摘要:

The ability of a grassland to regenerate following disturbance depends on the presence of seeds of native plants and the ability of the seeds to germinate. To examine whether the presence or absence of plant propagules influences reestablishment of tallgrass prairie on abandoned agricultural lands, we sampled the seed rain and soil seed bank across a transition from native tallgrass prairie to unmanaged successional grassland (old field). The native prairie seed rain was seven times greater than that of the old field, richer in species (33 vs. 27), and more diverse (diversity index 0.96 vs. 0.73). In addition, the native tallgrass prairie seed bank was three times as dense as the old-field seed bank and contained the seeds of more species (23 vs. 19), but had a lower index than did the old field (0.81 vs. 1.08). One species,Sphenopholis obtusata, present in the prairie, was observed dispersing to the old-field plot, but was absent in the old-field plot; this observation suggests that at least some species are unable to establish on the old-field plot. Thus, the ability of a native grassland to reestablish may be limited by the dispersal ability of native species and the ability to establish once dispersed.Key words: seed rain, seed bank, native tallgrass prairie, old-field succession.

ISSN:0008-4026    

DOI:10.1139/b97-001

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

The diversity and distribution of mating alleles in local populations of two litter decomposing mushroom species were investigated. The results from mating crosses between single-spore isolates were used to deduce mating genotypes among closely adjacent individuals.Collybia subnudahas a high mating allele diversity that is comparable to the diversity of other bipolar species. Adjacent individuals ofC.subnudadid not share mating alleles, which suggests that outcrossing usually occurs in this fungus. The estimate of mating allele diversity inC.subnudais 45, with a 95% confidence interval of 19–187. A simplified approach for designing and analyzing intercollection mating crosses for tetrapolar fungi was tested withMarasmiellus praeacutusand found useful. An unexpectedly low mating allele diversity was found inM.praeacutus, with adjacent individuals frequently sharing more than one mating allele. The pattern of shared alleles inM.praeacutussuggests the occurrence of di–mon crossing (the Buller phenomenon). We suggest that the observed low level of mating allele diversity inM.praeacutusis a consequence of limited spore dispersal, and we discuss the implications of these conclusions for population sampling in the higher fungi.Key words:Collybia subnuda,Marasmiellus praeacutus, mating, population.

ISSN:0008-4026    

DOI:10.1139/b97-002

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

Drought is the main climatic limitation to coconut palm (Cocos nuciferaL.) production. To identify early screening parameters for drought resistance, physiological responses to water deficit were investigated for the first time using containerized young plants grown outside. Three varieties were studied: 'West Coast Tall' (drought avoiding), 'Malayan Yellow Dwarf' (drought susceptible), and their progeny, the hybrid 'PB 121' (drought resistant). Leaf water status (relative water content, leaf water potential) and leaf gas exchange parameters (stomatal conductance to water vapor, net photosynthetic rate, and leaf internal CO2concentration) were measured throughout a drying cycle induced by withholding watering. On fully hydrated plants, the sensitivity of stomata to atmospheric water vapor deficit was also investigated. In the three varieties, stomatal conductance to water vapor declined before leaf water status parameters were affected. The existence of a root-to-shoot communication system was proposed. Net photosynthetic rate was highly dependent on stomatal aperture, but nonstomatal factors also participated in the reduction of CO2fixation. Since gas exchange rates were equally sensitive to drought in the three varieties, they could not be used as screening parameters for drought resistance. Under severe drought stress, both relative water content and leaf water potential differed significantly among populations. 'West Coast Tall' maintained a higher leaf water status than 'Malayan Yellow Dwarf'. Remarkably, the water status parameters of 'PB 121' were intermediate between those of the two parents. Similar ranking was obtained in experiments with excised leaflets. The high reproductibility of the results suggests that leaf water status parameters might be useful as early selection criteria for drought resistance in coconut palm.Key words:Cocos nuciferaL., gas exchange, leaf water status parameters, water deficit, water relations.

ISSN:0008-4026    

DOI:10.1139/b97-003

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

The objective of this study was to determine the spatial and temporal distribution of the peptide BN28 inBrassica napuscv. Cascade seedlings during low temperature acclimation. Immunoblots revealed that BN28 was present in leaves and shoot apical meristems of plants grown under low temperature but was absent from older tissues in the stem. Immunocytochemistry was used to determine the distribution throughout leaf and apical meristem tissues. BN28 was found throughout the apical meristems, was localized in the ground tissue and epidermis of young leaves, and was restricted to the ground tissue and guard cells in mature leaves. Differences in total accumulation were also noted, with the youngest leaves having the highest accumulation of BN28 and the quantity decreasing with leaf age. Despite these differences, plant developmental stage did not affect the accumulation of BN28 in individual leaves. Post-transcriptional controls are expected to regulate accumulation of the protein, asbn28mRNA accumulates during acclimation in both young and mature leaves. Immunolocalization studies of BN28 in acclimated leaf tissue confirmed that BN28 is cytoplasmically localized and has no apparent weak association with organelles or other cellular membrane systems.Key words: acclimation,Brassica, development, immunocytochemistry, low temperature, protein synthesis.

ISSN:0008-4026    

DOI:10.1139/b97-004

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

Mycorrhizal fungi of the genusTuberare classified by morphological characters that allow differentiation of most species. However, some economically important species are difficult to differentiate on morphological grounds. When morphological traits are not sufficient to discriminate between taxa, other markers are needed. Genetic variation of fruit bodies of 12Tubertaxa was studied by the random amplified polymorphic DNA (RAPD) technique. High interspecific variability was observed between most species. Moreover, important infraspecific variation occurred in all species, exceptTuber brumales.L,Tuber melanosporum, andTuber magnatum. Southern hybridization patterns of RAPD products of the various species were used to confirm the data. Relationships amongTuberspecies were determined by cluster analyses. UPGMA analyses revealed several main clusters and a low genetic similarity between taxa. These results indicate that RAPD and polymerase chain reaction are useful for analysing genetic variation withinTuberspecies. Most species can be identified by differences in their amplified DNA profiles. However, the two pairs of closely related taxaTuber aestivum–Tuber uncinatumandTuber brumalevar.brumale–Tuber brumalevar.moschatumdid not appear to differ genotypically.Key words:Tuber, RAPD, Southern, UPGMA, inter- and infra-specific variability.

ISSN:0008-4026    

DOI:10.1139/b97-005

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

Clonal growth and reproduction in tristylousLythrum salicariaL. were examined experimentally, using cloned genotypes of each of the three flower morphs, in field studies involving four moisture and three nutrient treatments. Clonal growth was measured in terms of diameter of clones, number of ramets per clone, and total length of ramets, and an index of reproduction was recorded as the total length of infructescence per clone. Neither clonal growth nor reproduction differed significantly among flower morphs, but both differed significantly as a consequence of both moisture and nutrient treatments. The pattern of seasonal growth indicates that ramet production was restricted mainly to the beginning of the season following vigorous vegetative growth. Although flowering began in June, it was restricted to plants in drier treatments in the water-gradient experiment. Characters intrinsic to tristyly (such as lengths of styles and stamens, and allocation of biomass to stamens and pistil) differed significantly among morphs. Soil moisture levels but not fertilizer treatments significantly affected the size of floral structures and biomass. Although absolute levels of biomass allocation to whole flowers and to attractive structures did not differ significantly among morphs, relative allocation to stamens increased progressively from long morph to mid-morph to short morph, with a corresponding decrease in relative mass of pistil. Although proportional allocation differed significantly among morphs, it was unaffected by moisture treatment, suggesting tight genetic control of herkogamy (spatial separation between anther and stigma). This should maintain the floral polymorphism in different ecological conditions.Key words:Lythrum salicaria, nutrient and water gradients, heterostyly, floral morphometry, floral allocation, clonal growth, sexual reproduction.

ISSN:0008-4026    

DOI:10.1139/b97-006

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

Ten species of white-rot fungi, mainly belonging to the family Polyporaceae (Basidiomycotina), were studied in terms of their ability to degrade14C-ring labelled synthetic lignin and secrete ligninolytic enzymes in liquid cultures under varying growth conditions. Lignin mineralization by the fungi in an air atmosphere did not exceed 14% within 29 days. Different responses to the elevated Mn2+concentration and the addition of a manganese chelator (sodium malonate) were observed among various fungal species. This could be related with the utilization of either lignin peroxidase (LiP) or manganese peroxidase (MnP) for lignin depolymerization, i.e., some fungi apparently had an LiP-dominating ligninolytic system and others an MnP-dominating ligninolytic system. The LiP isoforms were purified fromTrametes gibbosaandTrametes trogii. Isoelectric focusing of purified ligninolytic enzymes revealed the expression of numerous MnP isoforms inTrametes gibbosa,Trametes hirsuta,Trametes trogii, andAbortiporus biennisgrown under a high (50-fold) Mn2+level (120 μM) with the addition of the chelator. In addition, two to three laccase isoforms were detected.Key words: white-rot fungi, lignin degradation, lignin peroxidase, manganese peroxidase, manganese, malonate.

ISSN:0008-4026    

DOI:10.1139/b97-007

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

Experimental hand-pollinations were performed on a sample of wild radish,Raphanus raphanistrum, to determine whether female reproductive success was pollen limited. Fruit set was found to increase with receipt of supplemental pollen, but seed set did not. These results contradict findings in anotherRaphanusspecies but are expected if seeds are aborted or matured in packages.Key words: pollen limitation,Raphanus raphanistrum, female fitness.

ISSN:0008-4026    

DOI:10.1139/b97-008

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

Two strains ofMelampsora lini(flax rust) were identified that differed in their ability to produce a self-inhibitor of urediospore germination. Analysis of germination self-inhibitor production amongst 63 F2progeny derived from a sexual hybrid of these two strains revealed segregation of this trait. Segregation of urediospore germination self-inhibitor production was consistent with single-locus control with inhibitor production being recessively inherited.Key words: rust, germination, spore, inhibitor.

ISSN:0008-4026    

DOI:10.1139/b97-009

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

A field and laboratory study examined the hypothesis that the small-scale distribution pattern ofJuniperus virginianaon barrier islands is related to salinity patterns and plant responses to salinity. Temporal (May – October) and spatial variability in ground water availability, ground water salinity, and total soil chlorides were quantified across a Virginia barrier island. Groundwater depth and salinity increased throughout the summer; microtopographic position and location on the island also affected soil salinities. Highest salinities occurred near the ocean side beach and bay side marsh, as well as in low lying swales that flood during extreme high tides or storms. Median rooting zone chloride level forJ.virginianawas 54 μg/g. In contrast, laboratory germination and growth studies indicated thatJ.virginianawas significantly affected only at high salinity levels (1000 and 1400 μg/g), suggesting that salinity is not the only factor regulating small-scale distribution patterns. The broad tolerance to salinity may account for the abundance ofJ.virginianain coastal environments.Key words: barrier island, eastern red cedar,Juniperus virginiana, salinity response, water relations.

ISSN:0008-4026    

DOI:10.1139/b97-010

出版商:NRC Research Press    

年代:1997

数据来源: NRC