摘要:

Ipomoeacells grown in a medium containing ammonium and nitrate preferentially used ammonium during the initial stages of growth but in the later stages assimilated nitrate rapidly regardless of the presence or absence of ammonium. Cells grown on nitrate and maintained at pH 4.8 released ammonia into the medium, whereas when they were maintained at pH 6.5 they secreted nitrite. The enzymes of nitrate assimilation were inducible by nitrate and the activities changed considerably in response to nitrogen source. The addition of ammonium 3 days after inoculation to cells highly induced for the reductases did not result in the suppression of further synthesis of the enzymes. The levels of nitrate (EC 1.6.6.1) and nitrite (EC 1.6.6.4) reductases detected in cells grown on ammonium as the nitrogen source were about 25% and 66%, respectively, of the fully induced level. The addition of nitrate to ammonium-assimilating cells resulted in a low level of induction of both reductases. Addition of nitrite had no effect. With both ammonium and nitrate initially present in the medium, the ammonium was utilized quickly but no induction of the reductases was observed for 24 h. the time interval when the assimilation of nitrate was low. This was followed by the induction of the enzymes to a higher level than the activity in cultures of similar age that had been grown continually in nitrate, supplied at the same concentration. Thus, for nitrate and nitrite reductases, repression-like effects were produced by ammonium.

ISSN:0008-4026    

DOI:10.1139/b77-184

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Pinus taedaseedlings were grown for 10 weeks without ectomycorrhizae under low and high rates of complete soil fertility, as well as these rates minus N, P, K, or Ca. Seedling growth, inorganic chemical content of needles, and soluble-carbohydrate content of short roots were significantly affected by soil fertility, especially the high rates of N and P. Number and length of lateral and short roots were not affected by soil fertility. Sucrose and fructose contents of short roots were lowest at high levels of N and P; glucose was not detected. Seedlings from each of the 10 fertility combinations were inoculated with vegetative inoculum ofPisolithus tinctoriusand incubated for 19 to 21 days at a moderate level of complete soil fertility. Significantly more ectomycorrhizae were formed on seedlings from the complete low fertility rate than on those from the high rates of N and P. Ectomycorrhizal development on seedlings from the other fertility combinations were intermediate from these extremes. Sucrose content of short roots determined before inoculation was significantly correlated with ectomycorrhizal development and accounted for 85% of the variation in susceptibility of short roots to infection byP. tinctorius. Fructose content of short roots was not correlated with ectomycorrhizal development. These results indicate that high levels of N and Pin soil decrease sucrose content of short roots of loblolly pine and decrease their susceptibility to ectomycorrhizal development byP. tinctorius.

ISSN:0008-4026    

DOI:10.1139/b77-185

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Two new Laboulbeniales occurring on African Zuphiini are described:Eucantharomyces basilewskyi, parasitic onZuphiumspp., andLaboulbenia cajanii, parasitic onParaleleupidia uviranaBasilw.

ISSN:0008-4026    

DOI:10.1139/b77-186

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

The ultrastructure ofCeratocystis ulmi(Buism.) C. Moreau was studied in both synthetic and natural media (infected tissues of elm). In fungal cells located at the cultures' margin and therefore considered young, a primitive ultrastructure with the following characteristics was observed. (1) The relatively voluminous nuclear area has irregular contours and appears to be devoid of an enclosing membrane; structures identified as developing mitochondria are contiguous to the nuclear area; endoplasmic reticulum is not evident. (2) As aging and septation of cells occur, the cytoplasm becomes less dense and organelles appear to be better delimited. Use of the goniometer has permitted the confirmation in many cases of the absence of membranes, and in others, their presence. Radioautographic studies of material labeled with [6-3H]thymidine showed that incorporation was greater in younger cells than older ones. Labeling in the latter occurred in association with fibrillar material within the nuclear areas, developing mitochondria, and other unidentified fibrillar masses. The importance of these observations is discussed. A mimeographed English version of results and discussion parts is available from the junior author.

ISSN:0008-4026    

DOI:10.1139/b77-187

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

The pyrenomycete genusAcanthotheciellaHöhn. is revised to include three species:A. harbata, A. mirabilis, andA. tropicalissp. nov. The form genusYpsiloniais accepted as its conidial state and is shown to belong in the Coelomycetes. Four species are shown to belong inYpsilonia: theYpsiloniastate ofA. barbota, Y. mirabilis, Y. tropicalis, andY. cuspidata. Ypsilonia corticalisWolf is considered as anomen dubium, andY. vagansSpeg. isredisposed in a new genus of Hyphomycetes,Kazulia.

ISSN:0008-4026    

DOI:10.1139/b77-188

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

A new nuclear magnetic resonance (NMR) technique developed by Conlon and Outhred (1972. Biochim. Biophys. Acta, 288: 354–361) to measure diffusional water permeability was applied to the multicellular plant systemElodea Nuttallii(Planch) St. John leaves. This technique involves measuring a transverse relaxation time (T2) in the absence (T2 = Ta) and in the presence (T2 = Ta′) of extracellular paramagnetic cations. A valid estimate ofTawas measured forElodealeaves. The value ofTa′ was found to decrease continuously with time. Evidence is presented that the decrease ofTa′ with time is initially related primarily to the time required for the paramagnetic ion to diffuse throughout the extracellular space and then later related to influx of the paramagnetic ion into the cells. By extrapolating to zero time to correct for paramagnetic-cation influx into the cells it was possible to estimate the value ofTa′ required to calculate the water exchange time out of the cells. It was estimated from the NMR data that Mn2+(the paramagnetic ion used) flux into the cells occurred at a rate of 3.0 × 10−14 mol cm2 s−1. A procedure to determine whether the water-exchange time is controlled by intracellular unstirred layers or by membrane water permeability or by both is given. The water-exchange time ofElodealeaves is predominantly controlled by the intracellular unstirred layers. Thus it was only possible to set a lower limit on the diffusional water permeability coefficient (Pd) ofElodealeaf membranes of 3 × 10−2 cm s−1at 20 °C.

ISSN:0008-4026    

DOI:10.1139/b77-189

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Linear regression models were developed for Douglas fir needle, female cone, branch, and bark decomposition in seven stands representing four mature vegetation types in western Oregon. Rate constants (k) for annual weight loss of needles ranged from 0.22 to 0.31 year−1, from 0.047 to 0.083 year−1for cones, from 0.059 to 0.089 year−1for branches, and from 0.005 to 0.040 year−1for bark. The decomposition constant (k) of needles had a negative linear correlation (P < 0.01) with maximum plant moisture stress and temperature growth index of the seven stands. In comparing substrate quality of needle and woody litter components,kwas more closely correlated with lignin content than with C:N ratio.

ISSN:0008-4026    

DOI:10.1139/b77-190

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

EtiolatedAvena sativaL. cv. Victory coleoptiles were used to determine the influence of indoleacetic acid (IAA) or malate on in vivo and in vitro rates of CO2fixation. In addition, the influence of malate on IAA-stimulated growth was investigated. Concentrations of malate which stimulate growth did not influence the in vivo rate of dark [14C]bicarbonate fixation but did inhibit in vitro phosphoenolpyruvate carboxylase (EC 4.1.1.31) activity. IAA did not influence this enzymic activity or reduce the inhibition of the enzyme by malate, and the rate of [14C]bicarbonate fixation was not measurably influenced by 20 μMIAA within the time period required for IAA stimulation of growth to become apparent. In the absence of atmospheric levels of CO2, 1 mMmalate and 20 μMIAA stimulate growth in a weakly synergistic manner. These results are discussed in relationship to a suggestion that IAA-stimulated H+secretion and growth involves a rapid effect on CO2fixation.

ISSN:0008-4026    

DOI:10.1139/b77-191

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

A new species ofMoellerodiscus,M. dennisii, is described from India. This species, growing on rotting leaves of an unidentified angiospermic plant, has poorly developed stroma and biguttulate ascospores. The ectal excipulum is composed of flattened textura globulosa with large excipular hairs.

ISSN:0008-4026    

DOI:10.1139/b77-192

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

The effect of DBMIB, antimycine A, and FCCP on respiration and photosynthesis of intact chlorophyllic moss (Funaria hygrometrica) spore was investigated.Antimycine A (1 μM) strongly inhibited dark respiration, was without effect on photosynthesis at high light intensities (above the saturation plateau values), and stimulated photosynthesis at low light intensities (below the saturation plateau values).DBMIB (3 μM) inhibited photosynthesis and was without effect, even under light conditions, on the dark respiration. Low amount of FCCP (3 μM) partially inhibited oxygen production at high light intensities. In this case, the inhibition observed was partially relieved by 1 μMantimycine A or 30 μMof KCN; higher concentration of FCCP totally inhibited the oxygen production.It seems likely, therefore, that in the chlorophyllic moss spore the cytochrome oxidase pathway is not functioning under high light intensities and that this inhibition of respiration is attributable to the low cytoplasmic ADP:ATP ratio.

ISSN:0008-4026    

DOI:10.1139/b77-193

出版商:NRC Research Press    

年代:1977

数据来源: NRC