摘要:

ExogenousL-glutamine, the sodium salt ofL-glutamic acid, and casamino acids do not decrease glutamine synthetase (GS) level in isolated pea (Pisum sativumL. cv. Jupiter and cv. Proteus) roots cultured with 20 g∙L−1sucrose whileL-glutamic acid does decrease it. The effect ofL-glutamic acid is stronger in solutions lacking nitrate. By contrast, only the exogenous sodium salt ofL-glutamic acid does not enhance the decrease in GS level caused by sugar starvation in isolated roots cultured without any sugar while, the other compounds tested do enhance this decrease. These facts confirm our earlier conclusion that sugar availability and the concentration of H+ions are more important for GS level regulation in pea roots than nitrogen substrate availability and the presence of the end products. Nitrate reductase (NR) level is depressed by exogenousL-glutamine, the sodium salt ofL-glutamic acid, casamino acids, and a low (0.2 mM) concentration ofL-glutamic acid whereas it is increased by higher (0.8 and 1.0 mM) concentrations ofL-glutamic acid, by α-ketoglutaric acid (0.4 to 0.6 mM), and by nitric acid (0.2 to 0.4 mM) added to saturating concentration (10 mM) of nitrate present in the form of potassium and calcium salts. The negative effect ofL-glutamine, sodium glutamate, and casamino acids can be reversed byL-glutamic acid. This suggests that more mechanisms may be involved in NR regulation by these compounds and that the mechanism controlled by increased concentration of H+ions is of great importanc

ISSN:0008-4026    

DOI:10.1139/b81-153

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

Examination of driftwood, intertidal wood, and submerged panels from the New Brunswick coast of the Bay of Fundy yielded 34 species of marine fungi. With four exceptions, all are first reports for New Brunswick. Five are first reports for the Bay of Fundy and a further four species are first reports for Eastern Canada. Differences were observed between the species found by the various methods.

ISSN:0008-4026    

DOI:10.1139/b81-154

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

The interphase nucleolus, in the myxomycetePhysarum polycephalum, consists of granular and fibrillar zones, as in all eukaryotes studied so far. Each of these latter regions, however, is observed to be composed of a coarse filamentous element which is generally folded into a globular or cup-shaped structure characterized by a lighter core portion. These globular structures are bleached by EDTA and also react with both bismuth and phosphotungstic acid, thus showing that they contain chromatin. Similarly shaped nucleolar components are observed till late prophase and these show cytochemical properties identical to those seen during interphase. Following dispersion of the nucleolus at prometaphase, these globular nucleolar regions persist as characteristic remnants which contain DNA, RNA, and basic proteins. At anaphase, numerous similar bodies migrate with the chromosomes and can be demonstrated to become part of the chromatin masses which occupy the two poles of the dumbbell-shaped telophase nucleus. It is concluded from these observations that these nucleolar remnants originate from the fibrillar zones of the mature nucleolus and that these zones in turn correspond to well-defined structures possessing the general characteristics of chromatin. These structures are consequently referred to as minichromosomes.

ISSN:0008-4026    

DOI:10.1139/b81-155

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

The previous ultracytochemical investigation has revealed that the numerous nucleolar remnants observed during the mitotic stages inPhysarum polycephalumpossess the same characteristics as chromatin and originate from the fibrillar zones of the mature nucleolus. In the present study these nucleolar minichromosomes are shown to be incorporated as well-defined structural elements within the two daughter nuclei. At very early interphase these minichromosomes are first scattered throughout the nuclear cavity, but within a few minutes they aggregate to form several highly irregular masses corresponding to prenucleolar bodies. By the time these latter bodies fuse into typical horseshoelike nucleoli, pervading granular material starts accumulating in more noticeable amounts. Following labeling for 10 min with uridine radioautographic grains are already detected in very early interphase nuclei over dense regions undoubtedly corresponding to the minichromosomes. Incorporation of this RNA precursor increases as the minichromosomes fuse into prenucleolar bodies. By the time large nucleoplasmic zones have formed, radio-autographic grains are present in still larger quantity over the irregularly shaped nucleolus as well as over diffuse chromatin thoughout the nuclear cavity. Such early RNA synthesis is interpreted to indicate that the early stages of nucleolar formation do not merely involve fusion of the preexisting minichromosomes but also imply synthesis of new material.

ISSN:0008-4026    

DOI:10.1139/b81-156

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

Uptake of sucrose by excised tomato roots showed saturation kinetics and could proceed against an internal sucrose concentration of approximately 0.046 M. It was inhibited by a number of compounds structurally related to sucrose and was largely but not totally dependent on respiration. It is concluded that sucrose was taken up mainly by an active process and to a lesser extent also by a passive process. Low pH markedly increased the uptake and sodium ions, and ouabain had no appreciable effect.

ISSN:0008-4026    

DOI:10.1139/b81-157

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

Sucrose uptake by excised tomato root was found to be in part respiration independent and in part respiration dependent. In the presence of 5 × 10−4 Mof salicylhydroxamic acid (SHAM) which inhibited the alternate respiratory path, the cyanide-sensitive, respiration-dependent uptake occurred at a rate of approximately 250 nmol sucrose/(μmol O2consumed. By comparison, in the presence of 5 × 10−4 Mof KCN which inhibited the cytochrome oxidase path the SHAM-sensitive sucrose uptake occurred at a rate of from 56 to 128 nmol sucrose/(μmol O2consumed. The results indicate that both cytochrome oxidase and an alternate path could support the uptake of sucrose, but the latter was only half as efficient as the former.

ISSN:0008-4026    

DOI:10.1139/b81-158

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

Chromosome number determinations were made from 227 populations of 43 taxa ofEuthamiaandSolidago. Nearly all were confirmations of previous reports. The majority of the populations sampled were from Ontario. First report:Solidago hispidaMuhl. var.tonsaFern., 2n = 18.

ISSN:0008-4026    

DOI:10.1139/b81-159

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

Crosses were made in all combinations between the four allopatric taxa ofSullivantia. Artificial hybridizations between any twoSullivantiaplants almost invariably yielded viable seed that produced vigorous F1hybrids. The observation thatSullivantiaspecies are highly interfertile is in agreement with similar findings for many other north temperate perennial plants. In most cases, the average pollen fertility of interspecific hybrids is reduced compared with the fertility of parental plants and intraspecific hybrids. Since no meiotic aberrations were observed in hybrids, gross chromosomal rearrangements apparently are not responsible for the reductions in hybrid fertility. WithinSullivantiathere is a general correlation between geographical distance separating parental populations and reduction in hybrid fertility. Similar correlations have been reported for several other angiospermous species, but the present study is the first report of such a geographical distance – fertility correlation within an entire genus.

ISSN:0008-4026    

DOI:10.1139/b81-160

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

Tolerance of beans (Phaseolus vulgarisL.) to low temperatures is essential for growth under Canadian growing conditions. At air temperatures typical of a southern Alberta growing season (10–23 °C), 'Aurora' fixed 433 mg N per plant, more than 'Sanilac' and 'Comtesse,' which averaged 307 mg N per plant, and 'Kentwood,' which fixed the least: 214 mg N per plant. At a higher temperature regime (15–23 °C), typical of a southern Ontario growing season, 'Aurora' again fixed the most N2(456 mg N per plant), while the other three cultivars fixed an average of 370 mg N per plant. The amount of N2fixed increased as the time to reach maximum acetylene (C2H2) reducing activity lengthened. This suggested that it may be advantageous to select beans that have a longer vegetative stage to prolong the time of active N2fixation within the limits of acceptable season length to ensure maturity. 'Aurora' was not affected by the lower temperature regime, and although these temperatures delayed the initiation of N2fixation by 21 days, 'Aurora' compensated by producing 26% greater nodule dry weight and 40% higher maximum C2H2-reducing activity than that observed at the higher temperature regime. Growth and N2fixation of the other three cultivars were adversely affected by the lower temperature regime, not because of lower nodule numbers or mass but because of lower nodule activity. The good root growth of 'Aurora' at low temperatures may explain its superiority for N2fixation at lower temperatures. C2H2reduction and nodule dry weight were acceptable indicators of N2fixation only during early plant growth when all nodules were new and uniformly active. The ideal time to select the bean cultivars for N2-fixing ability was just before the peak of maximum C2H2-reducing activity and corresponded to the stage from buds-near-breaking to anthesis for both temperature regimes. Molar ratios of C2H2reduced to N2fixed suggested that the relative efficiency of N2fixation varied with temperature and growth stage but not with bean cultivar.

ISSN:0008-4026    

DOI:10.1139/b81-161

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

Patterns of alkane distribution in the epicuticular wax were determined for seven evergreen species of Ericaceae from western Oregon. Hentriacontane was the major alkane in most species. Total wax hydrocarbons were lowest in plants collected on the coast.

ISSN:0008-4026    

DOI:10.1139/b81-162

出版商:NRC Research Press    

年代:1981

数据来源: NRC