摘要:

The absorption, the exsorption, and the reduction of NO3-ions were examined in light and in darkness in relation to the prior accumulated nitrates in various seedling parts of four Moroccan tender wheat genotypes: Marchouch, Jouda, Khair, and Sais. The genotype Sais has the highest quantity of accumulated nitrates, and the genotype Khair has the lowest. Distribution of nitrates between the roots and shoots of these wheat varieties showed that, for each variety, the shoot accumulates three to five times more NO3-than the roots. Seedlings of the different varieties exposed to light showed a higher absorption and reduction of nitrates than seedlings exposed to darkness. The exsorption of nitrates of plants that are subjected to light was significantly lower than that of the seedlings exposed to darkness. This suggested that the stimulation of NO3-absorption, observed in plants that were exposed to light in comparaison with darkness, could be partly explained by the diminution of nitrate exsorption. The quantitative examination of N-nitrate in roots of plants that were exposed to light showed the presence of quantities of NO3-similar to those of the seedling roots maintained in darkness. These results suggest, that by stimulating the reduction of nitrates, light contributes to a substantial increase of nitrate ion absorption by means of a diminution of ion exsorption out of root cells.

ISSN:0008-4026    

DOI:10.1139/b99-114

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

The mitochondrial DNA (mtDNA) ofChondrostereum purpureum(Pers.:Fr.) Pouzar was extracted and purified, and the size ranged from 51.8 to 66.4 kb. One isolate each from British Columbia, Alberta, Finland, the Netherlands, and New Zealand were found to have identicalBamHI mtDNA restriction patterns, resulting in a mitochondrial genome of 63.8 kb. An additional isolate from British Columbia and one from Switzerland had different banding patterns, however, resulting in mitochondrial genomes of 66.4 kb and 51.8 kb, respectively. A sequence-characterized amplified region (SCAR) assay, based on a polymerase chain reaction, was developed to rapidly screen a larger population of 84 isolates from North America, Europe, and New Zealand. Two SCARs, one encoding the NADH 4 gene (3 kb) and the second encoding the ATPase VI and cytochromebgenes (5.1 kb), were digested with 24 restriction enzymes. There were no polymorphisms in the NADH 4 containing SCAR, while a single polymorphism was detected byNsiI in the ATPase VI - cytochromebcontaining SCAR. Two mitochondrial haplotypes that were distributed throughout the sample population were thus identified. The coancestry coefficient (<$Q7A0D00000010446D80BFFEFF88A524F5343905055B98C420120907B4DDA9ECB1F0>) for all subpopulations of the sample population was calculated to be 0.0353. The level of gene diversity in the mtDNA ofC. purpureumsuggested that the chance introduction of novel mitochondrial genes following biological control applications of the fungus is relatively low.

ISSN:0008-4026    

DOI:10.1139/b99-125

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

We examined the effects of vegetation and herbivores on the seedling establishment, survival, and inflorescence mass of purple loosestrife (Lythrum salicariaL.), a Eurasian plant that invades North American wetlands. The study was conducted in a stand of reed canary grass (Phalaris arundinaceaL.). All grass was removed experimentally from 1.2 × 1.2 m plots to simulate a disturbance. The establishment of sown seeds was compared in disturbed and undisturbed plots. Fifty-three percent of seeds became established in disturbed plots, while no seedlings became established in undisturbed plots, suggesting that disturbance is required for wetland invasion byL. salicaria. In plots without grass, the effect of herbivores onLythrum's survival and inflorescence mass (i.e., sexual reproduction) was assessed by excluding herbivores from some plots but not from others. After two growing seasons,Lythrum's survival did not differ significantly between plots with herbivores excluded (100% plant survival) and plots with herbivores not excluded (60-80% plant survival). However, only plants protected from herbivores produced inflorescences. Mammals such as deer and rodents ate the shoot tips of unprotected plants, which prevented terminal inflorescences from being produced. These results only partly support the claim that North American herbivores are ineffective predators ofL. salicaria. One mechanism underlying wetland invasion byL. salicariais likely a combination of disturbance permitting seedling establishment and insufficient herbivory in disturbed areas to prevent newly established plants from surviving

ISSN:0008-4026    

DOI:10.1139/b99-128

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

Tribal and subtribal boundaries within the Brassicaceae are often artificially drawn. Most of the currently recognized tribes and subtribes are separated by only a few morphological characters. Furthermore, these characters are variable even within genera, or they conflict with one another in their distribution patterns, resulting in controversial classification systems. Therefore, tribes and subtribes as traditionally delimited may not reflect natural groups. Up to now no cladistic analysis has been performed in tribe Lepidieae. In the current study, we have analyzed restriction site variation of chloroplast DNA among 41 species representing 19 genera to get insights into phylogenetic relationships within the Lepidieae. Phylogenetic lineages derived from our chloroplast data were critically compared with the traditional concepts. Our chloroplast DNA phylogeny most easily supports the classification of genera in the system of Hayek with some modifications.

ISSN:0008-4026    

DOI:10.1139/b99-129

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

Wood extractives cause production troubles during pulp and paper manufacture. The potentiality of fungal strains for biotechnological removal of extractives fromEucalyptus globulusLabill. wood is evaluated here. First, a survey of fungi present in eucalypt woodlands in western Spain was carried out, and 90 species, including fungi strictly associated with eucalypt trees, were collected. Then, a total of 33 basidiomycetes, 21 ascomycetes, and 19 conidial fungi (including some strains from culture collections) were compared in terms of their capacity to decrease the acetone extract of eucalypt wood. High extractive removal (50-70% of initial content) was obtained withOphiostoma,Mollisia, andPleurotusspecies, as well as withFunalia trogii(Berk. in Trog) Bond. & Singer,Melanotus hepatochrous(Berk.) Singer, andPaecilomycessp. Microscopic observation of the degraded wood revealed a correlation between extractive degradation and removal of spherical deposits in wood rays. Moreover, when extractive biodegradation was analyzed by gas chromatography - mass spectrometry it was found that some of the basidiomycetes were able to remove both free and esterified sitosterol (75-100% degradation byPoria subvermisporaPilát,Phlebia radiataFr.,F. trogii, andBjerkandera adusta(Willd.) P. Karsten), which has been identified as a major constituent of pitch deposits in eucalypt pulps, whereas the action of ascomycetes was mainly limited to hydrolysis of the sitosterol esters

ISSN:0008-4026    

DOI:10.1139/b99-127

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

Live trees within forest disturbances could support refugia populations of ectomycorrhizae fungi from which to reestablish ectomycorrhiza communities during forest succession. The effectiveness of refuge paper birch trees (Betula papyriferaMarsh.) in maintaining a forest ectomycorrhiza community on birch seedlings, both in clearcuts and forests, in northwest British Columbia was examined. Seedlings next to refuge birch trees in clearcuts had equal levels of average morphotype richness and eveness as seedlings next to mature birch trees in forests. Seedlings outside of the rooting zone of refuge trees had significantly less average morphotype richness in both clearcuts and forests, decreasing by 38 and 15%, respectively. The ectomycorrhiza communities were also more unique (lower community similarity) next to refuge trees than for seedlings away from refuge trees, especially in clearcuts. These treatment effects could be explained by differences in the ability to disperse and establish between early-stage, multi-stage, and late-stage ectomycorrhiza fungi. The results suggest refuge trees would be effective in forest management as sources of inocula for multi-stage and late-stage fungi.

ISSN:0008-4026    

DOI:10.1139/b99-132

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

Stomata and pollen from forest hollow sediments in the Great Lakes were evaluated for their ability to document stand-scale forest invasion. In surface sediments of 19 forest hollows, stomate presence is related most closely to tree presence within 10-20 m for eastern hemlock (Tsuga canadensis(L.) Carr.), pine (Pinusspp. L.), balsam fir (Abies balsamea(L.) Mill.), and northern white cedar (Thuja occidentalisL.). Although the abundance of hemlock pollen in surface sediments is positively related to the abundance of hemlock trees within 100 m, it does not consistently reflect the presence of hemlock trees within this distance. Pollen and stomata preserved in forest hollow sediments from northwestern Wisconsin were used to document two stages of stand invasion by eastern hemlock. First, hemlock stomata initially appear approximately 240014C years BP, representing the initial colonization of the forest stand. Hemlock pollen also first appears at this time but in such low abundance that the presence of hemlock trees at the site cannot be known with certainty. Second, hemlock pollen percentages increase sharply around 35014C years BP, approximately 2000 years following initial colonization, and represent an expansion of the local hemlock population not reflected by stomatal and needle abundance.

ISSN:0008-4026    

DOI:10.1139/b99-133

出版商:NRC Research Press    

年代:2000

数据来源: NRC