摘要:

The seed set of eight bog plants in the Ericaceae family was reduced by excluding insect flower visitors even though hand-pollination tests showed that all eight species were self-compatible. Floral morphology evidently minimizes the possibility that pollen will be transferred from anther to stigma in the absence of insect visitation. Bees were the most important flower visitors, collecting nectar and (or) pollen. The attractiveness (nectar and (or) pollen extractable per minute) of the ericad flowers varied considerably. This variability would promote forager specialization and flowering-timing diversification if the ratio of insect visitors to flowers was low.

ISSN:0008-4026    

DOI:10.1139/b77-259

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

The effect of plant and leaf age on CO2-exchange rates (CER) and transpiration rates in 15 genotypes of cassava (Manihot esculentaCrantz) was measuredin situby infrared gas analysis. The plants were grown in a controlled-environment room with a 14-h photoperiod, day–night temperatures of 29–24 °C, and 60–70% relative humidity.Plant age had no effect on leaf CER, whereas transpiration rates in 14-week-old plants were significantly greater than those in 7-week-old plants. Both CER and transpiration rates decreased with leaf age. The decline was negligible when measured at low photosynthetic photon flux density. At saturating light, however, both CER and transpiration rates decreased significantly in most of the genotypes. Significant genotypic differences were observed in the pattern of decline. Both stomatal (rs) and residual (rr) resistances to the diffusion of CO2increased with leafage in all the genotypes. The relative increase inrrwas much greater than the increase inrs. In all the genotypes the ratiorr:rswas greater than unity, suggesting thatrris the major component of the total resistance to photosynthesis. Chlorophyll content and specific leaf weight also varied significantly among the genotypes. However, chlorophyll content decreased and specific leaf weight increased with leaf age.

ISSN:0008-4026    

DOI:10.1139/b77-260

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Metabolism of 3-amino-1,2,4-triazole was studied in 28-day-old seedlings ofPinus pineainjected with 5-14C-labelled 3-amino-1,2,4-triazole into the hypocotyl or tip of one of the 13 cotyledons. The seedlings were allowed to metabolize the labelled triazole for a period of 4, 14, or 21 days and were harvested and separated into cotyledons, apex, hypocotyl, and roots. The label upon extraction from the various parts was partially purified through a Dowex 50 W-8 resin exchange column and eluted with NH4OH and water for thin-layer chromatography. The radioautographs showed several metabolites including unmetabolized amitrole in all parts after 4 days of metabolism. Two of the slower running metabolites correspond to 'unknown I' orX1 and X3 previously reported inPinus ponderosaandAbies concolorand the two faster running metabolites have not been reported before. The metabolism of amitrole seems to occur in both hypocotyl and cotyledons (sites of injection) and the metabolites, as well as unmetabolized, free amitrole, are transported to all other parts of the plant, concentrating in the apex and cotyledons. Injection of labelled amitrole into the xylem of hypocotyl and root respectively results in upward translocation through the apoplast. Application to the exposed phloem resulted in lateral movement from symplast to apoplast and transport to the upper regions of the seedlings. Injection into one cotyledon resulted in symplastic movement to the apex and hypocotyl, followed by transfer in the hypocotyl to the apoplast and subsequent redistribution to other cotyledons. These patterns of translocation support the proposals put forth by Crafts.

ISSN:0008-4026    

DOI:10.1139/b77-261

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Seedlings of the sweet fern,Comptonia peregrina(L.) Coult., grown aeroponically, were inoculated with a nodule suspension to allow infection by the actinomycete-like organism which causes nodule formation. Roots with early stages of infection and nodule initiation were fixed, embedded in resin, sectioned, and examined. Infection is infrequent inComptoniawith only a few nodules per seedling root system. Infection via root hair invasion causes the retention of the curled and deformed root hair in an intensely cytoplasmic state with ramification of multiple filamentous strands of the endophyte. A limited cortical proliferation occurs in response to the infection forming the prenodule; endophyte filaments grow radially inward from the base of the infected epidermal root hair and invade a portion of the prenodular cells resulting in their hypertrophy. Distal and proximal to the prenodule site, a number of primary nodule primordia are initiated, varying from a few up to a dozen or more. These primordia appear to develop more or less simultaneously under the stimulus of the invading endophyte; they are like lateral roots in their site of origin, occurring largely opposite the protoxylem poles and involving pericyclic and endodermal cell proliferation. They differ in that the cortical cells external to each primordium are stimulated to undergo divisions and these cortical cell derivatives are incorporated into the developing primordium. The endophyte enters the cortical tissues of the lateral root on which the prenodule has formed and then invades proximal and distal to the infection site, progressing into the cortical tissues of each of the developing nodule primordia. A cork-like layer develops on the original lateral root in areas not occupied by primordia by initiation of subepidermal cell divisions and wall thickening. Normal lateral root primordium formation occurs in the pericycle opposite the protoxylem poles and involves cellular derivatives of the pericycle and endodermis but no cortical cells, which instead are crushed and displaced by the lateral root primordium as it develops. Nodule formation clearly involves complex chemical interactions, which remain for further study, between the host cells and the invading endophyte.

ISSN:0008-4026    

DOI:10.1139/b77-262

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

A telium ofG. jttniperi-virginianaeconsists of a palisade-like layer of hyphae located beneath the host epidermis. The terminal cell of each hypha within the telium disintegrates before the onset of teliospore formation. The cell immediately beneath the terminal cell functions as a sporogenous cell giving rise to teliospore initials. Each sporogenous cell contains two nuclei which divide mitotically as each initial forms. Two daughter nuclei move into the teliospore initial and two remain in the sporogenous cell. The initial elongates and is delimited from the sporogenous cell by a basal septum. The nuclei within the initial then divide and a centripetally developing septum separates the initial into two binucleate cells. The lower cell dies and becomes the pedicel of the spore while the upper cell or teliospore mother cell continues to develop. The nuclei of the mother cell divide and a centripetally developing central septum divides the cell into two binucleate cells. At this stage, the young teliospore is delimited. Its wall thickens and the spore enlarges, becoming more ellipsoid. Eventually, the nuclei within each cell of the teliospore fuse. After karyogamy, synaptonemal complexes appear in the nuclei of spores still within the telium.

ISSN:0008-4026    

DOI:10.1139/b77-263

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

The injection of either ϵ-amino-n-caproic acid (EACA) orL-lysine–HCl into the tetraploid wheat parent (Triticum turgidumL. var. durum cv. Jori) as early as 1 day after pollination with rye (Secalesp.) significantly enhanced the development of hybrid embryos in vivo. The success with which the embryos could be artificially cultured was improved accordingly. One millilitre of either compound applied at 1.0 mg/ml concentration resulted in a significant increase in the frequency of normal-appearing embryos. It is concluded that the application of EACA or its analogueL-lysine could be used in a hybridization program involving certain strains of wheat and rye to partially overcome the physiological barrier to hybrid embryo development.

ISSN:0008-4026    

DOI:10.1139/b77-264

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

A study was made on the effect of various temperature regimes on the in vivo development of hybrid embryos from crosses between tetraploid wheat (T. turgidumL. var. durum cv. Jori) and an inbred rye (Secale cerealeL.). A day–night temperature of 17–17 °C was found to be optimum for development of embryos as classified on the basis of their morphological features and their level of totipotency in vitro. The application of ϵ-amino-n-caproic acid (EACA) to the female parent (tetraploid wheat) daily for a 10-day period during embryogenesis significantly improved embryo development but not independently of temperature regime. Both temperature and EACA effects were manifested by increased growth and differentiation of the hybrid embryo; endosperm development was unaffected by treatment.

ISSN:0008-4026    

DOI:10.1139/b77-265

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Lamellar and tubular inclusion bodies in the cell vacuole became more numerous as the severity of plant stunting was increased. In normal-appearing greenhouse plants, only a few of these inclusions were seen. In vacuoles of the severely stunted plants, much larger quantities of inclusion bodies were observed. In severely stunted plants, lamellar inclusions occurred that contained osmiophilic globules along the lamellar strands. These types of lamellar inclusions were also seen accumulating in the starch cavities of chloroplasts. From these observations, we postulated that a cell, with a given capacity to produce membrane material, produces membranous material in anticipation of growth. When the cell does not grow, owing to stunting, this excess of membrane material forms the large number of inclusion bodies seen in the vacuoles of stunted cells.

ISSN:0008-4026    

DOI:10.1139/b77-266

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Phloem cells of cherry trees with little cherry show deposits on the cell walls which stain with acridine orange and can be observed with the fluorescent microscope. A survey of healthy and infected trees showed that there was a strong correlation between the occurrence of numerous wall deposits and the presence of the disease. Although wall deposits are found occasionally in the phloem of healthy petioles, an arbitrary cutoff point of five deposits per section was set as the distinguishing point between healthy and diseased material. The deposits develop in the petioles during the first 2 months after flowering. The color of the fluorescence seems to indicate that they do not contain RNA. It is suggested that the presence of numerous wall deposits could be useful as a diagnostic tool for the detection of little cherry.

ISSN:0008-4026    

DOI:10.1139/b77-267

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

The structure and development of oospores ofAlbugo candidain the stagheads in rapeseed (Brassica campestris) were investigated by light microscopy, transmission electron microscopy of ultrathin sections, and scanning electron microscopy. Development of an oospore, in general, is similar to that inPythium. A reaction zone is formed in the oogonial wall at the point of contact by the fertilization tube of the antheridium. The oospore has a highly differentiated five-layered cell wall. The periplasm appears to play an active role in deposition of the cell wall of the oospore. Contents of the periplasm do not disappear after maturation of the oospore; instead, they forma persistent material between it and the oogonial wall. Hence, functionally, the oospore wall complex has two additional layers. Longevity of the oospore may be due to the heavily fortified cell wall.

ISSN:0008-4026    

DOI:10.1139/b77-268

出版商:NRC Research Press    

年代:1977

数据来源: NRC