摘要:

The storage rot pathogenPhoma betaenormally attacks the exposed stem pith of harvested sugar beets (Beta vulgarisL.) before invading adjacent stem and taproot tissues. A comparison of rotted and sound tissues of nonselected roots showed that increased polyphenoloxidase activity occurred in rotted stem tissue, but peroxidase decreased. Endopolygalacturonate transeliminase (endoPGTE) was more active in rotted pith tissue compared with other rotted tissue. Comparison of rotted tissue from resistant and susceptible inbreds showed the greatest difference in oxidase activity occurred in resistant taproot tissue. Higher polyphenoloxidase activity was associated with resistant stem tissue of nonselected roots when catechol was the substrate rather than chlorogenic acid.Phoma betaegrowth in liquid culture was inhibited more by oxidation products of catechol than by those of chlorogenic acid. Peroxidase activity was associated with resistance only in stem and taproot tissue of inbreds. Endo PGTE activity was low in infected resistant tissue. When isolated cell walls of nonselected sugar beets were used as the carbon source,P.betaegrew more and endo PGTE activity was greater on cell walls from pith than cell walls from adjacent stem or taproot tissue after 6 days incubation.

ISSN:0008-4026    

DOI:10.1139/b75-163

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Reparative tissue was observed around healed natural wounds in leaves of 53 species of 9 of the 12 magnoliaceous genera:Aromadendron,Elmerrillia,Kmeria,Liriodendron,Magnolia,Manglietia,Michelia,Paramichelia, andTalauma. Additional evidence was obtained from wounding experiments carried out on attached leaves of two evergreen species,Magnolia grandifloraandMichelia figo. Regeneration was studied over a 6-week period. Evergreen leaves produced more abundant regenerative tissues than deciduous leaves; a narrow-to-broad periderm forms consistently in all evergreen magnoliaceous leaves around wounds, but wounds in the deciduous species invoke little or no periderm development. The healing process in these leaves consists of three steps: (1) cells die along the wound, and cells immediately adjacent become physiologically altered; (2) a callus forms by randomly oriented cell divisions throughout mesophyll, vein sheath, and (in most species) epidermis; and (3) a periderm eventually forms in the band of callus parallel to the wound. The complete process takes 4 to 6 weeks in the evergreen magnoliaceous plants studied. The differences in healing processes are contrasted between evergreen and deciduous leaves. Of special interest is the observation that guard cells of mature leaves in several taxa dedifferentiate and undergo division in the area of wound repair.

ISSN:0008-4026    

DOI:10.1139/b75-164

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

The development of the epibiotic sporangium from resting spore zoospores of 18Physodermaspp. has been examined to determine whether or not this stage can assist in delimiting groups of species within the genus when associated with other morphological characters. It was found that 11 entities had a "bilateral" type of sporangial development and 7 had a "unilateral" type. These types could not be associated with other morphological features of either epibiotic or endobiotic stages to produce taxonomic groupings. Type of epibiotic sporangial development, at the moment, is regarded as simply another morphological parameter.

ISSN:0008-4026    

DOI:10.1139/b75-165

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Proplastids from developing castor beans,Ricinus communisL., were isolated using velocity gradient centrifugation on sucrose gradients with superimposed gradients of Mg2+. Preparations were free of contamination by mitochondria and showed only slight contamination by microbodies. The use of acetyl-CoA carboxylase as a cytochemical marker for castor-bean proplastids was demonstrated.

ISSN:0008-4026    

DOI:10.1139/b75-166

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Virulence differences on “standard”Puccinia graminis triticidifferentials are not chronologically related and do not form evolutionary series. Chronologically related virulence differences between strains of "standard" race 15B-1L on "single-gene" differentials form an evolutionary series of single-step virulence changes, while virulence differences between strains of "standard" race groups 11-32, 17-29, and 56-125 do not. Most virulence changes were from avirulence to virulence, or vice versa, but on varieties with resistance genesSr7aandSr11intermediate virulence occurred, which suggests that there was more than one kind of genetic change. There was no indication of an overall increase or decrease in the number of virulence genes present in all races, although virulence on genesSr7aandSr5has increased. Random virulence changes on single host resistance genes, probably the result of mutations, seem to occur frequently and may be the most common kind of change in North America under present conditions. They permit the rust to overcome single-gene resistance, but they are not very effective in overcoming complex resistance. The stability of complex resistance in North America suggests that other processes capable of producing a wider range of variability occur infrequently in nature.

ISSN:0008-4026    

DOI:10.1139/b75-167

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Biological nitrogen fixation was studied on Truelove Lowland, Devon Island, N. W. T., in three different habitats. Raised beach ridges, resulting from postglacial uplift, form well-defined xeric habitats, which are dominated by dwarf shrubs and cushion plants. Hummocky sedge meadows with associated mosses and forbs comprise the second intensively studied habitat. Waterlogged wet sedge meadows with moss were studied less intensively.Nitrogen fixation was estimated using acetylene-reduction assay. Incubation temperatures were moderated by burying the jars in soil pits (10 cm) on site.Available nitrogen was determined by microkjeldahl analysis of KCl soil extracts.Symbiotic nitrogen fixation by vascular plants is nil on Truelove Lowland. One lichen species,Peltigera aphthosa, reduced acetylene (5.1 μμmol∙mg−1∙h−1).Nostoc commune, a prominent blue-green alga on meadow soils, reduced acetylene at a rate 10 times that ofP.aphthosa. An estimated 30 and 7 mg N∙m−2∙year−1was fixed by bacteria and soil algae in beach ridge soil in 1971 and 1972 respectively, and 380 and 120 mg N∙m−2∙year−1was fixed in meadow soils in the

ISSN:0008-4026    

DOI:10.1139/b75-168

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Nicotiana tabacumL. cv. Coker 319 has been found to be sensitive to changes both in temperature and photoperiod. Within a given time period fewer leaves are produced at low temperatures than at high temperatures. The classical day-neutral flowering response was not observed for this plant under six photoperiods of varying lengths. The results thus indicate that the plant may be more appropriately classified as being "preferentially ambiphotoperiodic," rather than strict "day-neutral." Preconditioning the seedlings with a long-day photoperiod produced plants that had higher total leaf numbers and flowered earlier than seedlings treated with a short-day photoperiod. The morphology of the vegetative and reproductive stem apex was similar to that reported for other species and cultivars ofNicotiana. Apical meristems were systematically ranked according to their progressive developmental stages encompassing vegetative, transition, and reproductive development.

ISSN:0008-4026    

DOI:10.1139/b75-169

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Lipids measured as acyl glycerides and free fatty acids provided the major energy source during a 6-h motile and a 2-h germination period in zoospores and cysts, respectively, ofPhytophthora palmivora. Carbohydrates and proteins decreased slightly during the 6-h motile period but increased significantly during germination. Specific activity of isocitrate lyase decreased both during zoospore motility and cyst germination. Only trace amounts of malate synthase activity were detected in zoospores and cysts. The activities of both NAD-isocitrate and malate dehydrogenases increased slightly, while those of NADP-isocitrate and succinate dehydrogenases decreased during the 6-h motile period. During the 2-h germination period the specific activities of NAD- and NADP-isocitrate, malate, and succinate dehydrogenases increased. It appears that during the motile stage the glyoxylate cycle provided more metabolites for the Krebs cycle than it did during germination.

ISSN:0008-4026    

DOI:10.1139/b75-170

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Macrochemical reactions are reported on 15 species ofSuillus, 3 ofFuscoboletinus, 2 ofGyroporus, and 1 species each ofBoletellus,Boletinellus,Pulveroboletus, andStrobilomyces, together with a number of tests on species ofTylopilusandBoletusnot available for an earlier paper. Three species ofSuillusand threeBoletusspecies are new records for Nova Scotia, and two of these are new for Canada. Also included are tests for a new species ofBoletusto be described in another paper.Similarities in the macrochemical tests are used to divide 13 of the species ofgenus Suillusinto two groups.Suillus luteuswas selected as the type for group 1 andS.americanusfor group 2. Two species did not belong to either group and were distinctly different from each other. Two species ofFuscoboletinuscould be placed with group 2, but the third,F.paluster, differed widely.Boletus piperatus, which has been placed inSuillusby some authors, does not appear to be related on the strength of these tests. No attempt was made to group other species inBoletusorTylopilus.

ISSN:0008-4026    

DOI:10.1139/b75-171

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Emerson'sSaprolegniasp. 47-15amost closely resemblesSaprolegnia ferax(Gruith.) Thuret. Temperature is an important factor in determining the morphology of the isolate. At 21C oogonium development is inhibited and gemma production is enhanced. At 14C or less, oogonia are produced abundantly and gemma production is inhibited. The linear growth rate of the isolate doubles as the temperature doubles within a temperature range of 3 to 21C.

ISSN:0008-4026    

DOI:10.1139/b75-172

出版商:NRC Research Press    

年代:1975

数据来源: NRC