摘要:

Since it is known that successive applications of Hg2+and Cl−ions accelerates Apel pine seeds germination, a cytological study of the treated embryo was made during the first 6 days of imbibition. In comparison with control seeds germinating on filter paper imbibed with distilled water, treated seeds show precocious mitoses and an acceleration of lipolysis and proteolysis as well as synthesis of organelles. These phenomena are particularly evident in the radicle. Since water uptake occurs especially in the radicular pole of the seed, this result suggests a determining role of imbibition in the process of germination in the Alep pine. No abnormal ultrastructures are observed in treated seeds.not available

ISSN:0008-4026    

DOI:10.1139/b78-354

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Changes in the catalase activity and the effect of hydrogen peroxide (H2O2) were studied during the senescence of excised rice (Oryza sativaL. cv. Ratna) leaves. Catalase activity declined upon detachment of leaves. Regression analysis showed a strong positive correlation between the decline in the catalase activity with the decline in the soluble protein content (r = 0.9827;n = 13). Infiltration of H2O2into the leaves accelerated chlorophyll loss and α-amino nitrogen accumulation. Infiltration of glycolate or xanthine (serving as substrates for the formation of H2O2) into the leaves had a similar effect. Application of aminotriazole, a strong inhibitor of catalase, also accelerated the senescence of excised rice leaves. These results indicate that leaf senescence can be accelerated by increasing the endogenous H2O2level in the leaf tissues.

ISSN:0008-4026    

DOI:10.1139/b78-355

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

The filamentous fungi occurring onSpartina alternifloraseeds attached to inflorescences, on marsh sediments, and submerged in estuarine waters were studied. Seed-borne fungi commonly found on grain crops and graminicolous Ascomycetes were found on the seeds attached to the panicles. After 2 months on the marsh surface or in the adjacent sound and tidal creek, additional species, including marine fungi, were observed on the seeds. After 5–7 months marine fungi and graminicolous Ascomycetes were the only fungi found by direct observation, although seed-borne species could still be isolated by incubation methods. The seeds were completely degraded or barely recognizable after 11 months on the marsh sediments or in seawater.Claviceps purpureaparasitized the seed heads at all the marsh areas sampled. The greatest number of sclerotia were found on the tallS. alternifloranear the lower edge of the marsh in exposed areas and on inflorescences from dredge spoil areas. Up to 183 sclerotia/m2and sclerotia dry weight values of up to 2.72 g/m2were found. Eight Ascomycetes, one Basidiomycete, and 16 Fungi Imperfecti were identified.Ceriosporopsis halima, Corollospora maritima, Cirrenalia macrocephala, Halosphaeria hamata, andTrichocladium achrasporum, primarily known as 'wood-inhabiting' marine fungi, occur on submergedSpartina alternifloraseeds, suggesting that these fungi are general decomposers of plant debris in marine habitats.

ISSN:0008-4026    

DOI:10.1139/b78-356

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

The Jardine–Sibson Bkclustering method was applied to a dissimilarity matrix of genera of the Triticeae to obtain sequences of relationships in terms of overlapping clusters. In this way, the clinal relationships in the tribe were portrayed. Selected aspects of the findings are documented in detail and the results are discussed in the light of previous findings. In addition to those that are corroborated by the present study, new relationships are revealed also. For instance, theAegilops–Triticumgroup is reconfirmed here, but the relationship ofHenrardiato that group is a new finding which, along with others, should be tested by other means so that eventually it might be used in gene transfer.

ISSN:0008-4026    

DOI:10.1139/b78-357

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Membrane associations in the interfacial zone between host cytoplasm and haustoria of wheat stem rust are reported. The invaginated host plasmalemma (IPL) adhered tightly to the haustorial neck wall above an indistinct zone at the base of the neck. There was extensive proliferation of host endoplasmic reticulum (ER) near haustoria during the formative growth stages of the haustoria. Most of the proliferation occurred along the neck from the neck ring region to the area at the base of the haustorial body where the extrahaustorial sheath became evident. Closely spaced arrays of ER occurred along the neck and radiated into the host cytoplasm. The ER was closely associated with the IPL in the vicinity of the neck wall, and at points of contact or near contact, the ER was ribosome free and stained more densely. There was luminal continuity between ER cisternae and the extrahaustorial sheath matrix. In the host cytoplasm adjacent to haustoria, ER-derived membranous complexes were found. These complexes consisted of a lattice arrangement of large tubules and small tubules, the latter containing a thread of denser staining material at their centers. The large tubules were bounded by lightly stained membranes, whereas the membranes of the small tubules stained more densely. These complexes were interconnected by rough ER to form networks in host cytoplasm. The complexes formed part of the interface between host and pathogen through connections with the invaginated host plasmalemma.

ISSN:0008-4026    

DOI:10.1139/b78-358

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

A pollen mixture from three male quaking aspen (Populus tremuloidesMichx.) trees was irradiated at exposures of 484, 968, 1453, 1937, 3874, 7747, and 15 494 R and used to control-pollinate cut branches from three female trees. The pollen radiosensitivity was determined from various seed yield and seed quality factors. The pollen LD50exposure varied with the end point evaluated, ranging from 255 R for number of 50-mesh seed per catkin to 8800 R for total seeds per catkin. The mean LD50for nine seed yield and seed quality end points was 3995 R. A significant stimulatory response in seed yield was noted at low pollen irradiation levels, particularly at the 484-R exposure. The LD100was approached but not reached at 15 494 R. Irradiated quaking aspen pollen may be useful in breeding experiments.

ISSN:0008-4026    

DOI:10.1139/b78-359

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Metaphloem sieve elements ofLycopodium clavatumL. are elongated cells with steeply inclined end walls. Numerous pores of small diameter are present on all contact walls between sieve elements. At maturity, these elements lack a normal-looking nucleus, and their protoplast is partially degenerated. Parenchyma cells with a well-structured protoplast are associated with them, the symplastic continuity between the two types of elements being assured by plasmodesmata. Intense phosphatase and respiratory enzyme activities are identifiable in the parenchyma cells. A functional association appears to exist between sieve elements and parenchyma cells.The absence of refractive spherules from the phloem of all the Lycophyta studied up to now is underlined: this fact is in agreement with the hypothesis that the Lycophyta constitute a relatively isolated group amongst primitive Tracheophytes.

ISSN:0008-4026    

DOI:10.1139/b78-360

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Most haustoria inHyobanche(Scrophulariaceae) are formed directly from the scale leaves of the extensive rhizome system and may be found on adaxial surfaces, margins, or tips of such leafy organs. The only exceptions are occasional haustoria, emerging from rhizome areas between adjacent scale leaves, and the primary haustorium. Host roots appear to be attracted to the rhizome, growing along its surface and apparently eliciting haustorial formation in adjoining parasitic tissues. The established parasite is completely rootless.

ISSN:0008-4026    

DOI:10.1139/b78-361

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Two strains of aster yellows agent, one resembling a typical 'noncelery-infecting' or eastern type (EAYA) and the other a 'celery-infecting' or western type (CAYA), were compared for their ability to infect celery. Seventy-four percent of the plants inoculated with EAYA and 100% inoculated with CAYA developed symptoms. An average of 115.7 days was required for symptoms of EAY to appear while only 40.6 days were required for CAY. In aster, this difference was much less pronounced. EAYA was less efficiently acquired from celery than was CAYA. The status of this EAYA in the aster yellows complex found in nature is discussed.

ISSN:0008-4026    

DOI:10.1139/b78-362

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Tissue inPhaseolus vulgarisL. cv. Pinto bean bordering local lesions induced by tobacco mosaic virus showed cell wall deposition associated with paramural body formation in a narrow ring of viable cells extending one to three cell diameters around the lesions. Deposition, which led to secondary cell wall thickening, was greatest 3–4 days after inoculation, the time when the lesion stopped expanding. Secondary cell wall thickening, of similar appearance but less pronounced, was seen in tissue bordering local lesions which continued to expand; no significant secondary cell wall thickening was observed in leaves with a nonlocalized infection. Cells bordering mechanical lesions differed markedly in fine structure from cells bordering virus and chemical lesions. It is suggested that the deposition of extra cell wall material in the wall regions of cells bordering fully expanded local lesions is associated with virus localization.

ISSN:0008-4026    

DOI:10.1139/b78-363

出版商:NRC Research Press    

年代:1978

数据来源: NRC