摘要:

The classical concepts of wood decay are reviewed. All white rot fungi do not cause the same type of cell wall decomposition. At least two micromorphologically distinct types of cell wall attack have been found. Many factors can affect the type of macroscopic and microscopic decay patterns caused by white rot basidiomycetes. Host cell type and nutrients, as well as genetic and physiologic differences among these fungi, may influence the resulting decay.

ISSN:0008-4026    

DOI:10.1139/b86-121

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

Studies of soil samples from an apple orchard in Frelighsburg revealed the presence of seven species of Endogonaceae, six of which generated vesicular and arbuscular mycorrhizae onTagetes erectaL. WhileGlomus constrictumTrappe,Glomus mosseae(Nicol. & Gerd.) Gerd. & Trappe, andSclerocystis rubiformisGerd. & Trappe made up more than 90% of the organisms observed,Gigaspora calospora(Nicol. & Gerd.) Gerd. & Trappe,Glomus aggregatumSchenck & Smith, andGlomus etunicatumwere seen in approximately half of the samples. An enumeration of the Endogonaceae observed is followed herein by a discussion dealing with the frequency and the relative abundance of these species in the soil and with the practical interest which arises from this type of survey.

ISSN:0008-4026    

DOI:10.1139/b86-122

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

Pinto beans (Phaseolus vulgarisL. cv. UI 111) were exposed for 8 h to simulated fog solutions made up of 2:1 nitric acid: sulfuric acid plus background ions, acidified to pH 3.2, 2.8, 2.4, and 2.0. Rate of fog deposition was ca. 1 mm h−1. Examination of visible foliar injury development, scanning electron microscopy (SEM) examination, and measurement of leaf extract pH were performed every 2 h. Both visual and SEM observations during exposure showed no change in leaf surface characteristics for plants exposed to pH 3.2 and 2.8 fog solutions but 1 week after pH 2.8 exposures, injury was seen on primary leaves and young trifoliate leaves. The first indications of injury at pH 2.4 were seen under SEM after 8 h of exposure. Foliar injury was apparent after only 2 h of exposure at pH 2.0 and severe acid necrosis developed after 24 h. Changes in acidity of leaf extracts were closely correlated with subsequent injury development. No changes were observed in extracts of plants exposed to pH 3.2 simulated fog compared with controls. After 8 h of exposure, leaf extracts of plants exposed to pH 2.8 fog had dropped 0.05 pH units. Plants exposed to pH 2.4 and pH 2.0 for 8 h had leaf extracts that were 0.12 and 0.18 pH units lower, respectively. Comparison of the three measured parameters of acid fog effects (visible injury development, SEM examination of leaf surfaces, and determination of leaf extract pH) showed extract pH to be a simple, quantifiable, and sensitive indicator of the negative effects of acid precipitation on plants.

ISSN:0008-4026    

DOI:10.1139/b86-123

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

Fluoride accumulations and damage symptoms to foliage, cones, and seeds of balsam fir (Abies balsamea(L.) Mill.), black spruce (Picea mariana(Mill.) B.S.P.), and larch (Larix laricina(Du Roi) K. Koch) were monitored at six sites downwind from a phosphorus plant that emitted fluorides during 1982. Atmospheric fluoridation rates ranged from 347.4 μg F∙dm−2∙week−1(11.38 μg F∙m−3) at 1.4 km from the fluoride source to 2.5 μg F∙dm−2∙week−1(0.08 μg F∙m−3) at 18.7 km. Various degrees of foliar damage (chlorosis, necrosis, needle damage, and defoliation) occurred where fluoride accumulations in the foliage exceeded 20 ppm. This occurred at sites where the fluoridation rates were in excess of 26.0 μg F∙dm−2∙ week−1, and at distances less than 10.3 km downwind from the fluoride source. Reductions in seed size, percent germination, numbers of seeds per cone, number of cones per tree, number of fertile trees, and size reduction, distortion, or mortality of the cones occurred under the same fluoridation rates. Seed output on the windward sides of trees was significantly less than that on the leeward sides. At the most polluted site, seed production in balsam fir, black spruce, and larch, respectively, was reduced to 3.6, 2.6, and 0.0% of that at a control site. All three species in the study are considered to be susceptible to fluoride damage, with respect to both vegetative and reproductive symptoms. Reproductive failure and past mortality of fluoride-damaged conifers have resulted in their replacement by more tolerant hardwood species (e.g., birch (Betula papyriferaMarsh.), alder (Alnus crispa(Ait.) Pursh)) as the dominant forest species in the vicinity of the p

ISSN:0008-4026    

DOI:10.1139/b86-124

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

Mitosis is dimorphic in the protostelidCeratiomyxella tahitiensis. The spindle in the amoebo-flagellate state of the life cycle is open and centric; the microtubular rootlet system which surrounds the centrioles during interphase breaks down during mitosis. The spindle in the plasmodial state is open and acentric. The spindle develops outside the nuclear envelope during prophase and drops into the nucleus during prometaphase when the nuclear envelope breaks down. A polar microtubular organizing center appears at metaphase and lasts through telophase. Amoebo-flagellate mitosis is similar to that found in the amoebo-flagellates of other Eumycetozoa. Plasmodial mitosis is unique among the eumycetozoans. This provides support for the hypothesis that the flagellate Eumycetozoa are derived from a common flagellate ancestor and that certain groups of eumycetozoans have independently evolved unique, obligately amoeboid states.

ISSN:0008-4026    

DOI:10.1139/b86-125

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

A study was conducted to examine the influence of environmental conditions of boreal cutover sites on plant water status and needle conductance of newly planted bare-root black spruce (Picea mariana(Mill.) B.S.P.), white spruce (Picea glauca(Moench) Voss.), and jack pine (Pinus banksianaLamb.) seedlings. As absolute humidity deficit between the needles and air (AHD) increased, xylem pressure potentials (ψx) became most negative in black spruce, intermediate in white spruce, and least negative in jack pine seedlings. Needle conductance (gwv) was strongly related to AHD in all three species, with increasing AHD resulting in a decrease ingwv. However, at low levels of AHD,gwvvalues for black and white spruce seedlings were approximately 50 and 25% higher, respectively, than those for jack pine seedlings. For black and white spruce seedlings,gwvdecreased as ψxbecame more negative, while jack pinegwvresponded to more negative ψxwith a threshold for stomatal closure at approximately −1.7 MPa. In all three species, increasing photosynthetically active radiation (PAR) resulted in greatergwvat all AHD levels. However, at high AHD levels,gwv, response to PAR was suppressed. The findings of this study indicate species differences in physiological response to atmospheric conditions under nonlimiting soil moisture conditions. The implications for successful reforestation are discussed.

ISSN:0008-4026    

DOI:10.1139/b86-126

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

Mycorrhizal development and growth of flowering dogwood (Cornus floridaL.) seedlings were investigated in a field nursery and glasshouse. Seedlings and associated soil were collected from April to November from a fumigated nursery bed that contained areas of both stunted and rapidly growing plants. The rate of mycorrhizal colonization and associated spore formation were greater on the rapidly growing seedlings. In a glasshouse test, dogwood seedlings were inoculated with chlamydospores ofGlomus etunicatum,G.intraradices, or a control solution which contained microorganisms associated with the mycorrhizal fungi, and were fertilized weekly with Hoagland's solutions which had 0, 47, or 93 mg P∙L−1. After 12 weeks, seedlings inoculated withG.etunicatumhad greater survival, shoot dry mass, and root fresh mass than seedlings inoculated withG.intraradicesor the control. However,G.etunicatumdid not affect the concentration or total uptake of P into shoots. This fungus can apparently enhance the survival and growth of dogwood seedlings without improving P nutritio

ISSN:0008-4026    

DOI:10.1139/b86-127

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

Cochlearia anglicaL. (halophyte) andPhaseolus vulgarisL. (glycophyte) were grown in media of different salinities. The root cell walls were isolated and then equilibrated with various salt solutions. There were differences between cell walls fromC.anglicaandP.vulgarisin both the cationic exchange capacity (computed by the sum of parietal cations) and the cell wall selectivity (evaluated by the centesimal proportion of each cation). In cell walls from plants grown without NaCl, the number of exchange sites was greater for the halophyte than for the glycophyte. Growing the plants on 42 and 85 mMNaCl medium reduced or reversed the disparities between the two species: withC.anglica, the cell wall cationic exchange capacity decreased when the growth medium salinity increased whereas this capacity tended to rise forP.vulgaris. However, the culture medium salinity did not affect the cell wall selectivity of these species for major cations. For Ca2+, the selectivity of cell walls fromP.vulgariswas higher than that of cell walls fromC.anglica; for the other cations, the situation was reversed.

ISSN:0008-4026    

DOI:10.1139/b86-128

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

Calluna vulgarisL. Hull was culturedin vitroon a medium containing either nitrate or ammonium salts. Apical shoots, used as cuttings, regenerated twigs and roots after 15 to 25 days. The uptake of mineral nitrogen by roots had an influence on the pH of the medium. There was either an increase of pH when the N source was NO3or a decrease in pH of the medium with ammonium. Acidification began with the formation of the first new roots; an increase in pH occurred later with the formation of second order roots. The results were difficult to express, owing to rooting heterogeneity. This problem was overcome by changing the origin of the abscissa, the new origin starting with the date of rooting. This procedure allowed the study of pH changes in relation to different stages of plant growth. With the aid of a standard curve, the study of the leakage of H+and OH−showed great homogeneity in plant behaviour.

ISSN:0008-4026    

DOI:10.1139/b86-129

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

The presence of transfer cells in various regions of the postfertilization ovule of soybean is described. A developmental study shows that transfer cells, occurring in the micropylar nucellus, are formed after fertilization but destroyed by expansion of the embryo sac during transition from the zygote to the two-celled embryo. Subsequently wall ingrowths appear in five additional sites: (i) in the region where the embryonic basal cell wall is associated with the degenerated synergid, projecting into the basal cell; (ii) on the chalazal embryo sac wall projecting into the central cell; (iii) on the embryo sac wall projecting into the basal cell; (iv) on common walls of micropylar suspensor cells; and (v) on some cell walls at the micropylar end of the inner integuments. It is our opinion that these transfer cells are all involved in augmenting metabolite transport and that their orderly appearance in different areas of the ovule signifies changes in the nutritional environment of the young embryo and endosperm of soybean. Because these transfer cells are closely associated with the embryo sac wall, it is proposed that this wall is a common apoplast functioning as both a sink for metabolites from the nucellus and source for all solutes taken up by the cells of the embryo sac.

ISSN:0008-4026    

DOI:10.1139/b86-130

出版商:NRC Research Press    

年代:1986

数据来源: NRC