摘要:

Young, newly emergent sepal primordia of tobacco were halved vertically and left attached to their floral meristem. Sterile culture of these meristems on a Linsmaier and Skoog medium for 8 days facilitated regeneration of a new sepal primordium from each original half. Sepal rudiments thus exhibited regulative behavior and are structurally labile.

ISSN:0008-4026    

DOI:10.1139/b75-028

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Ryegrass plants grown in low NO3-N, high NO3-N, or high NH4-N nutrient culture were labeled by assimilation of14CO2by the tops. Plants were harvested 2, 6, and 24 h after labeling and percentage,14C incorporation was measured in ethanol-soluble, chloroform-soluble, and ethanol-insoluble fractions of leaves, stems, and roots. Low N roots accumulated the greatest and high NH4-N roots accumulated the least14C at the end of 24 h. Low NO3-N plants had higher levels of ethanol-soluble14C and lower chloroform-soluble and ethanol-insoluble14C than high NO3-N plants. Analysis of the ethanol-soluble fraction revealed higher,14C content in sugars and less in amino acids in low NO3-N plants than in high NO3-N plants. Labeling patterns in high NH4-N plants suggested incipient ammonium toxicity since14C metabolism was retarded, yet the plants showed no visual toxicity symptoms. When using percentage conversion of label from the ethanol-soluble to ethanol-insoluble fraction as a criterion for plant metabolism, roots appeared to be more sensitive to N deficiency than were tops. This result implies that reduced root growth and (or) function (nutrient uptake) may be one of the first effects of N deficiency.

ISSN:0008-4026    

DOI:10.1139/b75-029

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Lateral buds at the cotyledonary nodes of soybean plants grown under the conditions used in this study usually remain inhibited. These buds grow when the apical part of the plant is removed. They will grow, but less strongly, when the roots as well as the apex of the plant are removed and the basal end of the cut stem is placed in a mineral salt solution. Bud growth is further diminished by decreasing the length of stem left attached to the bud. The cotyledon is essential for bud growth on plant segments maintained in nutrient solution, but it can be replaced by a 1% sucrose solution during the early days of bud growth. Buds which are completely detached from the stem and placed in 1% sucrose do not elongate, but a small number of cell divisions are detectable, indicating that the early events of the release from inhibition have occurred. Buds elongate when they are apically or centrally located on stem segments. Increasing the length of the attached stem segments increases the growth of the buds. Additions of the cytokinin benzyladenine to plants causes a dramatic increase in bud growth when buds are attached to stem segments but does not stimulate growth of buds without stem segments. It is concluded that benzyladenine alone will not substitute for a factor(s) present in the stem which is necessary for bud growth. Increasing stem lengths above buds located at the basal ends of segments inhibits bud growth. It is suggested that this may be due to an accumulation of endogenous auxin at the site of the buds.

ISSN:0008-4026    

DOI:10.1139/b75-030

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

The nameStruthanthus haenkei(Presl) Engler has been variously applied in the past. Study of the type shows it to be synonymous withStruthanthus venetus(H.B.K.) Blume, an amplified description of which is given. The varietyangustusJohnston is based on a misinterpretation and is here given separate status asStruthanthus palmerin. sp.

ISSN:0008-4026    

DOI:10.1139/b75-031

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Most shoots ofCarex lacustrislive for about 12–14 months, emerging in autumn, overwintering as shoots of up to 50 cm in length, and maturing during the next summer. Others emerge in early spring but both groups die in late autumn. A third class emerges in late July or August, grow to be over 50 cm in length, and die in late autumn, living only 2 or 3 months.Flower initials in this species begin growth in the September–October period and overwinter while about 1.0 cm in length. The shoots that develop inflorescences are in general longer, heavier, and have a greater basal diameter than those shoots which do not flower. More shoots flower if the water level in the marsh was high the previous year.

ISSN:0008-4026    

DOI:10.1139/b75-032

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Electrophoretic analyses of isoenzyme patterns were performed with extracts of root, hypocotyl, and cotyledon suspension cultures derived from a single seedling. The enzymes studied included malate, glutamate, and glucose-6-phosphate dehydrogenases; peroxidase; polyphenol oxidase; esterase; acid phosphatase; and leucine amino peptidase. Peroxidase isoenzymes were also detected in the media. The isoenzymatic patterns of the three cultures were different for some enzymes, similar for others, and identical for the rest. The isoenzymatic patterns were recorded on a number of occasions over a period of 3 years and they remained relatively unchanged.

ISSN:0008-4026    

DOI:10.1139/b75-033

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Protoplasts from mesophyll cells of pea plants and from cultured cells ofViciawere agglutinated with polyethylene glycol (PEG) and subsequently fused upon elution of PEG to form heterokaryons. Ultrastructural studies have shown that during agglutination, localized areas of tight adhesion occurred between plasmalemmae; the membranes remained separated by a narrow gap. The plasmalemmae of adhering protoplasts were relatively smooth. Agglutination and subsequent fusion of protoplasts did not appear to be dependent on a minimum depth of cytoplasm in either partner. Fusion was first observed at the margins of the adhering surfaces. As the areas of cytoplasmic continuity enlarged, the agglutinated plasmalemmae dispersed in the cytoplasm. Cytoplasmic mixing in heterokaryons occurred within 3 h.

ISSN:0008-4026    

DOI:10.1139/b75-034

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

A speciesof Microsphaeraon oak leaf has been examined by scanning electron microscopy. The developing stages of the perithecium and perithecial appendages have been described. The perithecial surface at maturity is marked by ridges of two sizes. Appendages do not appear to be very rigid and are collapsed near the distal end. Multiple dichotomous branching produces an antler-like ornamentation at the appendage end.

ISSN:0008-4026    

DOI:10.1139/b75-035

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Hyphae were observed within diseased cortical tissue of hypocotyl lesions of both the susceptible and the resistant varieties but were not detected in symptomless tissues in advance of lesion margins. Hyphae ramified extensively intercellularly and, to a lesser extent, intracellularly. Only in severely diseased beets were hyphae found within the stele. Protoplasts of cortical cells in proximity to hyphae appeared to lose turgor early in pathogenesis; then the cells collapsed and cortical tissue was apparently macerated. Histochemically, cell wall constituents (pectin, hemicellulose, non-cellulosic polysaccharides, lignin, suberin, and cutin) were little changed in diseased beets as compared with healthy beets. Peroxidase and (at times) phenolase activity increased and phenols and quinones accumulated in the stele of diseased plants (adjacent to lesions) to levels above those found in healthy plants. Possibly these phenols and quinones may inhibit colonization of stelar tissues. No differences in accumulation or localization of these substances in the resistant as compared with the susceptible beet varieties were detected by histochemical methods.

ISSN:0008-4026    

DOI:10.1139/b75-036

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Changes in mesophyll ultrastructure with development and season are described forAbies balsamea. Cells mature sequentially during expansion of the needles. Most cells appear to be fully mature and actively photosynthesizing at the time of budbreak. Tannins appear early and accumulate throughout the growing season. Winter dormancy is marked by an accumulation of lipids throughout the cell, an aggregation of organelles around the nucleus, some loss of chloroplast structure, and a failure of chloroplasts to form starch grains. Reorganization of cell structure and resumption of synthetic activity in the spring occurs about 2 months before budbreak.

ISSN:0008-4026    

DOI:10.1139/b75-037

出版商:NRC Research Press    

年代:1975

数据来源: NRC