摘要:

The release of sucrose into the vessel water of sugar maple (Acer saccharumMarsh.) has been investigated with biochemical and enzyme-cytochemical methods. The amount of sucrose released into the vessels in isolated stem segments was found to be temperature-dependent. The release of sucrose also proved to be inhibited whenp-chloromercuribenzoate as an inhibitor of respiratory enzymes was present in the vessels. This suggests that the sucrose release is dependent upon the respiratory activity of some cells. In the cytochemical studies much increased activity of respiratory enzymes (succinate, NAD-dependent isocitrate, and alcohol dehydrogenases) and of acid phosphatases could be demonstrated in the contact cells of the ray and axial parenchyma. Phosphatase activity was concentrated on the large pits between contact cells and vessels. These increased enzyme activities in contact cells were restricted to the time when sucrose appeared in the vessels. Since contact cells are the only cells of the ray and axial parenchyma that show peculiar pit connections with the vessels and also show increased respiratory and phosphatase activity, these cells are considered to be the specific sites of a metabolically controlled sucrose release.

ISSN:0008-4026    

DOI:10.1139/b73-001

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Isolates ofBipolaris sorokinianawith hyaline conidia were obtained from subcrown internodes of single plants of fourTriticumspecies grown on land which, 15 years previously, had been planted with seed inoculated with two hyaline-spored strains. All isolates were pathogenic and produced a "toxin" in culture. Three distinct colony types were distinguished and representatives of both mating types, "A" and "a," appeared to be present. The new isolates were compared with isolate K3 which was one of the isolates used in 1956. Isolate K3 was equally pathogenic but produced no "toxin" in culture. On autoclaved straw, conidia of the new isolates were somewhat shorter than those of K3 but were otherwise similar. On minimal medium all the new isolates produced abundant small, subspherical conidia with one to two pseudosepta. Germ tubes were produced from one or both terminal cells.

ISSN:0008-4026    

DOI:10.1139/b73-002

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Systemic infection of sunflowers byPlasmopara halstediioccurs much more readily through hypocotyls than through roots, and through apical buds than through leaves.Systemic symptoms rarely develop from belowground infections of plants past the four-leaf stage, and from apical bud infections of plants past the eight-leaf stage. Necrotic lesions may occur and the pathogen may sporulate on hypocotyls and roots of plants with no typical systemic symptoms.Infection by sporangia produces local lesions in young leaves; some of these infections may become systemic.Immersion of 3-day-old seedlings in inoculum for 1 min resulted in some infection; highest infection resulted from 3- to 6-h exposure.Systemic infection resulted from apical bud inoculation with suspensions averaging one sporangium per plant.Optimum temperature during inoculation of 3-day-old seedlings was 15°, and during incubation was 20° to 25 °C. Optimum temperature during bud inoculation was 15°; incubation temperatures from 15° to 25 °C gave essentially similar results.

ISSN:0008-4026    

DOI:10.1139/b73-003

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Symptoms of Verticillium wilt on inoculated plants of the sunflower cultivar Sunrise appeared sooner and were more severe under long days (16 h light, 8 h dark), or short days with interrupted dark period (10 h light,dark,light,dark), than under short days (10 h light, 14 h dark). Uninoculated control plants flowered in 45 to 47 days under short-day conditions, but reached only the yellow bud stage in 50 to 55 days under long days or short days with interrupted dark period. Development of Verticillium wilt of sunflower is not dependent on the initiation of flowering as it is in some other hosts.

ISSN:0008-4026    

DOI:10.1139/b73-004

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

The nitrate reductase of etiolated field peas (Pisum arvenseL. cv. Century) is described. Enzyme activity is maximally extracted into a cysteine-free solution. Absolute enzyme activities, in dark-grown plants and in plants exposed for a short period to 600 μW∙cm−2of white light, and the extent of induction by light, were high in the terminal buds and declined rapidly in the basal direction along the shoot. Soluble protein distribution followed nitrate reductase activity in opposite direction to the acropetal decrease in nitrate concentration. Nitrate reductase in dark-grown terminal buds showed adaptation to the supply of nutrient nitrate concentration, and 2 h of white light also elicited an enzyme response that depended on nitrate. The effect of light is demonstrated to be largely independent of photosynthetic light utilization since 5 min of white light, followed by 115 min of darkness, led to activity increases that were about 80% of increases after 2 h of white light. Enzymologically, the nitrate reductase of dark-grown terminal buds appeared to be identical with the light-induced enzyme and also with the enzyme of green plant tissues as characterized in the literatur

ISSN:0008-4026    

DOI:10.1139/b73-005

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Histochemical tests for K+were carried out on the epidermis of aerial organs from plants which varied in evolutionary development (e.g., clubmosses, ferns, angiosperms) and general morphology (e.g., monocotyledons, succulent dicotyledons, woody dicotyledons). These tests made on epidermal tissue with open or closed stomata suggested that K+transport is implicated in stomatal movements regardless of the evolutionary level and the stomatal location in the plants investigated. In all species that displayed substantial stomatal opening, K+was detectable in the guard cells. With small stomatal apertures, K+was located in guard and subsidiary cells ofCommelina communisL. leaves andGlycine max. L. cotyledons. When stomata were closed, K+was detectable in the subsidiary cells of all the grass species,Kalanchoë pinnataPers.,C. communis, and, occasionally, in the epidermal cells surrounding the stomata of some ferns. A condition was also observed when virtually no K+was detectable in the guard or subsidiary cells ofC. communisleaves orG. maxcotyledons. Commonly, when stomata were closed, K+was not detectable in any cells of the epidermis. Exceptions were the "K+storage cells," trichomes and epidermal cells ofArachis hypogaeaL., and in the more primitive plants from and including the level of the ferns.

ISSN:0008-4026    

DOI:10.1139/b73-006

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Eight species of agarics in the Basidiomycetes from arctic and alpine tundra in Alaska and adjacent Canada are included. Four taxa are reported from North America for the first time including one new species. One taxon is reported for the first time from arctic tundra in North America. New ecological information, host ranges, and fruiting periods are presented for all taxa. Camera lucida drawings are included for five taxa.

ISSN:0008-4026    

DOI:10.1139/b73-007

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Spartina alterniflora, the dominant plant species of the tidal salt marshes on the east coast of the United States, contributes significantly to estuarine primary productivity. Energy stored by the plant is released through decomposition as detritus or decomposer biomass. The role of fungi in these transformations has not been elucidated and was investigated in the present study. Dried, dead grass was confined in nylon bags, exposed on a salt marsh and in an adjacent tidal creek in southern Rhode Island, and a quantitative and qualitative study made of the fungi found to be associated with the decomposing grass. Twenty-seven species of fungi were isolated. The average number of fungal colonies/g dry wt. of grass was found to be higher in material exposed on the salt marsh and subjected to immersion only at high tide (2436) than from material immersed in an adjacent creek (1021). The grass lost about 50% dry wt. after 6 months of exposure on the marsh.

ISSN:0008-4026    

DOI:10.1139/b73-008

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Zinc markedly stimulated growth ofVerticillium albo-atrumR. & B. in Czapek-Dox broth shake cultures. Minimum zinc concentration producing optimum growth response was 0.15 to 0.2 μg/ml. On a dry weight basis added zinc resulted in increased total nitrogen content and oxygen uptake. Oxygen uptake per unit total nitrogen was essentially unaffected. Cells from 5- and particularly 7-day-old zinc-free cultures showed less response to zinc than did those from 3- and 10-day-old cultures. Zinc response was greatest withL-alanine as the nitrogen source as compared with nitrate, urea, and ammonium nitrate sources.

ISSN:0008-4026    

DOI:10.1139/b73-009

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Two new species ofBalladynaRaciborski are described:B. magnasp. nov. onParamacrolobium coeruleum(Taub.) J. Leonard in Kenya, andB. tarennaesp. nov. found onTarenna pavettoides(Harv.) Sim. in Tanzania.

ISSN:0008-4026    

DOI:10.1139/b73-010

出版商:NRC Research Press    

年代:1973

数据来源: NRC