bluuebunny/crossref_metadata_2025 huggingface dataset:
TIME-LAPSE STUDIES OF CONJUGATION IN COSMARIUM BOTRYTIS: II. PSEUDOCONJUGATION AND AN ANISOGAMOUS MATING BEHAVIOR INVOLVING CHEMOTAXIS
Authors: Brandham P. E.
Published: August 2008

Techniques were devised for the continuous observation of the 24-hour process of cell pairing and gamete fusion in the morphologically isogamous heterothallic desmid Cosmarium botrytis by the use of time-lapse ciné-photomicrography. Several stages of early conjugation are described and their duration measured. Many pairings are temporary and the cells dissociate after a few hours. This phenomenon is termed pseudoconjugation. Dissociation is frequently caused by the nuclear or cell division of one partner. By the use of morphological variants to determine the mating type of individual cells observed in a mixture of two mating types, an anisogamous behavior during pairing was noted. In any particular cross between two compatible clones, cells of one clone become relatively immobile or passive during conjugation while those of the other clone are attracted towards them, probably by chemotaxis. This anisogamous behavior is not rigidly linked with mating type since some plus clones are either passive or chemo-tactically active, depending upon which minus clone they are crossed with. An interim explanation of the mechanism is given.NoteThe term “anisogamous” is usually defined as a difference in size or morphology between compatible gametes. In this paper the definition is extended to cover differences in the mating behavior of gametes that are otherwise identical.
LIGHT AND TEMPERATURE EFFECTS ON GROWTH AND SPOROPHORE FORMATION OF LENZITES TRABEA
Authors: Madhosingh C.
Published: August 2008

Growth, pigmentation, and sporophore formation in Lenzites trabea, a polypore fungus, are shown to be affected by differences in light and temperature. Growth occurred under all conditions provided, being greater on liquid substrate than on agar and with maximum mycelium production in continuous red light at 25 °C. Sporophores, however, were formed only under certain continuous fluorescent and red radiations on liquid substrate; and on agar at 15 °C, 20 °C, and 25 °C in darkness broken by occasional brief exposures to low intensity daylight. The growth form under the red radiation and in darkness at 25 °C was similar. The form of fructification varied from poroid resupinate at 15 °C, to somewhat raised structures with larger pores at 20 °C, to an assemblage of discrete upright bodies with lacerated surface at 25 °C. Yellow-brown pigmentation was consistently associated with the fruiting areas in contrast with the predominantly fawn-yellow pigments of the vegetative mycelium. The significance of these results in comparative morphological studies is discussed.
TAXONOMY OF PLANTAGO L. IN NORTH AMERICA: SECTIONS HOLOPSYLLIUM PILGER, PALAEOPSYLLIUM PILGER, AND LAMPROSANTHA DECNE.
Authors: Bassett I. J.
Published: August 2008

The taxonomy, chromosome numbers, distribution, and notes on phytogeography of the one introduced and the six native North American Plantago species in sections Holopsyllium Pilger, Palaeopsyllium Pilger, and Lamprosantha Decne. are presented. Although there has been considerable confusion among the species Plantago eriopoda Torr., P. tweedyi Gray, and P. canescens Adams, this investigation demonstrates that they can be readily separated and that each has a distinctive geographical distribution. Plantago macrocarpa Cham. & Schlecht., P. cordata Lam., P. eriopoda Torr., P. tweedyi Gray, P. sparsiflora Michx., and P. media L. were found to have 24 somatic chromosomes and P. canescens Adams, 12.
EARLY DEVELOPMENT OF WOUND-INITIATED DISCOLORATION IN POPULUS TREMULOIDES MICHX.
Authors: Sucoff Edward , Ratsch Hilman , Hook Donal D.
Published: August 2008

In aspen, wounds exposing the xylem to the atmosphere result in pigment production around the wound. Experiments were conducted to help clarify the early origins of this wound-initiated discoloration. Browning began within 7 days after wounding of tissues and spread vertically. The early pigments are probably phenolic compounds produced in the xylem parenchyma from stored lipids. Production of early pigments involves stepwise degeneration of the cell nucleus and cytoplasm. High concentrations of antimicrobial agents applied to fresh wounds increased the rate of pigmentation. Phloem girdling had no effect on pigment formation. Xylem did not discolor if killed without exposure to the atmosphere. These early pigments may be related to the dark pigments found in most aspen trees.
EFFECT OF LIGHT ON GEMMAE FORMATION: IN MYCENA CITRICOLOR
Authors: Rodrigues Jr. C. J. , Arny D. C.
Published: August 2008

Maximum production of gemmae and yellow pigment by Mycena citricolor occurred under a glass filter which transmitted near ultraviolet light (310–400 mμ) and infrared. Within the limits of test conditions involving four rather broad areas of the spectrum, gemmae formation decreased as wavelength of light increased. Optimum light intensity was between 20 and 160 ft-c. At 740 ft-c the optimum daily exposure time was 6 hours. Infected leaves of Coffee arabicz in the light produced lesions of limited size and having numerous gemmae, but, in the dark, lesion size was indeterminate and no gemmae were formed.
TAXONOMY OF INTERGENERIC HYBRIDS OF THE TRIBE TRITICEAE FROM NORTH AMERICA
Authors: Bowden Wray M.
Published: August 2008

Six hybrid genera of the tribe TRITICEAE are recognized from North America:[Formula: see text]Binomials and parentages are given for different combinations of species of the parental genera.Nomenclatural proposals include × Agrositanion Bowden; × Elysitanion Bowden; × Sitordeum Bowden; × Agroelymus dorei Bowden; × Agrohordeum macounii (Vasey) Lepage nm. valencianum Bowden; × Elyhordeum dutillyanum (Lepage) Bowden nm. dutillyanum and nm. littorale (Hodgson & Mitchell) Bowden; × Elyhordeum schaackianum (Bowden) Bowden; × Elyhordeum piperi (Bowden) Bowden; × Elyhordeum dakotense (Bowden) Bowden; × Elyhordeum triploideum (Bowden) Bowden; × Elyhordeum stebbinsianum (Bowden) Bowden; × Elyhordeum berkeleyanum (Bowden) Bowden; × Elyhordeum montanense, (Scribn. in Beal) Bowden; × Agrositanion saundersii (Vasey) Bowden; × Agrositanion saxicola (Scribn. & Smith) Bowden; × Elysitanion hansenii (Scribn.) Bowden; × Elysitanion aristatum (Merr.) Bowden; and × Sitordeum californicum Bowden.
A CANKER AND FOLIAGE DISEASE OF YELLOW BIRCH: I.’ DESCRIPTION OF THE CAUSAL FUNGUS, DIAPORTHE ALLEGHANIENSIS SP. NOV., AND THE SYMPTOMS ON THE HOST
Authors: Arnold Ruth Horner
Published: August 2008

Diaporthe alleghaniensis R. Horner Arnold, sp. nov., is described and illustrated in both the ascigerous and conidial (Phomopsis) states, and the cultural characters are given. This is the first species of Diaporthe described on the host Betula alleghaniensis Britt. It is distinguished morphologically from known species of Diaporthe by the narrow cylindrical ascus with truncate apex and by the narrow cylindrical-ellipsoid ascospores with variable position of the single septum. It is a facultative parasite of yellow birch (B. alleghaniensis) on which it causes an annual bark canker and foliage disease. The symptoms of the disease are described and illustrated.
GROWTH RETARDANTS IN RELATION TO THE GERMINATION OF SEEDS: I. A PARADOXICAL CONCENTRATION EFFECT OF N,N-DIMETHYLAMINO-SUCCINAMIC ACID ON THE GERMINATION OF KALE SEEDS AFFECTED WITH COUMARIN
Authors: Knypl J. S.
Published: August 2008

As the concentration of N,N-dimethylaminosuccinamic acid (DMASA) increases, the germination of kale seeds (Brassica oleracea L. var. acephala) treated with 100 mg of coumarin per liter is initially reduced and then increased. A curve of germination versus concentration of DMASA is parabola-like with a minimum at 10−3 − 5 × 10−3 M. Kinetin at 10−4 M and gibberellic acid at 10−4 M reduce and reverse the inhibition of germination caused by coumarin and the growth retardant. On the other hand, DMASA at 5 × 10−3 M, in spite of its slight inhibitory activity, reduces the toxic effect of kinetin applied in the supra-optimal concentration of 5 × 10−4 M. Indole-3-acetic acid increases the inhibitory effects of coumarin and DMASA.In the germinating seed of kale, DMASA possibly acts as the antagonist of gibberellin biosynthesis; coumarin possibly blocks an unknown metabolic pathway, controlled by kinetin.The paradoxical concentration effect of DMASA remains unexplained.
REPRODUCTIVE POTENTIALS OF RACES 15B AND 56 OF WHEAT STEM RUST
Authors: Katsuya K. , Green G. J.
Published: August 2008

Variations in the prevalence of races 56 and 15B-1 (Can.) of wheat stem rust (Puccinia graminis Pers. f. sp. tritici Erikss. and Henn.) have occurred that cannot be explained by changes in the wheat varieties grown in Western Canada. The reasons for the changes in prevalence were investigated by comparing in growth cabinets the reproductive potentials or aggressiveness of the two races and the factors that might influence them. When a mixture of urediospores of the two races was used to inoculate three susceptible varieties for successive uredial generations, race 56 predominated at 25 and 20 °C, and race 15B-1 (Can.) predominated at 15 °C. Experimentation showed that the urediospores of race 56 were more infective than those of 15B-1 (Can.) and that the incubation period of race 56 was shorter than that of race 15B-1 (Can.). Pustules of race 56 grew faster than those of race 15B-1 (Can.) during early stages of development but those of 15B-1 (Can.) ultimately became larger than those of race 56. Race 56 produced more urediospores per pustule than race 15B-1 (Can.) on the susceptible varieties Little Club, Red Bobs, and Marquis at 15 and 20 °C. Infection density markedly affected competitive abilities. Race 56 tended to predominate in light infections but race 15B-1 (Can.) tended to predominate in heavy infections. Pustule size decreased as infection density increased. The possible significance of these findings under field conditions is discussed. It seems likely that the rise of race 15B-1 (Can.) to predominance in 1950 resulted not only from the selection pressure of the widely grown varieties that were resistant to race 56 and susceptible to 15B-1 (Can.) but from the lower temperatures that prevailed and favored 15B-1 (Can.) over 56. The rise to predominance of race 56 from 1956 to 1961 may have resulted from the greater aggressiveness of that race under the moderate or warm conditions that prevailed.
FACTORS AFFECTING THE GERMINATION OF SPORES OF HYPOXYLON PRUINATUM
Authors: Hubbes Martin , d'Astous Raymond
Published: August 2008

The optimum temperature for germination of ascospores of Hypoxylon pruinatum was 32 °C. and for conidia was 25 °C. Ascospores germinated best at pH 6.1. Both conidia and ascospore germination was inhibited on both unwounded and freshly wounded aspen bark. Inhibition was greatest on freshly wounded bark. Ascospore germination was 1.9% after 96 h on 2% malt agar containing 660 p.p.m. pyrocatechol, while complete inhibition occurred at 330 p.p.m. of the chemical in distilled water. Experiments suggest that the 48-h delay in spore germination was not due to the direct action of contaminating microorganisms.
CELL BIOLOGICAL ASPECTS OF HOST–PARASITE RELATIONS OF OBLIGATE FUNGAL PARASITES
Authors: Shaw Michael
Published: August 2008

Obligate parasitism is defined, and the principles involved in host–parasite interactions are briefly described. In the absence of host tissue, the germination and development of rust uredospores stops with the formation of infection structures. Interaction with the host results in further development of the parasite. It has been shown that in rust-infected tissue there are increases in respiration rate, in the activity of the pentose phosphate pathway, and in the concentrations of many constituents, including RNA and auxin. Such studies have usually been conducted at relatively late stages in disease development, but there is evidence to indicate that critical interactions between host and parasite occur very shortly after inoculation. Valuable insight has recently come from electron microscope and other cell-biological studies in the early stages of the establishment of rust infections. In particular, quantitative cytophotometry has demonstrated an apparent decrease in histones and an increase in RNA in the mesophyll nuclei of rust-infected wheat leaves 48 h after inoculation. Studies on the effect of actinomycin D on the development of flax rust also point to the rapidity with which host–parasite interactions occur. This antibiotic (2.5 mg/l) does not inhibit uredospore germination. It does inhibit the development of rust infections on the host, but only if the treatment is given before 5 or 6 h after inoculation. Treatment after this stage is not effective.Attention is drawn to the possible importance of the apparent absence of nucleoli in uredospore nuclei and to the possibility that uredospore germination and the differentiation of infection structures may occur without the formation of new ribosomes. It is also suggested that successful establishment of obligate fungal parasites or their hosts may involve the derepression of host DNA and the synthesis of new proteins.
VIRUS–HOST INTERACTIONS, WITH EMPHASIS ON CERTAIN CYTOPATHIC PHENOMENA
Authors: Ragetli H. W. J.
Published: August 2008

The apparent role played by each participant in virus–plant interactions, as suggested by symptom expression, is discussed. To explain the markedly different reactions of identical hosts to closely related virus strains, it is proposed on the basis of present concepts regarding protein synthesis and RNA-virus replication, that the viral genome, insofar as it does not code for coat protein and for enzyme(s) required for replication of viral ribonucleic acid (RNA), may be "translated" into protein acting as the true cytopathic agent.Information on the nature of certain viral-cytopathogenic effects in hypersensitive and susceptible hosts, mainly as revealed by electron microscopy, is presented. The dramatic and fatal intracellular disorganization shown by hypersensitive hosts and suggestive of cytolytic processes invited a search for the presence and possible role of organelles containing hydrolytic enzymes (lysosomes). The in vitro detection of particle-bound acid phosphatase in different types of organelles, confirmed by electron microscopy, may explain at least some aspect of the observed cellular degeneration.
TWO NEW GENERA OF THE SPHAEROPSIDALES AND THEIR RELATIONSHIPS WITH DIACHORELLA, STRASSERIA, AND PLAGIORHABDUS
Authors: Sutton B. C.
Published: August 2008

Two new form-genera of the Fungi Imperfecti, Sphaeropsidales are described. Idiocercus n. gen. is characterized by punctiform, unilocular, pycnidia, annellophores and hyaline, aseptate conidia with an elongated basal frill, and contains two species: I. pirozynskii n. sp. (type species) and I. macarangae (T. S. Ramakrishnan) n. comb. Bellulicauda n. gen. is based on a single species, B. dialii (Syd.) n. comb., and features lacunose stromata, annellophores, and pale brown, aseptate conidia with an elongated basal frill. Idiocercus and Bellulicauda are compared and contrasted with Diachorella, Plagiorhabdus, and Strasseria, genera which are shown to produce appendaged phialospores. Plagiorhabdus is tentatively reduced to synonymy with Strasseria.
PHOTOSYNTHESIS IN ALGAE: III DISTRIBUTION OF SOLUBLE CARBOHYDRATES AND DIMETHYL-β-PROPIOTHETIN IN MARINE UNICELLULAR CHLOROPHYCEAE AND PRASINOPHYCEAE
Authors: Craigie J. S. , McLachlan J. , Ackman R. G. , Tocher C. S.
Published: August 2008

The 80% alcohol-soluble carbohydrates accumulated by 23 species of green marine phytoplankton were examined after [Formula: see text] of photosynthesis in NaH14CO3. The presence of dimethyl-β-propiothetin (DMPT) and H2S was also noted.The major radioactive products in the Chlorophyceae were sucrose (five isolates), glycerol (three isolates), and mannitol (two isolates). Mannitol and sucrose were never found in the same extract, although glycerol and sucrose were found together in two organisms. DMPT occurred in Chlorococcum sp., and H2S appeared only in one Chlamydomonas sp.All 13 organisms assigned to the Prasinophyceae produced 14C-mannitol, and all except Pyramimonas sp. contained DMPT. H2S was observed in one strain of Tetraselmis sp. Sucrose and glycerol were not found in this class.
ICE NUCLEATION AND PROPAGATION IN SPRUCE NEEDLES
Authors: Salt R. W. , Kaku Shosuke
Published: August 2008

Needles of Colorado blue spruce, Picea pungens Engelm., have a freezing curve with a single rebound when their water supply is adequate and a double rebound when it is deficient. Nucleation takes place in the stele, probably in the xylem, in all needles, whether fresh, watered, or dried, and regardless of season. When two rebounds occur the first is always small, representing freezing of a small mass of water, restricted to the stele; the second is much larger and represents freezing of the bulky mesophyll, predominantly. The second rebound is caused by impeded propagation of ice and not by a second nucleation.The barrier impeding ice propagation and giving rise to two separate rebounds is considered to be the endodermis, which acts as a moisture valve or regulator. When water supply is insufficient the endodermis stops transferring water, becomes somewhat dehydrated, and no longer permits the rapid ice penetration that results in a single rebound. However, endodermal dehydration is only partial; ice growth is slow, but when penetration is effected, the mesophyll freezes.The presence or absence of a moisture film lining the intercellular spaces of the mesophyll does not directly affect the number of rebounds. When a film is present, extracellular freezing of the mesophyll is likely; when absent, freezing of the mesophyll is intracellular, more specifically intrawall, with ice accreting interiorly on the wall. Condensation of a freezable film is shown to be impossible. A descriptive terminology relating ice location to details of cell structure is desirable.Since spruce needles supercool only to about −10 °C, they freeze and thaw frequently during the winter in southern Canada, normally without injury.
EJECTION AND DISSEMINATION OF ASCOSPORES OF HYPOXYLON PRUINATUM
Authors: Froyd J. D. , French D. W.
Published: August 2008

The duration of ejection of ascospores of Hypoxylon pruinatum was dependent on the moisture condition of perithecial stromata, which in turn was affected by relative humidity and air temperature. Times of peak spore collection were usually correlated with times of high relative humidity and low air temperature, but when stromata were kept moist, peak spore collections occurred on a 12-h cycle regardless of relative humidity and air temperature, presumably because of overcrowding of perithecia with spores. Felling aspen bearing Hypoxylon cankers did not significantly reduce the numbers of spores liberated from these cankers until after 23 months. Eradicating cankers from an isolated aspen stand over a several year period did not reduce the number of new infections in that stand because cankers overlooked in the surveys continued to liberate spores, and probably because spores were brought in by wind from outside the stand. The pattern of ascospore movement in a deciduous forest was traced from a known source and the significance of this movement in relation to long distance dissemination is discussed.
PHOTOSYNTHESIS AND METABOLISM IN MARINE ALGAE: VII. PRODUCTS OF PHOTOSYNTHESIS IN FRONDS OF FUCUS VESICULOSUS AND THEIR USE IN RESPIRATION
Authors: Bidwell R. G. S.
Published: August 2008

Samples of Fucus vesiculcsus fronds were permitted to assimilate 14CO2 for 5 h and were then maintained in alternating periods of light and darkness for 3 days. Samples were collected at intervals, and the radioactivity of various simple and complex compounds was measured. The major product of photosynthesis was mannitol; relatively small amounts of 14C entered other compounds. From its behavior, it appears that mannitol is the major substrate of respiration in these plants; there may be secondary substrates among the complex polysaccharides. The complex polysaccharides are not formed directly from mannitol in light, but from some common precursors, or else from a small isolated pool of mannitol which is separated from the main cellular supplies. In darkness, the complex polysaccharides appear to be derived from stored mannitol. One of the more active metabolites, judged from its behavior, is a component of the residue left after dilute acid and sodium carbonate extraction. This component undergoes turnover, i.e. breakdown and resynthesis from newly-acquired photosynthate in the light, and is formed from stored photosynthate in the darkness.
VIRULENCE OF UREDIAL AND AECIAL ISOLATES OF PUCCINIA CORONATA CORDA F.SP. AVENAE IDENTIFIED IN CANADA FROM 1952 TO 1966
Authors: Fleischmann George
Published: August 2008

Isolates of Puccinia coronata f.sp. avenae collected during a 15-year period were tested for virulence on the crown rust differential oat varieties. The proportion of cultures virulent on Landhafer increased relative to others during this period, and was related to the release in the United States of commercial varieties that contained this type of resistance. These varieties served to reduce the proportion of races avirulent on Landhafer in the crown rust population that reached Canada.The occurrence and subsequent increase in frequency of isolates virulent on Victoria was correlated with the release of the oat varieties Rodney and Garry which possess part of the crown rust resistance of Victoria. The increased proportion of cultures that attacked Ukraine also paralleled the release of these two commercial varieties. This suggests that Ukraine either contains the Victoria Pc-11 gene for crown rust resistance that was transferred to Rodney and Garry, or that it contains another gene in common with these varieties.Races of crown rust that are differentially virulent on the varieties Landhafer and Santa Fe have recently been found in Canada. One culture was virulent on the variety Bondvic but not on Trispernia. No increase in race 264 of crown rust, which attacks all the differential sources of resistance except Saia, has been observed since it was first identified in Canada in 1957.Presentation of the virulence of crown rust isolates for individual types of resistance was found to express the results of race surveys in terms which were more meaningful to the oat breeding program. This form of analysis also produced valuable information on the possible relationships of genes for resistance in different oat varieties not readily obtainable from conventional information on the occurrence and distribution of physiologic races of crown rust.
THE EFFECTS OF INDOLEACETIC ACID AND 2,4-DICHLOROPHENOXYACETIC ACID ON THE UPTAKE AND METABOLISM OF 14C-GLUCOSE AND ON THE INCORPORATION OF 14C-LABELLED AMINO ACIDS INTO PROTEIN IN PEA ROOT TIPS
Authors: Kim W. K. , Bidwell R. G. S.
Published: August 2008

The effect of indoleacetic acid and 2,4-dichlorophenoxyacetic acid on the uptake and metabolism of 14C-labelled glucose and amino acids by excised pea root tips was studied. The intention was to determine whether the observed reduction of root growth by growth hormones was caused by interference in the uptake or in the metabolism of compounds by roots. The results indicate that the main effect of auxins on sugar metabolism in root tips is not on uptake, but on the subsequent metabolism of glucose. Auxins also had several specific rather than general effects on the synthesis of proteins. The production of certain amino acids from glucose was prevented, and the entry of others into protein was affected. This indicates that effects of auxin on protein metabolism were specific, and not necessarily merely consequences of decreased rates of growth and metabolism.
THE PRODUCTION OF A PHYTOTOXIC SUBSTANCE BY ALTERNARIA ZINNIAE
Authors: White G. A. , Starratt A. N.
Published: August 2008

A new phytotoxic compound, zinniol, C15H22O4, was isolated from cultures of the pathogenic fungus Alternaria zinniae. The toxin causes severe shrivelling of plant stems, browning of leaf veins, and chlorosis of surrounding leaf tissue. Zinniol inhibits seed germination and shows weak activity against fungi and bacteria.
COCCOMYCES HETEROPHYLLAE N. SP., A HYPODERMATACEOUS FUNGUS FROM THE PERIDERM OF WESTERN HEMLOCK
Authors: Funk A.
Published: August 2008

A new species of Coccomyces is described. The life cycle and cultural characteristics are presented. The fungus is associated with various bark diseases of western hemlock (Tsuga heterophylla) in the Coastal forest of British Columbia and Washington State. Some evidence of weak parasitism was found in natural infections; artificial inoculations with the fungus were negative.
SPORES AND POLLEN FROM THE LOWER CRETACEOUS OF SASKATCHEWAN, CANADA: PART I. SPORITES
Authors: Steeves Margaret W. , Wilkins Lois R.
Published: August 2008

Dispersed spores from a core through Lower Cretaceous rocks near Saskatoon, Saskatchewan, are described and compared with spores from elsewhere in Western Canada and Europe. Consideration is given also to the problems of dispersed-spore nomenclature as they are raised by these specimens.
Lomasomes in wheat leaves infected by Puccinia graminis and P. recondita
Authors: Ehrlich Mary A. , Schafer John F. , Ehrlich Howard G.
Published: August 2008

Boundary formations (lomasomes) have been observed between the plasmalemma and wall of mesophyll cells in Puccinia graminis and P. recondita infected wheat plants. They were present in host cells from both resistant- and susceptible-type infection centers, and were especially frequent and massive in plants grown at low (65–70 °F) temperatures. They appeared to occur in response to the presence of the pathogen, but did not seem to be associated with either host resistance or susceptibility. The dark-staining masses present in the lomasomes were often dense and extremely irregular in shape, but some of the dark material occasionally appeared vesicular or tubular. The suggestion is made that the lomasomes observed in the present investigation may be associated with infection-induced alterations in the mesophyll cell wall.
Effects of ionizing radiation on nucleic acids during embryonic development—metabolism during embryogeny and at embryonic tissue level
Authors: Chang Chong W.
Published: August 2008

Observation was made of effects of X-irradiation on DNA and RNA metabolism by means of rates of 32P incorporation into the nucleic acids during barley embryogeny.Levels of disturbances in 32P incorporation rates into DNA caused by X-rays are correlated inversely with the periods of postirradiation and proportionally related to tissue heterogeneity at the time of X-irradiation with the exception of the oldest embryos. Changes in 32P labelling of RNA induced by X-rays during barley embryonic development, however, are independent of the postirradiation periods and differences in the tissue heterogeneity. The levels of differences due to X-rays in 32P incorporation rates into the DNA of the three different regions of a mature embryo reflect the degree of tissue heterogeneity within the embryos at the time of X-ray treatment. Disturbances in the rates of 32P incorporation into DNA are greatest in the root tissue and least in the scutellar region; the shoot part is rated between the levels of the two tissue regions. In contrast, responses of 32P labelling rates of RNA to X-rays in the three different parts of a mature embryo are found to be independent of the tissue heterogeneity at the time of X-ray treatment and the postirradiation period during embryogeny.
In vitro germination and pollen tube growth of maize (Zea mays) pollen. II. Pollen source, calcium, and boron interactions
Authors: Pfahler P. L.
Published: August 2008

Pollen grains from six single cross hybrids (Wf9 × H55, Wf9 × H50, H49 × H55, H49 × H50, Ky49 × Ky27, and K64 × K55) of Zea mays L. were cultured on an artificial medium containing 15% sucrose and 0.6% bacto-agar 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). The effect of Ca and B on germination percentage was found to be dependent on the genetic source of the pollen. At the 0.00% levels of Ca and B, the germination percentage of the hybrids ranged from 26.6% for Ky49 × Ky27 to 58.1% for K64 × K55. With either Ky49 × Ky27 or K64 × K55 pollen, the addition of Ca and B to the medium resulted in a lower germination percentage whereas the addition of Ca and B increased the germination percentage of the other hybrids. The addition of B in the absence of Ca sharply reduced the germination percentage in all hybrids while in the presence of Ca, the effect of B varied with the hybrid involved. For pollen tube length, highly significant interactions between hybrids and levels of Ca and B were found. However, maximum pollen tube lengths were obtained for all hybrids with both Ca and B in the medium. The addition of B in the absence of Ca reduced the pollen tube length of all hybrids whereas the addition of B in the presence of Ca increased pollen tube length. In general, the addition of both Ca and B increased the rate of pollen tube growth especially in the period 2 to 3 hours after inoculation.
Growth of isolated Phycomyces sporangiophores on nutrient media and simple sugars
Authors: Gruen Hans E.
Published: August 2008

Growth of isolated Phycomyces blakesleeanus sporangiophores was not promoted relative to growth on water either by a synthetic medium with two concentrations of dextrose or by concentrated and dilute potato dextrose solutions. A range of sucrose and dextrose concentrations also failed to promote growth. On the contrary, the more concentrated nutrient media and the pure sugar solutions at 0.08 M and higher reduced the final sporangiophore length measured after 64 h. The inhibition on dextrose was directly proportional to concentration up to about 0.7 M and increased more sharply at higher concentration, becoming complete at close to 1 M. At 0.9 M the incidence of branching was greatly increased. Sucrose caused almost the same inhibition as dextrose up to 0.3 M. On complete nutrient media, but not on water, considerable regeneration of mycelium occurred at the sporangiophore base, and the amount regenerated was greater on potato than on synthetic media. Sporangiophore growth was not influenced by the regenerated mycelium. Differences between the submerged regenerated mycelium and surface mycelium are pointed out. Growth of isolated sporangiophores was not affected by pH between 3 and 7.6, but pH 2 caused limited inhibition. The evidence suggests that a factor limiting the growth of the deficient isolated sporangiophores is normally supplied by the mycelium but is not a nutrient or growth factor present in media which support growth of mycelium with sporangiophores.
Accumulation of hypoxanthine in potato leaves and its effect on spore germination in Phytophthora infestans
Authors: Clark M. C. , Page O. T.
Published: August 2008

The accumulation of hypoxanthine (6-hydroxypurine) in blighted potato leaves and its effect on spore germination in the late blight organism, Phytophthora infestans, were investigated. Preliminary experiments on the translocation of this compound in whole plants and detached leaves were also conducted.Under in vitro and in vivo conditions, hypoxanthine had a pronounced stimulatory effect on the indirect germination of sporangia. Studies on the movement of this base indicate that it is freely translocated, but fails to be exported from detached leaves into aqueous solution. These observations, coupled with the finding that hypoxanthine readily accumulated in blighted leaves, suggest that this compound could be of importance in predisposing uninfected portions of the host to invasion by the pathogen.
The fine structure of Monoblepharella sp. zoospores
Authors: Fuller Melvin S. , Reichle Rudolf E.
Published: August 2008

Zoospores of Monoblepharella sp. a representative of the order Monoblepharidales, no members of which had ever been studied with the electron microscope, were fixed with glutaraldehyde, followed by OsO4, and their ultrastructure is described. The kinetosome, to which the flagellum is attached, has the appearance of a centriole in cross section. Radiating laterally from the kinetosome is a striated disc which is anchored in a pair of annular lamellae. Microtubules run forward in the cell from a ring in the striated disc. The nucleus is surrounded by a concentration of ribosomes, the latter being partially surrounded and traversed by membranous elements. The zoospores of this Monoblepharella sp. do not have a nuclear cap of the type found in the Blastocladiales. The nature and phylogenetic distribution of nuclear caps in the aquatic fungi is discussed. A highly organized tubular structure at the posterior end of the zoospores is described and its possible function as a photosensitive structure discussed. At encystment the flagellum is withdrawn and cross sections of the flagellum are shown within cysts.
Spectrophotometric identification of phytochrome in two species of Mnium
Authors: Giles K. L. , Maltzahn K. E. von
Published: August 2008

Phytochrome has been extracted and partially purified from two species of Mnium. The absorption values were found spectrophotometrically and compared to previously determined values in other species.
Microorganisms associated with heart rot in young grand fir
Authors: Maloy Otis C. , Robinson Vernon S.
Published: August 2008

Isolations from grand fir trees indicate a succession of organisms associated with decay in which bacteria invade the exposed heartwood first, imperfect fungi next, then basidiomycetes.
Spontaneous variability of single isolates of Phytophthora infestans. I. Cultural variation
Authors: Caten C. E. , Jinks J. L.
Published: August 2008

The variability in culture of mycelial isolates of Phytophthora infestans was studied by examining the variation among single zoospore, single sporangium, and single hyphal tip subcultures. Extensive variation in rate of growth and sporangium production on artificial medium was detected among the single zoospore progenies of three mass cultures. Differences in colony morphology and viability of zoospores were also apparent but were not studied in detail. Subcultures established by single sporangia or single hyphal tips were much more uniform than zoospore cultures, although significant differences in growth rate could still be detected. While, with continued culture, some of the single zoospore variants tended to revert to their parental type, others showed a remarkable degree of stability.Isolates established from single zoospores gave rise to as much variation in their asexual progenies as the original mass cultures. This persistence of variation was also observed with isolates whose derivation included two successive single zoospore propagations. Selection for high and low growth rate among the zoospore progeny of a single mass culture rapidly led to the production of populations of zoospore cultures with different mean growth rates. Such response to selection implies the existence of a genetic mechanism which allows the transmission of phenotypic characters from one asexual generation to the next.The origin of variation among single zoospore cultures is discussed with reference to five different asexual mechanisms of variation. It is suggested that variation is the result of cytoplasmic differences present in the original mass isolates, although the possibility of other mechanisms can not be completely dismissed. A review of the literature suggests that asexual variation associated with zoospore propagation is widespread in the genus Phytophthora.
Experiments on vegetative dissociation of the dikaryon and on lysis of hybrid sporidia of the cross Ustilago avenae × U. kolleri
Authors: Nielsen J.
Published: August 2008

Disintegration of the nucleus of Ustilago avenae at vegetative dissociation of the interspecific dikaryon U. avenae × U. kolleri, as well as lysis of the sporidia formed by hybrid spores of the same cross, are caused by suppressive interaction between a number of nuclear genes. Lysis can be partly prevented by subjecting the hybrid primary sporidia to temperatures between 25 °C and 40 °C. The higher the temperature the shorter the time required to induce subsequent continued growth at 20 °C. As lysis is confined to the haploid stage, it is not an effective barrier against production and propagation of hybrids between these smut species in nature, so that advantageous genes will continue to combine, disadvantageous ones will disappear.
Temperature-induced changes in the hyphal morphology of the psychrophile Sclerotinia borealis
Authors: Ward E. W. B.
Published: August 2008

Growth of the psychrophilic fungus, Sclerotinia borealis is arrested at, and above 20 °C. Such temperatures cause an immediate increase in diameter of the hyphae and loss of hyalinity. The peripheral hyphae of a colony subsequently shrivel but the older hyphae continue to thicken. Resumption of growth at the optimum temperature occurs from these older hyphae but otherwise it arises in a random manner, suggesting that the normal coordination between hyphae within the colony is destroyed.
Diaporthe lokoyae n. sp., the perfect state of Phomopsis lokoyae
Authors: Funk A.
Published: August 2008

A new species of Diaporthe, for which the name D. lokoyae Funk is proposed, is described on the host Douglas fir (Pseudotsuga menziesii (Mirb.) Franco) and in culture. This Diaporthe is shown to be the ascigerous state of Phomopsis lokoyae Hahn. An outbreak of dieback in Douglas fir associated with this Diaporthe is described and discussed; a single occurrence on western hemlock (Tsuga heterophylla (Raf.) Sarg.) is reported.
Some neutral constituents of the Rhodophyceae with special reference to the occurrence of the floridosides
Authors: Craigie J. S. , McLachlan J. , Tocher R. D.
Published: August 2008

Isofloridoside, in addition to floridoside, was demonstrated as a constituent of 16 species of the Bangiophycidae and Florideophycidae (Rhodophyceae). Photosynthetic experiments with Porphyra umbilicalis resulted in a very slow labelling of isofloridoside both in light and in darkness after photosynthesis in 14CO2. This observation supports the concept that the floridosides are not equivalent as metabolites.Trehalose was identified as a constituent of species of the Corallinaceae. A dideoxyinositol, D-(+)-14/25-cyclohexanetetrol, was isolated from Porphyridium sp., taurine from Polyides rotundus, and di-N-methyl taurine was obtained from Corallina officinalis.
A clarification of the generic limits of Trigonella and Medicago
Authors: Baum Bernard R.
Published: August 2008

The main steps in the history of delimitation of Medicago and Trigonella are given. The typical medicagos have been characterized by spirally coiled pods; the typical trigonellas, by cylindrical straight or curved pods. The cause of the long disagreement is due to the existence of species having flattened or compressed pods in both genera. Such species were considered by most botanists to be intermediate between Trigonella and Medicago. Some botanists included all these species in Medicago whereas others included them in Trigonella. Some proposed an intermediate genus, e.g. Pocockia, Melissitus. In 1873, Urban suggested the characters of the cotyledons as the only reliable criteria for delimitation between the two genera. New evidence based on floral characters supports Urban's generic concept. A possible parallel evolution of pod shape is assumed to have occurred in both genera.
Monacrosporium obtrulloides, a new hyphomycete capturing nematodes in constricting rings
Authors: Castaner David
Published: August 2008

A new hyphomycete capable of capturing nematodes in constricting rings is described. Monacrosporium obtrulloides Castaner has obtrulloid-fusiform conidia, 39–46 × 10–18 μ. A key to the fungi having constricting rings is included.
Some observations on zoosporogenesis in the female strain of Oedogonium cardiacum
Authors: Retallack Elizabeth Trerice , Maltzahn K. E. Von
Published: August 2008

Developmental cytological events in zoosporogenesis in Oedogonium have been studied in material stained with dilute solutions of acridine orange. Induction leads to isolation of successive protoplasts within the filament. Profound intracellular changes leading to zoospore formation are described and are considered to be the result of cellular isolation. Events during zoosporogenesis are briefly compared to those in oogenesis.
Some new species and distribution records of Rhizopogon in North America
Authors: Harrison Kenneth A. , Smith Alexander H.
Published: August 2008

The following 12 new species and two varieties of Rhizopogon are described from collections made around Nelson, British Columbia, and Santa Fe, New Mexico: R.amoenus Harrison and Smith, R.armeniacus Harrison and Smith, R. canadensis Harrison and Smith, R. cinnamomeus Harrison and Smith, R. columbianus Harrison and Smith, R. inversus Harrison and Smith, R. pachydermus Harrison and Smith, R. pinyonensis Harrison and Smith var. pinyonensis, R. pinyonensis var. sublutescens Harrison and Smith, R. pinyonensis var. albidus Harrison and Smith, R. praestans Harrison and Smith, R. singularis Harrison and Smith, R. tephrogleba Harrison and Smith, and R. vestitus Harrison and Smith. Additional information is presented on four recently described species, and the ranges of 29 species are extended. It has been found that, when rainfall conditions are favorable, a distinctive and characteristic Rhizopogon flora occurs under pinyon pines in the pinyon pine – juniper forests of the arid regions of the south west.
Nitrogen metabolism of Picea glauca. II. Diurnal changes of free amino acids, amides, and guanidino compounds in roots, buds, and leaves during the onset of dormancy of white spruce saplings
Authors: Durzan D. J.
Published: August 2008

In late August during the onset of dormancy in spruce, seasonal levels of soluble nitrogen, rich in arginine, were high. On a fresh weight basis, diurnal levels of total soluble nitrogen and most component amino acids in roots, buds, and leaves showed maxima, one at sunrise and another in the afternoon or near sunset.Arginine and glutamine in the different plant parts contributed 44 to 83% to the alcohol-soluble nitrogen. In buds and leaves, percentage of arginine remained high and decreased slightly at midday, whereas in roots a continual drop occurred. In all organs examined, changes in glutamine reflected the double maxima of total soluble nitrogen and were greatest in roots.On a fresh weight basis, most amino acids accumulated at sunrise and near sunset; however a few especially in leaves, increased at midday, e.g. glutamic and aspartic acid, lysine, γ-aminobutyric acid, and serine.Comparison of levels of free guanidino compounds in different organs showed remarkable out-of-phase patterns. Levels of these compounds are known from 14C-arginine studies to be closely related to the metabolism of arginine.
Métabolisme intracellulaire et extracellulaire de l'acide 3-indolylacétique dans les cultures aseptiques ou non aseptiques de pointes de racine du Pisum sativum
Authors: Collet G. F.
Published: August 2008

Studies on indoleacetic acid (IAA) metabolism with root tips of 3-day-old pea seedlings were carried out by thin-layer chromatography and 14C-labelled auxin of high specific activity at 10−6 M. After 16-h incubation, five metabolites of IAA could be recognized in the tissues and two in solution; one metabolite was identified as o-formamidoacetophenone from its chromatographic Rf and ultraviolet absorption spectrum. Under sterile conditions the rate of breakdown of IAA is higher in the medium than under nonsterile conditions (even after removal of the tissues). We noted, too, a decrease of the action of IAA on the growth. The decreased activity of solution under nonsterile conditions is believed to be due to the production of oxidase inhibition by microorganisms.
Sporeling development in the genus Exormotheca. 1. Exormotheca ceylonensis
Authors: Udar Ram , Srivastava S. C.
Published: August 2008

The sporeling development in E. ceylonensis has been described. The germ tube emerges through the distal face of the spore. The plate formation is of two types: the Stephensoniella type and the Asterella type. The germ rhizoid formation is of the Stephensoniella type.
New or otherwise interesting lichens from Darjeeling District, India
Authors: Awasthi Dharani Dhar , Agarwal Manjoo Rani
Published: August 2008

The paper deals with eight taxa of lichens from the district of Darjeeling, Eastern Himalaya, India. Of the taxa described, Tomasellia himalayensis, Phlyctella indica, Placopsis himalayensis, Bombyliospora laevigata, and Rinodina conradi var. megaspora are new to science; Tomasellia cinchonarum and Haematomma leprarioides are reported for the first time from the Indian subcontinent; and Haematomma wattii endemic in the Eastern Himalaya is critically examined.
The ecology of terricolous lichens of the Northern Conifer – Hardwood forests of central Eastern Canada
Authors: Lambert J. D. H. , Maycock P. F.
Published: August 2008

A quantitative analysis of the terricolous (ground) lichens in the Northern Conifer – Hardwood forests of central Canada is presented. Seventy-one forest stands were sampled to determine the composition of the tree and lichen strata. Tree composition was expressed in terms of a series of importance values determined from measures of frequency, density, and dominance on a relative basis, with the importance values for all trees in a stand totalling 300. A statistical analysis of lichen distribution showed that while lichens reacted in a similar manner to moisture conditions as the trees they were more commonly found in stands on dry sites. An ordination of stands indicated that optimum environmental conditions for lichen growth were found in dry young conifer stands of low absolute dominance with fairly open canopies, with slowly decomposing ground litter of decidedly acidic reaction.The increase of deciduous tree species in the mesic segments of the moisture gradient produced environmental conditions unsuitable for most of the lichen species recorded. The reduced occurrence of lichens in such sites was interpreted as being related to the lack of suitable substrates, reduction in light intensity at ground level, increased litter, and a more rapid turnover of organic matter.
A new species of Olpidium parasitic on cucumber roots
Authors: Barr D. J. S.
Published: August 2008

Olpidium cucurbitacearum sp. n., from roots of Cucumis sativus L. var. Windermoor Wonder, is described. The fungus is distinguished from other Olpidium spp. by its zoospore and resting spore morphology and its restriction to cucurbitaceous hosts, and from species of Pleotrachelus Zopf by the typical occurrence of a single exit tube per sporangium.
A pythium root rot of muskmelon
Authors: McKeen C. D. , Thorpe H. J.
Published: August 2008

Pythium ultimum was readily isolated from the necrotic roots of young and mature muskmelon plants growing in soil in which root rot had been severe. Muskmelons planted in steamed soils inoculated with P. ultimum developed necrotic roots and aboveground symptoms closely similar to those produced in naturally infested field soil. The fungus was considerably more pathogenic at low than at high soil temperatures. All of seven commercial varieties of muskmelon commonly grown in southern Ontario were moderately to highly susceptible to P. ultimum. Experimental data support the conclusion that P. ultimum probably plays an important role in the "sudden wilt" disease of mature muskmelon plants.