摘要:

Immunofluorescence microscopy with anti-tubulin has been used to study the effects of the dinitroaniline herbicide, oryzalin, on microtubule arrays in root tip cells of a number of species of plants. All species of grasses that were examined showed rapid microtubule depolymerization, as did the nongrassPotamogeton. All other nongrass monocotyledons and dicotyledons tested required much longer treatment times to achieve microtubule depolymerization in the majority of root tip cells. Correlated immunofluorescence and electron microscopy have been used to obtain details of depolymerization and repolymerization of microtubules during treatment and recovery in a resistant plant,Zinnia elegans, and in a sensitive plant,Lolium rigidum. Although rates of disruption differ, both plants displayed similar patterns of microtubule depolymerization and repolymerization. The microtubules that comprise the different categories of array in the root tip cells were differentially sensitive to oryzalin. In order of increasing stability they were as follows: polar microtubules in mitotic cells < interphase arrays < preprophase bands ≤ phragmoplastskinetochore microtubules. During recovery, microtubules are nucleated in the cell cortex in interphase and at the kinetochores during mitosis. The cells are able to reinstate cortical interphase arrays, preprophase bands, and phragmoplasts of apparently normal organization, but not normal, functional spindles. Our results provide basic information on the use of oryzalin in studying the organization and dynamics of microtubule arrays in higher plant cells.

ISSN:0008-4026    

DOI:10.1139/b88-320

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Phenol-soluble polypeptides were extracted from teliospores of six races of each ofTilletia laevisandT.tritici, and eight collections ofT.controversa. The polypeptides were separated by two-dimensional isoelectric focusing – polyacrylamide gel electrophoresis and the resulting patterns compared. Although the races and collections had the morphological and physiological features of their respective species and possessed different combinations of virulence genes, they all gave similar polypeptide patterns. There were 359 polypeptides common to all 20 races and collections. Another 56 polypeptides were found in only some races and collections, but none of these variable polypeptides were species specific, i.e., found in every race or collection of one species but absent from every race or collection of one or both of the other species. Therefore, no polypeptide could be correlated to a morphological or physiological feature typical of any one species. Furthermore, no correlation was found between the polypeptides and virulence. However, previous studies on interspecific hybridization, the overlap in spore morphology and germination requirements, and the high number of common polypeptides and absence of species-specific polypeptides demonstrated here prove a closer genetic relationship among the three fungi than is indicated by their current taxonomic designation. It is, therefore, proposed to treat them as varieties of one species:T.triticivar.laevis,T.triticivar.tritici, andT.triticivar.controversa.

ISSN:0008-4026    

DOI:10.1139/b88-321

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Physical maps of the mitochondrial DNA (mtDNA) ofHyphochytrium catenoidesandRhizidiomyces apophysatuswere constructed.Hyphochytrium catenoideshas a 54-kb (kilobase pair) circular mtDNA with an inverted repeat of 13.5–14.5 kb which contains the large ribosomal RNA gene at one extreme of the inverted repeat, adjacent to the small unique region. Genome complexity (genome size minus one arm of the inverted repeat) is 39.5–40.5 kb, identical with the average value for Oomycetes.Rhizidiomyces apophysatushas a 50-kb circular mtDNA with no inverted repeat. No obvious alignment of the two maps is possible. The occurrence of a typical inverted repeat in a group of fungi closely related to the Oomycetes indicates that the character is ancestral for the Oomycetes and that its modification or loss within the Oomycetes can be treated as a derived character for the purpose of phylogenetic analysis.

ISSN:0008-4026    

DOI:10.1139/b88-322

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Pre-emergence application of metribuzin stimulated the accumulation of nitrogen, especially in the form of protein. The application of metribuzin induced marked suppression of carbohydrates. The soluble sugars and polysaccharides in nontreated control plants declined throughout the experimental period. The inhibitory effect of metribuzin on carbohydrates was concomitant with changes in photosynthetic efficiency, biosynthesis of pigments (chlorophyll), and the nucleic acid contents. The chlorophylla/bratio was not affected by metribuzin application.

ISSN:0008-4026    

DOI:10.1139/b88-323

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Root apices ofApium graveolensL. resistant and susceptible to race 2 ofFusarium oxysporumf.sp.apii(R. Nels. & Sherb.) were studied at various times after inoculation, using light and electron microscopy to determine structural response(s) of the hosts during penetration and colonization by the pathogen. Penetration was intercellular and intracellular and involved mechanical and enzymatic mechanisms. At the onset of penetration, the host cell walls manifested fluorescence, induced with either aniline blue or sirofluor, at the point of penetration. The fluorescent area was more intense and larger in the resistant host. Fluorescence disappeared with time. After incubation with β-1,3 glucanase fluorescence disappeared, indicating β-1,3 polysaccharide (probably callose) presence. Callose deposits were 2 and 3 times greater in the epidermis and 4 and 9 times greater in the cortex of the resistant than in two susceptible hosts, respectively. Hyphal counts in the cortex of the resistant host were 50% fewer than in the susceptible hosts. Increased callose deposition on host cell walls was associated with reduced colonization. Callose formed in vascular tissue as the fungus colonized it. Callose detection with sirofluor was more sensitive; background fluorescence common with aniline blue without periodic acid – Schiff's reagent pretreatment was absent.

ISSN:0008-4026    

DOI:10.1139/b88-324

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

A field study was conducted in Maryland to estimate nonsummer stomatal conductances on clear days for two invasive woody vine species common to the southeastern United States. Before the first frost in late October, stomatal conductances were similar for kudzu (Pueraria lobata) and Japanese honeysuckle (Lonicera japonica). When minimum predawn air temperature fell to −0.6 °C, kudzu leaves were irreversibly damaged, whereas maximum daily conductance in honeysuckle was unaffected. Maximum conductances in honeysuckle increased to 14 mm s−1in late November and mid-December, similar to late-spring and summer values. When minimum air temperatures decreased to −2.8 °C in January, conductance still remained above 5 mm s−1. Maximum daily conductance was lowest in early March, corresponding with low leaf temperatures. By mid-April, maximum conductance increased to 10 mm s−1. Conductances suggested that rates of leaf gas exchange in honeysuckle during fall, winter, and spring were relatively high. Carbon gain during this period might thus contribute substantially to the invasive growth characteristic of the species.

ISSN:0008-4026    

DOI:10.1139/b88-325

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Plants may alter their growth pattern in response to being grown in elevated CO2concentrations. The nature of the change in carbon partitioning underlying those alterations was investigated inPhaseolus vulgariscv. Gold Crop grown to the third trifoliate leaf stage in CO2concentrations of 380, 800, and 1400 ppm. There was no effect of the CO2concentration on plant height, leaf area, or dry weight, but the specific leaf weight increased significantly with the CO2, concentration, indicating a denser leaf structure. The starch content of the leaves also increased significantly as the CO2level increased. A primary leaf was pulse labelled with14CO2and the depletion of label from that source leaf was monitored with a GM tube. The depletion of the count rate with time was described by a nonlinear curve fitting procedure that allowed the derivation of rate constants to describe the partitioning of carbon in a two-compartment model. Rates of carbon storage decreased in the light with increasing CO2concentrations with no effect on the rates of export or remobilization. Both export and storage were reduced in the dark at all CO2levels, with an increase in the residence time of carbon in the export pool. Reducing the CO2concentration around the source leaf just after labelling did not change carbon partitioning compared to controls. Increasing the CO2concentration around the source leaf just after labelling increased all carbon flux rates and reduced the residence times in the leaf pools.

ISSN:0008-4026    

DOI:10.1139/b88-326

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

The landforms, vegetation, water chemistry, and stratigraphy of four patterned fens (aapamires) in western Labrador and adjacent Quebec are described in a study investigating the origin and characteristics of surface patterns on northern peatlands. Phytosociological analysis by the relevé approach, in conjunction with analysis byTWINSPAN, is used to describe 11 floristic noda. The vegetational patterns are largely controlled by depth to the water table. Mire landforms discussed in detail include ice-push ridges, flarks and pools, peat ridges, and mire-margin hummocks. Water chemistry is typical of minerotrophic conditions, with pH ranging from 4.4 to 6.7 and calcium concentrations from 20 to 430 μiequiv. L−1. The water chemistry, vegetation, and landforms on the mires are compared with other studies from Labrador and circumboreal regions. Stratigraphic results and field observations support the theory that surface patterns on the mire develop slowly through the interplay of biological and hydrological processes, specifically differential rate of peat accumulation controlled by vegetation type and depth to water table. Pool formation apparently involves four steps: (i) gradual differentiation of shallow flarks on previously undifferentiated mire surface; (ii) expansion and deepening of flarks and development of ridges due to differential peat accumulation; (iii) degradation of flark vegetation into mud bottoms and open-water pools; and (iv) coalescence, continued expansion, and deepening of open-water areas. Hydrological controls over the rate and extent of pool formation are discussed as a probable explanation of the geographical distribution of patterned mires.

ISSN:0008-4026    

DOI:10.1139/b88-327

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

The acetylene-reduction technique was used on soil–root cores to examine the three species ofTypha(Typhaceae) found in Minnesota for differences in rates of nitrogen fixation by associated rhizosphere diazotrophs. In 20 cattail stands sampled in 1985,Typha angustifoliashowed a tendency for lower acetylene-reduction activity per ramet, with an average of 2.9 μmol∙ramer−1∙d−1, thanT.latifoliaandT. ×glauca, with averages of 6.5 and 7.1 μmol∙ramet−1∙d−', respectively. Regression analysis showed no significant differences in these values due to the variability within as well as between stands, and fixation rates were uncorrelated with the pH, soil percent carbon, and soil moisture of the study stands. In 1986,in situassays of soil–root cores of ramets ofT.angustifoliaandT.latifoliafrom adjacent monospecific stands produced average acetylene-reduction rates of 1.4 forT.angustifoliaand 1.8 μmol∙ramet−1∙d−1forT.latifolia, with a substantial reduction in variability within stands over the 1985 data. It is estimated that, contrary to previously published reports, populations ofTyphamay receive as little as 1–2% of their annual nitrogen requirement from nitrog

ISSN:0008-4026    

DOI:10.1139/b88-328

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Six C4grasses (Distichlis stricta,Muhlenbergia glomeratavar.cinnoides,M.mexicana,M.richardsonis,Spartina gracilis,S.pectinata) were found in grassy openings in the boreal forest of northwestern Canada. High carbon isotope ratios and Kranz anatomy confirmed that these northern populations are functionally C4grasses.Muhlenbergia mexicanawas assumed to be a C4grass on the basis of published data. Recent collections of C4plants tended to have more negative δ13C values than older collections from northern locations, which may reflect decreases in δ13C of atmospheric CO2over time. In general, northern C4species had lower δ13C values than those reported for their southern counterparts. The boreal climate in the north supports C4species only where the mean minimum temperature for July is at least 7.5 °C. C4grasses were found in microsites warmed by high irradiance or geothermal activity; many of the sites had saline substrates. Northern C4populations are rare and unique in the boreal flora and deserve special protection.

ISSN:0008-4026    

DOI:10.1139/b88-329

出版商:NRC Research Press    

年代:1988

数据来源: NRC