摘要:

Pythium marinumSparrow, isolated from lesions onPorphyra miniata, required Na+, Ca2+, and Mg2+in quantities far exceeding those reported to be required by terrestrial species ofPythium. Unlike most of its terrestrial counterparts,P. marinumrequired alkaline pH values for good growth, with a pH of 7.8 providing maximum growth under the conditions examined. The requirement for large amounts of Na+ions appeared to have a specific nutritional basis rather than a purely osmotic function. Growth at various temperatures indicated that the fungus is a facultative psychrophile with the optimum growth temperature between 15 and 20 °C. The nutritional data show thatP. marinumis able to grow in a wide range of salt concentrations and is well adapted to the marine environment.

ISSN:0008-4026    

DOI:10.1139/b73-086

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

The long-term measurement of aerobic fungal respiration, both on an agar medium and on wood blocks, was possible using a gas-chromatographic technique for the detection of the carbon dioxide. This method was fully automated to analyze gas samples sequentially from eight or more growth chambers, after variable but determined time periods. It provided a precise quantitative measure of the respired carbon dioxide, presented both in the form of punched computer tape and normal printed teleprinter output. This apparatus worked continuously for several years without serious breakdown.The fungiLentinus lepideus, Lenzites trabea, Poria monticola, and several strains ofConiophora puteanaall showed a rhythm in their respiration which was not controlled by temperature or light. The magnitude and frequency of the rhythmical peaks in carbon dioxide production varied between fungi and, although there was considerable variation between different isolates of the same species, the separation of these species of fungi based on their different patterns of respiration was possible.

ISSN:0008-4026    

DOI:10.1139/b73-087

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Crown rust of oats is widespread on wild and cultivated oats in Kenya and Ethiopia. The six oat species in the area have very little resistance to crown rust, which has a wide virulence range, much wider than required for local survival. Thirteen physiologic races were identified using 10 single resistancePcgene line cultivars. Kenya and Ethiopia appear to have distinct pathogen populations with only a few races in common.

ISSN:0008-4026    

DOI:10.1139/b73-088

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

The vacuolar resting potential and the membrane resistivity ofChara brauniiare studied (i) as a function of ionic composition of the bathing medium, (ii) in the presence of the metabolic inhibitors cyanide and salicylhydroxamic acid, and (iii) as a function of temperature. Substitution of acetate for chloride produces a marked hyperpolarization, sulfate for chloride a small hyperpolarization, sodium for potassium a marked hyperpolarization, and rubidium for potassium a small hyperpolarization; the membrane resistivity showed no readily discernible pattern of variation with these substitutions. The metabolic inhibitors produced a linear decline of resting potential accompanied by a several-fold increase of membrane resistivity. Cooling to levels near 0 °C produced a several-fold increase in resistivity but not necessarily a depolarization. Suitable heating at or above 40 °C could produce a linear depolarization and a several-fold increase in resistivity. The data are interpreted in terms of a depolarizing electrogenic cation-chloride influx pump, a hyperpolarizing hydrogen-ion efflux pump, and a membrane resistivity linked to the hydrogen ion pump.

ISSN:0008-4026    

DOI:10.1139/b73-089

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Diurnal exposure to ozone at low concentrations reduces the size of primary uredia of bean rust on bush bean, increases their number, and leads to secondary pustule formation. Infection does not protect the host tissues from ozone injury, since such injury can be observed immediately adjacent to pustules. Similarly, infection does not retard the enhanced rate of senescence induced by ozone treatment.

ISSN:0008-4026    

DOI:10.1139/b73-090

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Earlier described data from this laboratory were subjected to primary growth analysis. The plants had been grown in constant conditions of light intensity (200 to 2500 ft-c) and temperature (10° to 30 °C) at five different settings each. Multiple temperature optima were revealed and interpreted. The computed maximum plant growth coefficient was highest in value at 25 °C (plantkmL = 0.44 day−1) and secondarily so at 15 °C, but at the experimental light intensities the plant growth coefficient was maximal at 15 °C. The higher temperature optimum was characteristic of roots and "stems" (stem plus leaf sheaths) whose growth coefficients displayed a prominent peak at 25 °C (rootkmL ~ 0.8 day−1, "stem"kmL = 0.4 day−1). This optimum was shifted downward with decreasing light intensity until temperature insensitivity was attained at low light intensity. The low-temperature optimum at 15 °C was principally displayed by leaf blades (laminakmL = 0.47 day−1) whose computed maximum growth coefficient also showed a secondary maximum at 25°, but the 15 °C peak was the only one evident at low light intensities. It was tentatively concluded that the 25 °C temperature optimum was that of net translocation, and that the 15 °C temperature optimum was that of net photosynthesis in which photosynthesis was primarily balanced by photorespiration in wheat. The differential growth of the organs represented their relative sink strengths for attracting growth substrate, as dependent on light intensity and temperature. The availability of photosynthate was considered to be the dominating factor in the kinetics of growth free from inorganic limitations. When there was very little photosynthate the tissues benefited from translocation on a "first come first serve" basis. The high values ofkmLpushed the absolute maximum plant growth coefficient,kM, of Marquis wheat toward 0.5 or 50% per day, and the basis of the advantage over previous approximations must be elucidated by further experiments. The computed relative efficiency of the use of photosynthate for growth was temperature dependent, but its value at optimum temperature was similar to previous estimates.

ISSN:0008-4026    

DOI:10.1139/b73-091

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Respiratory activity in xylem tissues ofPinus radiatawas monitored during the growing and dormant seasons by manometry as well as by histochemical localization of malic and glucose-6-phosphate dehydrogenases and by quantitative estimation of malic dehydrogenase. During the dormant season, respiration and activity of malic dehydrogenase were significantly greater (1% probability level) in the transition zone separating sapwood from heartwood than in middle and inner sapwood. These results were supported by enzyme histochemistry, which indicated a substantial increase in activity of glucose-6-phosphate dehydrogenase in the transition zone, particularly during the dormant season. It is suggested that heartwood formation occurs mainly during this time.

ISSN:0008-4026    

DOI:10.1139/b73-092

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Twenty-one samples were examined for algal species diversity. Samples contained between one and 35 species with a mean of 10.6 species per sample. The greatest diversity of species occurred in samples collected from large flarks or bog lakes. Hummock communities, especially those with abundantSphagnum rubellumcontained fewest algae. All samples showed a predominance of Desmidiales.General ionic levels in the string mire were low; however, species of the generaEuastrum, Micrasterias, andStaurastrumoccurred frequently in the sites richer in nutrients. More species were found in wetter than in drier sites.The presence of species characteristic of more base-rich conditions may be related to the rate of water flow through the mire.

ISSN:0008-4026    

DOI:10.1139/b73-093

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

The hypothesis that photosynthate accumulation within a leaf inhibits the ongoing rate of photosynthesis was investigated in 6-year-old balsam fir trees. Rates of net photosynthesis and transpiration, and concentrations of starch, total sugar, chlorophyll, and water were measured in 1-year-old or fully expanded, current needles, and leaf resistances to carbon dioxide transfer were calculated. The several-fold rise and fall in the content of carbohydrate (mostly starch) that occurs naturally in 1-year-old needles before and after budbreak was correlated positively rather than negatively with the photosynthetic rate. Shading during the normal period of starch accumulation decreased the concentrations of both starch and total sugar, but did not increase photosynthesis. Continuous cooling of the base of a branch to 2 °C to inhibit translocation of photosynthate did not affect the photosynthetic rate during a 2-week period, nor did it cause carbohydrate accumulation, as measured at the end of the experiment. Removing a ring of bark from a branch base resulted in a large increase in the foliar concentration of starch (but not total sugar) and a small decrease in photosynthesis. However, the concomitant decrease in moisture content, not the accumulation of starch, was more probably the cause of the reduced photosynthesis. We conclude that the rate of photosynthesis in fir needles, at least under normal growing conditions, is not influenced by photosynthate accumulation.

ISSN:0008-4026    

DOI:10.1139/b73-094

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Avena canariensissp. nov., 2n = 14, is described from the Canary Islands. Its spikelets have non-disarticulating upper florets and bidentate lemmas, suggesting the evolutionary sequence:A, canariensis(2x) → A. magna(4x) → A. sterilis(6x). Hence it is a putative ancestor of the 6xcultivated oats. The karyotype consists of two pairs of satellited chromosomes, four pairs with median and one pair with submedian centromeres, suggesting affinity with the A genome diploid avenas. It was found on a diversity of natural and disturbed sites in the uplands of Fuerteventura, but not as a weed of field crops.

ISSN:0008-4026    

DOI:10.1139/b73-095

出版商:NRC Research Press    

年代:1973

数据来源: NRC