests and the Tsuga canadensis – Acer saccharum forests, are found on poorly drained marine deposits with edaphically identical lower horizons. However, the pH and major cation concentrations of the upper soil horizons are much lower under the cover of the hemlock forests than under the cover of the ash – basswood forests.
The assessment of net dry matter partitioning by stepwise multivariate analysis of variance
Authors: Jolliffe Peter A. , Hoddinott John
Published: October 2008

A serial procedure is described involving the analysis of variance, multivariate analysis of variance, and stepwise multivariate analysis of variance. The procedure identifies significant contributions by different plant components to changes in net dry matter partitioning induced by experimental treatments. The procedure was applied to results from a study of plants grown at different atmospheric CO2 concentrations. It confirmed that CO2 treatments caused significant changes in dry matter partitioning and that the set of plant components that best expressed the effects of CO2 treatments changed during plant growth.
Regulation of mRNA formation in plants: lessons from the cauliflower mosaic virus transcription signals
Authors: Sanfaçon Hélène
Published: October 2008

The cauliflower mosaic virus (CaMV) transcription signals are common tools of plant molecular biologists. In this article, the transcription signals are discussed in light of the life cycle of CaMV, a plant pararetrovirus. Production of mature 35S RNA, the terminally redundant genomic RNA, is regulated by the 35S promoter, a very strong promoter, and by the polyadenylation signal that is present twice on the RNA but recognized only at its 3′ end. Dissection of the promoter has identified several organ-specific elements acting in concert to express the 35S RNA in most plant cells. Studies on the polyadenylation signal have revealed upstream elements inducing recognition of the AATAAA sequence and have led to the proposal that the conditional recognition of this signal is dependent on its distance from the promoter. Comparison of the CaMV signals with other plant signals allows speculation on the plant transcriptional machinery and on some striking resemblances and differences to the animal and yeast systems. Finally, potential applications of this knowledge will be described such as the construction of hybrid plant promoters or polyadenylation signals using the 35S minimal elements. Key words: cauliflower mosaic virus, 35S promoter, polyadenylation signal, 35S RNA, transcription, retroviruses.
Cytology and morphology of Pseudoroegneria deweyi (Poaceae: Triticeae): a new species from the foot hills of the Caucasus Mountains (Russia)
Authors: Jensen Kevin B. , Hatch S. L. , Wipff J. K.
Published: October 2008

Cytological and morphological characteristics of a new species, Pseudoroegneria deweyi K. B. Jensen, from the Karachayevo-Cherkesskaya Avtonomnaya Oblast' Region of Russia are described. This species is cytologically stable, genomically similar to Pseudoroegneria tauri, highly fertile (cross-pollinating), and morphologically unique compared with most other species in the genus. Pseudoroegneria deweyi differs from other closely related species in the number of rachis nodes in the inflorescence. Pseudoroegneria stipifolia (2n = 2x = 14, SS) and Agropyron cristatum (2n = 2x = 14, PP) were used as male parents in crosses with P. deweyi. All three P. deweyi accessions studied were tetraploids (2n = 28) and behaved meiotically as allotetraploids with a mean chromosome association of 0.03 I + 13.30 II + 0.03 III + 0.26 IV per cell. In the hybrid P. deweyi × A. cristatum, average chromosome association was 5.92 I + 4.55 II + 1.83 III + 0.09 IV per cell, while the average chromosome association in P. deweyi × P. stipifolia was 4.98 I + 5.23 II + 1.73 III 0.04 IV per cell. Pseudoroegneria deweyi joins P. tauri as the only other known naturally occurring species with the genomic formula of SSPP. Cluster analysis of 21 morphological characters supports the inclusion of P. deweyi as part of the genus Pseudoroegneria rather than Agropyron. Key words: Agropyron, Pseudoroegneria, chromosome pairing, meiosis, Triticeae, new species.
Les cystides à cristaux des Inocybes (Agaricales): étude histochimique et cristallographique
Authors: Waterkeyn L. , Bienfait A. , Monniez T.
Published: October 2008

Histochemical and cristallographic studies were performed in light microscopy and scanning electron microscopy on crystal-bearing cystidia of several Inocybe spp. (Agaricales) and confirmed the excretory function of these sterile cells of the hymenium. At the apex of these bottle-like cells, the wall had an axial polysaccharidic matrix rich in carboxyl groups. It also presented an enhanced permeability and a local concentration of Ca2+. Functioning as an hydathode, the cystidium secreted, at its apex, an aqueous droplet into which twin crystals developed. In addition, crystal sand were found in the cystidium wall. These two crystalline products were calcium oxalate as confirmed with anthracene green and the Pizzolato test. A detailed crystallographic study showed that these twin crystals undoubtedly belong to the monoclinic system, i.e., the monohydrated form of the calcium oxalate or whewellite. In the case of Inocybe asterospora Quél., these grouped crystals were formed regularly by two pairs of twin crystals. The identification and localization of the Ca2+ ions have been determined with the scanning electron microscope by means of the X-emission pictures and the resulting energy dispersive X-spectrum for the latter element. Key words: Inocybe, cystidium, hydathode, calcium oxalate, whewellite.
Leaf structure of Besseya and Synthyris (Scrophulariaceae)
Authors: Hufford Larry
Published: October 2008

The leaf structure of Besseya and Synthyris was analyzed to provide characters for phylogenetic studies. Laminas of Synthyris have compound teeth whereas those of Besseya are simple. Compound teeth are aggregated in lobes in S. canbyi, S. dissecta, S. laciniata, and S. pinnatifida. Prior circumscriptions of S. canbyi, S. dissecta, and S. pinnatifida, which have deeply incised margins, are questioned, and realignments are suggested. Lamina form is generally ovate in Besseya and Synthyris (although some leaves of B. ritteriana are elliptic to oblanceolate). A reniform lamina (rounded apex, auriculately lobate base, and greater lamina width than length) characterizes S. laciniata, S. missurica, S. platycarpa, S. ranunculina, S. stellata, and some S. reniformis and S. schizantha. This leaf form is associated with small-diameter midribs (relative to lamina width) and large-diameter basal secondary veins (relative to the mid vein). Besseya tend to have relatively larger diameter primary veins than Synthris. The largest primary veins and smallest diameter secondary veins are found in B. oblongifolia, B. plantaginea, and B. ritteriana, which also have the greatest lamina length to width ratios. An endodermis with a Casparian strip surrounds petiole and lamina vasculature of most Besseya and Synthyris, although it is most extensive in S. cordata, S. reniformis, and S. schizantha. Key words: Besseya, Synthyris, lamina, leaf, petiole, systematics.
Population dynamics of the plant pathogenic fungus Uncinula necator
Authors: Chellemi Dan O. , Marois James J.
Published: October 2008

Cohort life tables were constructed and population parameters determined for Uncinula necator (Schw.) Burr. parasitizing the foliage of Vitis vinifera L. cv. Carignane at various temperatures. The net reproductive rate per individual conidium at 19, 22, 26, and 30 °C was 577, 2272, 1300, and 157 conidia per generation, respectively. Mean generation times ranged from 22.84 days at 19 °C to 13.60 days at 30 °C. Intrinsic growth rates (r) varied from 0.43 per day at 19 °C to 1.24 per day at 26 °C. Doubling times ranged from 0.56 days at 26 °C to 1.63 days at 19 °C. Matrix population models were used to project population growth. Stable age distributions at 19, 22, 26, and 30 °C were reached after 70, 50, 45, and 45 days, respectively. At a stable age distribution, greater than 96% of the population was contained in the first age-class (days 1 – 5). Key words: demography, cohort life table, grape powdery mildew, net reproductive rate, population growth rate.
Ecophysical and ultrastructural effects of copper in Thlaspi ochroleucum (Cruciferae)
Authors: Ouzounidou G. , Eleftheriou E. P. , Karataglis S.
Published: October 2008

The toxic effects of Cu on growth, element uptake, chlorophyll content, cellular ultrastructure, and morphometry of a Zn-and Pb-tolerant ecotype of Thlaspi ochroleucum have been investigated in hydroponic cultures. Increasing Cu concentrations in nutrient solutions caused a reduction of root growth, a decrease in total chlorophyll content in the leaves, an increased uptake of Cu, and a decreased uptake of nutrient elements such as Ca, Mg, K, and Fe. Gross anatomy and intercellular spaces of leaves of plants treated with Cu did not differ significantly from the controls. However, cells contained fewer and smaller chloroplasts that lacked starch grains and contained a number of large plastoglobuli. The volume fraction of the internal membrane system was reduced, but ultrastructurally it was similar to the control. These findings, in combination with the reduced quantity of chlorophyll, indicate that the existence of a well-organized internal membrane system does not necessarily imply the presence of high amounts of chlorophyll. Other leaf cell components, such as mitochondria, microbodies, and nuclei, displayed little ultrastructural malformation. In roots, however, all cell types were so disorganized by treatment with Cu that cell organelles could hardly be identified. Our results indicate that toxic effects of Cu appear to be manifested primarily in roots and secondarily on aerial plant parts. Key words: chlorophyll content, copper, element uptake, morphometric cytology, ultrastructure, Thlaspi ochroleucum.
In vitro and transplantation experiments with germination of date embryos
Authors: DeMason Darleen A. , Widney Daniel , Stillman James I.
Published: October 2008

In vitro experiments with date palm embryos were designed to determine (i) which carbon sources support growth and (ii) what culture conditions promote haustorial growth and development. Date palm embryos were also transplanted into Washington filifera seeds to deterine whether any developmental characteristics were determined by the seed or endosperm. Date embryos did not grow on media containing starch or galactomannan any better than they do on medium lacking a carbon source. Good growth occurred on medium containing mannose, glucose, or sucrose as the carbon source. Embryos imbibed in the seed for 6 days grew better and produced larger haustoria than those imbibed 2 days, imbibed in water, imbibed in 3% mannose, or unimbibed. Date embryos imbibed in Washington seeds grew as well as those imbibed in date seeds. Optimum seedling and haustorium weights occurred at pH 7. The transembryonic seedlings germinated and grew normally but the shape of the haustorium was altered. Haustoria produced by in vitro grown seedlings exhibited many normal anatomical features, but haustoria from transembryonic seedlings exhibited more normal histological features. Results support the hypotheses that (i) date embryos do not possess the enzymes necessary to digest mannans and (ii) haustorium development is controlled by at least two steps, an initial inductive step that occurs by 6 days of imbibition and a further step that occurs later. We hypothesize that diffusable substances from the endosperm are responsible for controlling haustorium initiation and development. Key words: germination, embryo culture, palms, palm tissue culture, Arecaceae, haustorium.
Étude des index d'ADN de huit espèces d'ignames (Dioscorea sp.) par cytométrie en flux
Authors: Hamon Perla , Brizard Jean-Paul , Zoundjihékpon Jeanne , Duperray Christophe , Borgel Alain
Published: October 2008

Nine species (wild and cultivated) and some interspecific (wild × cultivated) hybrids were analysed by flow cytometry. This study confirms various polyploidy levels within cultivated species. DNA index varied by a factor of 1 to 3 for Dioscorea alata, 1 to 2.25 for Dioscorea bulbifera, and 1 to 2 for Dioscorea cayenensis-rotundata, depending on the clone or cultivar considered. In wild species, only one DNA index per species was obtained. Whenever a relationship between DNA index and chromosome number could be established, the size of genome 1C was evaluated in picograms and base pairs. Two genome sizes were observed: genome A in D. cayenensis-rotundata, Dioscorea abyssinica, Dioscorea mangenotiana, and Dioscorea praehensilis and genome B in Dioscorea togoensis. These genomes were small sizes, only 1.5 to 2.1 times larger than that of Arabidopsis. Key words: yams, Dioscorea, flow cytometry, DNA index, genome size.
Immunogold localization of free abscisic acid in tomato root cells
Authors: Bertrand Suzanne , Benhamou Nicole , Nadeau Paul , Dostaler Daniel , Gosselin André
Published: October 2008

Ultrastructural localization of abscisic acid in tomato (Lycopersicon esculentum Mill. cv. Vedettos) seedling roots is determined with the indirect protein A–gold approach. Polyclonal antibodies recognizing specifically the free (+)cis, trans form of abscisic acid are used as the first step in the immunolocalization procedure. Evidence is presented that its distribution varies within the different tissues of the tomato root. In the root cap cells, free abscisic acid accumulates mainly in the apoplast, in the cytoplasmic vesicles, and in the amyloplasts, around starch grains. In columella and meristematic cells, it accumulates mainly at the junction area with root cap cells, in the wall, and in the mucigel layer outside the root. Abscisic acid accumulation in the wall, the middle lamella, and the mucigel layer of the root cap cells may play a role in the root response to environmental stimuli. The cytochemical labeling of polygalacturonic acids, as recognized by the Aplysia depilans gonad lectin complexed to colloidal gold, follows closely the immunolocalization of abscisic acid. The secretory process of the root mucilage and the translocation of abscisic acid may be related. The significance of the apparent relationship between abscisic acid accumulation and the secretion of polygalacturonic acids is not yet understood. A role for apoplastic abscisic acid in a root-to-shoot communication system is discussed. Key words: abscisic acid, root physiology, immunolocalization, tomato.
Infection and morphogenesis of Pythium marinum in species of Porphyra and other red algae
Authors: Kerwin James L. , Johnson Lisa M. , Whisler Howard C. , Tuininga Amy R.
Published: October 2008

A strain of Pythium marinum (Peronosporales: Pythiaceae) from Puget Sound, Washington, was isolated from lesions of Porphyra nereocystis. The fungus grew on a modified Vishniac medium, from temperatures of 4 to 25 °C, although growth was slow at the lowest temperature. Sexual and asexual reproduction also occurred within this temperature range. Mycelium diluted in seawater initiated zoospore release within 16 h and continued to release zoospores for over 200 h at temperatures from 4 to 20 °C. Zoospore encystment on several species of marine red, brown, and green algae was readily monitored following staining with lactophenol – cotton blue. Pythium marinum zoospore encystment occurred on rhodophyceaen species, including Porphyra (gametophytes), Gigartina exasperata (tetrasporophyte), Mastocarpus papillatus (gametophyte), Prionitis lanceolata (nonfertile), and Iridaea heterocarpa (gametophyte and tetrasporophyte), but not on Nereocystis leutkeana or Ulva lactuca. Over 50% of zoospores held in half-strength seawater at 4 and 20 °C encysted within 24 h, whereas those held at 12 °C reached 50% encystment only after 32 h. For 4-mm diameter discs of Porphyra nereocystis and Porphyra perforata (formerly Porphyra sanjuanensis) blades, there was only a transient relationship between cell damage and number of encysted zoospores. Zoospores did not attach to the conchocelis phase of two species of Porphyra. Sequential extraction of carbohydrates from the blades of Porphyra perforata implicated separate chemical signals for zoospore encystment and appressorium formation prior to the initiation of blade invasion. Addition of diverse monosaccharides and polysaccharides to zoospore suspensions suggested that these chemical signals are specific, with the attachment–encystment signal chemically related to polysaccharides consisting of sulfated or nonsulfated galactose and 3,6-anhydrogalactose found in commercial agars and carrageenans. There was no consistent relationship between zoospore encystment and the amount of 3,6-anhydrogalactose present in the blade phase of several species of red algae. Key words: Pythium, Porphyra, zoospore, encystment, sulfated galactans, 3,6-anhydrogalactose.
Influence of soil biota on Douglas-fir (Pseudotsuga menziesii) seedling growth: the role of rhizosphere bacteria
Authors: Chanway C. P. , Holl F. B.
Published: October 2008

The influence of soil biota on Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) seedling growth was investigated by sowing seed collected from two ecologically distinct zones in British Columbia, Chilliwack and Williams Lake, in soil collected from the same two areas. Seedling biomass of both Douglas-fir ecotypes was greatest in unpasteurized soil collected from the same area as was the seed, but pasteurization negated this effect. In addition, Chilliwack seedlings responded specifically to biota present only in Chilliwack soil. To determine if rhizosphere bacteria were involved in these growth responses, bacteria were isolated from the rhizosphere of wild Douglas-fir seedlings collected from both locations, and putative growth promoting bacteria were selected in a screening experiment. Selected bacteria were then tested for seedling growth response specificity using a factorial design in which seed, soil, and bacteria from both locations were evaluated in all combinations. Inoculation of Douglas-fir seed with some of the selected bacterial isolates increased seedling biomass in pasteurized soil to a level similar to that of seedlings grown in unpasteurized soil, but there was no evidence that adaptive relationships involving bacteria, Douglas-fir, and the soil in which they naturally grew were important in effecting seedling growth promotion. However, Douglas-fir shoot biomass increased 39% and root biomass 68% after bacterial inoculation in some treatment combinations involving pasteurized soil. Key words: Douglas-fir seedlings, growth, rhizosphere bacteria.
Progression of damping-off epidemics in Glycine populations of even-age and mixed-age structure
Authors: Neher D. A. , Wilkinson H. T. , Augspurger C. K.
Published: October 2008

Development of damping-off epidemics, caused by a random distribution of Pythium aphanidermatum in soybean populations, was quantified in even-aged and mixed-aged populations of Glycine max and Glycine soja (progenitor of cultivated species). Age structures were created to mimic naturally occurring even- and mixed-aged structures of G. max and G. soja, respectively. Damping-off epidemics developed more rapidly in populations of G. max than G. soja, in mixed-aged than even-aged populations of G. max, and even-aged than mixed-aged populations of G. soja. Diseased soybeans were distributed less uniformly, both temporally and spatially, and epidemics were longer in mixed-aged than even-aged structures and in populations of G. soja than G. max. Incidence of preemergence disease was greater near the inoculum source. Seedlings that damped-off after emergence and (or) those that remained symptomless were peripheral to the inoculum source. Epidemic development was dependent upon plant species and the temporal and spatial distribution of susceptible plants and virulent pathogen. Key words: Glycine max, Glycine soja, Pythium aphanidermatum, soybean, survivorship analysis.
Mating biology in Peniophora cinerea (Basidiomycetes)
Authors: Hallenberg Nils , Larsson Ellen
Published: October 2008

Mating tests were performed to analyze the genetic relationship between two intersterile sibling species in Peniophora cinerea (Fr.) Cooke in Europe. Two newly collected specimens from North Europe were found to be compatible with both sibling species, which strongly suggests a close genetic relationship and a sterility barrier of simple genetic origin. The two sibling species, which differ in their substrate selectivity, are accepted as subspecies. One subspecies is restricted to decorticated wood of Fagus, and occasionally the fruit bodies are associated with insect galls. Intersterility was also found in some combinations with two other specimens from Canada and Turkey, but no linkage was found with a particular substrate. Specimens from Taiwan were found to be partially compatible with specimens from Europe, Turkey, and Canada. Distinct differences between the subspecies were found in banding patterns from isoelectric focusing of buffer-soluble mycelial proteins. It is proposed that the kind of intersterility found here is intraspecific and should be looked upon as part of a propagation strategy. Key words: speciation, evolution, Basidiomycetes, isoelectric focusing, insect gall, mating test.
Monoclonal antibodies to an extracellular component of Pyricularia grisea
Authors: Xia Jun Q. , Lee Fleet N. , Kim Kyung S.
Published: October 2008

Monoclonal antibodies were produced from fusions of myeloma cells with splenocytes from BALB/c mice immunized with an extract of a liquid culture fluid of an isolate of Pyricularia grisea race IB—49. The hybridomas were screened with the immunogen, and three were selected and propagated in mice for antibodies in ascites fluid. The monoclonal antibodies 3C3 and 4E10, isotype IgG3, and 10G9, isotype IgA, were characterized by indirect ELISA, Western immunoblotting, and immunoelectron microscopy. All three monoclonal antibodies reacted similarly with the antigens in various serological techniques used and did not cross-react with any unrelated fungal isolates representing 11 genera but reacted positively with all 20 races or isolates of P. grisea. The monoclonal antibodies bound to a high Mr protein component (113 × 103) in extracts of liquid culture fluids and not to conidial antigens. The epitopes recognized by the monoclonal antibodies were densely distributed in the cell walls and lomasomes of hyphae and much less so in the cytoplasm of conidia. It is suggested that the antigenic component was synthesized in the cytoplasm of fungal cells, accumulated in the lomasomes, and secreted through cell walls as an extracellular molecule. The monoclonal antibodies could detect homologous antigen at about 60 ng fungal protein/mL and a fivefold dilution of the extracts of infected rice tissue by ELISA. Key words: fungus, monoclonal antibodies, ELISA, immunoassays.
Physiological and ultrastructural effects of fumonisin on jimsonweed leaves
Authors: Abbas Hamed K. , Paul Rex N. , Boyette C. Douglas , Duke Stephen O. , Vesonder Ronald F.
Published: October 2008

The physiological and ultrastructural effects of fumonisin B1, a phytotoxin obtained from Fusarium moniliforme, on jimsonweed (Datura stramonium L.) were studied. When fumonisin B1 was applied at concentrations of 3 to 1000 μg/mL (4.1 to 1388 μM) to jimsonweed leaves, effects such as electrolyte leakage, autolysis, and photobleaching of tissues were noted in less than 12 h after exposure to light (480 μmol∙m−2∙s−1, PAR) at 25 °C. The degree of damage was directly proportional to the concentration and duration of exposure in all cases. Chlorophyll reduction from 5 to 73% occurred after 48 h in the light. In darkness, electrolyte leakage above control levels was noted only in treated samples after 72 h. However, when these dark-treated samples were subsequently placed in the light, electrolyte leakage occurred in 12 h. Ultrastructural damage in mesophyll palisade cells exposed to 500 μg/mL fumonisin B1 began at 6 h and intensified after 12 h. Cytoplasmic degeneration occurred first, followed by disruption of the chloroplasts and accumulation of intracellular debris. The close structural analogue, AAL-toxin, has previously been reported to act by inhibiting nucleotide synthesis. The phytotoxic activity of both AAL-toxin and fumonisin was not influenced by supplying supplemental aspartic or orotic acid, indicating that neither toxin acts by inhibiting nucleotide synthesis. These results indicated that fumonisin B1 caused rapid, light-dependent cytoplasmic and chloroplast disruption, through an unknown mechanism. Key words: phytotoxin, mycotoxin, weed, mode of action, Fusarium moniliforme, AAL-toxin.
Mini-rhizotrons transparents pour l'étude du système racinaire de jeunes plantes. Application à la caractérisation du développement racinaire de jeunes chênes (Quercus robur)
Authors: Pages Loïc
Published: October 2008

A new type of root-observation box is described, which allows continuous observations on entire growing root systems of young plants. Each root-observation box consists of two transparent plastic plates separated by a few millimetres. On the internal face of each plate, a sheet of transparent filter paper is fixed, which allows absorption and distribution of water and nutrients to the root system. The root system can grow between these two plates, the roots growing on either one face or the other. Thus, the entire root system can be observed continuously. It is easy to manipulate it experimentally. The root-observation boxes are placed away from the light into a container. As an example, and to show the suitability of the method, we studied the development of the root system of young oak seedlings (Quercus robur L.). We compared their architectural characteristics with those described by different authors who have used other methods. The specific interests of this new method are emphasized. Key words: root, morphogenesis, rhizotron, root observation box, growth, development, Quercus robur.