摘要:

Export and distribution of14C assimilates during a period of steady-state photosynthesis were studied in attached leaflets of the second trifoliate ofPhaseolus vulgarisfor 2 weeks following inoculation withXanthomonas campestrispv.phaseoli. The control was the leaflet opposite the inoculated leaflet at the same node. On either a chlorophyll or leaf area basis, photosynthesis and export declined over time after inoculation compared with control tissue. By 14 days after inoculation, photosynthesis and export were 25 and 50% lower, respectively, in the infected leaflets, even though only 7–10% of the total area measured was necrotic. The reduced synthesis of sucrose was sufficient to account for the reduced export from the infected leaflets. Starch synthesis was reduced to a greater extent in infected leaflets than was sucrose synthesis. In leaf disks infiltrated with mannose or xanthan, an extracelluar bacterial polysaccharide containing mannose, photosynthesis was reduced by 20% and the partitioning of14C photoassimilates into sucrose was reduced but was slightly increased into starch. This is consistent with an effect of xanthan at least in vitro on the triose phosphate/phosphate exchange at the chloroplast envelope.Keywords: photosynthesis, export, xanthan,Phaseolus vulgaris,Xanthomonas campestrispv.phaseoli.

ISSN:0008-4026    

DOI:10.1139/b96-001

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

Some species of the generaPhillipsiaandWynneahave similar longitudinally ridged cyanophobic ascospore markings. Ultrastructural studies show that the cyanophobic spore markings are part of the primary wall. In contrast, the cyanophilous spore ornaments are formed by the secondary wall. The observation of spore wall development indicates that the sources of the spore wall components are the sporoplasm and the epiplasm. Based on the pinkish hymenial color of fresh young apothecia and the cyanophobic spore ridges found only in some members of the Sarcoscyphaceae,Wynneabelongs to the Sarcoscyphaceae.Keywords: Pezizales,Phillipsia, Sarcoscyphaceae, spore wall ontogeny, ultrastructure,Wynnea.

ISSN:0008-4026    

DOI:10.1139/b96-002

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

The effect of five mycorrhizal fungi on the growth of 10 wheat cultivars under three phosphorus regimes was assessed in a greenhouse study. Six of the cultivars responded positively, while four responded negatively or were nonresponsive to mycorrhizal inoculation. The responses of the individual cultivars were consistent regardless of inoculum source, suggesting that mycorrhizal responsiveness is an inherited trait rather than a response to individual fungi. Mycorrhizal responsiveness decreased with P fertilization for cultivars that were dependent on the symbiosis, but it was unaffected by P fertilization in cultivars that were negatively impacted by the mycorrhizae. Mycorrhizal and P responsiveness of each cultivar were highly correlated (r = 0.94), suggesting that P responsiveness may be a good predictor of the mycorrhizal dependence of selected wheat cultivars. The relationship between wheat biomass production and percentage root colonization was positive for cultivars, which responded favorably to the symbiosis, and negative for cultivars, which responded negatively or were nonresponsive to mycorrhizal inoculation. Amendment with P did not significantly affect these relationships. To determine whether differences in mycorrhizal responsiveness are related to nutrient uptake by the fungus,32P uptake of Turkey (responsive cultivar) and Newton (nonresponsive cultivar) was controlled by severing the mycorrhizal hyphae in a split-pot experiment. Plants with intact hyphae absorbed more32P than those with severed hyphae for both cultivars, and significantly more counts per minute of32P were evident in Newton than in Turkey, suggesting that mycorrhizal function is not impaired even in cultivars that do not display a biomass increase in response to mycorrhizal symbiosis.Keywords: vesicular–arbuscular mycorrhizae, pathogenesis, growth response, mycorrhizal symbiosis.

ISSN:0008-4026    

DOI:10.1139/b96-003

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

Nitellacell walls exhibit a major loss of pectin when the adsorbed bivalent ions are exchanged for monovalents. 2F4 monoclonal antibody, which recognizes a conformational epitope of homogalacturonic acid induced by calcium ions, was complexed to colloidal gold and used to localize, by means of the electron microscope, the wall regions from which the leakage occurred. Comparison of the labelling between nonpretreated cell walls and NaCl or LiCl pretreated ones, with or without incubation in CDTA or in NaOH, reveals that monovalent ions induce the solubilization of a pectic fraction rich in nonesterified galacturonic acids from the primary wall. Our results also indicate that in the secondary wall ofNitella, the pectic polysaccharides could be closely joined by covalent crosslinking.Keywords: pectin, gold labelling, monoclonal antibody, ionic exchange,Nitella.

ISSN:0008-4026    

DOI:10.1139/b96-004

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

Yellow-cedar (Chamaecyparis nootkatensis(D. Don) Spach) shoot water relations parameters were measured in response to (i) seasonal changes in photoperiod and temperature and (ii) controlled changes in root temperature and soil moisture. Pressure–volume curves determined measurements of shoot water relation parameters. Osmotic potential at saturation (Ψsat) and turgor loss point (Ψtlp) were lowest during February at −1.73 and −2.35 MPa, respectively. Both Ψsatand Ψtlpincreased in the spring to a high in July of −1.05 and −1.28 MPa, respectively, when shoot growth was occurring. Total turgor (ΨPTotal) was 18.2 MPa in December and declined to its lowest level of 5.98 MPa in July. Increased ΨPTotalfrom late summer through winter could be attributed to osmotic and (or) elastic components, while decreased ΨPTotalin the spring was due to a decrease in both osmotic and elastic components. Both Ψsatand Ψtlpdecreased as root temperatures were reduced from 22 to 1 °C. There was an increase in ΨPTotalas root temperatures declined from 15 to 8 °C because of both osmotic and elastic adjustment, with osmotic adjustment the primary factor. Turgor decreased at root temperatures below 8 °C, even though osmotic adjustment was occurring, and this was due to a reduction in the elastic component. Both Ψsatand Ψtlpdecreased in response to drought, though Ψtlpdecreased at a greater rate. Increased turgor during the initial stages of long-term drought results from an increase in both osmotic and elastic components, while increased turgor was solely due to the osmotic component as drought became more severe. Under rapid drought, turgor adjustment was minimal because the increased osmotic component was offset by a decrease in the elastic component. Results from these experiments indicate that turgor maintenance of yellow-cedar occurs through the use of both osmotic and elastic components in varying degrees at different times of the year and under differing environmental conditions.Keywords:Chamaecyparis nootkatensis, osmotic potential at saturation and turgor loss point, total turgor with osmotic and elastic components, seasonal patterns, root temperature, drought.

ISSN:0008-4026    

DOI:10.1139/b96-005

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

Suboptimal temperatures cause grain yield reductions generally associated with low seed-set in sorghum [Sorghum bicolor(L.) Moench]. Low proline concentration in pollen has been associated with cold-induced male sterility. This study was done to (i) determine free proline concentrations in grain sorghum pollen after low temperature exposure, (ii) determine the relationship between seed-set and proline concentration in pollen, and (iii) determine the association of proline concentration in pollen with grain yield in sorghums of different maturity. Eleven sorghum genotypes, grown in a greenhouse at 27/22 °C (day/night) until the early boot stage were transferred to 20/10 °C in growth chamber until physiological maturity. Concentration of proline in pollen was determined at anthesis and related to seed number and grain yield. Proline concentrations in pollen increased from 19 to 36 μg∙mg−1fresh wt. to 30 to 49 μg∙mg−1fresh wt. at low temperatures. Seed number and grain yield were reduced by low temperature in most of the genotypes. Percent seed-set in male sterile lines was significantly correlated (r = 0.45**) with free proline concentrations in the pollen from 13 fertile hybrids grown under cold or control conditions. Higher concentrations of proline in pollen under cool and also control temperatures seemingly contribute to greater pollen viability in grain sorghum. In 21 sorghum hybrids grown under control temperatures, seed number per panicle was found correlated (r = 0.42*) to free proline concentrations in pollen. Genotypic differences in pollen proline concentration were not associated with differences between maturity groups.Keywords:Sorghum bicolor(L.) Moench, pollen, free proline, low temperatures, seed-set, grain yi

ISSN:0008-4026    

DOI:10.1139/b96-006

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

Symptom development, virus multiplication, and distribution of tomato mosaic virus strains L and LS1were compared at 22 and 32 °C in the C4plantGomphrena globosa. In inoculated leaves, LS1accumulation was much lower at 32 °C compared with 22 °C, whereas the levels of L were similar at both temperatures. At 22 °C, spread of L and LS1from inoculated to uninoculated leaves (systemic movement) was dependent on the stage of plant development and the leaf inoculated. Under all conditions tested, LS1accumulated at a much lower level than L. Under specific conditions of leaf and plant age, LS1was confined to the inoculated leaf, whereas L moved systemically in all experiments. In a mixed infection with tobacco mosaic virus U1strain, LS1did not affect movement of U1within the inoculated leaf but inhibited systemic spread. InGomphrena, the single amino acid difference in the 30-kDa movement protein of LS1relative to L induced plant resistance to systemic spread of virus.Keywords: systemic movement, local lesion.

ISSN:0008-4026    

DOI:10.1139/b96-007

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

A new interspecificIsoeteshybrid,I.echinosporaDur. ×I.maritimaUnderw., is described from Vancouver Island, British Columbia and southern Alaska by means of cytology and the scanning electron microscopy of spores.Isoetes×pseudotruncataD.M. Britton and D.F. Brunton, hyb.nov. is the name proposed for this taxon. It is triploid and produces only aborted, sterile spores and has spore ornamentation features intermediate between those of its putative parents. Several concentrations of hybrids have been identified, each growing with both parents in shallow, freshwater habitat along the Pacific Coast of northwestern North America.Keywords:Isoetes echinospora,Isoetes maritima, hybrid, British Columbia.

ISSN:0008-4026    

DOI:10.1139/b96-008

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

Corollospora fuscais a marine ascomycete that based on light microscopy and scanning electron microscopy was previously described as possessing appendaged ascospores with fine longitudinal melanized striations and a ridged surface. Transmission and low voltage scanning electron microscope studies presented here do not support the existence of a ridged surface on the ascospore. Histochemical tests based on the reduction of silver nitrate were used at the electron microscope level to locate melanin in the longitudinal electron-dense deposits in the spore wall.Keywords: ascospores,Corollosporaspp., marine fungi, melanin, ultrastructure, wall structure.

ISSN:0008-4026    

DOI:10.1139/b96-009

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

The ultrastructure of current and previous year needles of Scots pine (Pinus sylvestrisL.) and Norway spruce (Picea abiesL.) Karst. was studied after exposures to several different ozone concentrations (100 to 600 nL∙L−1) and doses in a chamber system. The ultrastructural changes observed in different experiments in both of these species were qualitatively very similar. Changes were observed in the mesophyll tissue, in which increased density of chloroplast stroma and an increase of ribosome-like granules were the early symptoms, followed by a decrease of the size of chloroplasts and starch grains. Simultaneously a decline of needle starch content could be measured. After fumigation with the lower concentrations, hypertrophy of microbodies were also apparent. When the seedlings were fumigated with the highest concentration (600 nL∙L−1) a subsequent disintegration of cytoplasm and other cell organelles and finally a collapse of the contents of the mesophyll cells, leading to visible injuries, was found. Scots pine nursery stock seedlings appeared to be about equal in sensitivity to ozone as Norway spruce clonal stock. The spruce clones showed differences in sensitivity to the ozone fumigations. Since the observed symptoms are consistent in two species through a concentration gradient of ozone, and also agree with the information dealing with ozone injuries in literature, it is possible to use ultrastructural observations for diagnosing the presence of ozone injuries.Keywords: ozone,Picea abies,Pinus sylvestris, needle ultrastructure, sta

ISSN:0008-4026    

DOI:10.1139/b96-010

出版商:NRC Research Press    

年代:1996

数据来源: NRC