bluuebunny/crossref_metadata_2025 huggingface dataset:
Non-photosynthetic light requirement for the development of flowers in Chenopodium rubrum, a short-day plant
Authors: Sawhney Ramma , Cumming Bruce G.
Published: September 2008

Seedlings of Chenopodium rubrum do not develop flowers in continuous darkness even with high concentrations of sucrose in the medium. Irradiation of plants with 5 min of red and (or) far-red wavelengths on the 6th to 8th days of darkness leads to a high degree of flowering. This non-photosynthetic light effect on flowering can be duplicated by a gibberellic acid (GA3) and kinetic application. The lack of flowering in continuous darkness appears to be due to a low apical activity. Red and far-red irradiation (via the formation of a critical level of PFR) and the plant growth hormones may have promoted flowering of C. rubrum by stimulating apical activity. Thus, light may be required after induction of flowering, not only to provide photosynthetic energy substrates but also to create a favorable balance of growth hormones that are required to maintain optimal apical activity essential for flower development.
The temperature dependence of thallus nitrogenase activity in Peltigera canina
Authors: Maikawa E. , Kershaw K. A.
Published: September 2008

Comparative rates of nitrogen fixation in the lichen Peltigera canina from subarctic and temperate habitats have been examined using the acetylene reduction method. Maximum acetylene reduction at thallus saturation and with 20000 lx illumination takes place at 16 °C in subarctic material and at 21 °C in temperate material. This adaptation of nitrogenase activity to temperature in P. canina is discussed in relation to low levels of soil nitrogen in arctic systems.
The influence of soil water extract and thiamine on the growth of Cladophora glomerata
Authors: Moore Laurence F. , McLarty Duncan A.
Published: September 2008

Soil water extract (SWE) has been used for decades to supplement certain algal and fungal cultures, but its active components remain essentially unknown. Cladophora glomerata, an attached green alga which has become a problem in several of the Laurentian Great Lakes and elsewhere, is one species that grows well on synthetic media supplemented with SWE. Unialgal cultures were used to investigate the nature of the active components in SWE with the hope that insight of the nutritional requirements of this alga would be gained.Analysis of SWE showed that an organic heat-labile component was significant, and when thiamine was substituted for SWE, it was found to provide 80% of the stimulation induced by SWE. The presence of thiamine in two samples of SWE was verified, and concentrations of 3 and 10 μg/litre were determined using the Phycomyces bioassay. Subsequent investigations of the requirement of thiamine by C. glomerata demonstrated that 1 μg/litre, provided either by SWE or as the pure vitamin, stimulated satisfactory growth, while 10 μg/litre is the apparent optimum concentration.
Electron microscopy of African cereal streak diseased plants
Authors: Harder D. E.
Published: September 2008

The African cereal streak disease (ACS) was further characterized as to transmissibility and cytological changes produced in cells of affected plants. Virus-like particles were regularly associated with diseased plants grown under field conditions, but no similar particles could be found in diseased plants of wheat, triticale, rice, Harpachne schimperi, Chloris pycnothrix, or Eragrostis tenuifolia grown in a growth cabinet set on an 18-h–6-h light–dark cycle and a corresponding 24 °C–17.5 °C temperature cycle. The efficiency of continuous transmission by Toya catilina Fenn. under growth-cabinet conditions was low, at 5%, 3%, and 5% for females, males, and nymphs, respectively.Except for the absence of recognizable virus-like particles in infected plants grown in the growth cabinet, the symptoms and cytological features of diseased plants grown under growth-cabinet and field conditions were similar. The main cytological features of diseased plants were as follows. (1) A dense, fine ground substance which filled many of the phloem cells was developed. (2) Large numbers of inclusion bodies, which were of globular and hexagonal-elongated forms, were formed. These forms are probably related. Virus-like particles were occasionally associated with the inclusions in diseased field-grown plants (3) Non-specific changes, such as may be induced by various types of pathogens, or are associated with senescence, e.g. phloem cell necrosis, abnormal callose-like cell wall deposits, and degenerative changes in the chloroplasts, were observed.
Pollen and pollination in the genus Eupatorium (Compositae)
Authors: Sullivan Victoria I.
Published: September 2008

Pollen of 18 of the 19 species of Eupatorium (sensu stricto) was examined with the scanning electron microscope (SEM). The species studied included the three dog fennels with dissected leaves and 14 species with undissected leaves. All species had echinate tricolporate pollen. One dog fennel, E. capillifolium, was found to have reduced spines relative to the other species. This one had other anemophilous characters, such as a longer stigma and greater stigma exposure, lax inflorescence branches, and smaller floral heads, suggesting an anemophilous pollinating system. Eupatorium compositifolium, another dog fennel, showed characteristics indicative of anemophilous ancestry, such as a long, greatly exposed stigmatic surface and lax inflorescence, but it had showy flowers as well as autecological features conducive to entomophily. All other species had reduced stigma lengths and exposure, stiffly upright inflorescence, and showy heads, all features indicative of entomophily. The advantage of acropetal over basipetal development of the inflorescence for anemophily is discussed. The dog fennels have acropetal, indeterminate development and the undissected leaf species have basipetal, determinate development; the latter of which is the basic pattern of inflorescence development in the Compositae.
Photoperiodism and photosynthetic pathways
Authors: Evans L. T.
Published: September 2008

In a recent paper, Purohit and Tregunna (7) concluded that plants with low carbon dioxide compensation values are either short-day or day-neutral in their photoperiodic requirement for flowering. Although many plants with the C4 pathway of photosynthesis are short-day plants, there are also several Gramineae in which the C4 pathway of photosynthesis is known to be combined with a requirement for, or response to, long days for flowering, such as Paspalum dilatatum, Hyparrhenia hirta, Themeda australis, and Saccharum spontaneum. Consequently, response to short days for flowering is not a constant feature of the C4 pathway, and C4 plants could be selected for a long-day response in areas where this is advantageous.
The effect of lettuce seed extracts on lettuce seed germination
Authors: Speer Henry L. , Tupper Dorothy
Published: September 2008

Lettuce seeds (Lactuca sativa var. Grand Rapids) were found to contain inhibitory substances, one of which is probably abscisic acid. Extracts from seeds were characterized by gas–liquid chromatography, and peaks coincident with abscisic acid were found.The germination water surrounding seeds made secondarily dormant was subjected to gas–liquid chromatography and was also found to contain peaks coincident with abscisic acid. It was also determined that the inhibitory substances are localized in the embryo but not in the endosperm or seed coat.
Effect of D-amino acids on conidium size and numbers of pseudosepta per conidium in isolates of Bipolaris sorokiniana
Authors: Harding Howard
Published: September 2008

Isolates of Bipolaris sorokiniana grew to some extent on the D-isomers of 15 amino acids supplied as the sole nitrogen source. D-histidine did not support growth of any isolate. No conidia were produced by cultures grown on D-arginine. There was no consistent relationship between length of conidia produced by D- and L-isomers of the same amino acid. The trend was towards the production of shorter conidia on D-amino acids, although isolates varied considerably in their response. Conidia produced on D-phenylalanine were markedly shorter than those produced on the L-isomer, although isolates varied in the magnitude of response. A similar effect was recorded with aspartic acid as the nitrogen source but only in buffered medium. Conidia produced on D-ornithine were longer than those produced on L-ornithine, although this response was less-marked in buffered medium. Generally, the numbers of pseudosepta per conidium were higher in conidia produced on the L-isomer of individual amino acids. Although this increase in numbers usually paralleled the increased length of conidia, there was a large range in correlation coefficients between the two values over different isolate–substrate combinations.
Effect of polychlorinated biphenyl compounds on growth of Great Lakes phytoplankton
Authors: Glooschenko Valanne , Glooschenko Walter
Published: September 2008

Polychlorinated biphenyls (PCBs) have been used for a variety of industrial applications since 1929 and their presence is now widespread in aquatic and terrestrial ecosystems. In this study, three species of Great Lakes phytoplankton and one common soil alga exhibited growth inhibition when exposed to concentrations of PCB as low as 1 μg/litre while 50 μg/litre was toxic to all cultures. Photosynthesis, measured by Na214CO3 uptake was also depressed by PCB additions, but 14C uptake per cell was stimulated at times. Of the four PCB compounds tested, Aroclor 1016 appeared least toxic and Aroclor 1242 was the most toxic, while Aroclors 1221 and 1248 gave intermediate responses.Examination of cells by electron microscopy showed distortion of chloroplast lamellae and increased cytoplasmic vacuole formation in algal cultures treated with 50 μg/litre PCB. Gross cell morphology changes were also observed under the light microscope.Water quality criteria recommend that persistent organic chemicals which are toxic in concentrations of 5 μg/litre or less should not exceed environmental levels of more than 1/100th of this amount. Levels of PCBs in water from several areas of Lakes Erie and Ontario currently exceed these concentrations.
Studies on lichen-dominated systems. XII. The ecological significance of thallus color
Authors: Kershaw K. A.
Published: September 2008

Only minimal information is available from comparative studies on the temperatures that lichen thalli reach under field conditions, especially temperature levels attained by pale- and dark-colored thalli.A series of experiments in the laboratory, under controlled conditions, are described and show very large changes in thallus temperature during the drying-out of the lichen material, irrespective of the thallus color. These temperature changes were up to 20 °C under still-air conditions in the laboratory, but changes of 10 °C under field conditions were recorded. Temperature differences between dark and pale lichen thalli in still air were found to be 6–7 °C in laboratory experiments, falling to 2–3 °C under windy field conditions.The significance of these findings is discussed in relation to snow conditions and the contrasting ecology of Alectoria nitiditla and Cladina alpestris in northern Ontario. The relevance to their ecology of the supposed sensitivity of wet lichen thalli to high temperatures is also questioned.
Endogone spores in Australian sand dunes
Authors: Koske R. E.
Published: September 2008

Five types of spores of the endomycorrhizal fungus, Endogone, were abundant in the coastal sand dunes of New South Wales. Spores of Endogone have seldom been reported from marine dunes, and at least two of the spore types recovered from Australian dunes have not previously been reported from this continent. The density of spores in sand was greater in older, more stabilized dunes than in younger foredunes and mobile dunes.
Pyrimidine metabolism in seeds and seedlings of jack pine (Pinus banksiana)
Authors: Pitel J. , Durzan D. J.
Published: September 2008

Jack pine seedlings rapidly converted radioactive thymine-6-3H to dihydrothymine, β-ureidoisobutyric acid, and β-aminoisobutyric acid. Autoradiographs of hypocotyl cells showed radioactivity largely in the cytoplasm. A small percentage of radioactivity from thymine-2-14C was salvaged via uracil for the synthesis of RNA. DNA was not labelled significantly. The occurrence of a mechanism to utilize thymidine-methyl-3H for DNA synthesis was detected at low levels in germinating seedlings but was absent in seeds up to 16 h imbibition. Among pyrimidines tested thymidine was the most specific for the labelling of DNA and radioactivity was detected almost entirely over nuclei.The occurrence of an active pathway for the de novo synthesis of the pyrimidine portions of nucleic acids was demonstrated by the use of orotic acid-4-14C. Native DNA and all major types of RNA were labelled and radioactivity resided in pyrimidines. Synthesis of DNA involved the conversion of pyrimidine ribonucleotides to deoxyribonucleotides.
Raphidiopsis mediterranea in Canada
Authors: Gerrath J. F. , Nicholls K. H.
Published: September 2008

The rare blue-green alga Raphidiopsis mediterranea Skuja is reported for the first time from Canada. The alga was collected over a 3-year period from the Holland River in southern Ontario and was present in collections from June until September.
Factors affecting postharvest infection of stored cabbage tissue by Botrytis cinerea
Authors: Yoder O. C. , Whalen M. L.
Published: September 2008

Single-spore isolates of Botrytis cinerea from commercially stored cabbage exhibited a broad range of virulence. Spore germination and hyphal growth required an exogenous source of nutrients. The ability of either spores or mycelium to cause infection of stored cabbage tissue was also dependent upon exogenous nutrients. Nutrients required for infection could be supplied in the form of glucose, cabbage leaf extract, potato dextrose agar (PDA), or by a wound at the site of inoculation. The concentration of nutrients and (or) spores influenced the ability of B. cinerea to cause tissue decay whereas spore age and bacterial populations did not. Spores on the surface of cabbage leaves germinated within 4 to 8 h in nutrient solution; an additional 8 to 16 h in nutrient solution were required for successful infection. The optimum temperature for fungal growth and for infection was 20 to 25C. The optimum relative humidity for decay was above 97%; decay did not occur at relative humidities below 93%.
The genus Cristulariella
Authors: Redhead Scott A.
Published: September 2008

The generic description of Cristulariella is emended and the fungus C. depraedans is redescribed. Both C. depraedans and C. pyramidalis are characterized by multicellular propagules which are distinct from the phialides each produces in culture. Cristulariella is not a synonym of Myrioconium, but the combination M. depraedans (Cooke) von Arx, referring to the phialides, may be legitimate. Cristulariella depraedans is reported on Acer circinatum and Aruncus sylvester from British Columbia and on Acer pennsylvanicum, A. rubrum, A. saccharum, and A. spicatum from Ontario.
Modifications des relations quantitatives entre les acides aminés libres et les pigments photosynthétiques chez différents mutants chlorophylliens d'Orge et d’Arabidopsis
Authors: Bounias Michel
Published: September 2008

Photosynthetic pigments and free amino acids have been simultaneously determined in the leaves of barley and Arabidopsis, chlorophyll mutants and control plants, artificially grown under different physiological conditions. Several inverse-type relations (logarithmic, hyperbolic, or linear ones according to each case) have been determined between the concentrations of the photosynthetic pigments and those of some amino acids. The graphic plot of each of these relations is generally subdivided into two distinct curves, permitting the classification of biochemical effects due to mutations of different types and to physiological factors. The concentration of leucine undergoes large amplitude variations under dim light (400%) and, moreover, it presents specific relations with carotenoid pigments (β-carotene, lutein, violaxanthin, and neoxanthin).
Draba crassifolia, D. albertina, D. nemorosa, and D. stenoloba in Canada and Alaska
Authors: Mulligan Gerald A.
Published: September 2008

The cytotaxonomy of four species of Draba that are invariably confused with one another is discussed and a key is given. The species are D. crassifolia Graham (n = 20); D. albertina Greene (n = 12); D. nemorosa L. (n = 8); and D. stenoloba Ledebour (n = 20). Characteristics of sterile artificial first-generation hybrids between D. crassifolia, D. albertina, and D. stenoloba are presented and analyzed.
Some effects of urea and of soil moisture on solute translocation
Authors: Minshall Wm. Harold
Published: September 2008

In detopped plants, stump exudation resulting from root pressure provides a measure of the quantity of solutes and of water being transferred to the xylem. In dry soil the transfer of water to the xylem stops when the force required to remove the water from the soil is equal to the osmotic pull of the solutes in the xylem. In a sandy loam soil mixture, detopped tomato plants (Lycopersicon esculentum Mill.) treated with urea maintained stump exudation to a soil moisture content as low as 12.1% while water-control plants ceased exudation at 15.0% soil moisture. By maintaining the transfer of solutes to the xylem, the application of urea enhanced the ability of the detopped root system to remove water from the dry soil.By watering plants to pot capacity at different times before and after detopping, a series of soil moisture levels were obtained with detopped roots of tomato. In this clay loam soil mixture stump exudation started at 10% soil moisture (about −3.0 bars potential). With increasing moisture the rate of exudation increased rapidly to reach a maximum exceeding 5 ml per hour at soil moisture contents between 20 and 25% (about −0.05 bars potential). The rate then decreased gradually to 2.5 ml per hour as the soil moisture content increased from 25 to 45%. Starting at 10% soil moisture and continuing up to 25%, solute uptake increased proportionately with increasing moisture content, and at these dry and medium soil moisture levels, the supply of water to the root determined the quantity of solutes being translocated to the stump. The depletion of oxygen and accumulation of carbon dioxide in soils containing more than 25% moisture reduced the translocation of solutes in the plants.
Apical segmentation and leaf initiation in the tree fern Dicksonia squarrosa
Authors: Hébant-Mauri R.
Published: September 2008

From a precise study of the shoot apical region of Dicksonia squarrosa Swartz, the histogenic role of the apical cell is shown. Leaves are initiated at levels where the delineations of the segments remain identifiable without ambiguity. A delay in the division of certain pluripotential prismatic cells constitutes the first indication of a future leaf initiation. The sequence of events leading to the formation of a new leaf follows a fundamental pattern, around which variations may occur; this pattern could constitute a new feature for consideration in comparative morphology. No relation between leaf initiation and apical segmentation could be established. Comparison with some other ferns (e.g. Hydropterideae, Hymenophyllaceae, Schizaeaceae) suggests the possible existence of variable relationships between leaf initiation and apical segmentation in these plants.
Cell deformities in bark and sapwood caused by Rhytidiella moriformis and Keissleriella emergens infections in poplar
Authors: Zalasky Harry
Published: September 2008

The cambium of balsam poplar appeared to be stimulated by Rhytidiella moriformis and Keissleriella emergens infections of bark, colonized to the outer periphery of the phloem but not beyond. Instead of producing normal xylem in groups of four cells, it produced hyperplastic and hypoplastic deformed xylem, each group consisting of variable combinations of tracheids, vessel elements, and wood parenchyma. Deformities were accompanied by composite cell structures and rapid aging of thick-walled ray cells. Tracheids and vessel elements were branched, curvate, attenuate, and short. Vessel elements without perforations had more bordered pits arranged on all sides. Perforations, if present, were often lateral and not oriented for vertical transport of solutes. Morphogenetically, host tissues are believed to be chimeral, as evidenced by stunting, incomplete cell-plate formation, and hyperplasia and hypoplasia. Changes in structure of cells and tissues of the host were caused by both pathogens, but they occur over a larger surface area of the bark and sapwood on trees infected by R. moriformis in nature.
A seed trap for determining patterns of seed deposition in terrestrial plants
Authors: Werner P. A.
Published: September 2008

A seed trap for terrestrial plants having dry seeds or fruits is described which holds seeds upon contact and whose trapped seeds are protected to a high degree from loss due to invertebrate predation or wind action. The trap makes use of "Tanglefoot," a sticky non-drying material and is easily constructed, operated, and maintained at minimal cost. The traps are used to determine the pattern of seed deposition around a parent plant. The number of seeds deposited as a function of distance from a mature teasel plant (Dipsacus sylvestris Huds.) exhibit the negative exponential function log y = 2.74−1.69x (r = −0.9731).
Holoblastic conidiogenesis in Helminthosporium maydis
Authors: Brotzman H. G. , Calvert O. H. , Brown M. F. , White J. A.
Published: September 2008

Abundant conidiophores and conidia of Helminthosporium maydis were produced within 48 h on diseased corn leaf pieces. Observations of ultrastructure revealed that conidiogenesis in H. maydis is holoblastic; all layers of the conidiophore wall are involved in the initiation of conidia.
Wall fibrils and microtubules in normal and gibberellic-acid-induced growth of lettuce hypocotyl cells
Authors: Sawhney V. K. , Srivastava L. M.
Published: September 2008

The orientations of microtubules and wall fibrils in primary walls of epidermal and cortical cells of gibberellic-acid(GA3)-treated and untreated lettuce hypocotyls were studied during a 72-h growth period. In both treatments, the epidermal and some cortical cells have thick polylamellate walls in which lamellae with longitudinal orientation of fibrils alternate with those having transverse orientation of fibrils. The microtubules generally parallel the innermost wall fibrils, but the orientations of both these structures change during the 72-h period presumably in association with deposition of new wall material. In normal growth, there is considerable variability among individual cells with respect to orientation of these structures at any one time. When the cells are boosted to elongate several-fold by GA3, the variability is minimal and the cortical cells show preeminently a horizontal arrangement and the epidermal cells show a longitudinal arrangement of microtubules and innermost wall fibrils. These results suggest that cell elongation and wall deposition are separate processes but may occur simultaneously, and implicate cortical cells in control of directionality of growth of multicellular organs. They also necessitate a modification in the multinet hypothesis of cell growth for cells with polylamellate walls.
Germination of oospores of Albugo candida
Authors: Verma P. R. , Petrie G. A.
Published: September 2008

High percentages of Albugo Candida oospores from hypertrophied inflorescences of Brassica campestris were germinated by incubating them on moist filter paper for 21 days, by slowly leaching them for 15 days or more on sintered glass filters, or by washing them for a few days on a rotary shaker followed by a day of still-culture. Oospores germinated by the production of one or two simple or branched germ tubes, by release of zoospores from vesicles formed at the ends of germ tubes, and by release of zoospores from sessile vesicles. Germination by sessile vesicles was by far the most common. Forty-three percent of the oospores germinated in 4 days after dry storage for 21 years. The highest germination obtained in any sample was 88%. Seventy-one percent of the spores collected from the field in August germinated within 2 weeks. Good germination occurred at 10–20 °C.
Hyphomycetes from the West Indies and Venezuela
Authors: Crane J. L. , Dumont K. P.
Published: September 2008

Four fungi are described as new, and one previously known only from Africa has been found in Venezuela.
On the fine structure of sieve tubes and the physiology of assimilate transport in Alaria marginata
Authors: Schmitz Klaus , Srivastava L. M.
Published: September 2008

Alaria marginata Postels and Ruprecht has a sieve tube system which extends through the lamina, especially the midrib, and through the stipe. The sieve elements originate from the innermost cortex cells and are nucleate, highly vacuolated cells that contain the usual cell organelles and membrane systems. The plastids and mitochondria show some special features in their morphology and fine structure. P protein is absent. Sieve pores, 0.11–0.3 μm in diameter, occur in cross walls between two sieve elements. They are lined by plasmalemma, and the cytoplasms of the two cells are interconnected through them. Long-distance transport of photo-assimilate follows the source–sink relationship; but its normal basipetal direction can be reversed by creating "artificial" sinks. Translocation velocity is in the range of 25 to 40 cm/h. The translocate consists mainly of mannitol and free amino acids, which were analyzed qualitatively and quantitatively. Double-labeling experiments with 32P and 14C indicate that inorganic ions are not translocated together with the 14C-labeled photoassimilates and probably move only by diffusion.
The Galium aparine complex in Canada
Authors: Moore R. J.
Published: September 2008

The occurrence in Canada of Galium aparine sensu lato has been studied. It is concluded that two species are present: G. aparine L. sensu stricto (Cleavers) and G. spurium L. (False Cleavers). Although closely related and morphologically similar, these species differ morphologically, cytologically, and physiologically. The chromosome number of collections of G. aparine from Canada and the United States was found to be 2n = 66, that of G. spurium from the prairie provinces of Canada was 2n = 20. The latter species is an introduction from Eurasia and seems to be the more serious weed in fields of grain and rapeseed in western Canada. Galium aparine is believed to be native, as well as introduced from Eurasia, in North America. Galium aparine occurs usually in moist, shaded habitats, whereas G. spurium favors sunnier habitats. Both species have spiny or smooth fruits and these fruit variants have been recognized at various taxonomic levels. In this paper they are reduced to the rank of form.
Meiosis and sporogenesis in a haploid plant of Pellaea glabella var. occidentalis
Authors: Rigby S. Jane
Published: September 2008

In spore mother cells of a sporophyte of Pellaea glabella var. occidentalis (E. Nelson) Butters resulting from induced apogamy, the chromosomes did not pair during prophase I and separated randomly, usually into two groups. Meiosis II generally produced tetrads with nuclei of unequal sizes. Spore walls began to form around these nuclei, but most of the spores eventually aborted. One apparently normal spore, which later germinated, is assumed to have resulted from the formation of a restitution nucleus at the end of meiosis I.The total lack of pairing among the 29 chromosomes of this plant is evidence that this number represents the basic haploid complement of the species.
The uptake of sulfate by excised roots of rape seedlings (Brassica napus var. Target)
Authors: Shargool P. D. , Ngo T. T.
Published: September 2008

Excised roots from 5-day-old seedlings of Brassica napus L. var. Target, which had been grown in 2 × 10−4 M calcium chloride solution, were incubated in medium containing various concentrations of sulfate. The uptake of this ion by the roots was measured with the aid of [35S]-labelled sulfate and a liquid scintillation counting method. The membrane uptake system was shown to be sensitive to sodium cyanide and dinitrophenol. Kinetic examination of the process demonstrated that it was mediated by two separate systems each of which operated in a specific sulfate concentration range. One system was shown to have a low affinity for sulfate and was thought to remain inoperative until the second high-affinity system became saturated.
Injury-related phaseollin accumulation in Phaseolus vulgaris and its implications with regard to specificity of host–parasite interaction
Authors: Rahe James E. , Arnold Robert M.
Published: September 2008

Phaseollin accumulated locally at point-freezing injuries on hypocotyls of intact etiolated seedlings of Phaseolus vulgaris. Maximum amounts occurred within 24 to 30 h after injury. Smaller amounts accumulated at similar sites on hypocotyls excised at the time point-freezing injuries were made, and the accumulation was less localized. Increasing amounts of phaseollin occurred at sites increasingly distant from the cotyledonary nodes in both intact and excised hypocotyls. Much higher levels of phaseollin were elicited by excision per se than by point-freezing. Phaseollin was not detected after freezing of whole hypocotyls, indicating that living tissue adjacent to injuries is required for accumulation. The data are discussed in relation to host–parasite specificity, with particular reference to the interaction between P. vulgaris and Colletotrichum lindemuthianum.
Unilateral seed failure after reciprocal crosses of Secale cereale with Secale africanum
Authors: Price H. James
Published: September 2008

In crosses between Secale cereale and Secale africanum, viable seeds are formed when S. cereale is the seed parent. No viable seeds develop from the reciprocal cross. Histological comparisons of developing S. africanum × S. cereale seeds with those of S. africanum indicated that the ultimate cause of seed failure was abnormal endosperm development. The endosperm became cellular and contained small starch grains in a few cells. The endosperm cells progressively collapsed and deteriorated. No abnormalities in maternal tissues were observed. Excised embryos were cultured on nutrient-supplemented agar medium. One of these grew into a vigorous hybrid plant when transferred to soil, which thus indicated that the embryos from this cross are potentially viable.
Chemosystematic studies in the genus Tsuga. Leaf and twig oil analysis of western hemlock
Authors: von Rudloff E.
Published: September 2008

The chemical composition of the volatile oils of the leaves and twigs of western hemlock and the variations caused by transportation and storage, and those found within trees and within populations, were determined. Whereas the leaf oil was found to be well suited for chemosystematic studies, that of the twigs is unsatisfactory. The major components (3–25%) of the leaf oil were β-phellandrene, myrcene, α-pinene, β-pinene, cis-ocimene, limonene, and α-phellandrene and smaller amounts of α-terpineol, methyl thymol, terpinolene, cadinene and muurolene isomers and their corresponding alcohols, terpinene-4-ol, trans-ocimene, camphene, γ-terpinene, bornyl acetate, thymol, and nerolidol were identified. cis-Ocimene (8–14%) appears to be highly characteristic of the species and it, as well as other quantitative differences, may serve as a distinguishing feature with regard to mountain hemlock, eastern hemlock, and other species of the family Pinaceae. Leaf samples from 10 trees give terpene patterns that are representative of a population; no significant differences at different elevations (10–700 m) were recorded. Although the means of the major terpenes from different populations may vary by several percent, consistent differences between coastal and interior populations of British Columbia were not found.
Vascular epiphytes in the southern deciduous forests of Ontario
Authors: Maycock Paul F.
Published: September 2008

The occurrence of vascular epiphytes in the deciduous and deciduous–evergreen forests of southern Ontario, particularly in the southern deciduous forests of Point Pelee, Essex County, is presented. The general and specific ecology of vascular epiphytes is examined and compared in detail with that of such plants in other temperate areas of the world, particularly the United States and northern Europe. Twelve different species of plants have been found growing in 21 different epiphytic situations in the Pelee forests. Throughout the southern forests of Ontario a total of 25 plants has been recorded in a total of 34 arboreal habitats. In all, just 13 species of trees served as hosts for these vascular epiphytes and these are predominantly deciduous. Red oak and hackberry account for 50% of the epiphytic sites provided. General patterns associated with vascular epiphytism in temperate forest localities in North America and Europe are discussed.
Infection and temporal development of mycelium of Albugo Candida in cotyledons of four Brassica species
Authors: Verma P. R. , Harding Howard , Petrie G. A. , Williams P. H.
Published: September 2008

Cotyledons of four Brassica species were inoculated with zoospores of Albugo candida produced from germinating oospores or zoosporangia. The sequence of events in mycelial development appeared to be the same from both types of inoculum. Up to the time of formation of the first haustorium there appeared to be no difference in the infection process in susceptible (B. juncea, B. campestris), moderately susceptible (B. hirta), and resistant (B. napus) hosts. At 2–3 days after inoculation, growth in B. napus ceased and a marked encapsulation formed around each single haustorium. In the other hosts mycelial development increased rapidly after the formation of the first haustorium. Up to 14 haustoria were observed in a single mesophyll cell. Encapsulations were rarely observed around haustoria in susceptible tissue. The massive amount of fungal thallus tolerated by the susceptible hosts emphasizes the highly specialized type of parasitism evolved by A. candida.
Lichen substances. V. Methylated derivatives of orsellinic acid, lecanoric acid, and gyrophoric acid from Pseudocyphellaria crocata
Authors: Maass W. S. G.
Published: September 2008

Two tridepsides (tenuiorin and methyl gyrophorate) have been identified as major constituents of Pseudocyphellaria crocata. Two similarly substituted didepsides (methyl evernate and methyl lecanorate) and the monomer methyl orsellinate have been isolated as new natural products. A number of additional orsellinic acid derivatives occur in the same lichen as identified by cochromatography with reference compounds, which reveals a biosynthetical fingerprint pattern based on methyl ester formation, 4-O-methylation, and condensation.
Development of sperm cells in barley
Authors: Cass David D. , Karas Ilana
Published: September 2008

Ultrastructural events in barley sperm development were examined from the uninucleate microspore stage to establishment of two mature sperm cells in pollen grains. Microspore mitosis produces a vegetative nucleus and a naked generative cell, both embedded in vegetative cell cytoplasm. The generative cell membrane is enclosed by vegetative cell membrane. The generative cell, at first apparently unattached, becomes attached to the pollen wall and acquires a cell wall by centripetal vesicle accumulation. Wall formation may be complete at the time of generative cell karyokinesis; karyokinesis occurs while the generative cell is attached to the pollen wall. Cytokinesis of the generative cell is delayed. The subsequent stage is a binucleate, attached generative cell with a wall. Generative cell cytokinesis appears to involve formation of a partition between the two sperm nuclei. Eventual complete separation of the sperm cells occurs only after the two-celled derivative of the generative cell detaches from the pollen wall. Final stages in sperm cell separation are considered to result from degradation of the partitioning and surrounding wall, not from furrowing of a naked binucleate generative cell according to previous suggestions. Mature plastids were not observed in the generative cell or the sperms.
Studies on the reduction of 2,3,5-triphenyltetrazolium chloride as a viability assay for plant tissue cultures
Authors: Towill Leigh E. , Mazur Peter
Published: September 2008

Optimum conditions for the reduction of 2,3,5-triphenyltetrazolium chloride (TTC) to a water-insoluble red formazan have been determined for suspension tissue cultures of Acer saccharum and Haplopappus gracilus. The standard incubation mixture is 0.8% TTC dissolved in a 2:1 solution of 0.05 M sodium phosphate buffer:Acer growth medium, pH 7.5. After the cells are incubated for 18–20 h in the dark at room temperature, the red formazan is extracted with 95% ethanol, and the absorbance is read at 485 nm. The use of the TTC procedure as a viability assay is supported by studies with Haplopappus tissue cultures, in which viability can be assayed by both plating in agar and the TTC procedure. These studies show that there is a quantitative correspondence between the decrease in the plating assay and in the TTC assay when these cells are subjected to freezing stress and plasmolysis stress.
Kilometric distance
Authors: Phipps J. B.
Published: September 2008

A simple method of comparing species distributions, when the latter are in the form of lists of latitude–longitude coordinates, is described. The average of the distance in kilometres between the nearest neighbor of each individual of species A in species B and of species B in species A is used as a pair function. The matrix of pair functions for all species comparisons is then amenable for any of the techniques of numerical taxonomy. A small example using Turkish Papaver is given.
The theoretical time-dependent behavior of a Münch pressure-flow system: the effect of sinusoidal time variation in sucrose loading and water potential
Authors: Fermer J. M. , Tyree M. T. , Christy A. L.
Published: September 2008

Using the iterative model for the Münch pressure-flow mechanism derived by Christy and Ferrier (1973), the theoretical time-dependent behavior of the Münch pressure-flow system in a 15-m tree is computed in response to sinusoidal time variation in sucrose loading and water potential. Our calculations predict a "concentration wave" moving down the transport path of the type reported by Huber et al. (1937) in Quercus borealis L. The "waves" move with a phase velocity (= 3.5 cm min−1) greatly in excess of the velocity of the sieve-tube solution (= 0.4 cm min−1). It seems very likely that Huber et al. (1937) measured a phase velocity and erroneously interpreted it as the true solution velocity.
Some inconsistencies that arise when the Canny–Phillips model of phloem translocation is applied to known 14C-assimilate profiles in plant stems and petioles
Authors: Tyree M. T.
Published: September 2008

It is proved that when the Canny–Phillips model of translocation in phloem is used to fit known 14C-assimilate profiles in plants, the "apparent diffusion coefficient," K cm2 s−1, needed for curve fitting is physically inconsistent with the probable physical requirements of the system.
Environmental influences on light and dark CO2 fixation by Kalanchoe daigremontiana
Authors: Nalborczyk E. , Lacroix L. J. , Hill R. D.
Published: September 2008

The influence of day length, light quality, temperature, drought, and oxygen concentration on gas exchange of Kalanchoe daigremontiana was investigated. The ratio of photosynthesis to dark CO2 fixation with plants under a long-day and short-warm-night regime was 2.0 and under a short-day and long-cool-night regime, 0.2. With drought conditions this value may be less than 0.02. Under low oxygen concentrations high photosynthetic rates of about 20 mg CO2 dm−2 h−1 were observed with a compensation point of about 20 ppm. Restricting CO2 supply to dark periods produced plants with a δ13C value of −10.6‰. Restricting CO2 supply to light periods gave a δ13C value of −25.9‰, whereas no control of CO2 gave δ13C values of −15‰. The data obtained suggest that variations in δ13C values in Kalanchoe result from changes in the proportion of light and dark CO2 fixation.Far-red light and oxygen promoted the release of CO2 from Kalanchoe after the plants had undergone a period of dark CO2 fixation. Maximum release occurred within about 1 h. The effect could be reversed by removal of either far-red light or oxygen. Decreases in the acidity of the plants accompanied CO2 release, which indicated that decarboxylation of a C4 acid was the source of the CO2.
Septa ultrastructure and hyphal branching in the pleomorphic imperfect fungus Trichosporonoides oedocephalis
Authors: Haskins R. H.
Published: September 2008

Incomplete septa, complete simple septa, septa with simple pores, but mostly dolipore septa without pore caps or parenthosomes are present in this organism. Walls are distinctly laminar in aspect, especially with glutaraldehyde – osmic acid fixation. Cell division is by septum formation between previously formed septa. Conidia result from either blastospore or endospore (arthrospore) formation. Branching occurs irrespective of the type of adjacent septa, with each cell capable of bipolar germination. The organism shows features of both ascomycetous and basidiomycetous yeasts.
A further analysis of reciprocating flow in phloem tubes
Authors: Miller D. M.
Published: September 2008

A more stringent mathematical treatment of reciprocating flow in phloem tubes has shown that the original model (Miller 1973) would be too inefficient to provide a quantitative explanation for the rate of solute dispersion within the tube. A modification is suggested in which the mobile phase consists of the sieve tube sap, and the companion cells constitute the static phase. Lateral diffusion of the solute between these two phases could occur through the cell wall barrier separating them via plasmodesmata and would follow first-order kinetics. It is shown that for optimum dispersion in such a model, the period of oscillation should be about 3.6 times the half life of the lateral diffusion process. Estimates of the various parameters involved indicate that such a mechanism, if driven by protoplasmic streaming, predicts a dispersion coefficient of the same order as those found experimentally.
Stomatal distribution and size in southern Appalachian hardwoods
Authors: Carpenter Stanley B. , Smith Naomi D.
Published: September 2008

In 1972 and 1973 a scanning electron microscope was used to study stomata and cuticular surfaces of shade leaves collected from trees growing in the mountain and eastern coalfield region of Kentucky. Stomatal frequency and size determinations are presented for about 50 southern Appalachian forest species. Stomata varied from 6534/cm2 in Asimina triloba to 90 909/cm2 in Quercus palustris. Mesic species had fewer stomata per unit leaf surface area than xeric species. Stomatal frequency was not related to shade tolerance. The largest stomata (35 microns (μ)) were found in Populus gileadensis while the smallest (5μ) occurred in Quercus coccinea.
Ctenosporites and other Paleogene fungal spores
Authors: Lange Robert T. , Smith Peter H.
Published: September 2008

Ctenosporites, formerly considered to be restricted to the northwest Pacific and Arctic region, is recorded from Australia, and comments are advanced on some other taxa of fossil fungal spores.
Investigations on a new Beta (Chenopodiaceae)
Authors: Basu Rabindra Krishna , Mukherjee Kalyan Kumar
Published: September 2008

Both the common sugar beet and Indian spinach (locally called Palong) have so far been considered to be the same species, Beta vulgaris L. Critical morphological, karyological, and biochemical studies revealed that Indian spinach is strikingly different from B. vulgaris and is described here as Beta palonga Basu & Mukherjee sp. nov.
Verticillium wilt of chrysanthemum: development of wilt in relation to leaf diffusive resistance and vascular conductivity
Authors: Hall Robert , Ali Ahmed , Busch Lloyd V.
Published: September 2008

The relative contributions of transpiration rate and resistance to water flow in leaves to development of wilt in leaves of chrysanthemum plants (Chrysanthemum morifolium Ramat) infected with Verticillium dahliae Kleb. were examined. Diffusive resistances (inversely related to transpiration rate) of turgid leaves on infected and uninfected plants were similar. When wilt symptoms appeared, diffusive resistance of wilted areas increased (i.e., transpiration rate decreased) while in turgid areas it remained similar to that of turgid leaves on check plants. There was no evidence that transpiration rates changed before development of wilt. In uninoculated plants aqueous solutions of basic fuchsin and 14C-mannitol moved freely into turgid leaves and leaves wilted by withholding water. In inoculated plants these tracers moved into turgid areas but not into wilted areas of leaves. Wilted areas closely coincided with areas of restricted tracer movement. These areas first occurred near leaf margins and progressed basipetally to encompass finally the entire lamina. The evidence suggests that wilt of Verticillium-infected chrysanthemum plants is due to restriction of water movement in vascular elements within the wilted areas of the leaf and that restriction sufficient to cause wilt first occurs near leaf margins.
The genus Lasiobolus (Pezizales, Ascomycetes)
Authors: Bezerra J. L. , Kimbrough J. W.
Published: September 2008

The history of the genus is reviewed and its taxonomical position is discussed. Lasiobolus is characterized by small, usually yellowish, setose apothecia, non-septate setae, operculate, non-amyloid, eight-spored to multispored asci, and hyaline to yellowish, smooth, unicelled, thin-walled ascospores that contain gas bubbles. Species are distinguished by (1) the number of spores per ascus, (2) the type and arrangement of excipular cells, (3) presence or absence of cyanophilic markings in the setae, and (4) the relative size and shape of asci, spores, and sterile elements. Lasiobolus intermedius, L. microsporus, and L. trichoboloides are proposed as new species. A key, detailed descriptions, and illustrations are provided for all the 11 recognized species. A list of insufficiently known and excluded species is included.
The epidemiology of common root rot in Manitou wheat. II. Effects of treatments, particularly phosphate fertilizer, on incidence and intensity of disease
Authors: Verma P. R. , Tinline R. D. , Morrall R. A. A.
Published: September 2008

The effects of various treatments such as herbicide, irrigation, nitrogen, phosphate, and combinations of nitrogen and phosphate on common root rot (Cochliobolus sativus) in naturally infected Triticum aestivum cultivar ‘Manitou’ were studied at Matador, Saskatchewan, by sampling plants at intervals during 1969, 1970, and 1971. The treatments were compared for each of the following variables : number of diseased plants per square metre, percentages of diseased plants, and percentage disease ratings. Usually, disease assessed by each variable was higher in the checks than in the phosphate treatments. The effect of phosphate appeared maximal at midseason (growth stage 9–10.5). The differences between treatments such as herbicide, nitrogen, and irrigation and the checks were insignificant. A comparison with the results of other workers suggests interaction between phosphate and soil type, and between phosphate and cultivar.