摘要:

In primary growth, protoplasmic pressure expands the cell wall as its cellulosic framework is being built up and strengthened. Numerous micrographs provide evidence that as each lamella of the wall is differentiated, randomly spaced bonds tend to develop between its adjacent microfibrils. Apparently the number of bonds so developed, and the number retained unbroken subsequently, are related to the rate of cell wall extension.Between unbroken bonds, tensions associated with growth cause adjacent transverse microfibrils to bend successively to each side of their original general orientation. Thus, within a lamella they form lenticular, trellis-like configurations. Large extensions cause large local variations in direction; some microfibrils remain adjacent within groups, but the groups may be widely separated. Such microfibril configurations are generally incompatible with the multinet theory. Apparently also, the very large extensions of the lamellae formed soon after cell division can cause breaking of bonds, wide dispersion, and even breaking of microfibrils.In secondary growth, similar bonding between microfibrils occurs within lamellae and also between lamellae of the cell wall. Again, there is associated development of trellis configurations, but in this case it is due to swelling within the wall during lignification. Resulting changes in microfibrillar directions between bonded positions are much less extreme than in primary walls, but they are highly significant physiologically.

ISSN:0008-4026    

DOI:10.1139/b75-297

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

SJB 133 is an isolate of a variety ofCeratocystis minorthat is found in aSporothriximperfect state as an ectosymbiont ofDendroctonus frontalisZimm. Within the mycangium (fungal transport pocket of the beetle), SJB 133 grows in yeast-like fashion. Cells contain prominent vacuoles which appear to bridge between dividing cells. Hypha-like transition cells are also present. In continuous culture on potato carrot agar, SJB 133 produces sympodial conidiophores. The resulting conidia are quite similar to the yeast-like cells in the mycangium and the conidiophores resemble some of the transition cells.

ISSN:0008-4026    

DOI:10.1139/b75-298

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Cytological studies of starch, lipid, nuclei, dehydrogenases, and diaphorase activity in parenchyma of healthy and sandhill-declined trunk wood ofCitrus sinensis'Valencia' indicated that wood aged rapidly after a high metabolic activity near the cambium. Ethylene evolution and oxygen uptake were high in wood next to the cambium; ethylene was low in older wood and gas evolution was typical of older wood. Diseased wood contained less starch but more lipid than healthy wood. Lipid vessel plugs, caused by lipid leakage into vessels, and moisture content increased in wood as it aged. Characteristics of parenchyma cell ageing and wood color place it in the revised category of woods with a delayed, uncolored heartwood.

ISSN:0008-4026    

DOI:10.1139/b75-299

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

A rapid, sensitive, and non-destructive method for analysis of chlorophyll mutants of maize is described. The method, based on in vivo absorbance characteristics of leaf tissue, enables a quantitative description of the status and pattern of chlorophyll distribution within single maize leaves.

ISSN:0008-4026    

DOI:10.1139/b75-300

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Ultrastructural changes occurred in sunflower leaves that were infected byVerticillium dahliaeKleb. during the appearance of foliar symptoms. Early in symptom development major degenerative changes took place in the leaf mesophyll tissue particularly in the vicinity of the xylem of the major veins. During these early stages vessel wall breakdown occurred in the vicinity of the fungus, but this degradation was not accompanied by swelling. Occlusion of the vessel elements by fungus, fibrillar material, or electron-dense plugs was not significant until late in disease development. Comparison of these observations with those that were made in a previous parallel study ofVerticillium-infected chrysanthemum suggested that the ultrastructural changes induced by the fungus in the two hosts are similar but that the timing is different. In chrysanthemum, degenerative changes in the mesophyll are not extensive until after chlorosis, but vessel blockage is advanced before wilting is noticeable. The significance of this difference in the development of foliar symptoms is discussed in relation to the plugging and toxin theories of wilt induction in fungus-caused vascular diseases.

ISSN:0008-4026    

DOI:10.1139/b75-301

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Sapling-sized quaking aspen (Populits tremuloides)in five natural clones were inoculated with mass and single ascospore cultures ofHypoxylon mammatum. Fungus isolates varied in ability to produce cankers. 'Conidial-type' isolates generally produced few cankers, while 'mycelial-type' isolates produced cankers on 87.7% of inoculated branches. Isolates from a given ascus inoculated into a clone generally produced cankers of similar length after 2 months. However, some significant differences in canker length did occur. Clones varied in susceptibility to canker enlargement. No single isolate produced the largest cankers on all clones.

ISSN:0008-4026    

DOI:10.1139/b75-302

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

The primary phloem system in the rhizome ofHieracium floribundumhas transfer cells that have developed from companion cells and parenchyma cells, which are adjacent to sieve elements. In both cell types changes occur in the cytoplasmic organelles at the time of wall ingrowth formation. Dicytosomes and polyribosomes become more numerous and 'boundary formations' and other multivesiculated structures appear. Few microtubules were found in the cytoplasm at this time. After the wall ingrowths become obvious, the transfer cells develop numerous mitochondria and an enlarged nucleus. The phloem transfer cells become vacuolated with age and the wall ingrowths become less numerous. This may be associated with a change in the translocation pattern in the phloem after the inception of vascular cambium activity. Parenchyma cells in the secondary phloem usually become rather vacuolated and develop few wall ingrowths.

ISSN:0008-4026    

DOI:10.1139/b75-303

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Pyronema domesticum(Sow. ex Gray) Saccardo was cultured at temperatures ranging from 5 to 10 °C; relative humidities (RH) from 100% to near 0%; on an inorganic salts medium supplemented with 0.5–1.0 g dextrose, 0.5–3.5 g Casamino acids, 10 g charcoal, or 20 g inulin per litre; and on potato dextrose agar. The effects of these different cultural conditions on apothecial morphogenesis were evaluated. Fully expanded, globose ascogonia predominated in the control, at 20–25 °C, 93–100% RH, 0.5 g dextrose, or 0.5 g Casamino acids/litre. Undifferentiated (without a trichogyne) or poorly differentiated ascogonia predominated at extremely unfavorable conditions (5–10 and 30 °C; about 0–20% RH; 3.5 g/litre Casamino acids, 5–6.5 × normal concentration of inorganic salts). These latter conditions sometimes prevented fusion and (or) plasmogamy. Under all remaining conditions, the ascogonia were predominately clavate to obovate with a delimited trichogyne, and the normal sexuality was unaffected. Morphological abnormalities were common among the poorly differentiated gametangia but less common among those that were better differentiated. Ascogenous hyphae were produced by all types of ascogonia. There was generally some reduction in ascus production, and asci with mature ascospores were not formed at 5 or 30 °C, near 0% RH, on 3.5 g Casamino acids/litre, or on 3.5–6.5 × inorganic salts. There was some reduction in the sterile system under the most extreme conditions, and a palisade of paraphyses was not formed at 5–10 °C, and 4.5–6.5 × inorganic salts. Sclerotia were formed only on potato dextrose agar.

ISSN:0008-4026    

DOI:10.1139/b75-304

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Effects of variation in day length on spikelet and tiller development were studied in a two-rowed barley,Hordeum vulgareL. cultivar ‘Fergus.’ Spikelet number and the length of the spikelet-forming phase increased with progressive reductions in day length from 24 to 12 h. However, increases in spikelet number were offset by abortion of spikelet primordia during spikelet differentiation and elongation of the stem internodes. Floral initiation occurred at all day lengths, but intemode elongation and heading were markedly delayed at 12 h. The cessation of spikelet initial formation and the beginning of internode elongation did not occur simultaneously in any day length. The latter began just before or at double ridge formation.Tiller numbers were highest at 12 h and progressively decreased in longer day lengths. Each plant produced four primary tillers at all day lengths, and differences in tiller number were accounted for by secondary and tertiary tiller production.

ISSN:0008-4026    

DOI:10.1139/b75-305

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Three patterned fens in north central Alberta were analyzed to elucidate vegetation patterns in vascular plants and bryophytes. Two flark associations dominated byMenyanthes trifoliataandCarex limosa, both of which hadSphagnum jenseniiandDrepanocladus exannulatusphases, were recognized. The strings consist of two associations; one is dominated byBetula glandulosa,Tomenthypnum falcifolium, andAulacomnium palustre; the second is dominated byPicea mariana,Sphagnum magellanicum, andLedum groenlandicum. An intensive analysis of one fen reveals that these mires are ‘poor fens’ with a mean pH of 5.2 and Ca2+concentration of 2.3 ppm. The fens occur on low drainage divides and Ca2+is depleted as water flows through the fens. An ecological series of bryophytes is described in the transitions between flarks and strings.

ISSN:0008-4026    

DOI:10.1139/b75-306

出版商:NRC Research Press    

年代:1975

数据来源: NRC