摘要:

Wheat and rye calli were induced on Murashige–Skoog medium by the addition of 2, 4-D[(2,4-dichlorophenoxy)acetic acid]. The effect of Mecoprop [2(4-chloro-2-methyl)phenoxy propionic acid], an analogue of this auxin, was also tested and the rates of callus growth were compared with the ones obtained with 2, 4-D. On Murashige–Skoog medium, Mecoprop induced and supported callus growth of the various cereals tested more efficiently than did 2, 4-D. This effect was more pronounced on wheat callus. When both auxins were present in the culture medium, the enhancing effect of Mecoprop was slightly higher. The specific affinity of both auxins for wheat chromatin was measured. The results indicated that both substances, 2, 4-D and Mecoprop, selectively dissolve wheat chromatin. However, lower concentrations of Mecoprop than of 2, 4-D are required to dissolve the same amount of chromatin. It is concluded that in cereal cell cultures, Mecoprop is a more efficient growth factor than 2, 4-D.

ISSN:0008-4026    

DOI:10.1139/b79-183

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

A new species ofStemphyliumWallr, is described and illustrated. This species,Stemphylium arnyi, is pathogenic onSmilacina stellataand it is the onlyStemphyliumspecies reported on this host.

ISSN:0008-4026    

DOI:10.1139/b79-184

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

The development of the union of pea roots splice grafted when 8 days old is followed with optical microscopy. Cell divisions are induced close to the wound in both partners in 1 to 2 days. Content of cytoplasm increases in some cells of the pith, cambium, pericycle, and cortex, and these cells proliferate to form both disorganized callus within the vascular cylinder and organized nodules of cells in the cortex of each partner. There is more proliferation proximal to the graft. The resulting cells invade the graft gap, completely filling it and effecting union by day 7. The first wound-repair vascular tissue differentiates on day 4 in both partners. Wound-repair xylem bridges the union on day 7, phloem on day 8, and a cambium by day 12. The necrotic layer (cells killed by cutting), initially thick, is disrupted by day 4 and largely disappears, as do its phenolic staining properties, by the time of cohesion. Growth of the whole plant resumes by day 9. During development of the union, the cortex and pith proliferate most, the pericycle less, the endodermis and cambium least, thus disproving the dogma that the cambium is the sole proliferative layer in graft formation.

ISSN:0008-4026    

DOI:10.1139/b79-185

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

The vegetation at a Lesser Snow Goose breeding colony was examined to determine if particular plant species or species associations were characteristic of the nest sites of the geese. A stepwise discriminant analysis revealed that nest sites could be satisfactorily distinguished from the ambient vegetation using 2 of the 29 plant species growing in the quadrats. These two species, lyme grass (Elymus arenariusssp.mollis) and arctic daisy (Chrysanthemum arcticumssp.polare) were strongly associated with Snow Goose nest sites.Possible explanations for the association are examined. It is suggested that rather than a cause and effect relationship between plants and nest sites,E. arenariusandC. arcticumhave similar ecological requirements to those of the geese for a nesting site.

ISSN:0008-4026    

DOI:10.1139/b79-186

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Mesophyll cells were isolated rapidly from the cladophylls ofAsparagus sprengeriRegel, by gentle grinding of the tissue by hand. About 60 to 65% of the leaf cells on a chlorophyll basis were released, of which 85 to 90% were cells with an intact plasmalemma. The isolated cells had photosynthetic rates of 50 to 80 μmol O2per milligram chlorophyll per hour at pH 7.2 and 25 °C although rates of 90 to 105 μmol O2per milligram chlorophyll per hour were recorded. The apparentKmof photosynthetic bicarbonate uptake at pH 7.2 was 176 μMin air and 104 μMunder nitrogen, which corresponds to apparentKm's of CO2fixation of 23 μMand 13.5 μMrespectively. The isolated cells maintained high photosynthetic rates for 50 h when stored in the light at 4 °C and for over 160 h after storage in the dark at 4 °C.

ISSN:0008-4026    

DOI:10.1139/b79-187

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Experiments in which winter wheat plants were exposed to two different controlled hardening-temperature regimes (constant 3 °C, and 5.5 °C (day): 3.5 °C (night)) for long periods (up to 15 weeks) indicate that cold hardiness changes with time.The cold hardiness in plants grown from seed at 3 °C drops rapidly immediately after moistening and reaches a minimum 2–3 weeks later. Hardiness then begins to increase and reaches a maximum that lasts approximately from the 7th to the 11th week of growth after which it slowly declines.The patterns of change in cold hardiness during growth at 3 °C, and 5.5 °C:3.5 °C were almost synchronous if hardiness was plotted against duration of hardening, but were not synchronous if hardiness was plotted against stage of development as measured by the number of leaves produced. A somewhat similar result was obtained if plants grown for 3 weeks at 21 °C before hardening were compared with plants grown from dry seeds under the same hardening conditions. These experiments show that duration of hardening is more important in determining the level of cold resistance and the ability of wheat to retain its cold resistance than is stage of development, as measured by the number of leaves produced at the time cold resistance is measured.When plants seeded outdoors in mid-September were transferred at various dates (0–30 weeks after seeding) during the fall or winter to standardized hardening conditions in a growth cabinet for 0–15 weeks before freezing, their cold resistance changed in a way that suggests that plants in the field undergo the same pattern of changes in cold resistance as plants reared continuously in a growth chamber. This result suggests that the long exposure to hardening temperatures is one of the reasons why wheat in the field has less cold resistance in late winter than in autumn. Loss of carbohydrate reserves during winter may be an additional reason for this phenomenon.Under both growth cabinet and field conditions, increasing cold hardiness coincided with vernalization. Maximum cold hardiness was retained for several weeks after the completion of vernalization. These results suggest that the development of the maximum level of cold resistance may be related to the vernalization process.

ISSN:0008-4026    

DOI:10.1139/b79-188

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Two new specimens ofAnachoropterisfrom Belgian coal balls from the Bouxharmont coal seam are described. Anatomically the specimens are characterized by very slight abaxial curvature of a uniformly thick, foliar vascular strand corresponding to the speciesA. gillotiiCorsin, and morphologically, by a type of trifurcation of a foliar member which gives rise to two lateral foliar organs and a median, slightly adaxial cauline strand which shows the initiation of a petiole trace. The foliar members bear secondary pinna traces which immediately divide to give basiscopic tertiary traces. Metaxylem tracheidal pitting is simple scalariform in the stem and scalariform bordered in the leaves. One foliar specimen clearly supports Corsin's idea that in this genus there are two persistent adaxial protoxylem poles which divide alternately to supply pinna traces.

ISSN:0008-4026    

DOI:10.1139/b79-189

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Plasmolysis of rust-infected flax tissue after treatment with sucrose, mannitol, or calcium chloride solutions caused withdrawal of the host plasmalemma from the cell wall and movement of the host protoplast towards the haustorium. The extrahaustorial membrane, however, was not displaced from its position along the haustorial neck or around the haustorial body. In sucrose and mannitol solutions the extrahaustorial matrix was unchanged in volume, which suggests that it is either a more rigid structure than has usually been suggested or an artifact of fixation. After calcium chloride treatment, the matrix was frequently slightly distended and some plasmolysis of the haustorial protoplast was generally observed; this did not occur in the sucrose or mannitol solutions. The possible significance of these findings is briefly discussed.

ISSN:0008-4026    

DOI:10.1139/b79-190

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

The characteristics of phosphatase activity ofCladina rangiferina(L.) Harm, have been studied. Calculations of enzyme activities were based on the liberation ofp-nitrophenol fromp-nitrophenyl phosphate. The phosphatase activity was found to be linear both with increasing sample size (enzyme concentration) and increasing time, showed highest activity at acidic pH, and had a Michaelis–Menten constant of 8.9 × 10−3 M. The enzyme activity was maximal in the range 61 ± 10 °C, was independent of light, and was completely eliminated by boiling the thalli. Various cations and anions were tested for their effect; uranyl and vanadyl ions inhibited activity by 60% whereas copper, nickel, and silver enhanced activity by 10%. The anions biselenite, cyanide, fluoride, molybdate, phosphate, and vanadate all greatly reduced activity (≥ 50%). Phosphatase activity was demonstrated in other lichen species.

ISSN:0008-4026    

DOI:10.1139/b79-191

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

The discomycetePyronema domesticumrequires light for the production of its gametangia and apothecia. Effects of a single exposure to light (150 ft-c (1 ft-c = 10.76391 lx)) for periods ranging fromto 168 h on cultures aged 0–10 days were evaluated. A timetable for major developmental events (e.g., gametangial maturation) was established to determine the reactions of specific morphological events to light. Light was required to initiate gametangial production, but was not required at the time of gametangial differentiation. A minimum single exposure of 6 h was required to initiate gametangia, whereas a single exposure of 12 h was required to allow maximum development of the ascogonia to the fully globose form. Development of the ascogenous hyphae, asci, and ascospores was favored by exposure to a longer period of light and reached maximum development with exposure to at least 36 h of light. Although light favors ascospore formation, they can be delimited in the dark. An extended period of light (over 96 h) inhibits ascospore maturation.Neither gametangia nor apothecia were formed in cultures that were either too young (less than 2 days) or too old (6 days or more) at the time of light exposure. The age of 3 days at the initiation of light exposure was optimum for gametangial production, for development of the ascogenous hyphae and ascospores, and for apothecial expansion. In those cultures that were 4 days old at the time of exposure, many of the apothecia either lacked paraphyses, had very short paraphyses, or had an unusually high proportion of sterile asci.Sclerotia were only formed in the cultures which were exposed to light for comparatively short (18 h or less) periods of time. These sclerotia were intermixed with apothecia in the cultures.

ISSN:0008-4026    

DOI:10.1139/b79-192

出版商:NRC Research Press    

年代:1979

数据来源: NRC