摘要:

The early mushroom gill development in a primordium ofCoprinus cinereuswas studied by electron microscopy. Extensive cell degeneration and cell death were found in gill cavities but not within gill domains. These degenerative cells were found to contain multivesicular and membranous residual bodies, suggesting that the multivesicular bodies are part of the cell degeneration. Cellular debris was observed in intercellular spaces probably as a consequence of cell lysis. The presence of multivesicular bodies was also observed in cells shortly beforeCoprinusbasidiocarps underwent autolysis: a high dose of hydrolytic enzymes can be extracted from such basidiocarps. The high numbers of multivesicular bodies, the membranous residual bodies, and the cellular debris in the primordial tissues are manifestations of cell degeneration that may be a prerequisite to gill remodelling during early primordial development.Key words: cell degeneration, gill remodelling, multivesicular body, residual body, mushroom development.

ISSN:0008-4026    

DOI:10.1139/b91-149

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

Drought was induced in Turface and vermiculite-grown seedlings ofZea maysL. by withholding water. Despite a 34-day drought period, the roots of stressed plants increased in dry weight by continued elongation of existing roots and initiation of new roots. A differential response to desiccation, with respect to structure and cell vitality, was observed along the root axes. In apical regions (terminal 20 mm) of seminal roots, all cell layers typically remained alive. In midlength regions (half way between the apex and base), the epidermis died in both control and treatment plants. The cortex of control roots displayed some distortion, but most of the cells were alive; the cortex of stressed roots displayed severe collapse and death of the majority of these cells. In basal regions (20 mm distal to the kernel), cells of the outer cortex were sclerified and less susceptible to collapse. Cells of stelar tissues retained their normal shapes and vitality. Upon rehydration, the root systems of stressed plants resumed growth by elongation of existing seminal, adventitious, and lateral roots and, in some cases, also by emergence of previously dormant lateral root primordia. The root systems' capacity for recovery diminished with increasing stress.Key words: drought, roots,Zea maysL., exodermis, hypodermis.

ISSN:0008-4026    

DOI:10.1139/b91-150

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

Pollen-cone and seed-cone development, from bud burst to maturity, was investigated onLarix laricina(Du Roi) K. Koch in three young plantations. The pollination mechanism was emphasized. Pollen cones grew rapidly to shed pollen, shrivelled, and remained on the trees for a year or more. Pollen was directed to the ovular regions by the bracts of the seed cones. Pollen adhered among papillae on the larger of two integument extensions. Degeneration of the centre of the papillate integument tip caused a collapse that drew pollen in as the papillate rim grew inward. This ingrowth was joined by that of the smaller integument extension, resulting in a sealed tubular structure that enclosed a dry micropylar canal. Pollen was held by the ingrown plug of degenerated tissue as the nucellus tip expanded into the base of the canal. As this occurred, the ovules, with or without pollination, grew to ultimate seed size, and the initially small ovuliferous scales overgrew the bracts. First bract, then ovuliferous-scale growth was associated with a double-sigmoid form of cone elongation. In mature cones the bracts decreased and the ovuliferous scales (except near the tip) increased in size acropetally.Key words: bract, integument, ovuliferous scale, pollen cone, seed cone, tamarack or eastern larch.

ISSN:0008-4026    

DOI:10.1139/b91-151

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

Somatic embryos have been produced from petioles and hypocotyls of Zonal geranium and from petioles of Regal geranium. Somatic embryos of both species have been desiccated and subsequently germinated. Some important factors that influence the rate of somatic embryo production in geranium are discussed. They include culture medium factors such as auxin and auxin dosage, carbohydrates, amino acids, pH, and basal medium composition. The donor plant genotype also appeared to have an effect on somatic embryogenesis and survival after desiccation.Key words:Pelargonium×hortorum,Pelargonium×domesticum, geranium, somatic embryo, artificial seed.

ISSN:0008-4026    

DOI:10.1139/b91-152

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

Levels of endogenous amino acid pools were measured for two species of the unicellular green algaChlamydomonas. InC.reinhardtii, opposite mating types, designated + and −, of strain 137c were examined. The soluble pool of glutamic acid was most abundant in strain 137c−. In strain 137c+ similar levels of this amino acid were present, and high levels of cystine were observed. A soluble pool for the amino acid methionine was not detected in either strain. In opposite mating types ofC.eugametos(strain Nos. 9 and 10), a soluble pool of alanine was most abundant, whereas neither cystine nor methionine were detected. WhenC.reinhardtiistrain 137c+ was grown in the dark, cystine was not detectable, and proline markedly increased. Similarly, growth of strain 137c+ on nitrogen-deficient medium supplemented with a limited amount of arginine as a nitrogen source resulted in an apparent disappearance of pools of cystine. No apparent difference in the growth patterns of strains 137c+ and 137c− was observed. Tetrad analysis indicates that the high cystine content found in strain 137c+ is neither a characteristic of mating type nor under control of a single Mendelian gene.Key words:Chlamydomonas reinhardtii,Chlamydomonas eugametos, amino acid pool, cystine.

ISSN:0008-4026    

DOI:10.1139/b91-153

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

The cytological responses to the monokaryotic primary hyphae of the cowpea rust fungus (Uromyces vignaeBarcl.) were observed in vein epidermal cells of a resistant and a susceptible cowpea cultivar. Unlike the previously examined response to haustoria of a nonpathogenic powdery mildew fungus, plant cell walls did not become autofluorescent in response to fungal penetration, and the primary hypha only rarely became encased. Following fungal penetration, the response of invaded cells of the resistant, intact plant could be divided into the following stages: (I) cytoplasmic streaming normal; (II) cytoplasmic streaming slow or stopped, Brownian motion of particles visible in the vacuole, granulated cytoplasm aggregated along the cell walls, some host nuclei disappeared; and (III) protoplast collapsed. Epidermal tissue of the resistant cultivar did not exhibit stages II–III when detached and mounted in water 12 h after inoculation and examined 9 h later. The frequency of stage III increased when the tissue was mounted in CaCl2, Ca(NO3)2, and KNO3, but only in a kinetin solution did it approximate that in attached tissue. Although kinetin inhibited fungal growth in both the resistant and the susceptible cultivar, the hypersensitive response occurred only in the former, suggesting that kinetin affects the hypersensitive response directly rather than through its inhibitory effect on the fungus.Key words: cowpea,Vigna unguiculata, cowpea rust fungus,Uromyces vignae(Barcl.), hypersensitivity.

ISSN:0008-4026    

DOI:10.1139/b91-154

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

The rust fungusPuccinia substriatavar.indicaestablished a compatible relationship with host cells, characterized by large numbers of haustoria and an extensive system of intercellular hyphae, in seedling leaves of the susceptible pearl millet cultivar Tift 23DB. At some infection sites, however, necrotic host cells and papillae formed by plant cells adjacent to infection hyphae or haustorial mother cells were noted. In seedling leaves of the moderately resistant cultivar 86-8770, the initial interaction between host cells and the pathogen was quite variable and included successful haustorium formation as well as papilla deposition. Necrosis of host cells apparently developed as a gradual disorganization of the cytoplasm of invaded and surrounding host cells and occurred at all infection sites by 2 days postinoculation. In seedling leaves of the highly resistant cultivar Tift 85DB, haustoria were established at early stages of development, followed by a rapid necrosis response at 1 day postinoculation. Host cell disintegration was noted both before and after abnormalities in haustoria were observed. In mature leaves of all three cultivars, wall deposits were quite extensive at 12 h postinoculation. In addition, necrotic plant cells appeared rapidly in both susceptible and resistant cultivars. Both of these factors may have contributed to the increased resistance to fungal colonization observed in mature leaves.Key words:Puccinia substriatavar.indica, pearl millet rust, host resistance, ultrastructure.

ISSN:0008-4026    

DOI:10.1139/b91-155

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

A new member of the Neocallimasticaceae (Spizellomycetales),Neocallimastix hurleyensissp.nov., is described. This species was isolated from the ovine rumen and has been referred to previously asNeocallimastixsp., strain R1. It has a classical monocentric type of life cycle, with polyflagellated zoospores, endogenous development of the zoosporangium, and death of the thallus following zoospore release. AlthoughN.hurleyensisis similar to two other members of the genus,N.frontalis(the type species) andN.patriciarum, the zoospores possess 8–16 flagella, have no equatorial constriction, and exhibit segregation in the localization of intracellular organelles. A large organelle (presumptive hydrogenosome) is situated in the posterior portion of the cell, in close proximity to the kinetosomal apparatus. It is the size, location, and complexity of this organelle that explicitly distinguishesN.hurleyensisfrom other members of the genus.Key words: systematics. Neocallimasticaceae,Neocallimastix,Neocallimastix hurleyensis, anaerobic fungi, rumen fungi.

ISSN:0008-4026    

DOI:10.1139/b91-156

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

When containerized black spruce seedlings (Picea marianaMill.) are grown rapidly, their stems can become deformed, i.e., they bend over, grow horizontally, and obtain a permanent crook. To determine what physiological differences exist between these stem-deformed and healthy seedlings, we fed labeled amino acid,14C-phenylalanine, a precursor of lignin and phenolics as well as a constituent of proteins, to both kinds of seedlings and followed the partitioning of this14C after a chase period of 24, 48, and 72 h. For one group of seedlings, intact plants incorporated thel4C-phenylalanine through their root systems, whereas for a second group of plants, root systems were excised and the14C-phenylalanine was incorporated directly by stems. When the14C was incorporated by roots, stem-deformed seedlings partitioned morel4C to protein and less to lignin and phenolics. However, when the14C was incorporated directly by stems, the differences between stem-deformed and healthy seedlings nearly disappeared. Furthermore, the distribution of14C following root incorporation in stem-deformed seedlings was the same as that for stem incorporation in both types of seedlings. Thus, stem-deformed black spruce seedlings behave as if their root systems are not performing their normal role in metabolizing phenylalanine into lignin precursors. The ratio of14C allocated to phenolic-containing compounds associated with growth to14C allocated to those compounds associated with the differentiation of existing plant structures was 3.7 times higher in stem-deformed seedlings than in healthy ones. These results demonstrate that roots can play an important role in controlling the partitioning of carbon between growth and differentiation.Key words: black spruce, differentiation, lignification, phenolics, stem deformation, secondary metabolism.

ISSN:0008-4026    

DOI:10.1139/b91-157

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

Three monocentric and two polycentric obligately anaerobic zoosporic fungi were isolated from the rumen, freshly voided feces, and dry and moist feces. Rumen isolates were morphologically similar to fecal isolates from the same animal. The monocentric isolates werePiromyces communis,Neocallimastix frontalis, andCaecomyces communis. The polycentric isolates wereOrpinomyces bovisandOrpinomycessp. type PC3.Piromyces communisandN.frontaliswere obtained from feces stored for 3 and 6 months, respectively.Orpinomyces bovisandOrpinomycessp. type PC3 were isolated from dry feces, but not moist feces, stored for 3 and 6 months, respectively.Caecomyces communiswas isolated only from feces stored for 6 weeks. All the isolates, exceptC.communis, formed melanized sporangia in pure culture. Structures that were morphologically similar to the melanized sporangia of rumen fungi were observed in fecal smears.The fecal isolates grew under conditions similar to the rumen, but not under aerobic conditions.Key words: rumen fungi, Chytridiomycetes, fecal fungi.

ISSN:0008-4026    

DOI:10.1139/b91-158

出版商:NRC Research Press    

年代:1991

数据来源: NRC