摘要:

The present communication deals with induction of callus from mechanically isolated mesophyll cells ofIpomoea quamoclitLinn. Growth of the callus and potentiality for differentiation are also examined.

ISSN:0008-4026    

DOI:10.1139/b74-272

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Sequential developmental stages from synchronously sporulating cultures ofPhialocephala dimorphosporaKendrick have been examined. Apical vesicles characterize growth of the primary conidium. These are not, however, seen during secondary conidium formation; instead, large vesicles containing minute membrane fragments develop just below the phialide neck and contribute to wall formation as they fuse with the plasmalemma. The occurrence of microtubules in the neck of the phialide is restricted to primary conidium formation. Just as the primary conidial initial begins to swell, electron-dense granules 50-75 nm in diameter arise in association with the plasmalemma. Such granules are not seen during secondary conidium formation; they are thought to be involved in pigment deposition in the collarette. During both primary and secondary conidium production the conidia go through a sequence of maturation in which the cytoplasm becomes very dense and contains lipid bodies and flocculent aggregations of electron-transparent granules. Subsequently the conidia become less electron dense and reveal a simple internal substructure consisting of a nucleus, mitochondria, micro-bodies, free ribosomes, and presumed storage bodies. The plasmalemma becomes convoluted in a network of interdigitated grooves. Septum formation occurs rapidly and involves the fusion of vesicles with the lateral wall. Mature septa are non-perforate. Although Woronin bodies have been repeatedly observed in young conidia, they are never seen in mature conidia. Myelin figures associated with mitochondria occur consistently in the body of the phialide during conidiation. These may be the source of the lipid bodies in the conidia. In phialides from cultures over 1 week old, signs of senescence are apparent. These include vacuolization of the upper portion of the phialide and the presence of many disorganized sheets of membrane. Spores still present within the collarette of such phialides are smaller than those produced early in the life of the phialide.

ISSN:0008-4026    

DOI:10.1139/b74-273

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

A common North American fungus resemblingDiatrype stigma(Hoffm. ex Fr.) Fr. and previously described under several epithets in the Diatrypaceae is placed inGraphostroma, a new monotypic genus of Xylariaceae, asG. platystoma(Schw.) comb. nov. It is compared with the EuropeanXenotypa aterrima(Fr.) Petrak, representing another monotypic genus segregated from the Diatrypaceae and belonging in the Diaporthaceae.

ISSN:0008-4026    

DOI:10.1139/b74-274

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Concentric bodies about 280 nm in diameter were often observed as inclusions in hyphae of the perithecial wall and infrequently were seen in the vegetative hyphae and conidiophores ofVenturia inaequalis. These apparently spherical bodies were found singly or in clusters and consisted of several distinct layers. The inclusions appeared to be identical with those found in a number of lichen mycobionts.

ISSN:0008-4026    

DOI:10.1139/b74-275

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Photomicrographs of chromosomal configurations in nuclei of squashed whole mounts of mature oospores (cultures 32 days old) ofPhytophthora capsicistained with iron hematoxylin were interpreted to indicate that meiosis occurred in the oospore. Chromosomes in dividing oospore nuclei were observed in synapsis, diakinesis, metaphase I, and metaphase II. Comparison of polar metaphase I and metaphase II plates revealed a reduction in chromosome size and number and nuclear size. The haploid number of chromosomes was interpreted to be 6.

ISSN:0008-4026    

DOI:10.1139/b74-276

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

A black imperfect fungus isolated from 3-year-old nursery seedlings ofPinus resinosawas tested for its ability to form mycorrhizae on red pine in monoxenic culture. It was found to stimulate seedling growth. The fungal invasion passed through three successive stages of development during the 7 months after inoculation. At 3 months, intracellular hyphae occurred in all long- and short-root branches, with intercellular hyphae scattered only at isolated loci in the intercellular spaces. After 5 months the infection in the cortex changed abruptly from an intracellular infection to a completely intercellular Hartig net. Although the Hartig net was remarkably thin when first initiated, at its culmination it reached a massive thickness and sent penetrating hyphae into the cortical cells, resulting in the formation of distinctive ectendomycorrhizae. By the end of 7 months the secondary intracellular invasions were often found in the vicinity of the meristems in all root branches except the largest-diameter long-roots, and the fungus-root association had developed toward a predominant ectendomycorrhizal condition. The ectendomycorrhizal infection was distinctively different from the one produced by the so-called E-strains that have been commonly observed in coniferous nurseries.

ISSN:0008-4026    

DOI:10.1139/b74-277

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

A modified method of measuring litter decomposition using mesh bags is suggested in which the bags are reused during several time increments. The chief objections to this method are that litter may be lost through spillage and that repeated artificial drying may affect decomposition rates. Experimental results are presented to show that spillage represents a significant source of error with finely divided litter, even using conventional litter bag methods. A method for handling litter bags is suggested in which corrections may be made for spillage. In a second experiment it was found that decomposition rates were not significantly altered by repeated artificial drying of old-field litter so that repeated drying of litter in field experiments may be valid.

ISSN:0008-4026    

DOI:10.1139/b74-278

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Early stages of development of the male and female flower are similar; two second-order bracts arise in the transversal plane on either side of the floral apex before the apex flattens and becomes somewhat concave because of growth activity at the flank of the apex. In the female flower, the gynoecium develops as an extension of the girdling gynoecial primordium and the two primordial stigmas each result from more rapid growth in the median plane at the distal portion of the gynoecial wall. The floral apex resumes growth to form the unitegmic ovule. Third-order lanceolate-shaped bracts develop from a meristem situated in the axil of each second-order bract. In the male flower, staminate primordia arise at three or four loci on the ridge surrounding the apex. The apex briefly resumes growth. Growth of the second-order bracts terminates at an early stage. The floral construction is compared to other myricaceous species. It is concluded that the axillary scale-like bracts of the female flower are third-order bracts; the gynoecium does not overtop the second-order axis and the female flower is not a reduced cyme; the male flower is more floral- than inflorescence-like compared to some other myricaceous species.

ISSN:0008-4026    

DOI:10.1139/b74-279

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Lychnis albapollen possesses 0.73–0.79% elemental silicon (dry weight), and levels at least as high as in pollen exines have been indicated in tapetal orbicules upon maturation. Even higher levels of elemental silicon (1.30–1.37%) were recorded fromImpatiens sultaniipollen. This may indicate that silicon is an important elemental component of exine materials characteristic of many types of pollen, in which silicate compounds may aid in the high degree of pollen resistance to geological weathering, microbial decay, and acetolysis treatments. Further, the data for the incorporation of silicon inL. albapollen in this report support the concept that exine materials are derived from tapetal cell secretions during pollen ontogeny.

ISSN:0008-4026    

DOI:10.1139/b74-280

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

A species ofPhyllactiniaon oak was examined by scanning electron microscopy. The naturally dried fungus was minimally manipulated in preparation for study. Development was followed by examining various stages from initial to mature perithecium. Immature perithecial appendages were found to be less rigid than those which had matured. The sticky apical mucilage droplet on the maturing perithecium was observed, but the penicillate cells that form the droplet were not easily seen. As the appendages dried they lifted the perithecium off the surrounding surface. Some perithecia were found that had overturned and adhered to the hyphae-covered leaf by means of the mucilage droplet. This study has resulted in visualization ofPhyllactiniasurface structure in more detail than heretofore reported. Other plant pathogenic fungi, especially those producing naturally dry mature fruiting bodies, should be amenable to study by this method.

ISSN:0008-4026    

DOI:10.1139/b74-281

出版商:NRC Research Press    

年代:1974

数据来源: NRC