摘要:

The distribution and the ontogenesis of lateral roots have been investigated in the Mediterranean woody speciesQuercus suberL. (cork oak). Lateral roots arose in protoxylem-based ranks and a tendency to clumping was observed. Three stages are distinguished in lateral root primordium development. Lateral root primordia are derived mainly from pericycle cells. The endodermis contributed to the initial lateral root development, forming an endodermal cover that sloughs off with lateral root emergence. The unemerged lateral roots show an incipient layered root meristem; this meristem can be classified as a closed type meristem. Primary vascular connection takes place with the xylem strand opposite the lateral root primordium and the two adjacent phloem strands. Primary vascular connector elements are derived from pericyclic derivative cells. Vascular parenchyma cells contribute mainly in the development of the cambium and the subsequent secondary xylem and phloem connector elements. The secondary vascular elements of the lateral root and parent root differentiate in continuity. Vascular connection is discussed in relation to the root vascular plexus described in monocotyledonous and in some herbaceous dicotyledonous plants. An endodermis with suberized lamellae is continuous between the lateral and parent root in emerged lateral roots.Key words: lateral root, development pattern, apical lateral root meristem, root vascular connection,Quercus suberL.

ISSN:0008-4026    

DOI:10.1139/b00-077

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

Flavonoid chemistry and chromosome numbers ofFallopiasect.Pleuropteruswere examined to gain insights into the relationships among the taxa within the section. Twenty-seven flavonoid compounds were isolated and identified from taxa of sectionPleuropterus; most of them were glycosylated derivatives of the flavonols kaempferol, quercetin, and myricetin, and of the flavones apigenin and luteolin. The flavonoid data appear to be useful for taxon delimitation, because all taxa examined are readily distinguished by their flavonoid profiles. In addition, the flavonoid data revealed the presence of two chemical entities in the section; the first group includesFallopia multiflora(Thunb. ex Murray) Haraldson (with varieties) andFallopia ciliinervis(Nakai) Hammer and the second group includesFallopia baldschuanica(Regel) Holub andFallopia koreanaOh & Kim. These groupings suggested by the flavonoid chemistry are well-corroborated by the chromosome number of these taxa. Taxa of the first group have chromosome numbers based onx= 11 (2n= 22, 44), whereas chromosome numbers of the second group are based onx= 10 (2n= 20). Our counts forF. multifloravar.hypoleuca(Nakai ex Ohwi) Yonekura & H. Ohashi (2n= 44),Polygonum multiflorumThunb. ex Murray (=F. multiflora) var.angulatumS.Y. Liu (2n= 22),F. ciliinervis(2n= 22), andF. koreana(2n= 20) are the first reports for these taxa. Based on these results, and in conjunction with morphological evidence, it is strongly suggested that the two groups of sectionPleuropterusrevealed by this study are not closely allied and may represent separate lineages in the genusFallopia.Key words: Polygonaceae,Fallopiasect.Pleuropterus, flavonoids, chromosome number, chemotaxonomy.

ISSN:0008-4026    

DOI:10.1139/b00-079

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

The physiological mechanisms associated with resistance of cabbage to black rot disease seem to be associated with the hydathodes. To investigate the role of hydathodes in disease resistance, total peroxidase activities, anionic peroxidase isozyme expression, and lignin deposition were determined in hydathodes of resistant (Hancock and Green Cup), partially resistant (Cheers), and susceptible (Strukton and Perfect Ball) cabbage varieties (Brassica oleraceaL.) during pathogenesis withXanthomonas campestrispv. campestris. Four-week-old plants were petiole-inoculated with a highly virulent strain ofX. campestrispv. campestris(FD91L). Hydathodal fluids were collected daily over a 14-day period from infected plants as well as noninfected, mock-inoculated control plants. Hydathodal fluids of resistant varieties had greater peroxidase activity when compared to susceptible ones, with infected plants having higher peroxidase levels than noninfected plants. Isoelectric focusing revealed the presence of four anionic peroxidase isozymes in hydathodal fluids, with the most anionic one (pI of 3.6) accumulating only upon infection. Lignin deposition in and around the hydathodes was associated with the accumulation of this particular isozyme in hydathodal fluids. The evidence suggests that a rapid, systemic response is associated with resistance to the bacterial pathogen.Key words: peroxidases, hydathodes, isozymes, black rot disease, cabbage,Xanthomonas campestrispv. campestris.

ISSN:0008-4026    

DOI:10.1139/b00-086

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

Our analysis of the genetic variability and phylogenetic relationships among the isolates of mitosporic entomopathogenic fungiPaecilomyces fumosoroseus(Wize) Brown & Smith (10 isolates),Paecilomyces farinosus(Holm ex S.F. Gray) Brown & Smith (3 isolates),Paecilomyces lilacinus(Thom) Samson (1 isolate), andVerticillium lecanii(Zimmerman) Viegas (6 isolates) was based on the use of random amplified polymorphic DNA (RAPD) markers. Neighbor-joining analysis characterizedP. fumosoroseusandV. lecaniias monophyletic taxa. The analysis also supported monophyly of the genusPaecilomyces. We have used the distribution of genetic distances to demonstrate the genetic variability within studied species, inPaecilomycesspp. (Hyphomycetes) andAschersoniaspp. (Coelomycetes) in particular. We conclude that the RAPD-based analysis is useful for the reconstruction of intraspecific and interspecific relationships of the entomopathogenic fungi. Moreover, it can be employed to study the intergeneric relationships, especially in the case of closely related genera of the hyphomycetous entomopathogenic fungi. We propose that RAPD-based phylogeny and genetic variability reflect their life strategy. In our opinion, the mobility of spores represents a factor with major influence on the evolution of these entomopathogenic fungi.Key words:Paecilomyces,Verticillium,Aschersonia, RAPD, phylogeny, genetic variability.

ISSN:0008-4026    

DOI:10.1139/b00-087

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

The effects of GA3, KNO3, and NaHCO3on germination percentages and rates were determined for cypselas (seeds) of four local populations of Scotch thistle,Onopordum acanthiumL., collected during a 2-year period. Three (1996, stored cypselas) and four (1997, fresh cypselas) concentrations (0.025, 0.05, and 0.1% for both years, plus 0.0125% for 1997) of the three compounds were used. Both freshly collected cypselas and those stored for 67 days at room temperature exhibited a range of germination responses from readily germinable to strongly dormant. GA3, even at a very low concentration, caused most viable cypselas to germinate, but 5-6% of viable cypselas in two populations did not respond to any GA3treatment. In general, dry-stored cypselas germinated faster than fresh ones. Populations with more germinability (= proportion of cypselas capable of germinating) responded faster to GA3than those with less germinability. KNO3usually increased germination percentages but reduced the rate of germination. When treated with KNO3, stored cypselas from the two populations with less germinability germinated more slowly than those of the other two. In general, germination percentage decreased with an increase in NaHCO3concentration. Overall, stored cypselas that were treated with NaHCO3germinated more slowly than those in the control. The large differences among four local populations in response to these chemicals suggest that the effects of germination stimulators and other chemicals should be observed on several populations per species.Key words: cypsela, germination promoters, germination inhibitors, local populations,Onopordum acanthium, Scotch thistle.

ISSN:0008-4026    

DOI:10.1139/b00-088

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

We examined the effect of the lower lip ofMonarda didymaL. on pollen removal by ruby-throated hummingbirds (ArchilochuscolubrisL.) through comparisons of hummingbird visits to natural, lipped flowers versus those that had their lower lip experimentally removed. Birds missed the openings of lipless flowers more often than lipped flowers and thus spent more time attempting to insert their bills into them. Once their bills entered the floral tube, handling times of hummingbirds were significantly longer at lipped than at lipless flowers. Contact durations with anthers and amounts of pollen removed by hummingbirds were significantly greater at lipped than at lipless flowers. Videotapes indicated that lips enhanced pollen removal by slowing a hummingbird's bill insertion into the floral tube, which increased the amount of time that a bird was positioned under a flower's anthers. Unlike the conventional view of hummingbird-flower evolution, which argues for the loss or reduction of lips, our results suggest that lower lips may be maintained in some hummingbird flower species, because they are preadaptations that act as nectar guides for hummingbirds and positioners for optimum pollen removal, in addition to possibly serving as landing platforms or attractants for secondary pollination by bees.Key words:Monarda didyma, pollination, flower morphology, hummingbirds.

ISSN:0008-4026    

DOI:10.1139/b00-089

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

The influence of simple sugars, salts, andBotrytis-specific monoclonal antibodies on the binding of three bacteria (Enterobacter aerogenesHormaeche & Edwards,Enterobacter cloacae(Jordan) Hormaeche & Edwards, andOchrobactrum anthropiigen.nov.) and three yeasts (Candida sake(Sarto & Ota) van Uden & Buckley,Candida pulcherrima(Lindner) Windisch, andTrichosporon pullulans(Lindner) Diddens & Lodder) toBotrytis cinerea(Persoon:Fr) was examined. Solutions of 0.1 M D(+)-galactose, L-fucose, orBotrytis-specific monoclonal antibodies significantly reduced populations ofE. aerogenesandE. cloacaeadhering to pathogen germlings, whereas 0.1 M raffinose significantly reducedC. sakeorC. pulcherrimaadhesion. In cytochemical studies, lectin-gold labeling demonstrated the presence of galactose moieties in the walls or matrix ofE. aerogenes, and this labeling was diminished in bacteria that were attached toB. cinerea. Immunolabeling with aBotrytis-specific monoclonal antibody that recognizes a glycoprotein was particularly intense in condensed regions of the pathogen matrix associated with adherentE. aerogenes, whereasC. sake-B. cinereainteractions revealed a loose encapsulation of adherent yeast cells by the matrix ofB. cinerea. Results from this study suggest the presence of several adhesion mechanisms that can be distinguished according to yeast or bacterial binding and further defined according to the genus.Key words: adhesion, bacteria, biocontrol,Botrytis cinerea, ultrastructure, yeast.

ISSN:0008-4026    

DOI:10.1139/b00-091

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

We compare fossil pollen and stomate assemblages in 29 lake sediment surface samples from mountainous regions in northwestern Canada to characterize the relationship between modern vegetation, and pollen and stomate deposition. Modern pollen spectra were dominated by arboreal taxa originating from lower elevation sites.Pinuspollen frequently reached 30% of the pollen sum, regardless of elevation. Alpine-tundra vegetation has lower pollen abundance, even in the alpine-tundra zone, where it dominates the sparse vegetation cover. Fossil stomates were observed in all but one site where trees currently exist in the vicinity of the lake, while no stomates were found in the sediments from alpine-tundra sites. The highest concentration of stomates occurred in lake sediments from closed-canopy forested areas. Our data suggest that different boreal forest types may be differentiated based on pollen assemblages and that the presence of stomates clearly distinguishes vegetation zones dominated by arboreal vegetation from alpine-tundra zones where trees are not present.Key words: pollen, conifer stomates, treeline, Pacific Northwest.

ISSN:0008-4026    

DOI:10.1139/b00-092

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

We examined the effect of prolonged (up to 450 days) soil burial in the field on seed morphological traits (seed coat structure, permeability) to identify their potential roles in seed dormancy and release. Such traits were examined in species with seeds that demonstrated an obligate requirement for soil storage before germination: the dormant seeds ofAnigozanthosmanglesiiD. Don,Conostylis neocymosaHopper,Stylidium affineSonder, andStylidium crossocephalumF. Muell., and the deeply dormant fruits ofLeucopogon conostephioidesD.C. We detected species-specific and environmentally induced variation in seed morphology following soil burial. InA.manglesiiandL.conostephioides, a significant deterioration of the seed coat or fruit wall and an increased permeability of the seed coat to water and solutes were correlated with germination responses. In these species, the seed coat and (or) fruit wall delayed germination until (morpho) physiological dormancy was broken. InC. neocymosa,S. affine, andS. crossocephalum, weathering of the seed coat, permeability, and germination were not correlated traits. These species appeared to possess physiological dormancy mechanisms and required environmental cues for dormancy release.Key words: physiological dormancy, soil burial, seed coat, morphology.

ISSN:0008-4026    

DOI:10.1139/b00-093

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

Dormancy-breaking requirements and type of dormancy were determined for seeds ofDiervilla loniceraMill. Seeds have an underdeveloped linear embryo that is about 35% of the length of the seed at maturity. Embryos (in intact seeds) grew at 25:15°C but not at 5°C. Up to 85% of the freshly matured seeds had morphological dormancy (MD), and thus, they germinated within about 30 days on a moist substrate in light at 30:15°C; a maximum of 3% of the seeds germinated in constant darkness. The other portion of fresh seeds had nondeep simple morphophysiological dormancy (MPD) and required a period of warm stratification or treatment with GA3to break dormancy. These seeds also required light to germinate. In contrast, cold stratification induced dormancy, and dry storage for up to 1 year did not effectively break dormancy. Seeds with MD germinated to significantly higher percentages on soil than on filter paper or on sand. Seeds sown on soil in a non-temperature-controlled greenhouse in mid-November germinated mostly in late May, whereas those sown in mid-April germinated in early May. Apparently, embryos of November-sown seeds were induced into physiological dormancy during winter. Thus, seeds had MPD in spring and needed several weeks of warm temperatures for dormancy break, embryo growth, and germination. This is the first report on seed dormancy in the genusDiervilla.Key words: embryo growth, germination phenology,Diervilla lonicera, morphological seed dormancy, morphophysiological seed dormancy, underdeveloped linear embr

ISSN:0008-4026    

DOI:10.1139/b00-094

出版商:NRC Research Press    

年代:2000

数据来源: NRC