摘要:

Morphology and geographic variation of pollen grains of three genera of the Rosaceae (Dryas,Fragaria,Holodiscus) of western Canada were studied using the light microscope and scanning electron microscope.Dryasspp. pollen is tricolporate with a weakly developed fusiform aperture in the colpus, which upon expansion of the grain becomes a large rectangular opening. Sculpturing consists of ridges and valleys (striate or rugulate), the latter containing perforations, which grades to a network of ridges and perforations (reticulate) at colpus margins. Ridges are parallel to the colpus or form looping patterns.Dryas integrifoliaandDryas octopetalapollen in silicone oil usually are larger than those ofDryas drummondii.Fragariaspp. pollen is tricolporate with a well-developed complex equatorial aperture.Fragaria chiloensisandF.vescaexhibit a lobed and equatorially extended endoaperture, which is overarched by sexine.Fragaria virginianausually has a less distinct endoaperture.Fragariaspecies have a fusiform colpus operculum. Sculpturing consists of nonasastomosing ridges parallel to the colpus and valleys containing obscure microperforations.Holodiscus discolorpollen is tricolporate. Sculpturing is striate to reticulostriate, consisting of ridges and valleys with perforations. A distinct zone, either lacking ridges or of densely packed ridges, borders the colpus.

ISSN:0008-4026    

DOI:10.1139/b88-086

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Death was induced in cowpea leaf epidermal cells by the application of the metal salts CuCl2, CuSO4, and HgCl2. When unfixed, salt-treated cells were observed by light microscopy, their degeneration and death were seen to follow a series of stages: (1) cessation of cytoplasmic streaming, (2) morphological changes in the cytoplasm such as the formation of large vesicles and the appearance of particles in the vacuole, and (3) protoplast collapse. The relative timing of these stages after salt application was affected by the nature and concentration of the chemical used. The application of fluorescein diacetate and plasmolysing sucrose solutions before or after the addition of the copper salts suggested that the semipermeability of the tonoplast was lost during stage 2 and that of the protoplast boundary at stage 3. Following the cessation of cytoplasmic streaming, the changes observed in unfixed cells occurred rapidly and correlated well with the ultrastructural changes observed in the same cells after fixation. First, microtubules appeared to decrease in abundance. Then coiled polyribosomes, endoplasmic reticulum, and Golgi bodies rapidly became undetectable, mitochondrial cristae became dilated, and the cytoplasm consisted of aggregates of ribosome-containing material interspersed with vesicles. However, the study also showed that the first observable sign of degeneration seen in unfixed cells (i.e., the cessation of cytoplasmic streaming) appears to have no clearly diagnostic feature detectable by electron microscopy.

ISSN:0008-4026    

DOI:10.1139/b88-087

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Cowpea leaves were inoculated with the plantain powdery mildew fungus,Erysiphe cichoracearum, and fresh epidermal cells overlying veins were examined by light microscopy before being cleared or prepared for electron microscopy. Fungal appressoria usually formed a haustorium in the underlying nonhost cell, but only after what appeared to be an unsuccessful penetration attempt that induced a transient cytoplasmic aggregate, a ring of autofluorescence in the plant wall (best seen in cleared tissue), and in two examples observed ultrastructurally, a small penetration peg embedded in a callose-like papilla. The haustorium developed from a different penetration peg and elicited the death of the invaded cell. As reported for the death of cowpea epidermal cells elicited by CuCl2, cytoplasmic changes that occurred rapidly in fresh tissue after cytoplasmic streaming had stopped correlated closely with changes in ultrastructure. Compared with the CuCl2study, microtubules and Golgi bodies disappeared faster and membranes appeared more disorganized. These data suggest that in cowpea epidermal cells, ultrastructural changes accurately predict the onset of cell death and may also reflect differences in its modes of induction.

ISSN:0008-4026    

DOI:10.1139/b88-088

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Seven crosses, involving either nondormant × dormant or dormant × dormant pure lines of wild oats (Avena fatuaL.), were made. Selfing of the hybrid and further hybridization were carried out to produce the F2and reciprocal backcross generations. The seed germination time-course curves of the parents, their F1, and segregating generations over a 20-week period were studied. Differences in time course of germination in these generations were interpreted in terms of a minimum of three interacting loci. Two pure lines, AN51 and MO73, differed in their response to sodium azide, a respiratory inhibitor, with the former being more responsive. In crosses between these lines, the F1seeds were also more responsive when AN51 was used as the maternal parent. This differential response of two dormant pure lines and their reciprocal F1s suggests maternal influence in germination response to sodium azide.

ISSN:0008-4026    

DOI:10.1139/b88-089

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Agrobacterium rhizogenes(Rikeret al.) Conn genetically transforms the roots of many dicotyledonous plants, causing them to produce numerous functional secondary roots. The intentional inoculation of forest, nursery, or vegetable transplants withA.rhizogenesmay have some value in promoting rapid establishment after transplanting. We examined some factors that may influence the development of roots in plants inoculated withA.rhizogenes(by the carrot disc assay). A pH near neutrality, a temperature of ca. 25 °C, and a freshly cut root surface serving as the inoculation site favoured root development. Roots that were inoculated and then stored at 10 °C did not produce secondary roots at that temperature. However, upon placement at 23 °C for 2 days new roots began to form. Octopine at 10 mM stimulated root production. Carrot roots stored for 9 months produced few if any roots upon inoculation withA.rhizogenes, suggesting the importance of tissue age in genetic transformation.

ISSN:0008-4026    

DOI:10.1139/b88-090

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

A modified specimen stub, for use with the EMscope SP2000 Sputter Cryo Preparation Unit, that will facilitate the production of complementary fracture faces is described. The application of complementary fractures for studying hypha–host surface adhesion within freeze-fractured leaves is reported for the first time. Freeze fracturing results in the rupture of either the hyphal wall or the host cell wall or both, at the edge of, or just beyond, the adhesive matrix pad that binds the two together. The implication that the adhesive is stronger than either of the two individual apposed walls is discussed in relation to the mechanics of bonding and to the process of penetration of the host cell by the fungus.

ISSN:0008-4026    

DOI:10.1139/b88-091

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Spotted knapweed (Centaurea maculosaLam.) is an introduced noxious weed on grasslands in the northwestern United States and adjoining Canadian provinces. This research examined germination responses of spotted knapweed to stratification, temperature, and water stress under controlled conditions. Immediately after harvest, germination was sharply reduced by sub- and supra-optimal temperatures and water stress; as seeds aged, germination increased at sub- and supra-optimal temperatures. Total germination was enhanced and days to 50% of final germination (D50) was reduced by cool–moist stratification. Under water stress, germination of unstratified seeds was limited at suboptimal temperatures, but seeds pretreated with cool–moist stratification germinated more rapidly and to a higher percentage over a broader range of temperatures and osmotic potentials.

ISSN:0008-4026    

DOI:10.1139/b88-092

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Chromosome 5A in the hardy winter wheats 'Winalta' and 'Kharkov 22 MC (Triticum aestivumL.) carries at least one of the several loci controlling the expression of cold hardiness, low temperature induced reduction in leaf length, percent dry matter in leaves, prostrate growth habit, and proportion of peak I to peak II invertase in leaves.

ISSN:0008-4026    

DOI:10.1139/b88-093

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

In evergreen oak leaves collected at a western Mediterranean site (Var, France), the amounts of both hydrolyzable and condensed tannins decrease through the depth of the leaf litter. The decrease in condensed tannins could be partly explained by the cellular degradation of the lower epidermis and the mesophyll of leaves, as observed in histological sections. However, the condensed tannins may also be degraded by microbial enzymes because their average molecular weight decreased by about 50%. In contrast, the decrease in hydrolyzable tannins seems to be initiated by microbial enzymatic action, which is then followed by the same degradation process described above.

ISSN:0008-4026    

DOI:10.1139/b88-094

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

The lichenRamalina duriaei(De Not.) Bagl. was transplanted to 10 biomonitoring sites during the period December 1981 – December 1982. The amounts of Ni, Cr, Cu, Zn, and Pb in the lichen material were measured at the beginning and at the end of the exposure period. These data were compared with the metal amounts detected inR.duriaeitransplanted to the same stations during the period February 1979 – March 1980. After the 1981 – 1982 period, the regional amounts of Ni, Cr, and Pb in the transplanted lichen were found to be higher than in the lichen transplanted to the same sites during the 1979–1980 period, prior to the operation of the coal-fired power plant. The increase of Pb in the lichen after the second period (1981 – 1982) reflects the increase in the total number of motor vehicles in the country during that time. The increase of the amounts of Cr and Ni in the latter period is probably related to emissions of these substances from the power-plant stack. The regional decrease in Zn amount in the lichen in the latter period is probably related to a decrease in the use of Zn as a constituent of foliar nutrients in agriculture.

ISSN:0008-4026    

DOI:10.1139/b88-095

出版商:NRC Research Press    

年代:1988

数据来源: NRC