摘要:

Studies on the growth of batch suspension cultures of a plant cell line, initiated fromIpomoeasp. root explants, at temperatures ranging from 15 to 34 °C are reported. Maximum growth of cultures of this cell line occurred between 25 and 32 °C, with temperature variations within this range having little effect on growth rates based on dry cell yields. Cultivation at 20 °C substantially reduced the growth rate. However, cells grown at 20 °C failed to grow on transfer to fresh medium at 20 °C. Thus cultivation at suboptimum temperatures is not a satisfactory method for routine maintenance of the suspension culture.

ISSN:0008-4026    

DOI:10.1139/b75-040

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Exposure of dormant sugar maple seedlings to over 2000 h of winter temperatures of 5 °C and below was required for rapid and normal growth when seedlings were transferred to a warm greenhouse and extended photoperiods. Although chilling requirements were not fully satisfied until mid-March, a resurgence of metabolic activity occurred in early February. There was a marked shift in the potential for budbreak from the axillary to the terminal buds, and a surge in root growth occurred after a period of inactivity when the ground was frozen from late December to mid-January. The water content of the buds followed a pattern similar to that of the roots. It fell to a plateau in late fall well before the soil froze but began a steady increase with the resumption of active root growth in February. Inhibitory substances present in the buds did not exhibit significant changes during the overwintering period. However, cytokinin activity was observed beginning in February at the same time that root growth and bud succulence showed upward inflections. By the beginning of April there were two distinct peaks of activity which persisted through budbreak in early May.Seedlings that were brought into the greenhouse in the fall and never exposed to chilling temperatures did not break dormancy or show significant cytokinin activity or exhibit the physiological changes that occur under normal winter conditions.

ISSN:0008-4026    

DOI:10.1139/b75-041

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

EightSphagnum-dominated kettle-hole bogs in northern Michigan were analyzed to elucidate vegetation patterns of both vascular plants andSphagnumspecies in relation to measured bog gradients. Methods of both direct and indirect gradient analysis, including ordination and cluster analysis, were used. Community types as delineated in the ordination are discussed, including species distribution forSphagnumand vascular plants. Segregation of community types followed gradients of pH, light, and calcium and magnesium ion concentrations. Two types of kettle-hole bogs were distinguished surrounding acid and alkaline bog lakes respectively, each with its own continuum of community types.

ISSN:0008-4026    

DOI:10.1139/b75-042

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Taxonomic characters such as sporangium size, sporangium wall behavior at the time of spore discharge, presence or absence of basal rudiments, and cleavage patterns of an isolate ofThraustochytrium(isolate 70–2) were found to vary. Variations occurred between individuals under presumably the same environmental conditions. Variations also occurred when the organism was grown under different conditions and compared. Repeated emergence and motility of cells with and without visible ectoplasmic nets were observed. Amoeboid and amoeboflagellate cells were produced in cultures contaminated with bacteria.

ISSN:0008-4026    

DOI:10.1139/b75-043

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

The appearance of apogamous buds was studied inPteridiumgametophytes grown on medium containing sucrose and supplied with ethylene continuously or for brief periods followed by transfer to a flowing-air system without exogenous ethylene for the duration of the experimental period. Apogamy was induced in response to ethylene during a minimal 8-day induction period. Differentiation and growth of the apogamous sporophytes to observable buds occurred during the remaining 28 days of the experimental period. Ethylene was required for the induction period but was active only if supplied in conjunction with sucrose. Development of the buds, once induction was complete, was independent of ethylene but dependent on exogenous carbohydrate.

ISSN:0008-4026    

DOI:10.1139/b75-044

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Canopy net carbon dioxide exchange (NCE) rates are needed to understand the effect of light on crop growth and development. NCE rates of sorghum, soybean, and wheat canopies were determined using field chambers and an infrared gas analyzer throughout a growing season. Whereas sorghum attained peak NCE rates early in season, soybean and wheat did not reach maximum rates until the late reproductive growth stage. Frequently during the season, NCE rates of sorghum were nearly four times those of soybeans and wheat. Solar radiation had a much greater affect on the NCE of sorghum than on that of soybeans. Apparent light saturation was observed in both soybeans and wheat. An expression for dry matter production of sorghum was derived using chamber data. The expression simulated the total dry matter production for sorghum in 1973, 1972, and 1970 within 20%.

ISSN:0008-4026    

DOI:10.1139/b75-045

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

When flax (Linum usitatissimumL.) seedlings were grown in sand culture under controlled conditions, growth of the lateral buds and their release from apical dominance showed a positive correlation with the N supply. The response of the buds was related to their position on the shoot and a well-defined gradient of bud growth potential was apparent at all N levels. Removal of the basal buds, which have the highest growth potential, induced the outgrowth of buds at higher nodes and increased the growth of the main shoot apex. Similar effects were produced by increasing the N supply to the intact plant.Providing N only as nitrate inhibited apical growth and caused severe leaf necrosis. These effects were due to zinc deficiency and could be prevented or significantly reduced not only by increasing the zinc supply but also by reducing the N level, providing some NH4-N, reducing the light intensity, or increasing the depth of planting. They could also be prevented by removal of the lateral buds at the basal nodes, thus indicating that the shoot apex and lateral buds may compete for the limited zinc supply. The obviously complex relationship between zinc and nitrogen nutrition in this species requires further investigation.

ISSN:0008-4026    

DOI:10.1139/b75-046

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

An ultrastructural study of mitosis in a diploid strain ofCochliobolus sativusshowed the event to be intranuclear. Two nucleoli occasionally were present in interphase nuclei. During division the spindle pole body peripheral to the nuclear envelope divided; spindle microtubules radiated into the nucleoplasm from the amorphous granular region abutting the nuclear envelope beneath the bodies; chromosomes condensed at prophase, approached the equatorial plane at metaphase, and moved asynchronously at anaphase; single microtubules appeared attached to kinetochore-like structures. At telophase, nuclei exhibited maximal elongation; fissures of the nuclear envelope appeared in the interzonal region; the nucleolus dispersed. The polar nuclear areas became new daughter nuclei with nucleoli.

ISSN:0008-4026    

DOI:10.1139/b75-047

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Nine woody plant species typically found in non-acidic substrates, and 12 woody plant species typically found in acidic substrates, were cultivated at three levels of manganese availability. Considered collectively, the group of plants from the acidic habitats accumulated less manganese in the foliage compared with the group of plants from non-acidic habitats, suggesting adaptation by means of exclusion to the potentially toxic levels of manganese of acid soils. No significant differences were found for the two groups with respect to manganese accumulation in the stems.

ISSN:0008-4026    

DOI:10.1139/b75-048

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Wild oats (Avena fatua), naturally infected with barley stripe mosaic virus, were detected in Manitoba in 1973 and 1974. The identity of the virus was confirmed on the basis of particle morphology, infectivity, and serological assays. Infected wild oats were rare and were found only in fields of barley in which a high proportion of the latter plants were also infected. The virus was transmitted through 22% of the seeds collected from naturally infected wild oats. Pale green spindle-shaped stripes were the most prominent symptom in leaves of naturally infected wild oats, whereas in leaves of seedlings infected by seed only mosaic symptoms developed.

ISSN:0008-4026    

DOI:10.1139/b75-049

出版商:NRC Research Press    

年代:1975

数据来源: NRC