摘要:

A laboratory method is described for determining the survival ofHelminthosporium sativumspores in soil. An oil–water emulsion containing the spores is mixed with potato dextrose agar supplemented with molasses; microscope slides are then dipped into the mixture, incubated, and examined for spore germination. Application of the method showed that viability of spores in a dry soil did not decline over a 9-month period whereas survival of spores in saturated soil dropped markedly in the same period. Intermediate moisture levels had intermediate effects on the spores. Studies on spores obtained directly from cultivated fields indicated little mortality from fall to spring. A summerfallow year between two wheat crops resulted in a substantial decline in percentage of viable spores.

ISSN:0008-4026    

DOI:10.1139/b58-024

出版商:NRC Research Press    

年代:1958

数据来源: NRC

摘要:

TheF1generation of selfed plants ofFragaria chiloensis,F.ovalis, andF.yukonensiscontained seedlings resistant to the verticillium wilt disease. SelfedF.orientalisplants yielded seedlings that carried considerable tolerance but selfedF.vesca,F.bracteata, andF.virginianaplants yielded neither tolerant nor resistant seedlings. Asexually propagated plants of the seven species were all susceptible to the disease.

ISSN:0008-4026    

DOI:10.1139/b58-025

出版商:NRC Research Press    

年代:1958

数据来源: NRC

摘要:

Specimens of numerous marine species of the green, red, and brown algae from the Atlantic coast of Canada have been analyzed for total ash, Na, K, Ca, and Si, and the trace elements, As, Co, Cu, F, I, Mn, Mo, Ni, Pb, and Zn. Figures for fluorine in seaweeds are recorded for the first time. Thorough washing with tap water lowered the content of the ash, Na, K, and Si, but did not affect appreciably the concentrations of other elements.Accumulation from the sea water was apparent in greatly varying degrees in the following ascending order: F, Mo, Co, Cu, As, Ni, Mn, Zn, I. The ranges in concentration observed were Na 1.6–4.7, K 2.3–7.1, Ca 0.9–2.3, Si 0.5–2.0, as percentage of dry matter; I 20–2490, Zn 35–97, Mn 20–50, Cu 6–62, As 2–75, F 2–22, Pb 0.8, Ni 0.3–2, Co 0.1–0.7, Mo 0.2–1.4 as p.p.m.No seasonal variation was detectable in the concentration of trace elements inChondrus crispus. Differences in concentration were observed between frond and stipe in two species ofLaminaria.

ISSN:0008-4026    

DOI:10.1139/b58-026

出版商:NRC Research Press    

年代:1958

数据来源: NRC

摘要:

The effect of 1% glutamic acid, banana sap, water, and carbon dioxide on multiplication (sporulation) ofFusarium oxysporumf.cubense(E.F.S.) Sny. and Hans. in infested soil was studied under laboratory conditions. Increases in population were determined by microscopic examination and dilution plating on peptone dextrose agar containing rose bengal and streptomycin. Amount of fungus multiplication varied among different soils, samples from the same soil, and different experiments. This is attributed to unknown variables influencing multiplication and survival in soil microhabitats.Carbon dioxide stimulated multiplication of the fungus in aqueous soil extracts and in soil amended with 1% glutamic acid or banana sap, and sometimes in soils moistened with water. Initially low and high population increases in control soil in air required 42 hours' exposure in an atmosphere containing 4 to 25% and 8 to 25% carbon dioxide, respectively, for optimum multiplication. In some instances, multiplication was stimulated as a result of 8 hours' exposure to 4% carbon dioxide in air, and amount of stimulation increased with longer exposures up to 24 or 42 hours. Oxygen did not consistently limit multiplication in soil plates at a concentration of about 4% in nitrogen containing 4% carbon dioxide. Differences in amount of multiplication between a series of acid loams or sandy loams and alkaline clay loams were, in general, more consistent in air enriched with carbon dioxide than in air. Multiplication was greater in soil previously flood fallowed and in soil subjected to anaerobiosis than in non-flood fallowed soil.The above evidence supports the thesis thatF.oxysporumf.cubensecan multiply saprophytically in soil.

ISSN:0008-4026    

DOI:10.1139/b58-027

出版商:NRC Research Press    

年代:1958

数据来源: NRC

摘要:

The osmotic pressure of the root cells of water hyacinth [Eichhornia crassipes(Mart.) Solms.] decreased approximately one-half an atmosphere from its normal value of 5.0 to 5.6 atmospheres (a) in roots severed from the plant, (b) in roots of plants that were darkened for 24 hours or more, and (c) in roots of plants growing in a nutrient solution without renewal for a week or more. This decrease in osmotic pressure was associated with a decrease in the internal concentration of inorganic ions. In excised roots an exosmosis of nitrate and potassium was demonstrated. This exosmosis did not appear to be connected with the passive leakage of diffusion processes. A deficiency of oxygen in the internal aeration system of the plant appeared to be the most likely cause of the exosmosis of ions from severed roots and from roots of plants held in the dark. Root cells of water hyacinth accumulated the vital stain neutral red but were not able to retain this stain when transferred to tap water or to a hypotonic sugar solution.

ISSN:0008-4026    

DOI:10.1139/b58-028

出版商:NRC Research Press    

年代:1958

数据来源: NRC

摘要:

The rates and products of photosynthesis of 14 species of brown, red, and green marine algae have been determined. C14O2was supplied in a special apparatus which gave a continuous record of uptake. This apparatus is described in detail. The products of photosynthesis were extracted, separated by paper chromatography, and their radioactivity was determined. The main product was invariably mannitol in the brown algae, floridoside or a glycerol-mannoside in the reds, and sucrose in the greens. Hydrolysis of the insoluble residues released radioactive amino acids, glucose, galactose, and other carbohydrates. Although the soluble products were characteristic of each group, the insoluble products were much the same in all three groups. The rates of CO2assimilation ranged fromto 4 mg. of CO2per hour per gram of fresh plant. No correlation of the rate of CO2uptake was observed with either the morphology or the taxonomy of the algae.

ISSN:0008-4026    

DOI:10.1139/b58-029

出版商:NRC Research Press    

年代:1958

数据来源: NRC

摘要:

Plants of common barberry (Berberis vulgarisL.) were inoculated to determine their reaction to race 15B of wheat stem rust (Puccinia graminisPers. f. sp.triticiErikss. & Henn.). Only resistant-type infections occurred on plants inoculated with two pure cultures of race 15B-4 (Can.). Strong circumstantial evidence for the resistance of common barberry to race 15B was obtained from inoculations with sporidia from teliospores produced in the field. Sporidia from teliospores collected from the emmer wheat variety Vernal, which is selective for race 15B, produced only infections of a resistant type, and those from the common wheat variety Lee, also selective for 15B, caused both resistant and susceptible types of infections. Transfer of aeciospores to wheat from the susceptible type demonstrated that 15B was not present. Sporidia from teliospores on the varieties Reliance and Mentana, which are not selective for this race, caused infections of a susceptible type. Resistant-type and susceptible-type infections appeared when barberry leaves were infected with races 29 and 48A.

ISSN:0008-4026    

DOI:10.1139/b58-030

出版商:NRC Research Press    

年代:1958

数据来源: NRC

摘要:

Observations bearing on the rates of vertical travel of moisture in normal and treated trees of several species are presented. Differences in the speeds of movement deriving from a specific experimental treatment are analyzed statistically, and brief consideration given to a particular aspect of the mechanism of moisture movement in trees.

ISSN:0008-4026    

DOI:10.1139/b58-031

出版商:NRC Research Press    

年代:1958

数据来源: NRC

摘要:

Polyporus leucospongiaCooke & Harkness, a wood-rotting fungus heretofore known only from montane and subalpine zones in North America, is reported to occur commonly in India in temperate regions above 6000 ft. in the Western Himalayas, on stumps and logs ofCedrus deodara,Picea morinda, andAbies pindrow. A detailed description is given of the fungus as it occurs in India as well as the culture characteristics displayed in pure culture.

ISSN:0008-4026    

DOI:10.1139/b58-032

出版商:NRC Research Press    

年代:1958

数据来源: NRC

摘要:

Measurements of rate of exudation and also of biopotentials have been made with excised corn roots growingin vitroand with excised sunflower root–stem preparations growing in pots. Exudation cycles have been found to be controlled by factors endogenous to the living plant. Biopotential cycles correlated with the exudation cycles with maximum exudation at the time when the exudate electrode was most negative. Freshly excised green sunflower stems showed water absorption concurrently in both ends with the rates of water movement variously influenced by air speed, temperature, and light. Biopotential changes were again closely correlated with changes in water movement. The electrokinetic theory of transport will consistently account for all these observations.

ISSN:0008-4026    

DOI:10.1139/b58-033

出版商:NRC Research Press    

年代:1958

数据来源: NRC