摘要:

14C-tracer experiments revealed that both endogenous and exogenous substrate was incorporated in the fructosans synthesized in leaf disks during incubation on phosphate-buffered sugar media. At least some of the endogenous substrate was derived from a source which was insoluble in 80% ethanol at the start of the incubation period. Endogenous and exogenous substrates were distributed in the fructosans in a pattern which was qualitatively similar regardless of the type of sugar supplied exogenously. A complex relationship was exhibited between the specific activity of various fructosan oligomers, expressed on a gram basis, and their chain length. However, expressed on a molar basis, the specific activity of the fructosyl tail portion of each homolog appeared to be linearly related to the number of hexosyl residues that it contained. Such a relationship suggests that enzymes similar to the Jerusalem artichoke tuber transfructosylases are present in leaf disk tissue after 72 h incubation and indeed may function in thede novosynthesis of fructosans in vivo.

ISSN:0008-4026    

DOI:10.1139/b74-021

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

The procedure described in this paper, when applied to data collected in a pilot study, enables determination of an efficient sampling intensity for studying beta diversity in a plant community. A statistic,Sβ, is introduced as a measure of beta diversity. The method can be applied where (1) many species are to be observed, (2) quadrat sampling is to be used, and (3) presence:absence data are desired.

ISSN:0008-4026    

DOI:10.1139/b74-022

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

One dikaryotic variant and nine monokaryotic variants, which arose spontaneously from axenic cultures ofPuccinia graminisPers. f. sp.triticiErikss. & E. Henn, were tested for pathogenicity on wheat. Four variants (including the dikaryon) were highly pathogenic, the remaining six showing little or no pathogenicity. Non-pathogenic variants produced no detectible necrotic reaction in the host. Pathogenic variants sporulated after infection of wheat, although the type of spore and their relative abundance varied widely between strains. Successful infection of detached leaves was always accompanied by formation of 'green islands' at the infection site. A histological and cytological study showed that wheat leaves infected with a pathogenic monokaryotic variant resembled wheat infected with wild-type (dikaryotic) rusts. The results are discussed in relation to host-pathogen compatibility.

ISSN:0008-4026    

DOI:10.1139/b74-023

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Glycollate oxidase (glycollate: oxygen oxidoreductase EC. 1.1.3.1) levels in tobacco leaves from plants grown under three different photoperiods and three different temperature regimes were compared. Leaf extracts obtained from mature plants grown at moderate temperatures (25–20C; day/night) and with intermediate day lengths (10 h) showed highest activity. In contrast, peroxidase (EC. 1.11.1.7) was highest in extracts from plants grown at low temperatures and short days while chlorogenic acid oxidase (EC. 1.10.3.1) was highest in leaf extracts from plants grown at high temperatures. Other investigations revealed that old leaves contained consistently lower glycollate oxidase levels than young leaves from the same plant. The addition of chlorogenic acid to the assay medium tended to equalize differences in enzyme activity. Photosynthetic efficiency as determined by O2evolution (Hill reaction) and photophosphorylation in isolated chloroplasts improved with leaf maturity but this development did not appear to be a direct consequence of low photorespiratory activity. Measurements of the conversion of glycollate-1-14C to14CO2by leaf disks under light or dark conditions indicated that chlorogenic acid affects glycollate metabolism in vivo. It is postulated that chlorogenic acid moderates photorespiration by interacting with glycollate oxidase.

ISSN:0008-4026    

DOI:10.1139/b74-024

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Acetylene reduction by bacteria in the rhizosphere ofGlyceria borealisandTyphasp. was studied under anaerobic and aerobic conditions. Under anaerobic conditions, when roots and rhizomes were incubated with rhizosphere sediments at 25 °C without glucose, acetylene reduction to ethylene was calculated to be 37 μmol g−1day−1and 3.6 μmol g−1day−1forGlyceriaandTypharespectively. The rates were generally lower under aerobic conditions. Washed roots (without sediment) also showed high activity. The reduction of acetylene to ethylene had aQ10of 4.5 in theGlyceriasystem. It is estimated that N2fixation in the rhizosphere of this species may reach 60 kg ha−1year−1.

ISSN:0008-4026    

DOI:10.1139/b74-025

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

The primordia of the floral appendages appear in acropetal succession and develop in the order in which they appear. The primordia of each whorl of appendages are formed in a rapid sequence. After the inception of outer tepal primordia, the floral apex becomes triangular. On each angle, one inner tepal primordium together with the primordia of a pair of outer stamens and an inner stamen is formed. The triangularity of the floral apex might be interpreted as an indication of the formation of petal–stamen (CA) primordia as reported forAlismaandHydrocleis. If this is the case, the primary pattern of organogenesis of theButomusflower is trimerous and tetracyclic, i.e. one whorl of outer tepals, one complex of inner tepals and stamens, and two whorls of pistils. The floral apices have a two-layered tunica surrounding a central corpus. The initiating divisions in the formation of all floral appendages occur in the second tunica layer. In the case of stamen primordia, the outer corpus is also involved. Procambial development is acropetal. One procambial strand differentiates into each floral appendage shortly after its inception. Additional procambial strands are formed in the pedicel and the perianth and gynoecium. The relationships ofButomusto the Magnoliidae are discussed.

ISSN:0008-4026    

DOI:10.1139/b74-026

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Sunflowers bud-inoculated withPlasmopara halstediibecame systemically infected with downy mildew and produced infected seeds at 15 to 30 °C. Oospores were observed in seeds of inoculated and also naturally infected plants from the field. Infected seeds gave rise to symptomless plants. Infected seeds proved effective as inoculum, inducing infection in 14 to 89% of the plants inoculated at 20 °C. Most of the infections (80%) were symptomless (latent).Systemic infection occurred, but latent infection was more frequent, in plants grown in soil containing debris of mildewed plants. Latent infection also occurred in uninoculated plants through belowground contact with systemically infected plants. Seed produced by plants with latent infection may carry the pathogen, and may give rise to more plants with latent infection, accounting for widespread dissemination of the disease before plants with typical symptoms are observed.

ISSN:0008-4026    

DOI:10.1139/b74-027

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

The role of photosynthetically active cotyledons in the growth of young woody angiosperm seedlings was studied over a 35-day period under controlled environmental conditions. Two experiments were performed. In the first, cotyledons ofRobinia pseudoacacia, Ulmus americana, andAilanthus altissimawere removed or covered at 7, 14, or 21 days after seedling emergence. In the second experiment, seedlings ofRobinia pseudoacacia, Betula alleghaniensis, andAcer saccharumwere grown over a range of light intensities. Removing or coveringRobiniacotyledons of seedlings of any age resulted in lower dry weights of roots and stems than in controls. Removing or covering cotyledons of only 7-day-oldRobiniaseedlings retarded dry weight increase of foliage.Robiniaseedling heights were unaffected by cotyledon covering or removal. CoveringUlmus americanacotyledons had no significant effect on dry weight increment of stems or foliage or on seedling height. Removal ofUlmuscotyledons from 7-day-old seedlings inhibited dry weight increase of roots, stems, and leaves and inhibited height growth. Removal ofAilanthuscotyledons inhibited dry weight increment of roots, stems, and leaves more than did covering of cotyledons. Species varied greatly in cotyledon development and response to light intensity. Cotyledon size was affected by light intensity inRobinia, but not inBetulaorAcer. Responses of cotyledons to light intensity differed from those of foliage leaves. Cotyledon photosynthesis appeared to have a very important role in seedling growth inRobiniaandAilanthusand a less important role inUlmus.

ISSN:0008-4026    

DOI:10.1139/b74-028

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

A pale-colored, strongly plicate species ofCyathus(Nidulariaceae), at present known only from Mysore (India), is described asC. ellipsoideussp. nov. It is the only species known to possess peridioles and basidiospores both of which are ellipsoidal in outline.Cyathus ellipsoideusbears close relationship toC. berkeleyanusandC. bulleribut has much larger spores than either.

ISSN:0008-4026    

DOI:10.1139/b74-029

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Corn coleoptile nodal tissue was used to study the callusing of corn inbred and hybrid varieties. A comparison of callus cells and coleoptile parenchyma cells was made with electron micrographs. The callus cells resembled meristematic cells in having more ribosomes, and had a greater number of mitochondria and plastids than nodal parenchyma cells. There was a high incidence of lomasome-like bodies in both types of cells. The callus cells were characterized by having small vacuoles scattered throughout the cell, whereas the nodal parenchyma tissue was composed of cells with mostly a single large vacuole surrounded by a thin parietal cytoplasm.

ISSN:0008-4026    

DOI:10.1139/b74-030

出版商:NRC Research Press    

年代:1974

数据来源: NRC