bluuebunny/crossref_metadata_2025 huggingface dataset:
Apical dominance in the rhizome of Agropyron repens. Evidence of competition for carbohydrate as a factor in the mechanism of inhibition
Authors: McIntyre Gordon I.
Published: September 2008

When plants of Agropyron repens L. Beauv. are grown at a high nitrogen level (210 p.p.m. N) apical dominance in the rhizome is sufficiently reduced to permit the continued growth of the lateral buds. If, however, the rhizome is isolated from the parent shoot the dominance of the apex is markedly increased and lateral bud growth is strongly inhibited.Experiments with these isolated, high-nitrogen rhizomes showed that apical dominance could be significantly reduced either by increasing the length of the rhizome or by retarding the growth of the rhizome apex by exposing it to light. The growth potential of the lateral buds declined rapidly as the duration of their attachment to the rhizome apex was increased. This effect was associated with the translocation of carbohydrate to the rhizome apex and could be overcome by providing the isolated buds with a 2% sucrose solution. When buds were isolated from the rhizome apex before their growth potential was exhausted a marked increase in their carbohydrate content was apparent after 48 h. This increase was associated with their resumption of growth. Buds still attached to the apex could be released from inhibition by supplying sucrose solutions to the cut end of the rhizome.The results suggest that, under the experimental conditions, apical dominance was due primarily to competition for a limited carbohydrate supply.
Régulateurs de croissance et stabilité du RNA de transfert
Authors: Briquet M. V. , Leblus R. G. , Wiaux A. L.
Published: September 2008

not available
The effect of temperature on stomatal aperture in different species
Authors: Hofstra G. , Hesketh J. D.
Published: September 2008

Stomatal apertures were measured at midday on sunny days on leaves of a number of different species growing at day temperature ranging from 15 to 36 °C. In most of the species the apertures increased with increasing air temperatures up to 36 °C. Two cool climate species, pea and broad bean, had the widest apertures at about 27 to 30 °C, and the apertures decreased slightly at higher temperatures. Stomata do not appear to close at midday in leaves of most species at air temperatures of 36 °C or lower provided that the leaves are not under water stress.
Genes for pathogenicity in Cochliobolus heterostrophus
Authors: Nelson R. R. , Kline D. M.
Published: September 2008

The pathogenicity of 291 ascospore isolates, obtained from four different crosses between isolates of Cochliobolus heterostrophus (Helminthosporium maydis) to nine differential gramineous species, was evaluated in 37 differential segregations. A minimum of 13 different genes for pathogenicity were identified. Segregation ratios and comparisons of responses of paired differential species indicated that pathogenicity to four host species is controlled by five different genes and pathogenicity to four species is conditioned by five different sets of two genes each. All of the pathogenic capacities are inherited independently. The studies illustrate the genetic complexity for pathogenicity in C. heterostrophus.
Xylaria polymorpha. I. Cytology of a form with small stromata from Minnesota
Authors: Rogers Jack D.
Published: September 2008

The ascus cytology of a form of Xylaria polymorpha with small stromata was examined. The chromosome number apparently is n = 8. Before ascospore formation the asci are 16-nucleate. Eight uninucleate ascospores are then delimited. The fate of the eight nuclei not incorporated into ascospores is unknown.
On the occurrence of root thorns on a Central American palm
Authors: McArthur I. C. S. , Steeves T. A.
Published: September 2008

The palm Cryosophila guagara Allen bears three types of adventitious roots on the stems of young plants, prop roots, trunk roots, and crown roots. The latter two are modified into thorns; but crown roots are lacking in older plants. Crown roots arise endogenously near the apex of the stem and grow vertically downward in the stem tissues, emerging near the attachment of an enveloping leaf sheath. The root then changes its direction of growth at the site of leaf attachment, grows vertically upward to the top of the sheath, and ultimately gives rise to a pendulous, branched thorn. Trunk roots or spines arise as laterals from the bases of crown roots embedded in the tissues of the stem. The conversion of a root apex to a thorn involved the cessation of meristematic activity, the acropetal extension of tissue differentiation with an associated attenuation of the conical root apex, and the extensive development of cortical and stelar sclerenchyma. The root cap does not contribute to the thorn.
Pycnidium production by Botryodiplodia theobromae. II. Development of the pycnidium and fine structure of the maturing pycnospore
Authors: Ekundayo J. A. , Haskins R. H.
Published: September 2008

The pycnidium of Botryodiplodia theobromae Pat. originates from a primordium where growing vegetative hyphae interweave to form a loose network and not from a single hyphal cell as do those of many pycnidia-forming fungi. The primordium develops by further branching of the hyphae of the network. These branches interweave to form the structure which becomes the pycnidium.Fine structure studies of mature pycnospores revealed the presence of a secondary spore wall and a septum continuous with secondary wall not present in immature spores.
The translocation of photosynthetically assimilated 14C in corn
Authors: Hofstra G. , Nelson C. D.
Published: September 2008

A detailed study was made of translocation of photosynthetically assimilated 14C in 3- to 6-week-old corn plants. Corn assimilated 14C via malate and aspartate, and incorporated most of the 14C into sucrose, the only translocation compound. Lowering the temperature from 26° to 8 °C delayed the incorporation of 14C into sucrose, but had no effect on the distribution of 14C among the intermediates. Recent 14C assimilate was translocated very rapidly from the fed area, the amount remaining in the fed area decreasing logarithmically with time. The translocate moved down the vascular bundle it entered in the fed area, with no detectable lateral movement. The logarithmic profile in the leaf blade appeared to be the result of a temporary accumulation of the labelled pulse in the separate vascular bundles. This accumulation of sucrose in the veins could be eliminated by cutting out the fed area. Between 80 and 90% of the assimilated 14C was translocated from the fed area of the leaf in 24 hours with 50% moved out in the first 30 minutes. Both the rate of translocation and the total amount moved out of the fed area increased as the temperature was changed over the range 7 to 26 °C. Each leaf of young corn plants both imported assimilates from and exported assimilates to all other parts of the plant.
Ethyl acetate produced by Ceratocystis paradoxa and C. adiposum and its role in the inhibition of the germination of sugarcane buds
Authors: Kuo Tsong-Teh , Chien Mei-Mei , Li Hsien-Wen
Published: September 2008

A phytotoxic substance, identified as ethyl acetate by gas chromatography and physical properties, was isolated from the sugarcane tissue infected by Ceratocystis paradoxa and C. adiposum. Ethyl acetate in the diseased tissue could reach 1% by volume and was sufficient to inhibit the germination of sugarcane buds. The saturated vapor of ethyl acetate could kill seed cane buds after 1 hour exposure. In solution the lethal concentration of ethyl acetate was 1:100.In sugarcane medium, ethyl acetate could be detected after 24-hour incubation. More ethyl acetate was produced in young than in old sugarcane tissue. Both fungi grew better at 28 °C but produced more ethyl acetate at 20 °C, possibly explaining why pineapple disease was serious at the lower temperature. Ethyl acetate also could be isolated from soil containing diseased plant material.
Endocronartium, a new genus for autoecious pine stem rusts
Authors: Hiratsuka Y.
Published: September 2008

A new genus, Endocronartium, is erected to accommodate two caulicolous pine rust species, E. harknessii (J. P. Moore) comb. nov. and E. pini (Pers.) comb, nov., which have endocyclic life cycles.
Estimation of the CO2 free exchange pool size in wheat and corn leaves
Authors: Jolliffe P. A. , Tregunna E. B.
Published: September 2008

The quantity of carbon that exchanged freely with atmospheric CO2 was found to be very small or nonexistent in wheat and corn leaves.
Physiology of thick-walled spores of soil-borne plant pathogenic fungi. I. Respiration and germination of Helminthosporium sativum and H. pedicellatum spores
Authors: Mathre D. E.
Published: September 2008

Spores of Helminthosporium sativum germinated well at temperatures 30–39 °C while spores of H. pedicellatum germinated best at 39 °C with a lower percentage germination at lower or higher temperatures. Although germination of spores of both species occurred in the absence of an exogenous energy source, it was enhanced by various mono- and di-saccharides as well as by various plant extracts such as orange juice. The viability of these spores remained high (above 80%) for over 2 years when stored with a moisture content of 11% at 4 °C. The constituents of spores of both fungi were quite similar with lipids composing about 10% of the dry weight and carbohydrates 5.5–8.3%. Trehalose and mannitol were the most abundant carbohydrates. Spores of H. sativum had an endogenous respiration rate that was about 2–3 times greater than that of H. pedicellatum spores. The respiration rate of spores of both fungi could be stimulated by various energy sources, including sugars and some polyols. The greatest stimulator of respiration was buffered orange juice. As spores aged up to 25 months the respiration rates varied but to no significant extent. Respiration rate of spores of both fungi was not greatly affected by temperature but spores of H. pedicellatum that had been incubated for 15 h at either 30° or 39 °C did exhibit a greater oxygen uptake at 39 °C than at 30 °C. Use of various metabolic inhibitors indicated the presence of a functioning oxidative phosphorylation system in spores of both fungi. Lack of response of H. pedicellatum spores to high concentrations of dinitrophenol and azide may indicate that these inhibitors may have difficulty in penetrating into the cytoplasm.
Observations on bud formation and proliferations on cytokinin-treated root segments of Ophioglossum petiolatum
Authors: Peterson R. L.
Published: September 2008

Root segments of the fern Ophioglossum petiolatum with either an intact root apex or with the apex removed were treated with distilled water (control) or a range of concentrations of kinetin or benzyladenine in aqueous solution. Buds initiated on segments treated with distilled water or low concentrations of cytokinins had an apical meristem consisting of an apical cell with derivatives and a few leaf primordia located immediately beneath an air cavity formed by the lysis of cortical cells of the parent root. There was little cortical proliferation associated with the initiation of these buds. However, application of cytokinins at relatively high concentrations induced considerable proliferation of root tissue and a concomitant organization of numerous apical meristems in this tissue. Each induced meristem was structurally similar to those initiated on control root segments or those treated with low concentrations of cytokinins with the exception that leaf primordia were not as readily visible. Groups of tracheid-like cells were present in the callus-like outgrowths and, in root segments treated with 10.0 mg/l kinetin, large starch-filled parenchyma cells were evident at the periphery of the proliferations.
A thin-layer chromatographic study of the phenolics of Triticale and its parental species
Authors: Dedio W. , Kaltsikes P. J. , Larter E. N.
Published: September 2008

The phenolics of young leaves from a hexaploid and three octaploid Triticale lines, and their rye and wheat parents were investigated by two dimensional thin-layer chromatography. Matching coefficients, coefficients of similarity, biochemical distances, and correlation coefficients were calculated to determine the degree of similarity of phenolics between the different groups. Chromatographic patterns and the calculated similarity measures showed a close relationship of phenolics between Triticale and its wheat parent. These patterns were even more closely related if the wheat parent was hexaploid. Two wheat varieties (Prelude and Kharkov) had identical chromatographic patterns while the variety Chinese Spring showed a reduced number of spots. The pattern of Stewart, a durum wheat variety, was intermediate between Chinese Spring and Prelude or Kharkov. Generally, the number of flavonoid compounds increased with the level of ploidy but did not increase proportionally with the number of genomes.
Fine structure of the growing point of the coenocytic alga, Caulerpa sertularioides
Authors: Mishra Arun K.
Published: September 2008

The coenocytic alga Caulerpa sertularioides (Gmelin) Howe was used for the study of the ultrastructure of cell wall and cytoplasm. After ultrasonic maceration and metal shadowing of the cell wall the microfibrils were observed to be random at the tip and parallel for each lamella of the subtip region and the mature portions of rhizome. The microfibrils in the two adjacent lamellae crossed each other at about right angles. The microfibrils of wall trabeculae were parallel to each other and to the long axis of the trabeculae. Fine structure studies of the algal cytoplasm were made using material fixed with glutaraldehyde and osmium tetroxide. The rhizome growing point was studied in detail. A gradient in the differentiation of cytoplasm was observed. The appearance varied from compact, homogeneous cytoplasm in the tip to a reticulate, vacuolate organization in the region farther back. Compartmentation in the cytoplasm was noted in the region immediately behind the compact, homogeneous cytoplasm of the tip region. Numerous smooth-walled vesicles were scattered throughout the growing point of the alga and were observed close to the plasmalemma near the cell wall. Microtubules with axial orientation were observed near the side walls of the alga. These also occurred in parallel orientation with respect to the microfibrils in the trabeculae at the growing points of the latter. The results were discussed with respect to the roles of microtubules and the cytoplasmic vesicles in the process of wall formation.
Carbohydrate and nitrogen fractions of the inner bark of loblolly pines under moisture stress
Authors: Hodges John D. , Lorio Jr. Peter L.
Published: September 2008

In comparison with controls, 40-year-old loblolly pines (Pinus taeda L.) subjected to drought showed a marked increase in reducing sugars, nonreducing sugars, and total carbohydrates; and an approximately equivalent decrease in starch. The increase in sugars apparently was primarily the result of a decrease in growth rate and not hydrolysis of starch. Changes in the inner bark of trees stressed by continuous flooding followed the same basic pattern except that the marked increase in sugars occurred later, after severe stress had been established; stress probably was due to root failure. Drought and flooding had no effect on accumulation of amino N. Initially, synthesis of insoluble (protein) N was depressed but later the trend was reversed.
Effect of 2-chloroethylphosphonic acid and gibberellic acid on survival of tall and dwarf peas grown in root rot soils
Authors: Benedict W. G. , Thomas D. des S.
Published: September 2008

Seeds of peas, Pisum sativum L. varieties Alaska and Early June, were soaked for 3 hours in 2.3 × 10−3 M 2-chloroethylphosphonic acid (CEPA) or 3 × 10−5 M gibberellic acid (GA3), sown in steamed or root rot soils, and grown to flowering stage at controlled soil temperatures with 14 hours per day of 32 000 lumens per square meter. CEPA delayed emergence and decreased survival in var. Alaska, but increased survival in var. Early June between 14 C and 18 C. GA3 decreased survival in both varieties. Early emergence was followed by increased wilting. CEPA showed antigibberellin activity, in most instances counteracting the adverse effects of GA3.
The influence of temperature on the exudation of nutrients from cotton seeds and on preemergence damping-off by Rhizoctonia solani
Authors: Hayman D. S.
Published: September 2008

Evidence is presented suggesting that increased seed exudation is a major factor contributing to increased preemergence damping-off of cotton seedlings by Rhizoctonia solani at low temperatures.About seven and three times as much total amino acids and sugars were exuded at 18 and 24 °C, respectively, as at 30 °C, by germinating cotton seeds of equivalent physiological age. Sixteen amino acids and five sugars were exuded. Seed exudation is not related to rate of germination or to respiration.Accumulation of seed exudate at low temperatures was related to increased pathogenesis in vitro and in soil. This appeared to be because R. solani competitively used this exudate to increase its inoculum potential near the germinating seed, thereby becoming more virulent on the susceptible juvenile tissues of the seedling.
The uptake of phenylalanine during imbibition by seeds of the garden pea, Pisum sativum
Authors: Paul K. B. , Nozzolillo Constance
Published: September 2008

The uptake of phenylalanine during imbibition by seeds of the garden pea (Pisum sativum, var. Alaska) was studied using 1-14C-L-phenylalanine. The distribution of the radioactivity within the seed was observed using a radioautographic procedure. The results indicate that phenylalanine, while presumably diffusing passively with water, nevertheless exhibited some independence of movement. This conclusion is based on (a) the decline in counts per milliliter of the imbibition medium, and (b) the low activity observed in the axis tissue, an area which becomes hydrated early in the imbibition process. Entry of phenylalanine into the seeds appears to be entirely through the micropyle, with rapid diffusion across the cavity occupied by the shoot–root axis and between the seed coat and cotyledon, followed by diffusion inwards through the cotyledon tissue.
A new hybrid between blue spruce and white spruce
Authors: Hanover James W. , Wilkinson Ronald C.
Published: September 2008

Controlled pollinations were made within and between blue spruce (Picea pungens Engelm.) and white spruce (Picea glauca (Moench) Voss) in 1967 and 1968. Interspecific hybrids were obtained and verified by comparative measurements of several traits. The cross was successful when either species was used as the female parent. Hybrid seed germinated more rapidly than that of either species and hybrid seedlings showed some heterosis for early growth. Also, hybrid seedlings had needles intermediate between, and significantly different from, the parental seedlings. Growth form of the hybrid was quite variable compared with that of either species. Further evidence for the successful crossing of blue spruce and white spruce was provided by biochemical analyses of monoterpene compounds in the parents and progeny.
Histological studies of Melampsora lini resistance in flax
Authors: Littlefield Larry J. , Aronson Sandra J.
Published: September 2008

Histological comparisons were made of immune, intermediate, and susceptible reactions of Linum usitatissimum to Melampsora lini at intervals after inoculation. All reactions were quite similar for the first 36–48 h. Immunity was correlated with length and number of hyphae per infection site as well as the number of haustoria per infection site. Haustorial size was not related to host reaction. The number of collapsed host cells and the area of starch accumulation were useful for comparison of widely divergent, but not of similar reaction types. Tissue transplant studies showed that the mycelium was killed, rather than retarded in the immune reaction.
Effects of water potential on germination of lettuce, sunflower, and citrus seeds
Authors: Kaufmann Merrill R.
Published: September 2008

The effect of nearly constant water potential on germination of citrus, sunflower, and lettuce seeds was studied. Water potential equilibration was achieved by placing soil above a cellulose acetate membrane which was in contact with a solution of polyethylene glycol-6000. Selection of solute potentials in the solution resulted in controlled water potentials in the soil over a range of 0 to −14.9 bars for citrus and 0 to −8.0 bars for sunflower and lettuce. The water stress experienced by germinating seeds in this system is largely the result of a matric effect rather than a solute effect.Citrus seeds germinated at water potentials as low as −4.7 bars and lettuce at −4.1 bars, but sunflower germinated at −8.0 bars. Sunflower germinated as rapidly at −4.1 bars as lettuce at −2.3 bars, both reaching 50% germination at about 8 days. Citrus germinated much more slowly, requiring 26 days at 0 bars.
Meiotic prophase in Prunus avium cultivar Lambert
Authors: Whelan Ernest D. P. , Hornby C. A.
Published: September 2008

Meiotic prophase in the sweet cherry cultivar Lambert contains a diffuse stage. It is suggested that the meiotic sequence is pachynema–schizonema–diffuse–diplonema–diakinesis.
Haustoria-like branches in axenic cultures of Puccinia graminis f. sp. tritici
Authors: Williams P. G.
Published: September 2008

Hyphae of the wheat stem rust fungus form short, lateral projections under conditions of artificial culture that are unfavorable for saprophytic growth. It is suggested that the structures are homologous with the haustoria of intercellular rust mycelium.
Self-sterility in Streptotinia caulophylli
Authors: Elliott Mary E.
Published: September 2008

A hyphomycete with streptoform, Botrytis-like conidiophores has been isolated from Caulophyllum thalictroides (L.) Michx., Thalictrum polygamum Muhl., and Sanguinaria canadensis L. Under cultural conditions mass-conidial isolates from both Caulophyllum and Thalictrum produced apothecia but isolates from Sanguinaria did not. The isolates from Caulophyllum and Thalictrum are considered to be the imperfect state of Streptotinia caulophylli Elliott. Sexuality studies with single-ascospore cultures show that this species is hermaphroditic and self-sterile.
Isolation and maintenance of endoparasitic nematophagous Hyphomycetes
Authors: Barron G. L.
Published: September 2008

A technique has been developed using differential centrifugation which allows the isolation of endoparasitic nematophagous Hyphomycetes belonging to the genera Harposporium, Meria, Nematoctonus, and Verticillium. Both ingested and adhesive parasites have been isolated by this technique. The method eliminates most of the large-spored predaceous species which usually complicate the recovery of endoparasites. Methods for maintaining endoparasitic fungi in association with nematodes or in pure culture are described.
Notes on the genus Microthecium
Authors: Udagawa Shun-ichi , Cain Roy F.
Published: September 2008

The non-ostiolate character of the perithecia of Microthecium is used to separate it as a genus distinct from Melanospora which is ostiolate. Species and varieties accepted in Microthecium are M. zobelii Corda, the type, M. levitum sp. nov., M. epimyces, M. geoporae, M. hypomyces, M. compressum sp. nov., M. retisporum sp. nov., and M. retisporum var. inferior var. nov. The generic description is emended. A key to the species is presented. Six species previously included in Microthecium are excluded. Melanospora tulasnei sp. nov. is described.
Vessel element development in the earlywood of red oak (Quercus rubra)
Authors: Zasada John C. , Zahner Robert
Published: September 2008

Earlywood formation was observed in 60-year-old forest-grown red oak trees in southern Michigan. Extreme care in removing samples from the cambial region of the main stem at 1.4 m and 18 m, and from small branches at about 24 m, permitted the following conclusions. First vessel elements were initiated in the second or third xylem derivative radially removed from the previous year's latewood, possibly in overwintering derivatives, simultaneously throughout the bole and branches of the tree, some 2 weeks before bud enlargement. Vessel elements enlarged first in the tangential dimension (to about 200 μ.) within a few days after initiation of differentiation. Enlargement in the radial direction required up to 2 weeks to grow 300 μ, occurring as the entire xylem mother cell zone was displaced outward by cambial growth to either side—tangentially—of the vessel element. The duration of earlywood formation was about 10 weeks, while the duration of shoot elongation was less than 2 weeks. First earlywood vessels were fully mature about 5 weeks after initiation, coinciding with the unfolding of first leaves. All foliage was mature several weeks before complete maturation of later formed earlywood vessels. Detailed stem analysis and bark peeling studies revealed that stem sections clear of branching contained few lateral junctions between axial vessels. There were many such junctions where twigs joined larger limbs and where limbs joined the main stem; all such junctions were between adjacent vessels from the same limb.
The quality of short-wave radiation within plant canopies
Authors: Daynard T. B.
Published: September 2008

In this paper, a mathematical attempt is made to predict the effects of leaf area index, leaf angle, and leaf spectral properties on changes in the relative composition of short-wave radiant fluxes as they penetrate plant canopies. Results of this theoretical analysis indicate that a sizeable change in the quality of visible radiation will only occur if the canopy is sufficiently dense to intercept at least 98% of the incident flux one or more times. By contrast, a significant increase in the proportion of infrared radiation is predicted within plant communities, even those of a low effective leaf area index. For natural plant communities, the results would indicate a minimal change in the composition of penetrating radiation at solar noon and a maximal change at sunrise or sunset.The implications of these phenomena to plant morphogenesis and to radiation-measuring techniques are discussed.
Automated system for following stomatal behavior of plants in growth cabinets
Authors: Allaway W. G. , Mansfield T. A.
Published: September 2008

An automatic porometer recording from eight leaves is described. The apparatus has enabled experiments lasting several days to be performed, with porometer readings every half-hour from each leaf. The porometer cups apparently did not alter the behavior of stomata even after long attachment, and readings were closely correlated with measured stomatal apertures on the upper surface of amphistomatous leaves.
Presence of plasmodesmata in callus cultures of tobacco and carrot
Authors: Spencer D. F. , Kimmins W. C.
Published: September 2008

Cultures of crown-gall callus and normal callus isolated from Nicotiana tabacum cv. Samsun and carrot callus were examined by light and electron microscopy for plasmodesmata. Both methods indicated their presence in crown-gall callus of tobacco. While plasmodesmata were not found in normal callus of tobacco and carrot using light microscopy, they were demonstrated with the electron micro-scope. The implication of these observations as related to movement of plant viruses within cultured tissue is discussed.
Nuclear divisions in the vegetative hyphae of Rhizopus nigricans and Phycomyces blakesleeanus
Authors: Flanagan Patrick W.
Published: September 2008

The process of division in somatic nuclei of Rhizopus nigricans and Phycomyces blakesleeanus was studied with the aid of an acetoorcein stain - fixative technique. The nuclei in the vegetative hyphae of these fungi were found to divide by conventional mitosis. Chromosomes were counted and in Rhizopus nigricans, n = 16. In Phycomyces blakesleeanus, n = 14. Other proposed modes of nuclear division in the fungi are discussed in relation to these findings.
Uredospore development in Puccinia graminis
Authors: Ehrlich M. A. , Ehrlich H. G.
Published: September 2008

The present paper reports a number of electron microscope observations on the protoplasm and walls of developing spores which provide additional information on uredospore wall and spine development and on the fine structure of organelles, particularly of mitochondria and endoplasmic reticulum and of lipid bodies in developing spores. Micrographs of partially extracted uredospore walls and of chromium-shadowed extracted sections demonstrate the architecture of the wall as seen in cross and tangential section. Three distinct wall zones are clearly visible with the external wall layer forming the boundary of the germinal pore.
Ultrastructural studies of cold-dormant and germinating uredospores of Puccinia graminis var. tritici
Authors: Sussman Alfred S. , Lowry Robert J. , Durkee Thomas L. , Maheshwari Ramesh
Published: September 2008

Uredospores of Puccinia graminis var. tritici that have been subjected to temperatures below freezing are shown not to differ ultrastructurally from fresh uredospores, although a need for a heat-shock has been induced. Moreover, no ultrastructural differences have been observed between germinating uredospores of both types. Germination results in the formation of large numbers of vesicles and in the change in shape of mitochondria from ellipsoidal and spherical to elongate. A unique aspect of germinating uredospores is found in permanganate-fixed cells wherein electron-transparent patches appear, giving the cytoplasm a "foamy" appearance. The consequences of the suspension of cold-dormant uredospores in liquid medium without a prior heat-shock include irreversible failure to germinate and severe disruption of lipid inclusions and other cytoplasmic elements.
Inoculation of loblolly pine seedlings with Fomes annosus in the greenhouse
Authors: Kuhlman E. G.
Published: September 2008

A reliable method of inoculating loblolly pine seedlings with Fomes annosus under greenhouse conditions is described. Type of wound, wounding vs. nonwounding, and soil temperature influenced the number of pine seedlings killed. Inoculum weight and orientation of the inoculum block had less effect on mortality. No variation in virulence of eight isolates of the fungus was demonstrated. Seedling mortality occurred at soil temperatures from 10 to 30 °C, but the disease index was highest at 15–25 °C.
Forest microfungi. III. The heterogeneity of Pestalotia deNot. section sexloculatae Klebahn sensu Guba
Authors: Sutton B. C.
Published: September 2008

Pestalotia pezizoides deNot., P. valdiviana Speg., P. cornu-cervae (Brenckle) Guba, and P. corni Allesch., the four species comprising Pestalotia deNot. section sexloculatae sensu Guba are shown to represent three different genera. P. pezizoides is retained as the type and only accepted species of Pestalotia, the name P. valdiviana is considered a nomen dubium, P. cornu-cervae is maintained as the type and only species of Labridella Brenckle, and P. corni is referred to Seiridium Nees ex Fr. as S. corni (Allesch.) n. comb. (≡ Pestalotia corni Allesch.). The generic concepts of Monochaetia (Sacc.) Allesch. and Seiridium are expanded to include species with single apical branched appendages, thus necessitating nomenclatural changes including Monochaetia karstenii (Sacc. & Syd.) n. comb. (≡ Pestalotia karstenii Sacc. & Syd.), M. karstenii var. gallica (Stey.) n. comb. (≡ Pestalotiopsis gallica Stey.) and M. nattrassii (Stey.) n. comb. (≡ Pestalotiopsis nattrassii Stey.).
The sporulation of two isolates of Mycosphaerella citrullina on agar media
Authors: Curren Thomas
Published: September 2008

Two isolates of Mycosphaerella citrullina sporulated well under constant or intermittent illumination. Sporulation was poor in darkness. Both isolates produced abundant pycnidia on potato dextrose agar and on a peptone–dextrose–salts medium. Good production of perithecia occurred only on V-8 juice agar.
The anthocyanins of Dicentra (Fumariaceae)
Authors: Fahselt Dianne
Published: September 2008

The main anthocyanin pigments of the genus Dicentra have been characterized through the use of spectroscopy and chromatography. This combination of techniques, particularly suited to anthocyanins, has demonstrated that all are glycosides of cyanidin (3,5,7,3′,4′-pentahydroxyflavylium) and that none are acylated. The simplest, found in several species, is cyanidin-3-monoglucoside, while the most complex is cyanidin-3-rhamnoglucosido-7-xyloside. This triglycoside is present in only one species as well as in certain experimental interspecific hybrids, and this is its first reported occurrence in nature. A rapid method is described for identification of anthocyanin sugars using thin-layer chromatography.
Changes in cell size and number associated with the effects of light intensity and temperature on the leaf morphology of wheat
Authors: Friend D. J. C. , Pomeroy Marion E.
Published: September 2008

In a spring variety of wheat an increase in light intensity over the range 200 to 5000 ft-c reduced the length of the lamina by reducing both the number and length of epidermal cells. The optimal temperature for cell length was 30 °C or above, but the number of cell divisions along the lamina decreased over the range 20 to 30 °C so that lamina length was greatest at 25 °C.Similar results were obtained with a winter variety of wheat chosen to avoid complications caused by possible interference between leaf and inflorescence growth. Changes in the size of the mesophyll cells were generally similar to those in the epidermis. The thicker leaves formed at high light intensities also had thicker mesophyll cells.
Regeneration on Phycomyces sporangiophores. II. Regeneration on isolated segments from different positions along the sporangiophore axis
Authors: Ootaki Tamotsu , Gruen Hans E.
Published: September 2008

Apical, middle, and basal 5-mm segments from decapitated Phycomyces blakesleeanus sporangiophores cultured on plain agar blocks regenerated sporangiophores after wound closure. Hyphae formed very rarely. Maximum regeneration frequency decreased between apex and base from 100% to close to 70% in stages 1 and 3, and from 80% to 23% in stage 4. The regeneration speed declined along the axis. The frequency of two or more initials per segment decreased basipetally in stages 1 and 3, but not in stage 4. Most segments formed sporangiophores at the apical end but regeneration from the basal end alone increased towards the base in stages 1 and 3, and was found on up to 30% of the stage 4 segments without gradient along the axis. A few segments regenerated at both ends at all positions. Initials emerged laterally at the apical end of most top segments and from the wound closure wall on almost all others. The diameter of single sporangiophores on apical segments was larger and their maximum stage 1 length shorter than on the rest. Both were less on stage 4 than on 1 and 3. The final length on either stage 1 or 4 was the same at all positions but the former was more than twice as great as the latter. One-millimeter stage 1 segments regenerated very thin sporangiophores but polarity was much weaker than in 5-mm pieces.Almost 90% of stage 1 segments with whole apices and open basal ends continued growth without branching. Most of those which stopped regenerated near the tip. Stage 3 and 4 segments tied off basally continued growth without regenerating above the tie, but if the end was open the sporangia stuck to the agar because of turgor loss, elongation stopped, and regeneration occurred close to the sporangia at slower speed than on decapitated apical segments.Cytoplasmic extrusion and formation of exudation drops were studied, wound closure was followed on middle stage 1 segments, and preliminary observations were made on movement of cell contents during regeneration.
In vitro germination and pollen tube growth of maize (Zea mays) pollen. III. The effect of pollen genotype and pollen source vigor
Authors: Pfahler P. L.
Published: September 2008

Pollen grains from three inbreds (H49, H55, and H50) and two of their single cross hybrids (H49 × H55 and H49 × H50) were cultured on an artificial medium containing 15% sucrose and 0.6% bactoagar supplemented with all possible combinations of two levels (0.00 and 0.03%) of calcium nitrate (Ca) and two levels (0.00 and 0.01%) of boric acid (B). For all characteristics measured (germination percentage, germination with more than one pollen tube percentage, rupturing percentage, length and growth rate of the pollen tubes), significant differences between inbreds were obtained on most combinations of Ca and B. Since the inbreds were presumably homozygous and, as a result, each produced pollen grains of only one genotype, these differences in germination characteristics were apparently produced by the genetic differences between the inbreds. Therefore, the in vitro germination characteristics of pollen grains are associated with pollen genotype. The response of the hybrids could not be accurately predicted from the behavior of their inbred parents. In general, the hybrid mean was in the range between the means for the two inbred parents. However, the value of the mean for the hybrid relative to the values of the parental means depended on which hybrid combination was involved. The results indicated that the germination characteristics of pollen grains on various combinations of Ca and B are influenced in large part by pollen genotype but that the genetic expression is quite complex. Vigor of the pollen source per se was not a factor.
The Pezizales of Eastern India
Authors: Kar A. K. , Pal K. P.
Published: September 2008

Four operculate discomycetes belonging to the Pezizales have been collected and described from Eastern India (West Bengal). They are Saccobolus glaber (Persoon) Lambotte, Wynnea macrotis (Berk.) Berk., Pulvinula orichalcea (Cooke) Rifai, and Humaria orthotricha Sacc.
Aseptic synthesis of ectomycorrhizae on Pinus taeda by basidiospores of Thelephora terrestris
Authors: Marx Donald H. , Ross Eldon W.
Published: September 2008

Basidiospores of Thelephora terrestris introduced into root substrates of aseptic loblolly pine seedlings formed abundant ectomycorrhizae after 2½ months. Cultures isolated from the mycorrhizae were identical with the culture used to form the basidiocarp.
Epicuticular wax forms on leaf surfaces of Zizania aquatica
Authors: Hawthorn W. R. , Stewart J. M.
Published: September 2008

The epicuticular wax forms on the leaves of the three varieties of Zizania aquatica L. were determined from control plants in the field and greenhouse, and served as a reference for interpreting changes in the wax forms of plants grown under different experimental conditions. Short stubby wax rodlets first appeared 15 cm below the water's surface on the portion of the adaxial surface of young leaves which eventually became floating (leaf numbers 4 to 6). Wax rodlets and platelets were present on both surfaces of the aerial leaves (leaf numbers 7 to 12). The relationship between wax appearance and leaf numbers could be varied by manipulating the water level; for as long as water surrounded the permanently submersed leaves or the submerged portions of the floating leaves, wax production was inhibited. Growth under continuous light and constant temperature conditions indicated that factors other than the day–night cycle were responsible for wax ultrastructure.
Pollen germination of Larix sibirica (Siberian larch) in vitro
Authors: Ho Ronghui , Rouse Glenn E.
Published: September 2008

Mature pollen grains of Siberian larch were successfully germinated in vitro for the first time. Mature grains, containing two prothallial cells, a generative cell, and a tube cell, were incubated in stock solution B for periods up to 5 days. At the 2-day stage, the generative cell had divided into a stalk cell and body cell. In 5 days, the body nucleus had divided into two male nuclei contained within the body cell. Pollen germination was limited to elongation of the intine towards the distal pole, accompanied by a splitting of the exine, but without any suggestion of the formation of a pollen tube. This supports the suggestion of previous studies in vivo on other species of Larix pollen that a pollen tube does not form before the pollen grain reaches the nucellus of the ovule.
Apical dominance in long shoots of white pine (Pinus strobus)
Authors: Little C. H. A.
Published: September 2008

The roles of auxin and nutrition in determining the expression of dominance within a whorl of current shoots were investigated. It was demonstrated that the removal of shoots from a whorl induces compensatory growth in the remaining shoots. Treatments that block auxin movement (triiodobenzoic acid (TIBA), girdling) or decrease auxin production (defoliation, decapitation) also induce compensatory growth, at the same time inhibiting growth in the treated shoot. On the other hand, capping a decapitated and defoliated shoot with indoleacetic acid (IAA) in lanolin maintains diameter growth in the shoot stump and prevents the occurrence of compensatory growth. It is concluded that the shoots in a whorl compete for dominance by competing for a common supply of nutrients transported from the preceding internode. The quantity of nutrients diverted into a shoot, hence growth, is a function of the shoot's capacity to produce growth substances. Hormone synthesis, as well as shoot length, fascicle number, and number of buds in the current whorl are predetermined in the winter bud.The degree of dominance, expressed as the ratio of the sizes of the terminal and the longest lateral in the whorl, depends on the nutrient supply available during the period of winter bud development as well as during the period of shoot expansion.
Plasmalemmasomes in sporelings of the brown alga Petalonia debilis
Authors: Cole Kathleen , Lin Shu-Chang
Published: September 2008

Plasmalemmasomes were noted in 6-week-old sporeling cells of the brown alga Petalonia debilis (Scytosiphonales). These membranous bodies had formed in pockets between the plasmalemma and cell wall. They consisted of a complex series of vesicles, tubules, and flattened cisternae, each of which was bounded by a unit membrane similar to the plasmalemma. Continuity was observed between the plasma membrane and some membranous structures, as they seemed to be forming by the processes of invagination and evagination.
An instrument for rapid and precise point sampling of vegetation
Authors: Morrison R. G. , Yarranton G. A.
Published: September 2008

The design, construction, and operation of an instrument for point sampling of vegetation is described. Its use makes possible vertical or inclined sampling of the vegetation from the ground to the canopy; a crosswire is used to indicate the sample point.
New species of Chaetomium and Gymnoascus
Authors: Wener H. M. , Cain R. F.
Published: September 2008

Two new species, Chaetomium leproplocinum and Gymnoascus rhousiogongylinus, are described and illustrated from soil in the Parry Sound District, Ontario.
Cellular differentiation and peroxidase isozymes in cell culture of peanut cotyledons
Authors: Verma D. P. S. , Huystee R. B. van
Published: September 2008

A suspension culture obtained from peanut (Arachis hypogaea L.) cotyledons was passed through three standard sieves of 0.15, 0.5, and 2.0 mm and the subsequent four fractions were studied for morphological differences and molecular heterogeneity in peroxidase isozymes. Quantitative and qualitative differences occur in this enzyme between groups of cells of different sizes. The appearance of two new peroxidase isozymes is correlated with cellular differentiation as the cell mass enlarges from 0.5 to 4.0 mm in diameter.
Identification and morphology of the aecial state of Pucciniastrum sparsum in northwestern Canada
Authors: Hiratsuka Y.
Published: September 2008

From inoculation experiments and morphological examinations, the aecial state of Pucciniastrum sparsum (Wint.) E. Fisch. (= Thekopsora sparsa (Wint.) Magn.) has been identified for the first time in North America from specimens collected in the Northwest Territories and the Yukon Territory. Picea glauca (Moench) Voss, P. mariana (Mill.) BSP., and P. pungens Engelm. (from inoculation only) are reported as new hosts of this fungus. An expanded description of the spermogonia and aecia of the fungus is given.
Carbon dioxide transfer resistance as a factor in shade tolerance of tree seedlings
Authors: Wuenscher J. E. , Kozlowski T. T.
Published: September 2008

Net photosynthesis and transpiration rates of single leaves of Quercus velutina Lam., Q. macrocarpa Michx. var. olivaeformis, and Acer saccharum Marsh. were measured at light intensities of 0.03 to 0.24 cal cm−2 min−1 (400–700 mμ). Resistance to water vapor and carbon dioxide transfer were calculated. Net photosynthesis of the Quercus species was not light saturated until light intensity was increased sufficiently to induce complete stomatal opening, indicating possible limitation of CO2 uptake at low light intensities by high CO2 transfer resistance. Rates of light-saturated net photosynthesis of all three species were highly correlated with CO2 transfer resistance.
The antifungal factors in barley. V. Antifungal activity of the hordatines
Authors: Stoessl A. , Unwin C. H.
Published: September 2008

The hordatines, antifungal substances previously isolated from barley seedlings grown in the dark, are also produced under conditions which approximate those in the field. The compounds, and some of their derivatives, inhibit the spore germination of a number of fungi in concentrations as low as 10−5 M. Inhibition is reversed by the addition of some divalent cations; this observation supports the identity of the hordatines with the natural defense agents of barley which have been demonstrated in earlier work.
The effects of aflatoxin B1 on protein synthesis by cucumber cotyledon discs
Authors: Truelove B. , Davis D. E. , Thompson Olivia C.
Published: September 2008

The effects of aflatoxin on amino acid uptake and incorporation into protein by discs of cucumber cotyledon tissue showed that incubation for relatively short periods with low concentrations of aflatoxin reduced the amount of 14C-leucine absorbed without affecting incorporation into protein; increasing incubation time or increasing aflatoxin concentration inhibited the incorporation of absorbed leucine into protein. The effects of aflatoxin and actinomycin D on leucine absorption and incorporation were compared in a time course study.The data are discussed in relation to the possible mode of action of aflatoxin in plant tissues.
Vegetative development of the gametophyte of Bonnemaisonia hamifera from a filamentous state
Authors: Chen L. C-M. , Edelstein T. , McLachlan J.
Published: September 2008

Gametophytes of Bonnemaisonia hamifera Hariot developed vegetatively from sterile filamentous plants which resembled the tetrasporophyte of this species (i.e. the trailliella phase). Under the culture conditions used, light intensities exceeding 1000 lux prevented formation of gametophytes. Antheridia, identical with those of plants in nature, were produced after 6 months' incubation.
The life cycle of Ralfsia clavata and R. borneti
Authors: Edelstein T. , Chen L. C-M. , McLachlan J.
Published: September 2008

The life cycle of Ralfsia clavata (Harvey) Crouan and R. borneti Kuckuck has been completed in culture. In both organisms the sequence and morphology of the various stages were similar, and these two species are considered as a single entity. Zoospores from unilocular sporangia of the crustose stage in nature gave rise to two morphological forms: (1) crustose thalli with erect filaments, paraphyses, and unilocular sporangia; (2) branched, uniseriate filaments with discontinuous parenchymatous areas and unilocular sporangia. Petalonia-like, thalli, which produced embedded plurilocular sporangia characteristic of the genus Petalonia, were initiated from both the crustose and filamentous forms. Fusion was not observed, and swarmers from both uni- and pluri-locular sporangia gave rise to the crustose and filamentous forms. On the basis of these results, and other culture studies, these two species of Ralfsia are merely stages in the life cycle of species of Petalonia.