bluuebunny/crossref_metadata_2025 huggingface dataset:
Delayed cotyledon senescence following treatment with a cytokinin; an effect at the level of membranes
Authors: Gilbert M. L. , Thompson J. E. , Dumbroff E. B.
Published: April 2011

Application of 10−4 M benzyladenine to Phaseolus vulgaris germinated under etiolating conditions markedly delayed the onset of cotyledon senescence. Weight loss was curtailed, hydrolysis of starch and protein reserves was delayed, and the rate at which hydrolysis products were translocated out of the cotyledons was reduced in treated plants. Microsomal membranes of cotyledons from control seedlings acquired increasing proportions of gel phase lipid as senescence of the tissue intensified. The resulting mixture of liquid-crystalline and gel phase lipid within the membrane matrix renders the membranes leaky and may partially contribute to metabolite translocation out of the cotyledon storage cells during seedling development. This prospect is supported by the observation that in benzyladenine-treated plants the onset of gel phase lipid, and hence of membrane leakiness, was delayed in a manner that corresponded temporally with the decreased rate of metabolite translocation out of the cotyledons.
The nucellar epidermis and micropyle of Ornithogalum caudatum (Liliaceae) with a review of these structures in other taxa
Authors: Tilton Varien R.
Published: April 2011

The nucellar epidermis of Ornithogalum caudatum is modified in its micropylar region to form a nucellar cap. The cells become palisadelike with lignified walls and dense, RNA-rich cytoplasm and a large distal vacuole. High vesicular activity is associated with the greatly thickened proximal walls. The micropyle is formed by the inner integument and at anthesis, it is filled with an exudate secreted by the nucellar cap and inner integument. The exostomium is sealed by a hymen. The exudate and hymen probably function as surfaces for localized deposition of synergid-synthesized chemotropic agents. After fertilization the micropyle is occluded by a plug of flocculent material which appears to be more dense than the prefertilization material. This plug probably serves to preclude pathogen invasion and prevent desiccation of embryo and endosperm.
Thermophilous fungi of decomposing sugarcane bagasse
Authors: Sandhu D. K. , Singh Surinder , Waraich M. K.
Published: April 2011

Twenty species of thermophilous fungi were identified from sugarcane bagasse at Batala in Northern India. Seven fungal species are reported from bagasse for the first time and Aspergillus caespitosns is a new record for India. Aspergillus fumigatus was the most common fungus followed by Mncor pusillus. The temperature responses of the fungi revealed 5 microthermophiles, 11 thermotolerant, and 4 true thermophiles. Three species of thermophilous fungi are reported in addition to those already recorded in the literature.
Scanning electron microscopy of Fusarium oxysporum f.sp. lycopersici in xylem vessels of wilt-resistant and susceptible tomato plants
Authors: Stromberg Erik L. , Corden Malcolm E.
Published: April 2011

Vessels in stems of 'Jefferson' (race 1 resistant and race 2 susceptible) and 'Bonny Best' (race 1 and 2 susceptible) tomato cultivars inoculated with Fusarium oxysporum f.sp. lycopersici race 1 or 2 were examined by scanning electron microscopy. Four days after inoculation of Jefferson with conidia of race 1, the inoculum conidia and resultant hyphae generally were collapsed, whereas in the susceptible host–pathogen combinations the inoculum conidia and hyphae appeared normal. Neither the plants of the resistant nor the susceptible host-pathogen combinations had perforation plates or tyloses within vessel elements capable of trapping conidia or effectively blocking hyphal growth. The perforation plates of all vessel elements are reduced to slightly lipped rims and thus provide unrestricted apertures for hyphal growth and conidial movement in the transpiration stream. In the susceptible host–pathogen combinations, mycelial growth often filled the vessels, but no sporulation was noted. Frequent lateral spread of the pathogen occurred between adjacent vessels through the bordered pit-pairs. Infrequent occurrence of tyloses and a lack of occlusions by tyloses in the resistant host–pathogen combination suggest that vascular wilt resistance within the stem is not due primarily to physical containment of the pathogen in the vessels. Collapsed conidia and hyphae in the resistant host–pathogen combination suggests that fungitoxic materials in the vessels suppress the pathogen and contribute to resistance.
Chlorophyll fluorescence quenching by oxygen in plants
Authors: Vidaver William , Colbow Konrad , Hall Gordon , Wessel Silvia
Published: April 2011

Three distinct phases of chlorophyll a fluorescence quenching were observed in green plants by applying O2 pressures of up to 400 atm. These phases are interpreted as indications of three different mechanisms of O2 quenching. The most sensitive phase is dependent on intersystem electron transport. For dark-adapted bean leaves this fluorescence was quenched to half the initial yield with an O2 pressure of about 3 atm. The second mechanism was observed with 3-(3,4)dichlorophenyl)-1,1-dimethylurea (DCMU), namely the quenching of variable fluorescence in leaves, chloroplasts, and green algae cells. This effect of O2 is thought to be closely associated with the photochemical system II reaction centers. Half of the variable fluorescence was quenched with about 40 atm of O2. Finally, the antennae pigments are quenched, as observed by the effect of O2 on the O-level fluorescence yield, when all photochemical system II reaction center traps are presumably open. The O2 pressure required for half-quenching in this case was about 400 atm.The possibility that the quenching of fluorescence occurs with O2 concentrations low enough for endogenous O2 to have an effect on in vivo fluorescence was investigated. We suggest that O2 quenches by competing with photochemical system I for electrons derived from water splitting, and may thus function as a feedback regulator of photosynthesis.
Fonctionnement sympodial continu et multiplication végétative chez l’Arum italicum
Authors: Nougarède A. , Rondet P.
Published: April 2011

The vegetative and floral development of Arum italicum Mill. displays no resting period under western European climatic conditions. Between two flowering seasons several sympodial units ending with an inflorescence are successively built. The meristem of each new unit is generally initiated in the axil of a sagittate leaf of the preceding unit but it can also grow in a nonaxillary position at the base of the meristem. The leaves of the first unit spend the winter season above the ground. Their petiole sheaths surround all the later sympodial units. On each sympodial unit a number of axillary buds give rise to tunicated bulbils which provide for the asexual multiplication of the species. The ontogeny of the bulbils on the mother plant and their behaviour after they become autonomous are described, as well as those of young plantlets grown from seed germination. In rhizomes, bulbils, and plantlets the shoot apex is in close contact with a subapical region (base plate) built from interlocked leaf or scale bases which are rich in storage products. This base plate will give rise to a new rhizome. Although Arum italicum has a tuberous rhizome with sympodial growth, it has nevertheless some characters of a bulbous plant (base plate and bulbils) but it differs from it by continuous growth and development and the lack of dormancy of the bulbils.
A new chromosome number in Arctostaphylos uva-ursi
Authors: Rosatti Thomas J.
Published: April 2011

Populations resembling Arctostaphylos uva-ursi (L.) Spreng. var. coactilis Fernald and MacBride growing on Long Island, New York, U.S.A., provided material for cytological study which resulted in the discovery of a new chromosome number for the species, 2n = 78. These plants differ from the most common expression of this variety in having more linear leaves, a condition that may be associated with a physiological tolerance for relatively high levels of salt in the substratum.
Generation-dependent patterns of variation and population differentiation in Abies amabilis and A. lasiocarpa (Pinaceae) from north-coastal British Columbia
Authors: Maze Jack , Parker William H. , Bradfield Gary E.
Published: April 2011

To investigate generation-dependent patterns of variation and differentiation in populations of Abies amabilis and A. lasiocarpa from north-coastal British Columbia, seven leaf variables were analyzed by multivariate methods. Principal-components analysis of leaf data from sexually immature trees of Abies amabilis and A. lasiocarpa indicated no evidence of hybridization between these two species, even on a disturbed site where sexually mature individuals of both species are sympatric. Regression analysis indicated that a change with altitude occurs in A. amabilis. Evidence of population differentiation in immature individuals of both species was demonstrated by canonical variates analysis: (1) in A. amabilis a canyon bottom population appeared distinctive; (2) in A. lasiocarpa population differentiation is related to latitude. Variation patterns in both species suggest that geographic distance and taxonomic distance between populations are independent. Such patterns would be predicted if selection were a more important determinant of population differentiation than gene flow. There is some indication that mature populations are more variable than immature.
Cytology of mucilage production in the seed coat of Candle canola (Brassica campestris)
Authors: Caeseele L. Van , Mills J. T. , Sumner M. , Gillespie R.
Published: April 2011

The development of mucilage in the epidermal cells of canola seeds (Brassica campestris L. cv. Candle) was studied with light and electron microscopy from 5 days after pollination to maturity. During the first 17 days starch was deposited in amyloplasts. At or near the 17th day mucilage appeared between the plasmalemma and the outer tangential wall of the epidermal cells. As the volume of mucilage increased, starch grains disappeared and were totally absent by 25 days. Membrane-bound structures and Golgi bodies were visible within the cytoplasm adjacent to the site of mucilage deposition. At maturity the seed epidermal cells were totally devoid of cytoplasm and engorged with mucilage.
Growth and reproductive development of alfalfa as influenced by 2,3,5-triiodobenzoic acid
Authors: Phillips J. C. , Chilcote D. O.
Published: April 2011

The plant regulator 2,3,5-triiodobenzoic acid (TIBA) at concentrations of 0, 10,50, 100, or200 ppm(0, 2 × 10−5, 1 × 10−4, 2 × 10−4,or4 × 10−4 M, respectively) was applied to leaves of alfalfa grown at 14-h day length, 12 000 μW cm−2, 20 °C day–16 °C night. The number of racemes per primary stem and on axillary branches was recorded daily for 34 days after TIBA application. Length of primary stems and branches and number of nodes and branches were determined 34 days after TIBA application.TIBA did not affect number of nodes or branches per primary stem, but at a concentration of 10 ppm it promoted the elongation of both primary stems and axillary branches and also raceme formation on both stems and branches. This resulted in a fivefold increase in total branch length per primary stem and a highly significant increase in total raceme production. These results may explain in part reported effects of TIBA on seed production of alfalfa and are also consistent with reported effects of TIBA on flowering and axillary bud development in several other legumes.The observation that two structures (branches and (or) racemes) may typically arise from an alfalfa leaf axil may be useful in understanding the phenomena of branching and floral initiation in this crop.
Variability in photoperiod and the inhibition of flowering in a high latitude population of Saxifraga rivularis
Authors: Teeri J. A. , Tonsor S. J.
Published: April 2011

A population of Saxifraga rivularis L. collected at Truelove Lowland, Devon Island, N.W.T., Canada (75°41′ N) exhibits a photoperiodic control of flowering in controlled environment chambers. The plants respond in a manner typical of long-day plants with flowering inhibited by either a 6-h daily dark period, or by a 6-h daily low intensity irradiance regime of incandescent light. The inhibition of flowering by 6 h day−1 of incandescent light does not occur if the incandescent light is given in twelve 0.5-h doses, each followed by 1 h of red-rich high intensity irradiance.
Effect of leachates from the shoots of red bartsia (Odontites verna) on four crop species
Authors: Schewe Anita , Staniforth Richard
Published: April 2011

The hemiparasite, Odontites verna (Scrophulariaceae), has previously been reported to have strongly negative allelopathic interactions with certain perennial grasses and leguminous crops (including several proven host species). In this study, applications of leachates from living and dead foliage of O. verna on seeds and seedlings of two grass and two legume species had no significant effects on germination and negative growth in most treatments. Two exceptions were germination in Medicago sativa (increased) and leaf production in Poa pratensis (decreased).
Response of SO2-fumigated Pinus resinosa seedlings to postfuniigation temperature
Authors: Norby R. J. , Kozlowski T. T.
Published: April 2011

Effects of postfumigation temperature on SO2-fumigated seedlings of red pine (Pinus resinosa Ait.) were studied. Seedlings were fumigated with either 0.2 ppm SO2 for 91 h or with 0.5 ppm SO2 for 30 h. Seedling injury was much greater at the higher SO2 concentration. At the lower SO2 concentration, only root weight of fumigated seedlings was affected, and it was about 20% less than that of unfumigated controls after 6 weeks at 12, 22, or 32 °C; there was no interaction between SO2 treatment and postfumigation temperature on growth rate. Postfumigation growth was reduced more by the higher concentration of SO2. Significant interaction between SO2 and postfumigation temperature occurred, with growth of roots, primary needles, and secondary needles being reduced most at 12 °C. At higher postfumigation temperatures, SO2-fumigated seedlings recovered (partially) and initiated secondary needles, thereby providing a new source of photosynthate and further reducing growth inhibition. But at 12 °C, shoot growth was slow and injured needle tissue was not replaced; hence the dry weight of roots of plants fumigated at the higher SO2 concentration was <30% of that of controls after 6 weeks. Interpretation of effects of fumigation temperature on SO2 toxicity should also consider influences of postfumigation temperature regimes.
Fixation d'azote chez les espèces ligneuses symbiotiques. I. Ultrastructure des nodules, mycorhizes à vésicules et à arbuscules et activité réductrice de C2H2 de jeunes plants de Robinia pseudoacacia cultivés au laboratoire
Authors: Moiroud André , Capellano André , Bärtschi Henry
Published: April 2011

Black locust (Robinia pseudoacacia L.), a native species of North America, has found a specific and efficient Rhizobium strain in French soils. Ultrastructural studies of young nodules showed that infection of the host cell occurred by numerous infection threads. Rhizobia are liberated in the cell by endocytotic processes. No important differences were found between rhizobia in the infection threads and bacteroids in the host cell; the bacteroid cells were only enlarged, without any structural change. This Rhizobium strain is a "fast grower".Roots were also infected by an endomycorrhizal fungus producing numerous vesicles and arbuscules in the root cortex.Nitrogen-fixing activity, assayed by the acetylene reduction method, was measurable only 5 to 10 days after nodular development. Until the 50th day after seed germination, the activity increased slowly, then more rapidly. By the 80th day, fixing activity was about 9 μmol/h per plant.No relationships between the form, age, and fixing activity of the nodules were found.
Unicarpellate floral development in Potamogeton zosteriformis
Authors: Posluszny U.
Published: April 2011

Floral development in the species Potamogeton zosteriformis is compared with that of other species of Potamogeton previously investigated (P. densus and P. richardsonii). A spike inflorescence is found on which 6 to 20 flowers develop. These flowers develop their appendages acropetally; first, the four tepals are initiated followed by the four stamens opposite the tepals. As in the flower of P. densus, the two lateral stamens are each initiated as two separate primordia. Unlike any other Potamogeton species where four carpels generally arise, alternating with the tepal and stamen pairs, in P. zosteriformis a single carpel consistently develops on the central portion of the remaining floral meristem. Histological preparations did not reveal any vestigial procambial strands differentiating in the gynoecium. This unique floral development is examined from several points of view. Morphogenetic comparisons are made with other species of Potamogeton which develop tetramerous gynoecia. Morphologically the nature of the Potamogeton flower is reexamined and phylogenetically the possibility of P. zosteriformis as a link or transition between the bisexual and unisexual groups within the Najadales is considered.
The effect of auxin on cell volume elastic modulus in storage tissue of Helianthus tuberosus
Authors: Ferrier J. M. , Dillon E. M. , Chang A. , Dainty J.
Published: April 2011

Linear displacement transducers were used to study the effect on elasticity of exogenous indole acetic acid (IAA) applied to aged sections of parenchyma storage tissues of Helianthus tuberosus. The treated sections were found to have a decreased cell volume elastic modulus, by about 25% relative to controls after 1 day in auxin, and by about 80% relative to controls for periods of 2 days to more than 9 days in auxin. The theory and some possible difficulties associated with the measurements are discussed.
Paraquat influences development and efficacy of the mycorrhizal fungus Glomus fasciculatus
Authors: Pope P. E. , Holt H. A.
Published: April 2011

Paraquat (1,1-dimethyl-4,4′-bipyridinium chloride) applied at 2 kg/ha significantly reduced the amount of mycorrhizal hyphae and number of vesicles and chlamydospores formed by Glomus fasciculatus (Thaxt.) Gerd. and Trappe when compared with the control or the 0.5 kg/ha paraquat treatment. When compared with inoculated control, paraquat applied at 0.5 kg/ha tended to increase the amount of mycorrhizal hyphae, and significantly increased chlamydospore production. For noninoculated white ash (Fraxinus americana L.) seedlings, total dry weight and stem height tended to decrease with increases in rates of paraquat applied. In contrast, seedling height and foliar P concentration of inoculated seedlings tended to be greatest for the 0.5 kg/ha paraquat treatment followed by the control and the 2 kg/ha chemical treatment. The amount of mycorrhizal hyphae was significantly correlated to seedling height and diameter, total dry weight, and percentage foliar elemental P.
Demethylation of the phytoalexin pisatin by Stemphylium botryosum
Authors: Higgins Verna J.
Published: April 2011

The initial product formed from pisatin by Stemphylium botryosum was identified as 3,6a-dihydroxy-8,9-methylenedioxypterocarpan(6a-hydroxymaackiain) by spectrophotometric, thin-layer chromatographic and gas–liquid chromatographic comparisons with an authentic standard.
Puccinia pulchella: a new Viola–Carex rust from Japan
Authors: Ono Yoshitaka , Kakishima Makoto
Published: April 2011

Carex aphanolepis Fr. & Sav. infected with uredinial and telial stages of Puccinia sp. was found to occur near Aecidium-infected Viola grypoceras A. Gray and V. yezoensis Maxim. Reciprocal inoculations with basidiospores and aeciospores onto nine species of Viola and C. aphanolepis, respectively, showed the genetic relation between these different spore stages. This is the first caricicolous rust fungus which has an aecial stage on Viola, and is described as a new species; Puccinia pulchella Ono & Kakishima.
A reinvestigation of the origin of the peribacteroid membrane in root nodules of Vicia faba
Authors: Newcomb William , Creighton Susan , Latta Lenore
Published: April 2011

A transmission electron microscopic study of nodules of Vicia faba has demonstrated that rhizobia are released from the infection threads by an endocytotic process. The rhizobia escape from unwalled regions of the infection thread or unwalled droplets of thread matrix and upon escape are surrounded by a peribacteroid membrane which is derived from the plasma membrane bounding the unwalled regions of thread matrix. Thus, the release of bacteria in V. faba nodules is essentially identical to that reported in other leguminous nodules and the peribacteroid membrane does not arise de novo as previously reported by other workers.
The effect of a water stress on the cold hardiness of winter wheat
Authors: Tyler N. J. , Gusta L. V. , Fowler D. B.
Published: April 2011

Crowns of winter wheat plants water stressed with polyethylene glycol (PEG) (molecular weight 20 000) prior to hardening were more cold hardy than tender crowns or crowns hardened for 2 days (p ≤ 0.05). After 16 days of hardening, plants from all treatments reached the same level of hardiness. Winter wheat crowns water stressed with PEG (210 g/L) for either 0,5, or 21 days reached the same level of hardiness after 2 days of acclimation. In both short- and long-term stress studies, the crown moisture content of the stressed plants was lower (p ≤ 0.05) than that of the controls prior to acclimation. With increasing hardiness both leaf osmotic potential and crown moisture content decreased (p ≤ 0.05). Short-term water stress also resulted in an increase in sugars, specifically sucrose (p ≤ 0.05) prior to cold hardening. However the total sugar content did not parallel the increase in hardiness.Changes in several metabolic parameters were also considered. Significant correlations were found in both studies between the LT50 and osmotic potential, moisture content, and dry weight. Most of the variability in LT50 could be explained by changes in leaf osmotic potential and crown moisture content.
Seasonal changes in germination responses of buried seeds of Verbascum thapsus and V. blattaria and ecological implications
Authors: Baskin Jerry M. , Baskin Carol C.
Published: April 2011

In a 2-year study buried seeds of Verbascum thapsus and V. blattaria were exposed to natural seasonal temperature cycles, and at monthly intervals they were exhumed and tested in light and darkness over a range of alternating temperatures simulating those in the habitat throughout the growing season. At any time from spring to early autumn, seeds of both species germinated in light at prevailing habitat temperatures. Seeds of V. blattaria germinated in darkness in spring at spring temperatures but did not germinate in darkness at any temperature in summer or autumn. Unlike V. blattaria, seeds of V. thapsus germinated to 25–85% in darkness in summer at summer temperatures. In the second spring of burial, seeds of both species showed a reduction in ability to germinate in darkness at spring temperatures. Only 5% of the V. blattaria and 16% of the V. thapsus seeds germinated while they were buried. The germination characteristics are discussed in relation to the ecology of these two early successional species.
The diatoms and dinoflagellates of Hudson Bay
Authors: Anderson J. T. , Roff J. C. , Gerrath J.
Published: April 2011

Phytoplankton samples from 130 stations in Hudson Bay taken during summer 1975 were examined. Diatoms formed the largest group of phytoplankton comprising 27 genera and 59 species, 24 of which are not previously recorded from Hudson Bay. Twelve genera and 45 species of dinoflagellates were identified of which 33 have not been previously reported from the Bay.Various patterns of distribution were observed; some species were only found inshore, while others were distributed throughout the Bay with the exception of the low salinity waters of the southwest coast. Highest cell counts were found inshore; diatoms reached 200 000 cells per litre around the Belcher Islands. Dinoflagellates reached 125 000 cells per litre south of Mansel Island, and exceeded 60 000 cells per litre in the Chesterfield Plume and along the southwest coast. Thus certain areas of Hudson Bay have much higher phytoplankton standing crops than previously believed, often greatly exceeding counts from Foxe Channel and Hudson Strait. The lowest diversity indices of diatoms, dinoflagellates, and diatoms and dinoflagellates combined, were observed at lower salinities along the southwest coast. The diversity index of diatoms and dinoflagellates combined was otherwise high throughout the Bay (> 3) and was highest in the Coats and Mansel islands area.
Influence of light and darkness on RNA synthesis in Xanthium
Authors: Gupta D. N. Sen , Ghosh J. K. , Mitra B. , Sen S. P.
Published: April 2011

In the short-day Xanthium strumarium L. 32P incorporation in RNA during the dark period increased initially but declined after the critical dark period. [14C]uracil incorporation in nuclei, chloroplasts, and mitochondria also decreased with induction. DNA template availability for RNA transcription decreased as the dark period was prolonged beyond the critical length and as the number of inductive cycles increased. Night interruption with red light had opposite effects and far red light reversed the red light effect. Competitive DNA–RNA hybridization indicated differences in the DNA templates used for RNA transcription. [14C]arginine incorporation in nuclear basic proteins also increased with induction treatment.
The soil microfungal community of a South Dakota grassland
Authors: Clarke Dennis C. , Christensen Martha
Published: April 2011

The soil microfungi of a western South Dakota grassland were quantitatively surveyed using the dilution plate technique. A 250-membered sample yielded 62 taxonomic entities. Principal forms included Acremonium sp. 4407, Aspergillus fumigatus, A. niveus, A. terreus, Chrysosporium pannorum, Fusarium oxysporum, F. solani, Mammaria echinobotryoides, Mortierella gracilis, Paecilomyces marquandii, Penicillium funiculosum, Penicillium janthinellum, Penicillium lilacinum, and Trichoderma harzianum. Comparison to other grassland surveys has revealed that the South Dakota community is most like that from the Pawnee National Grassland in eastern Colorado with less similarity to mycofloras reported for grasslands in Wisconsin and Oklahoma. Aspergillus terreus, A. fumigatus, A. niveus, Fusarium oxysporum, F. solani, Penicillium janthinellum, P. lilacinum, and Mortierella gracilis are prominent in temperate grassland communities worldwide. A slight seasonal trend was detected at the species level. Aspergillus fumigatus and Paecilomyces marquandii were predominant forms in the spring collection while Penicillium janthinellum and Papulospora sp. were present in greatest numbers in the fall. Relative densities for other species indicated that there may be heightened activity in populations of infrequent taxa in the spring. Twenty-seven and 10% of the colonies developing on dilution plates prepared in the fall and spring, respectively, grew from spores.
Fine structure of the root nodules of Dryas drummondii Richards (Rosaceae)
Authors: Newcomb William
Published: April 2011

The root nodules of Dryas drummondii (common name: mountain avens; Family Rosaceae) possess numerous nodule lobes devoid of nodule roots and thus they exhibit the Alnus-type of nodule morphology. Each nodule lobe possesses a nodule meristem, infected cortical cells, and a central vascular cylinder. The endophyte is prokaryotic and has two forms: septate hyphae, 0.3–0.6 μm in diameter, and nonseptate vesicles, ca. 2 μm in diameter; thus, the endophyte appears to be an actinomycete similar to those of other Frankia-induced nodules. A polysaccharide capsule surrounds both forms of the endophyte and contains numerous electron-dense inclusions near the hyphae in host cells containing both forms of the endophyte.
Camarops rickii sp. nov. from Brazil and comments on C. peltata
Authors: Rogers Jack D.
Published: April 2011

Camarops rickii sp. nov. is described from a Brazilian collection. It is noteworthy among described Camarops species for its comparatively large ascospores. Ultrastructural aspects of the ascospore germ pore are discussed. Camarops peltata, until recently known only from type material collected in Puerto Rico, is discussed and redescribed on material collected in Colombia.
Stachyose synthesis in isolated mesophyll cells of Cucurbita pepo
Authors: Madore Monica , Webb J. A.
Published: April 2011

A pure preparation of isolated mesophyll cells and a preparation of minor veins heavily contaminated with mesophyll and epidermal tissue were obtained from leaf strips of Cucurbita pepo by enzymatic digestion. The preparations were incubated for 10 min in sodium [14C]bicarbonate in the light to determine their ability to synthesize the major translocated sugar stachyose and its precursor galactinol. Stachyose, galactinol, sucrose, and hexoses accounted for ca. 0.5, 2.5, 55, and 30% respectively of the total 14C in the neutral sugar fraction in both preparations. The close similarity was believed due to the heavy contamination of the minor vein preparation with mesophyll tissue. Intact leaf tissue incubated under similar conditions incorporated an approximately equal amount of 14C into the sugar fraction but with a highly dissimilar distribution. Stachyose, galactinol, sucrose, and hexose accounted for up to 50, 20, 13, and 0.2% respectively of the total 14C activity. Plasmolysis of intact tissue caused a more than 50% decrease in the 14C incorporation into stachyose and galactinol and a large increase into sucrose and particularly hexoses. The enzymes synthesizing galactinol and stachyose were extracted from the mesophyll preparation but their specific activities on a total chlorophyll basis were 10-fold lower than when extracted from intact tissue. It was concluded that the procedure for isolating free cells, while not affecting sucrose synthesis, was highly detrimental to the synthesis of galactinol and stachyose, and that synthesis of the latter two compounds was most probably confined to the mesophyll.
Inhibition of Sclerotium rolfsii by Pseudomonas aeruginosa
Authors: Brathwaite C. W. D. , Cunningham H. G. A.
Published: April 2011

Germination of sclerotia, growth, production by Sclerotium rolfsii were inhibited by the bacterium, Pseudomonas aeruginosa in culture and in soil. Inhibition of growth in soil was demonstrated by a new soil–agar plate technique. Preliminary evidence is presented which suggests that inhibition of S. rolfsii by P. aeruginosa is associated with the production of the antibiotic, pyocyanin.
Dinitrogen fixation by surface peat and Sphagnum in an ombrotrophic bog
Authors: Chapman Rachel R. , Hemond Harold F.
Published: April 2011

Annual dinitrogen fixation at the surface of ombrotrophic Thoreau's Bog in eastern Massachusetts, U.S.A., is estimated at 1.0 g N∙m2. The rates of acetylene reduction are lower but still significant in the dark, suggesting that fixation is carried out both photosynthetically and heterotrophically. The ratio 15N2 fixed: C2H2 reduced was 1 mol: 3.5 mol in in vitro calibration experiments. Dinitrogen fixation is ecologically important in this bog as it exceeds the only other known input of nitrogen, namely deposition of NO3− and NH4+ in bulk precipitation.
Role of nutritional factors and light in the sporulation of two isolates of Myrothecium roridum
Authors: Mani Malathy , Swamy R. N.
Published: April 2011

Among single-spore isolates of Myrothecium roridum obtained from leaf spots on Croton sparsiflorus, some required light for sporulation on natural media while others sporulated in the dark. A dark-sporulating (DSP) isolate and a light-requiring one (LSP) were studied. Sporulation of the DSP isolate was also better in light. Amino acids were, generally, the best sources of N for this isolate. The LSP isolate failed to sporulate on a medium containing nitrate. This isolate, however, showed moderate sporulation, even in the dark, on a medium with cellulose as the C source and around the inoculum plug on a medium lacking C. Appreciable sporulation was seen in the LSP isolate when nitrate was replaced by casaminoacids or tyrosine. While tyrosine did not enable sporulation in the presence of nitrate, a few other aromatic compounds did. The aromatic nature of tyrosine, rather than its role as an N source, has been suggested as being responsible for its effect on the LSP isolate.
A new hyphomycete parasitic on the ciliated protozoans Vorticella and Opercularia
Authors: Barron G. L. , Szijarto E.
Published: April 2011

Meria harposporioides is described as a new hyphomycete attacking ciliated protozoans. The crescent-shaped conidium attaches to the host pellicle, invades the cell, and produces branching chains of beadlike assimilative hyphae. A unique feature is that assimilated nutrient is passed back out through the original penetration tube to the infective conidium which then produces fertile hyphae and phialoconidia. This is the first record of a hyphomycete attacking ciliated protozoans.
Partial purification of galactinol synthase from leaves of Cucurbita pepo
Authors: Webb John A.
Published: April 2011

An enzyme synthesizing galactinol, UDP-D-galactose:myo-inositol-1-α-D-galactosyl transferase (galactinol synthase), has been isolated and partially purified from mature leaves of Cucurbita pepo. The enzyme showed optimal activity between pH 7.5 and 8.0 and required Mn2+ and the presence throughout isolation, storage, and assay of a sulfhydryl protectant (β-mercaptoethanol). EDTA was completely inhibitory. From a range of metal ions only Mg2+ partially replaced Mn2+, while Co2+, Zn2+, Cu2+, and Ni2+ were inhibitory. The uridine nucleotides and UDP-glucose were from 40 to 80% inhibitory and probably constitute part of the in vivo control system. High concentrations of galactose, melibiose, and xylose were partially inhibitory. The enzyme appeared highly specific for myo-inositol and showed no ability for galactosyl transfer to any other naturally occurring sugar or sugar alcohol. Some reactivity was obtained with the isomeric scyllo-inositol but the product was not identified. A range of other sugar nucleotides were unreactive.
Net aerial primary production of a James Bay, Ontario, salt marsh
Authors: Glooschenko Walter A. , Harper Nancy S.
Published: April 2011

Aboveground plant biomass and litter measurements were made at four intervals between mid-June and late August 1977 on a subarctic salt marsh located at North Point on the southwestern shore of James Bay, Ontario. We sampled six salt marsh zones ranging from a lower intertidal flat dominated by the grass Puccinellia phryganodes to the edge of willow thickets characterized by Juncus balticus.Peak aboveground biomass was reached in nearly all zones by early August, and ranged from 119.3 to 240.4 g dry weight∙m−2. Litter accumulated in all zones except the lower two zones which were subjected to tidal flows. The highest zone where Juncus balticus occurred had the highest litter mass, 572.8 g dry weight∙m−2, while the lowest, 24.7 g∙m−2, occurred in the lowest zone. Estimates of net aerial primary productivity using Smalley's method ranged from 119.3 g∙m−2 in the upper salt marsh to 384.0 g∙m−2 in the zone dominated by Juncus balticus. The mean marsh net aerial primary productivity was 227.7 g∙m−2 which was low compared with other salt marsh data. The 1977 aboveground biomass was lower in 1976, probably as a result of a cooler summer.
Defense patterns in nonhost higher plant species against two powdery mildew fungi. I. Monocotyledonous species
Authors: Johnson L. E. B. , Bushnell W. R. , Zeyen R. J.
Published: April 2011

Fifteen monocotyledonous species were separately inoculated with spores of Erysiphe graminis f. sp. hordei (a parasite of barley) and E. cichoracearum (a parasite of cucurbits) to learn cytologically what types of parasite failures and host-cell responses protect nonhosts from disease. Tissues were stained with acid fuchsin and aniline blue, 24 and 72 h after inoculation, and examined microscopically. For each combination of higher plant species and fungus, fungal development and host responses were recorded for 2022–4679 spores and 15–2206 germlings, using a binary pathway system to tabulate and statistically analyze results.Nonhosts showed a battery of defenses, each of which could stop a large part of an attacking powdery mildew population. These defenses were expressed sequentially during fungal differentiation, leading to a progressive attrition in the number of germlings able to continue. The defenses were expressed on or in the following host structures: (i) the leaf surface, which was often inhospitable to germination and differentiation of infection structures; (ii) the cuticle and cell wall, which the fungi frequently failed to penetrate; (iii) the papilla, which was frequently induced but rarely penetrated; and (iv) the first cell invaded, which had a high probability of collapsing hypersensitively in the relatively few instances in which the fungi successfully entered a cell.Erysiphe cichoracearum germinated poorly and rarely developed beyond the appressorial stage on any monocotyledonous nonhost, suggesting that monocotyledonous leaf surfaces are unsuited for growth and differentiation of this fungus. Erysiphe graminis rarely developed beyond the appressorial stage on members of the Iridaceae and Liliaceae, suggesting that leaf surface environments in these plant families contain substances unfavorable for powdery mildew development.On species within the Graminae, E. graminis f. sp. hordei germinated and produced appressoria at lower rates on plants thought to be resistant to all powdery mildews (indiangrass, sorghum, big bluestem, and corn) than on plants which are susceptible to certain formae speciales of E. graminis (wheat, oats, and rye). Thus, within the Graminae, the amount of E. graminis development on nonhosts was negatively correlated with taxonomic distance between nonhost and appropriate host. However, the results with other combinations of fungus and nonhosts suggest that fungus development is usually controlled by resistance factors which are characteristic of the plant family and are unrelated to the taxonomic distance between nonhost and appropriate host.
Coadaptation of seed dormancy and hormonal dependence of α-amylase production in endosperm segments of Avena fatua
Authors: Upadhyaya Mahesh K. , Naylor James M. , Simpson Graham M.
Published: April 2011

Autonomous (independent of the germinating embryo) α-amylase production was compared in the endosperm segments of some genetically pure lines of Avena fatua L. (wild oats) differing in the duration of their seed dormancy. Endosperm segments from six randomly taken dormant lines showed no α-amylase production unless gibberellic acid (GA3) was supplied. In contrast, endosperm segments from four out of six nondormant lines produced and released substantial amounts of α -amylase and reducing sugars. Thus, natural selection has resulted in coadaptation of seed dormancy and a rigorous dependence of endosperm hydrolysis on gibberellins produced by the germinating embryo. The variability in the degree of autonomy amongst nondormant lines indicates that the observed coupling of these two traits in dormant lines is not due to simple pleiotropy, but probably reflects the action of multiple genetic loci or multiple alleles. These results also indicate that long-term endosperm stability confers little advantage in wild oat seeds predisposed to brief periods of residence in soil.
Étude ultrastructurale des tubes polliniques angiospermiens : application de quelques techniques cytochimiques
Authors: Pargney J. C.
Published: April 2011

The use of a variety of cytochemical techniques (test of PATAg, staining with phosphotungstic acid, Swift's reaction, digestion with pectinase, extraction with EDTA and dimethyl sulfoxide (DMSO)) affords a better approach to the study of the mechanism of the growth of pollen tubes. Vesicles produced by the Golgi apparatus accumulate in the tip of the pollen tubes. Their membranes are gradually transformed and become cytochemically similar to the plasmalemma with which they fuse, participating in its renewal. Their contents contribute to the tube wall formation. The structure of the tube wall is complex and appears to be formed of a loose matrix of cellulose fibrils impregnated with pectic materials.
Gibberellin-like activity in shoots of Salix pentandra as related to the elongation growth
Authors: Junttila Olavi
Published: April 2011

Activities of acidic gibberellin(GA)-like substances in shoots of Salix pentandra trees growing under natural conditions (69°39′ N, 18°37′ E) were studied in relation to shoot elongation and tip abscission. Bioassay after separation on SiO2 partition columns was accomplished with the lettuce hypocotyl and dwarf rice 'Tan-ginbozu' assays. The GA-like activity in the apical part of the shoot greatly decreased before cessation of growth and shoot tip abscission. In the basal part of the shoot the marked reduction of GA-like substances occurred well before shoot tip abscission and even before shoot elongation had ceased. Low GA-like activity in the shoot may be a prerequisite for apical growth cessation and for the development of lateral flower buds.
Isolation and properties of filamentous viruslike particles associated with little cherry disease in Prunus avium
Authors: Ragetli H. W. J. , Elder M. , Schroeder B. K.
Published: April 2011

Filamentous viruslike particles (VLP) associated with little cherry disease were purified directly from leaves of naturally infected field-grown and graft-inoculated, greenhouse-grown sweet cherry trees. A procedure was developed which effectively released the VLP from the phloem elements and simultaneously protected them against the denaturing and interfering agents known to become increasingly more abundant in the leaves as the season progresses. Milk was selected as the extraction medium because of its excellent protection against tannins and polyphenol oxydase and mucoid action. Milk extracts were clarified by filtration after addition of 20% (NH4)2SO4. VLP were isolated by differential centrifugation and further purified by polyethylene glycol precipitation. Electron microscopy of negatively stained preparations revealed very flexuous particles with a characteristically open, electron-transparent outer helix with pitch 4.25 nm and a prominent opaque central core. Particles had a constant width of 10.6 nm, a dominant length around 1.5 μm, and possibly a second major length category around 1.8 μm. Purified particles were very stable. They had an isoelectric point of about 4.25, degraded at 80–85 °C, fragmented at room temperature in 2% sodium dodecyl sulfate, and when denatured in urea were vulnerable to proteinase K. Levels of VLP in situ were always very low. Purified preparations from good source material contained not more than 30 μg VLP/mL.
Beech–maple coexistence and seedling growth rates at Mont Saint Hilaire, Quebec
Authors: Cypher Jean , Boucher Douglas H.
Published: April 2011

We tested the hypothesis that coexistence of forest tree species is promoted by canopy-dependent seedling growth, such that each tree species grows faster under adults of a different species. The study was carried out in the forest of Mont Saint Hilaire, P.Q., using seedlings of American beech (Fagus grandifolia) and sugar maple (Acer saccharum). The main hypothesis was confirmed, while an auxiliary hypothesis for coexistence involving differential longevity and light gap growth was not confirmed.
Late Glacial fossil leaves of Thuja occidentalis from Manitoulin Island, Ontario
Authors: Warner Barry G.
Published: April 2011

A leafy twig fragment of Thuja occidentalis L. was isolated from sediments dating about 10 000 years before present (B.P.) from Manitoulin Island, Ont. This is the earliest known record of Thuja leaves in postglacial deposits in eastern North America. Thuja may have arrived in Ontario in association with boreal spruce forests, but was a component of early pine forests.
Effect of naphthalene and aqueous crude oil extracts on the green flagellate Chlamydomonas angulosa. V. Heterotrophic responses
Authors: Hellebust J. A. , Soto C. , Hutchinson T. C.
Published: April 2011

Chlamydomonas angulosa shows a relatively weak capacity for heterotrophic growth on acetate in the dark. The cell doubling time on acetate in the dark is about 62 h as compared with about 17 h for growth in the absence of acetate under optimal light conditions. The cell's capacity for acetate uptake and its isocitrate lyase activity are also relatively low. No [14C]glucose is taken up by the cells, in agreement with the inability of C. angulosa to grow on glucose in the dark or of glucose to stimulate growth under light-limiting conditions. The Km and Vmax for acetate uptake for cells cultured on 12 h light: 12 h dark cycle, at the end of a 12-h dark period, are 0.05 mM and 1.3 fmol cell−1 min−1, respectively. The uptake capacity increases strongly upon dark incubation, while the presence of light during short uptake experiments enhances the uptake rate. There is only a moderate 2.5 times increase in isocitrate lyase activity upon incubation of light-grown cells in the dark with acetate.Cells incubated in 100% naphthalene-saturated media undergo a rapid and complete loss of acetate uptake capacity. Media, 50% saturated with naphthalene or 100% saturated with aqueous crude oil extracts, cause an initial stimulation of acetate uptake. Media, 50% saturated with aqueous crude oil extracts cause a much longer (at least 7 days) stimulation of acetate uptake capacity. Similarly, 50% saturated-naphthalene media cause an increase in isocitrate lyase activity on a per cell basis over control cells. While 50% naphthalene-saturated media permit almost no cell division in closed acetate-containing cultures in the dark, very dramatic increases in cell size occur over long time periods. Moderate concentrations of crude oil components dissolved in algal culture media, thus, permit significant rates of acetate uptake and assimilation but inhibit cell division. It is possible that the observed stimulation of acetate uptake by moderate concentrations of crude oil components is due to the following reasons: (i) hydrocarbon-induced permeabilization of the cell membrane and (ii) an increased availability of energy from photosynthetic light reactions owing to decreased CO2 photoassimilation.
Typification of Oxytropis monticola
Authors: Elisens W. J. , Packer J. G.
Published: April 2011

The authors agree with the choice of lectotype for Oxytropis monticola Gray made by Barneby in 1952 and present reasons for its retention.
The effects of propagule size on germination and seedling growth in Mirabilis hirsuta
Authors: Weis I. Michael
Published: April 2011

Mirabilis hirsuta, a fugitive prairie plant species, occurs only on disturbances (mounds) resulting from the foraging activity of badgers on the Cayler Prairie Preserve in northwestern Iowa, U.S.A. Seedling survivorship and later competitive success are predicated upon the root's rapid extension to and occupation of a moisture-retentive layer of buried vegetation which forms the base of these disturbances. Seed size, which varies from <2 to >6 mg, is a predictor of the likelihood of establishment success through effects upon germination and seedling vigor. Regressions indicated that germination increased by 10.2% per milligram increase in seed weight, leaf area of 30-day-old seedlings increased by 47.8 mm2/mg seed weight, and dry weight biomass of these seedlings increased 40.2 mg/mg seed weight. Germination also occurred more rapidly with heavier seeds. Differences in seedling growth with increases in seed size are largely due to the capital provided by initial food reserves. The instantaneous rate of increase in seedling biomass is nearly identical for seeds of all different weights. Absolute growth rates of seedlings are thus proportional to seed size, at least through the establishment phase. These results are of demographic importance because droughts frequently begin in early summer on this prairie.