摘要:

Hypostomatous lady slipper orchids,Paphiopedilumspp., were found to have non-chlorophyllous epidermal cells, including guard cells. The lack of chlorophyll within the guard cells was demonstrated by fluorescence microscopy. A "normal" chlorophyllous mesophyll was present. The leaf resistances of intact leaves were about 5–10 s cm−1in the light and were greater than 100 s cm−1in the dark, indicating light opening and dark closure of the stomata. A CO2-dependent stomatal response (i.e., a tendency to close at elevated CO2levels) was demonstrated, as was a CO2-independent light response (i.e., greater opening in blue light than in red). This provides direct evidence to support the idea that guard cell chlorophyll is not necessary for stomatal functioning.

ISSN:0008-4026    

DOI:10.1139/b75-001

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Basidiospores ofPucciniastrum goeppertianum(Kühn) Kleb. are globose, 5.8 μ in diameter, smooth-walled, apiculate, and have granular contents. The cardinal temperatures for their discharge were found to be 10, 18 to 20, and 25 °C. Development of new brooms from infected blueberry rhizomes started late in May, but shoots tested monthly in the laboratory released spores only from the next January until mid-June. The natural overwintering requirements of the fungus were mimicked by storing broom material at −4 °C from December until February.On balsam fir needles at 15 °C, germination of basidiospores usually produced a single, short germ tube, and exceeded 40% after 7 h of saturation and reached 70% by 48 h. Repetitive germination, commonly seen on glass slides or water agar, may only be typical of the reaction on non-host substrates. Only current-year needles were susceptible to infection and only from bud break until early in the 5th week, (corresponding approximately to the period of shoot elongation) provided that a minimum of 6 h at 15 °C under conditions of saturation preceded any period of drying of the foliage surface.

ISSN:0008-4026    

DOI:10.1139/b75-002

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Thirty-five plants ofAgropyron trachycaulumfrom northern Canada were categorized as to the latitude of origin. Categories were 53–55, 55–58, 58–61, and 61–68° north latitude. In field plots at Beaverlodge (latitude 55° N) the plants originating from farthest north had the shortest number of days from heading to maturity and lowest average height and seed yield. Controlled environment studies confirmed that plants from north of 60° latitude have reduced capability of producing seed culms in summer environments with less than continuous light. Seed production of such species would be suspect in the current farming areas at lower latitudes. If large quantities of seed were required, new seed production areas may have to be developed in northern latitudes.

ISSN:0008-4026    

DOI:10.1139/b75-003

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Rhymokalon trichium, gen. et sp. nov., is a new plant with cladoxylalean anatomy from Upper Devonian rocks (Oneonta Formation) of New York. The new plant consists of three orders of helically arranged branches. Compressed axes have numerous longitudinal ridges, which are interpreted as resulting from the collapse of external tissues onto the dissected xylem during compaction of the sediment. Distal branchings bear small numbers of fine hairs. Petrified basal branches contain a multiribbed stele, from which are produced numerous xylem strands which enter the branches. Lateral branches have many xylem strands, which divide and anastomose freely. This type of anatomy relatesRhymokalonbest with Cladoxylales, a group of Devonian and Carboniferous plants with dissected xylem.

ISSN:0008-4026    

DOI:10.1139/b75-004

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

The pollen stratigraphy of a 6.7-m section of bog peat from west–central Nova Scotia shows three major pollen zones, viz., the zone of spruce maximum (9180–8505 before present (BP)); the zone of pine and oak maxima (8505–6290 BP); and the upper deciduous zone, which could be more accurately described as the bimodal hemlock zone (6290 BP to present day). The zone of hemlock minimum is dated at 4415 BP. The spruce assemblage denotes a cool, wet climate. The decrease in spruce and increases to maxima of pine and oak are interpreted in terms of higher temperatures and lower precipitation. Further temperature increase, perhaps accompanied by increased precipitation, resulted in the migration of hemlock into the area subsequently suppressed during the period of maximum warmth and dryness. Increased precipitation followed by decreased temperatures led firstly to a second hemlock stage and later to increased coniferous growth. Increased representation of grasses and adventives in the upper levels of the assemblage are indicative of European colonization.

ISSN:0008-4026    

DOI:10.1139/b75-005

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Rhizomorphs ofArmillaria mellea(Vahl ex Fr.) Kummer absorbed ammonium and radio-actively labelled chloride and orthophosphate ions; ammonium uptake was associated with synthesis of amino acids in the rhizomorphs. Uptake of labelled ions occurred primarily at the unpigmented growing tip. Nutrient uptake by rhizomorphs may explain why the dry weight of rhizomorphs is related to the nutrient status of the soil in which they are growing.

ISSN:0008-4026    

DOI:10.1139/b75-006

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

The haploid chromosome number ofHypoxylon serpensis seven. Ascospores are initially uninucleate, becoming binucleate after a mitosis. One nucleus is cut off in a cellular appendage which degenerates before ascospores become colored. Mature ascospores are uninucleate and devoid of appendages. Taxonomic implications of these data are discussed.

ISSN:0008-4026    

DOI:10.1139/b75-007

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Ascospores ofCookeina sulcipesgerminate by one of two modes: (1) by the production of blastoconidia on sympodially proliferating conidiogenous cells which may arise from any point on the spore surface, and (2) by a thick polar germ tube. No ascospores were seen to germinate both ways. The conidiogenous cells are occasionally modified into narrow hyphae. The blastoconidia germinate readily but are evidently very short-lived. Ascospores ofPhillipsia crispatagerminate by two polar germ tubes; there is no formation of blastoconidia. In both species the inner ascospore wall separated from an outer wall layer during germination. In culture bothC. sulcipesandP. crispataform arthroconidia. The arthroconidia are uninucleate; they germinate readily and reproduce the species when transferred to fresh plates.

ISSN:0008-4026    

DOI:10.1139/b75-008

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Stem circumference, xylem pressure potential (P), and leaf surface resistance were measured in a dominant forest-grown white oak (Quercus albaL.) tree from the beginning of, through the development of, and to recovery from a major drought in mid-Missouri. Continuous recording of several environmental variables and periodic measurements of soil moisture were made in coordination with the above plant variables. As baseP(Pmeasured just before sunrise) and soil moisture decreased, net day-to-day and even week-to-week stem shrinkage was observed. Periodic thunderstorms alleviated soil and plant water deficits and stem circumference recovered. Excellent relationships were noted between soil moisture in the upper 30 cm of a 107-cm profile and either basePor stem circumference.Four clear and 2 cloudy days with rain are presented to illustrate diurnal patterns in the aforementioned variables. The generalized pattern of diurnal fluctuations in stem circumference consisted of early morning shrinkage, which continued to a 1500- to 1700-h. (true solar time) minimum, and subsequent recovery. Hysteresis loops resulted when stem circumference was plotted againstP. Maximum diurnal fluctuations in stem circumference were greatest when soil moisture had been depleted slightly below field capacity. Further depletion led to lower values ofP, stomatal closure, restricted plant water loss, and reduced stem shrinkage. The relationship between flux (vapor pressure deficit – leaf surface resistance) andPis also described and it provided a possible means of modelingPin plants. The possible role of the stem reservoir in augmenting foliar water deficits is presented and discussed.

ISSN:0008-4026    

DOI:10.1139/b75-009

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Haplonts of the fungusTremella mesentericagrew in synthetic media containing any of the following nitrogen sources (in order of decreasing growth rate): glutamine, aspartate, leucine, glutamate, alanine, ammonium sulfate, serine, soytone, casein hydrolysate, phenylalanine, and asparagine. Cultures with potassium nitrate, cysteine, glycine, histidine, lysine, or proline as sole N source did not grow. Thiamine was the only vitamin required. Asparagine slowed the growth of some strains and also caused the cells to become large and spherical.

ISSN:0008-4026    

DOI:10.1139/b75-010

出版商:NRC Research Press    

年代:1975

数据来源: NRC