摘要:

Carbon dioxide exchange of a mixed grassland sward dominated byAgropyron dasystachyumandA. smithiiwas measured over two growing seasons using field chambers and infrared gas analysis. Net photosynthesis of the sward began in late April and rose to a peak in early July (ground area h−1). Drought during the later part of the summer, a typical feature of the climate of the region, caused net photosynthesis to decline drastically. Air temperature and reduced green leaf area inhibited photosynthesis early and late in the growing season. A multiple regression analysis showed that soil moisture and air temperature together accounted for 44% of the variability in net photosynthesis. Solar radiation and dew-point temperature explained an additional 16%. The ability of the dominant grasses to adapt to fluctuations in water availability is discussed.

ISSN:0008-4026    

DOI:10.1139/b78-240

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Transmission electron microscopic observations made on the ascus tip ofOrbilia luteorubellashowed that it is truncate and that the outer ascus wall is relatively thicker at the shoulders than on the top or sides. There is no demonstrable discharge mechanism in the ascal apex of this fungus comparable with that found in the ascus tip of other supposedly related inoperculate Discomycetes, includingMollisia cinerea.Ascospores ofO. luteorubellacontain a single, electron-opaque spore body that appears to evolve from a mitochondrion that is attached, at one end, to the inner wall of the spore apiculus. The function of the spore body is unknown.A blue-green alga, probably of the genusAnacystis, is associated with this and at least one otherOrbiliaspecies. Since theseOrbiliaspecies are here shown to be lichenized and they do not have an ascal pore discharge mechanism, the transfer of these fungi from the Helotiales is proposed. They can probably best be treated as lichens of uncertain affinities, perhaps related to those members ofLecanoraleswith iodine-negative asci.

ISSN:0008-4026    

DOI:10.1139/b78-241

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

During the 100-h period from quartet breakup until first pollen grain mitosis, mean cell, nuclear, and nucleolar volumes were calculated at 10-h intervals in hexaploid triticale (×TriticosecaleWittmack cv. Rosner). Changes in DNA content per microspore were also measured to determine the time of DNA synthesis. From 0 to 30 h (G1), (1) cell volume increased at a constant rate from 9400 to 48 297 μm3, (2) nuclear volume initially increased from 1674 to 3261 μm3but then returned to 1568 μm3. and (3) nucleolar volume did not change. From 30 to 70 h (S), cellular volume increased to 79 090 μm3, nuclear volume did not change, and nucleolar volume initially increased twofold but then returned to the G1value. From 70 to 100 h (G2), there was no change in cell volume, while nuclear and nucleolar volumes increased to 4365 and 344 μm3, respectively. Regression analysis throughout microsporogenesis indicated a constantly changing significant relationship between the volume of a cell and its nucleus and nucleolus. However, no significant regression coefficients were obtained during early prophase. These results are interpreted as indicating that critical cellular, nuclear, or nucleolar volumes are not necessary for the development of a cell through interphase.

ISSN:0008-4026    

DOI:10.1139/b78-242

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Picea mariana–Vaccinium uliginosumvegetation was sampled in a north–south transect near Inuvik, N.W.T., Canada. Four stages in the postfire recovery sequence were described. Little qualitative change in vascular plants was found in the transect or with time since burning, although quantitative changes were found to exist. Contrary to vascular plant development, an orderly postfire succession of cryptogamic species was found. The postfire recovery sequence by comparison with other open boreal forest studies has a persistent shrub-dominated stage. Burning, with few exceptions, occurred within 100 years of examination along the transect. Objective analyses by Bray–Curtis ordination and reciprocal averaging ordination were used to analyse the vegetation data and proved useful in the data reduction and interpretation of results.

ISSN:0008-4026    

DOI:10.1139/b78-243

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Various clustering and ordination techniques are used on data collected from 88 cultures of Fungi Imperfecti and imperfect states of Ascomycotina to produce classifications. The data consist of 98 characters representing the morphology, conidium ontogeny, and physiology of the cultures. Although 23 genera are represented, emphasis is placed onGraphiumsensu lato andCeratocystisto which half the cultures belong. Seven groups which cluster consistently in all the techniques used are recognized, groups A to G. Group A contains species which have the annellidic type of conidiation, namelyTrichurus. Scopulariopsis, Doratomyces, andMicroascus. Group B contains the phialidicChalara-typeCeratocystisspecies. Group C is characterized by the sympodial type of conidiation of theSporothrixtype and contains species fromPetriellaandSporocybe. Group D contains an assortment of species which display the typical phialidic conidiogeny. Group E contains species fromCeratocystisandGraphiumsensu lato which have holoblastic conidia with conidiogenous cells of the ramoconidium type. Group F is a loose cluster of species characterized by sympodial conidiation and contains species fromGraphiumsensu lato,Ceratocystis, andVerticicladiella. Group G contains species ofPericoniawhich produce large conidia polyblastically. This numerical classification provides new evidence to support the classifications based on conidium ontogeny.

ISSN:0008-4026    

DOI:10.1139/b78-244

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Protein bodies from almond (Prunus dulcis), Brazil nut (Bertholletia excelsa), and quandong (Santalum acuminatum) have been studied in thin sections of fixed and embedded tissue, in freeze-fracture replicas of unfixed tissue, by chemical analysis of tissue for P, K, Mg, and Ca, and by energy dispersive x-ray (EDX) analysis of both sections of glutaraldehyde-fixed tissue and freeze-dried tissue powders. The protein bodies in all three species contained globoid crystals, protein crystalloids, and proteinaceous matrix regions. Results of EDX analyses were consistent with globoid crystals being rich in phytin. Variation in both the structure and the elemental composition of globoids was common. In almond some globoids were lobed rather than spherical, and large globoid crystals often contained considerable calcium whereas small globoid crystals contained little if any calcium. The globoid crystals of Brazil nut often contained barium in addition to P, K, Ca, and Mg. Protein crystalloids of Brazil nut were compound crystals. Protein bodies of quandong seed, which is largely endosperm rather than embryo, were unexceptional.

ISSN:0008-4026    

DOI:10.1139/b78-245

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Thin sections, freeze-fracture replicas, energy dispersive x-ray (EDX) analyses, and chemical analyses of cotyledon tissue from seeds of sunflower (Helianthus annuus), golden everlasting daisy (Helichrysum bracteatum), cashew (Anacardium occidentale), and pistachio nut (Pistacia vera) showed that in all four species the protein bodies consisted of a proteinaceous matrix surrounding numerous globoid crystals. Some variation in globoid crystal size did occur, but they were generally small in relation to the size of the protein body. No protein crystalloids were found in the cotyledon protein bodies of these four species. EDX analysis results were consistent with the globoid crystals being phytin rich. Results of this study, combined with an evaluation of protein body structure in other dicot embryos that have been studied, support the theory that protein body structure is related to taxonomic grouping.

ISSN:0008-4026    

DOI:10.1139/b78-246

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

This paper presents the results of thin-section, freeze-fracture, energy dispersive x-ray (EDX) analysis, and chemical analysis studies of cotyledon tissue from dry seeds of macadamia nut (Macadamia integrifolia), walnut (Juglans regia), and hazel nut (Corylus avellana). Studies concentrated on mineral elements in the storage protein bodies. Protein bodies of macadamia nut contained no protein crystalloids but did contain some globoid crystals. Aqueous fixation of macadamia tissue appeared to result in a rapid solubilization of proteinaceous matrix material. EDX analysis of macadamia nut globoid crystals revealed the presence of P, K, and Mg in most cases but the occasional crystal was very high in calcium. Walnut protein bodies often contained many large protein crystalloids. Globoid crystals were present between the protein crystalloids and in the proteinaceous matrix. EDX analysis indicated the presence of P, K, and Mg as the main elements in walnut globoid crystals. Hazel nut protein bodies contained one or more small protein crystalloids, globoid crystals of various sizes, and proteinaceous matrix. Some protein bodies contained druse crystals. EDX analysis showed that the druse crystals were rich in calcium and thus are presumably calcium oxalate. EDX analysis of globoid crystals revealed the presence of elements consistent with the phytin-rich nature of globoid crystals. Variations in globoid crystal composition are discussed.

ISSN:0008-4026    

DOI:10.1139/b78-247

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Druse crystals of calcium oxalate are known to occur in some protein bodies of some plant seeds. This paper reports observations on crystals, and other contents, of protein bodies ofEucalyptus erythrocorysandSimmondsia chinensis(jojoba). Results are presented from thin section studies of glutaraldehyde–OsO4fixed, dehydrated, and embedded tissue; freeze-fracture studies; energy dispersive x-ray (EDX) analysis studies of freeze-dried tissue powders (Eucalyptusonly); and chemical analysis studies of P, Mg, K, and Ca content (Eucalyptusonly). ManyEucalyptusprotein bodies contained large druse crystals rich in Ca but devoid of P, K, and Mg, and an occasional protein body from jojoba contained some dispersed crystals.Eucalyptusseeds were exceptionally high in Ca content. EDX analysis results provide evidence favouring the phytin-rich nature of globoid crystals in the two species. Structural variation in the globoid crystals was great, especially in jojoba.Eucalyptus, whose protein bodies contained very large globoid crystals rich in P, Mg, and K, was found to have higher levels of these elements than most species investigated to date.

ISSN:0008-4026    

DOI:10.1139/b78-248

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

The new speciesChrysopsis godfreyi(Compositae–Astereae),n = 5, is endemic to the Gulf Coast islands of West Florida. The plants are biennial or perennial, forming basal rosettes of woolly, oblanceolate leaves. The species inhabits open sand dunes and in some areas stabilizes the dunes. The plants typically have weakly ascending stems branching near the base, although more erect plants occur in sheltered areas away from salt spray. Two forms occur: the typical one with white woolly stem leaves and one with green, densely stipitate glandular leaves. The species is morphologically similar toChrysopsis lanuginosaandC. gossypinaf.decumbens.

ISSN:0008-4026    

DOI:10.1139/b78-249

出版商:NRC Research Press    

年代:1978

数据来源: NRC