摘要:

The early growth of two hybridPopulus×euramericana(Dode) Guinier clones and a species clone each ofP. deltoidesBartr. ex Marsh, andP. nigraL. in controlled environments was studied in terms of growth of organs, partitioning of dry weight among parts, and growth analysis parameters. The hybrid clones grew more vigorously compared with the species clones with regard to most of the parameters measured. From 7 weeks after planting onward, the hybrid clones had greater plant dry weight, leaf dry weight, leaf area, and root dry weight than did the species clones. The hybrids developed a larger root system and greater leaf area per unit weight earlier than did the species clones. The greater leaf area was associated with lower specific leaf area. At all times the hybrid clones had significantly greater relative growth rates which were associated with early differences in unit leaf rate and later differences in leaf area ratio among the clones.

ISSN:0008-4026    

DOI:10.1139/b84-001

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

Wheat cv. Timgalen and cv. Gabo, sunflower cv. HA 124, and sorghum cv. RS 610 plants were grown at normal atmospheric or an elevated CO2concentration (atmospheric + 500 μmol CO2mol air−1). Enrichment with CO2advanced floral initiation by 1 – 3 days in wheat and sunflower but had no such effect in sorghum. The rate of differentiation of the primordial inflorescence was unaffected in sunflower but was reduced slightly in wheat and significantly in sorghum. Exposing plants to a brief CO2enrichment in series during the vegetative phase showed that the sensitive period for stimulation of floral initiation in wheat commenced within 10 days before the formation of double ridges. The sensitive period for retardation of inflorescence differentiation in sorghum commenced within 6 days before floral initiation. For sunflower the sensitive period was short, with peak stimulation occurring 7 days before floral initiation. It is concluded that the flowering response to CO2enrichment was not due solely to a general growth response; rather, direct morphogenic effects were involved.

ISSN:0008-4026    

DOI:10.1139/b84-002

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

Two Ecuadorian species belonging toCalatheaseriesComosae(Petersen) Schumann are described as new. Their inflorescences are characterized by the presence of both fertile and sterile bracts. The fertile and sterile bracts are similar morphologically inC. ecuadorianabut strongly dimorphic inC. contrafenestra. Differences in floral morphology and chromosome number which correlate with bract morphology indicateCalatheaseriesComosaeas currently defined is probably diphyletic.

ISSN:0008-4026    

DOI:10.1139/b84-003

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

The inclination, shape, and disappearance of individual fusiform initials were studied in the storeyed cambium ofTilia. Changes in inclination were accomplished through oriented cell-end shifting and pseudotransverse divisions combined with intrusive elongation. Rapid reorientation was associated with an increase in both radial and pseudotransverse anticlinal divisions, resulting in an overproduction of daughter cells; surplus cells were eliminated, creating space for the intrusive elongation of adjoining initials. The storeyed pattern was both disrupted and restored as a consequence of pseudotransverse divisions and intrusive elongation. Abnormally elongated cell ends shortened to the level of the storey border. Movement between storeys occurred as a result of intrusive elongation of one cell end in association with either pseudotransverse division or a gradual shortening of the opposite end. The combined findings of fluctuations in cell inclination, movement between storeys, and continual disturbance and restoration of the storeyed pattern indicate that developmental changes in the storeyed cambium are much more dynamic than previously suspected.

ISSN:0008-4026    

DOI:10.1139/b84-004

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

Sublittoral collection of fungal-infectedChondrus crispusover a 2-year period has allowed for a taxonomic reappraisal of the loculoascomyceteDidymosphaeria danica(Berlese) Wilson et Knoyle, an obligate parasite on the reproductive regions of host plants. A new genus,Lautitia, is proposed withLautitia danicacomb. nov. as the type species.Lautitia danicahas restrictedPleospora-typecentrum development; possesses septate pseudoparaphyses and hyaline, asymmetrically two-celled ascospores; and is placed in the Phaeosphaeriaceae, Pleosporales. In addition, the life historyof Lautitia danicais clarified.

ISSN:0008-4026    

DOI:10.1139/b84-005

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

Self- and cross-pollinations were made within and between selected species belonging toBoykinia,Peltoboykinia,Bolandra,Suksdorfia,Sullivantia, andJepsonia(Saxifragaceae). Self-incompatibility is reported for the first time inBoykinia. No intergeneric hybrids were produced, supporting the separate integrities of the genera involved, particularly the segregation ofPeltoboykinia. Intrageneric hybrids were made inBoykiniaandPeltoboykinia. In the case ofBoykinia, this supports the retention within it of the often segregatedTelesonix. Crosses between the two North AmericanSuksdorfiaspecies failed, but for various reasons, this was taken to reflect the existence of two "biological species" rather than two separate genera.

ISSN:0008-4026    

DOI:10.1139/b84-006

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

The effect of white clover mosaic virus infection on several factors relevant to symbiotic N2fixation was determined in nodulated red clover (Trifolium pratenseL.) plants at 10-leaf, preblooming, blooming, and flower-senescence stages of growth, corresponding to 3, 6, 9, and 12 weeks after virus inoculation, respectively. Virus infection caused a significantreduction of plant growth (top and root weight), nodulation (number and weight of nodules), rhizobial population, nitrogenase activity, and leghemoglobin concentration in the nodules. The presence of a high concentration of virus within nodules at all harvest times was indicated by infectivity assays. The leghemoglobin was shown to be localized in the peribacteroidal space by a cytochemical technique. A significant increase in inducible nitrate reductase activity was associated with virus infection of plants.

ISSN:0008-4026    

DOI:10.1139/b84-007

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

The seed bank of aPinus ponderosa–Symphoricarpos albusstand in east-central Washington was examined with respect to species composition, depth distribution, and germination responses to heat and shade treatments. Seeds of 57 species were present in the seed bank to a depth of 10 cm. Twenty-one of these species were not found in the aboveground vegetation of the study area. Estimated viable seed densities in spring and autumn collections were 13 052 ± 1481 and 14 463 ± 1356 seeds m−2, respectively.Stellaria mediaandPoa pratensis, both alien species, accounted for 50% of the buried viable seed. Seed density was highest in litter samples. Total seed density decreased with soil depth, although seeds of some pioneer species were more abundant in the mineral soil than in the litter. Species dominating the seed bank were generally unimportant in the aboveground vegetation. Woody species, which dominated the aboveground vegetation, accounted for only 1% of the seed bank. Annual forbs dominated the seed bank (45% of total buried viable seed) but were not dominant in the vegetation. Seeds of several species survived prestratification heat treatments. Poststratification heat treatments inhibited germination or destroyed seed of nearly all species. As shading increased, germination of most species decreased. However, shade did not inhibit germination of species characteristic of mature successional stages.

ISSN:0008-4026    

DOI:10.1139/b84-008

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

Chloroplast ultrastructure, pigment content, and composition were investigated during growth of 'Puma' rye at warm and cold-hardening temperatures. Cytological characteristics of leaf mesophyll cells were altered upon growth at cold-hardening temperatures as indicated by an apparent increase in the amount of cytoplasm. Univacuolate and multivacuolate mesophyll cells were found in leaves from cold-hardened plants, but only univacuolate mesophyll cells were found in leaves from warm-grown plants. Chloroplast ultrastructure was affected by growth at low temperature as indicated by a higher frequency of smaller granal stacks. However, there was no significant difference in the number of grana per chloroplast in mesophyll cells from either warm- or cold-grown plants. Chlorophyll per plastid increased by a factor of 1.67 upon growth at cold-hardening temperatures, as did β-carotene and the xanthophylls. However, there was no significant difference in photosynthetic unit size based on P700 measurements between chloroplasts from warm- or cold-grown tissue. Analysis of freeze-fractured thylakoid membranes indicated a loss in the bimodal nature of particle size distribution on the exoplasmic fracture face and a general increase in particle size on the protoplasmic fracture face upon growth and development at cold temperatures. However, particle densities on the exoplasmic and protoplasmic fracture faces were not significantly different in thylakoids from plastids developed at either warm or cold temperatures. It is concluded that chloroplast ultrastructure and pigment content but not composition are altered upon growth and development at cold-hardening temperatures.

ISSN:0008-4026    

DOI:10.1139/b84-009

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

Chlorophyll–protein complexes of thylakoid membranes from rye plants (Secale cerealeL. cv. Puma) grown at warm and cold-hardening temperatures were investigated by gel electrophoresis. Complex IV from cold-grown tissue was detectable in the presence of dodecyl sulfate if and only if solubilization and electrophoresis were performed at 4 °C, whereas complex IV from warm-grown material was detectable if membrane solubilization and electrophoresis were performed at either 4 or 23 °C in the presence of dodecyl sulfate. In the presence of octyl-β-D-glucopyranoside, the chlorophyll–protein complexes from cold-grown tissue were less stable at 23 °C than those from warm-grown tissue. Regardless of the detergent used, there was always more oligomer of the light-harvesting complex present in samples prepared from thylakoid membranes of warm-grown tissue than those from membranes of cold-grown tissue. It is concluded that the pigment–protein interaction in those complexes associated with photosystem II and the light-harvesting chlorophylla/b– protein complex has been altered upon growth and development at cold-hardening temperatures.

ISSN:0008-4026    

DOI:10.1139/b84-010

出版商:NRC Research Press    

年代:1984

数据来源: NRC