摘要:

Cambial reactivation and xylogenesis have been studied in diffuse porous (Betula verrucosaEhr.,Acer campestreL.) and ring porous (Castanea sativaMill.) trees more than 25 years old. Our results show that the basipetal and overall cambial reactivations coexist in the two groups of trees, in contrast to what is generally admitted. The basipetal cambial reactivation occurs in the terminal parts of the branches and is controlled by the buds. The overall cambial reactivation affects the trunk and the older parts of the branches; it shows a certain autonomy from the phenomena occurring within the upper part of the tree.

ISSN:0008-4026    

DOI:10.1139/b85-187

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Thallus samples ofEvernia prunastri, rehydrated in the light, accumulate both mannitol and arabitol as products of the conversion of photosynthates which have been translocated from the photobiont to the mycobiont. The concentration of accumulated polyols, measured as milligrams mannitol per gram dry thallus, is about 600 times higher than that of glucose. By supplying urea to the thallus, a urease is induced to produce carbon dioxide and ammonia from urea. However, the increase in CO2availability does not lead to an increase in the concentration of photosynthates, since the ratio of mannitol to glucose decreases to a third of its initial value. This decrease does not result from the loss of polyols to the incubation media but from an inhibition of the conversion of glucose to polyols.

ISSN:0008-4026    

DOI:10.1139/b85-188

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

The lichenEvernia prunastrishortly after collection shows low nitrate reductase activity. The enzyme is induced by nitrate in the dark and this effect is enhanced by red light, the action of which is reversed by far-red light. Nitrate reductase is located in both symbionts, but mycobiont cells are responsible for the increase of enzyme activity in whole thalli floated on nitrate in the dark. When this increase is achieved in the light, it can be related to the Pfrcontent of the photobiont cells, whereas changes in the activity of the fungal enzyme are negligible.

ISSN:0008-4026    

DOI:10.1139/b85-189

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

The species ofValsaandCytosporafound on hardwoods in North America are reevaluated, based on morphological studies of type specimens, herbarium specimens, and fresh collections. Three sections are accepted inValsa: sectionsValsa,MonostichaeNits., andCypriUrban, distinguished by the number, size, and arrangement of perithecia, the distribution of ostioles in the disc, and the size of ascospores. Four sections are accepted inCytospora: sectionsCytospora,Torsellia(Fr.) Gvrit.,Cytophoma(Hoehn.) Gvrit., andCytosporopsis(Hoehn.) Gvrit., based on the number and shape of the locules. Correlations between the teleomorphic and anamorphic sectionsValsa–Cytospora,Monostichae–Torsellia, andCypri–Cytophomaare reaffirmed. Six species ofValsaon North American hardwoods are accepted, and two new subspecies are proposed:V. ambienssubsp.ambiensandV. ambienssubsp.leucostomoides(Peck) Spielman. Six species ofCytosporaare accepted.

ISSN:0008-4026    

DOI:10.1139/b85-190

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

A newly discovered tetraploid oat species from Morocco is described morphologically and karyotypically. Some important morphological and karyotypical features are stressed and documented. Its main features are summarized with those of its allied species,Avena canariensisandAvena atlantica. Its habitat and distribution are also described.

ISSN:0008-4026    

DOI:10.1139/b85-191

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Trapping organs ofAcaulopage pectosporaDrechsler, a nematode-destroying fungus, were examined by electron microscopy at various stages of infection. The trapping organs arise from sparsely developed nonseptate hyphae as short, lateral branches, each with a slightly inflated terminal knob. Nematodes arc captured by adhesive secreted from the knob. Electron microscopy revealed the following ultrastructural aspects: (i) the trap's cytoplasm is occupied by large electron-dense vesicles (0.5–0.9 μm) before secretion of the adhesive; (ii) the secreted adhesive derived from the large vesicles has a high electron density and contains a number of bubbles; (iii) the cell wall of the traps becomes doubled after the secretion of adhesive and an aliquot of the adhesive remains in the intervening space between the outer and inner cell wall; (iv) the outer wall of the terminal knob exhibits a rimose appearance. Ultrastructural evidence indicates thatAcaulopage pectosporais very similar toZoophagus insidiansSommerstorff.

ISSN:0008-4026    

DOI:10.1139/b85-192

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

The vascular cambium and the growth ring it produces are continuous from trunk to branch, but the cells formed by the cambium in the upper junction of branch and trunk are oriented at approximately right angles to the normal orientation in the trunk and branch. Branch tissues begin to develop before trunk tissues early in the growing season. Maturation of branch tissues proceeds basipetally. The branch xylem is oriented downward at the branch base and encircles it to form a collar. The collar tissues meet on the trunk below the branch. The branch collar is enveloped later in the growing season by a collar of trunk xylem. Xylem in the trunk collar meet above and below the branch. Conduction into and out of the branch follows the pathway of the branch collar. The branch is structurally attached to the trunk by a series of trunk collars that envelop the branch collars every growing season. When the trunk collar was injured or removed by branch pruning, the trunk xylem above and below the cut was rapidly and extensively infected and decay developed. When pruning cuts did not injure or remove the trunk collar, no infections developed in the trunk xylem. Dye movement and the patterns of spread of bacterial and fungal pathogens also suggested that there was no local direct conduction between trunk xylem above a branch and within a branch.

ISSN:0008-4026    

DOI:10.1139/b85-193

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Sclerotia were produced by growingPisolithus tinctorius(Pers.) Coker and Couch in association withPinus strobusL. andPinus resinosaAit. in plastic growth pouches. Developing and mature sclerotia were collected, fixed, and embedded for light microscopy and scanning and transmission electron microscopy. They were found to consist of an outer pigmented rind, an inner and outer cortex, and a large central medulla. Cortical and medullary areas were comprised of pseudoparenchyma which contained large deposits of glycogen, as well as protein and lipids. The structure of these sclerotia indicates that they are persistent propagules. Sclerotia may be important in nature for the recolonization of root tips after environmental stresses. They may also be useful for storing valuable strains ofP.tinctoriusand as a source of inoculum for experimental studies.

ISSN:0008-4026    

DOI:10.1139/b85-194

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Sclerotia ofPaxillus involutus(Batsch) Fr. were produced in association withPinus strobusL. andPinus resinosaAit. in plastic growth pouches and on agar-solidified nutrient medium. They were fixed and embedded for light microscopy and scanning and transmission electron microscopy. Sclerotia consisted of an outer pigmented rind, a thin cortical layer, and a large central medulla of isodiametric cells. Large deposits of glycogen, as well as smaller deposits of protein and lipid, were present in medullary and cortical cells. Structural characteristics indicate that these sclerotia are persistent propagules which may function to reinfect tree roots following environmental stresses. Since they can be produced in pure culture, it may be possible to inoculate seedlings directly with sclerotia.

ISSN:0008-4026    

DOI:10.1139/b85-195

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Uredospore production by axenically grown flax rust (Melampsora lini(Ehrenb.) Lev.) was measured as carotenoids (extinction units at 458 nm) per milligram protein. Sporulation was not affected by raising (flushing with 1–5% (v/v) CO2in air) or lowering (KOH well in culture flasks) the level of CO2in the air space above the cultures. Significant (two- to four-fold) increases in sporulation occurred beneath impermeable membranes of Parafilm or Saran wrap placed on the surface of young (3 weeks from seeding) mycelial mats for 2 weeks. The stimulatory effect was confined strictly to those areas of the mycelial mats in contact with the membranes. Both Parafilm and Saran wrap were easily and cleanly peeled away from the mycelial mats. Permeable Unipore and HVHP membranes, to which the fungus adhered strongly, did not stimulate sporulation. The fungus did not adhere to Unipore or HVHP membranes treated with silicone or paraffin oil; membranes thus treated stimulated sporulation. The stimulatory effect of membranes on sporulation appears to depend on the nature of the contact between the membrane surface and the mycelium and to be unrelated to the effect of the membranes on the diffusion of gases or other volatile substances.

ISSN:0008-4026    

DOI:10.1139/b85-196

出版商:NRC Research Press    

年代:1985

数据来源: NRC