摘要:

Ammonia stimulated photosynthetic14CO2fixation in isolated spinach cells under conditions of saturating light intensity and adequate CO2supply. Increasing temperature increased photosynthesis and promoted the stimulation of photosynthesis by ammonia. Ammonia increased carbon traffic into organic acids and amino acids without affecting the total,14C incorporation in the neutral fraction, although the relative distribution of14C incorporation in the neutral fraction as a percentage of the total soluble14C incorporation was decreased. The increased carbon flow into the amino acid fraction led to an increase of,14C incorporation, principally into glutamine, glutamate, and aspartate. The role of ammonia in photosynthetic carbon metabolism is discussed.

ISSN:0008-4026    

DOI:10.1139/b80-060

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Photosynthetic14CO2fixation in spinach leaf cells was stimulated by ammonia. CO2fixation in the presence of NH3was inhibited by glutamate, NO2−, methionine sulfoximine, azaserine, or aminooxyacetate. In all instances, though, the decrease in14CO2fixation was largely due to decreased14C in the neutral fraction rather than to decreased14C in the basic or acidic fractions which are those fractions specifically increased by ammonia addition. Ammonia appears to stimulate "dark"14CO2fixation in addition to photosynthetic14CO2fixation. The treatments mentioned above did not abolish this "dark"14CO2fixation but rather slightly inhibited photosynthetic14CO2fixation so that total14CO2fixation was reduced. It would seem that the mechanism by which nitrogen assimilation stimulates14CO2incorporation into the basic fraction is still unresolved.

ISSN:0008-4026    

DOI:10.1139/b80-061

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

In spinach leaf discs the accumulation of nitrite from nitrate reduction under anaerobic conditions in the light in the presence of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) was inhibited by air. The inhibition of nitrate reduction by air was reversed by antimycin A but not by rotenone or amytal. The nitrate-reducing system of DCMU-inhibited leaf discs in the light appeared similar to noninhibited leaf discs in the dark. In aerobic conditions, the addition of malate stimulated nitrite accumulation. This stimulation was unaffected by malonate. Under anaerobic conditions, malate reversed the inhibition of nitrate reduction caused by either iodoacetate or arsenite to rates similar to those observed in the dark and in the light with DCMU. Malate can apparently provide a direct source of cytosolic NADH for nitrate reduction.

ISSN:0008-4026    

DOI:10.1139/b80-062

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Eleven fungicides were examined in five tests for their effects on endomycorrhizal development in sour orange seedlings. Copper, metalaxyl, thiabendazole, captan, captafol, chloroneb, and formaldehyde were tested for their effects onGlomus etunicatus, and chlorothalonil, sodium azide, benomyl, and maneb were tested for their effects onG. mosseae. Captafol, chloroneb, metalaxyl, and captan did not adversely affect growth of mycorrhizal plants, although some adverse effect on the fungus was apparent with all rates of captafol and the high rate of captan. All rates of benomyl and thiabendazole reduced plant growth, and mycorrhizal infection and sporulation decreased as rates of thiabendazole increased. Plant growth was better and fungus sporulation higher than that of the mycorrhizal control in all sodium azide treatments. Copper at rates of 112 and 224 kg/ha significantly depressed plant growth but not infection and fungus sporulation. Maneb and chlorothalonil, which had no effect onG. mosseaeat the low rate of 5.6 kg/ha, sharply reduced fungus sporulation and mycorrhizal plant growth at 11.2 and 22.4 kg/ha. Formaldehyde at three rates was toxic toG. etunicatus.

ISSN:0008-4026    

DOI:10.1139/b80-063

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

The recent changes in the submersed macrophyte communities of Lake Wingra, Wisconsin, have been dominated by the dynamics of one exotic species. After a decade of abundance,Myriophyllum spicatumhas undergone a sustained decline in the Madison lakes. A pattern of explosive growth followed by declining abundance may describe mostM. spicatuminvasions.No simple single-factor explanation can adequately account for the biomass dynamics ofM. spicatumin Lake Wingra. The decline inM. spicatumbiomass appears to be the result of a complex of synergistically interacting factors, perhaps including nutrients, epiphytes, competitors, and parasites or pathogens.Invasions of lake districts byM. spicatumare hypothesized to follow a wave pattern. When interlake distances are accounted for, departure from a simple wave is hypothesized to result from lags in infestation of lakes which are not susceptible to colonization byM. spicatum. Several testable hypotheses are suggested by this view ofM. spicatuminvasions.

ISSN:0008-4026    

DOI:10.1139/b80-064

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Events in the development of powdery mildew fungi and responses of barley epidermal cells were compared not only among combinations of barley and among races of mildew differing in virulence but also between epidermal cells adjacent and nonadjacent to stomata. Differences in fluorescence intensity and in the size of papillae and haloes were not observed until 12 h after inoculation; however, the fluorescence intensity and size of papillae increased rapidly and the differences became obvious 15 h after inoculation when the parasite penetrated into host cells. Failure of fungal penetration in incompatible combinations was mostly associated with papillae either with or without collapse of epidermal cells. The greater the resistance of barley, the greater was the rate of fungal cessation of growth at the papilla stage and the stronger was the fluorescence intensity of papillae. Haloes were larger in susceptible than in resistant hosts, but they usually did not form at sites where haustoria were produced.On the other hand, in incompatible combinations (with thegenes), host epidermal cells adjacent to stomata (A cells) were less resistant than the nonadjacent ones (NA cells). More than 80% of haustoria formed were restricted to A cells, and about half of the conidia located in A cells formed haustoria. Many parasites of the remaining population in A cells ceased growth, followed by host cell collapse. In NA cells, most penetration pegs were terminated at the stage of papilla formation. The fluorescence intensity of papillae in NA cells was much stronger than that in A cells.It was suggested that cytologically specific events of compatibility or incompatibility are expressed at the papilla stage and that the fluorescent compounds deposited at the infection sites might represent chemical factors which are associated with resistance expressed at the stage of penetration, although it is not known whether the compounds as well as papillae themselves are a primary cause of resistance or a result of some unknown resistance mechanism.On compare des aspects du développement des champignons responsables du blanc de l'orge et les réactions des cellules épidermiques de l'orge, non seulement entre combinaisons d'orge et entre races de blanc différant par leur virulence, mais aussi entre cellules épidermiques adjacentes ou non aux stomates.

ISSN:0008-4026    

DOI:10.1139/b80-065

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Germinating macroconidia from a strain ofFusarium acuminatumcan produce microconidia either directly from the macroconidium or from the primordial hyphae. The most abundant microconidial production occurs when the macroconidia are allowed to germinate on media containing raffinose or sucrose. Moderate microconidium production occurs when the medium contains lactose, but on media containing fructose, galactose, glucose, trehalose, or mixtures of some of these, microconidium production is generally low.

ISSN:0008-4026    

DOI:10.1139/b80-066

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Quantitative terpene analysis of the leaf oils of 433 wild Douglas-fir trees from 87 northwestern localities, 66 wind-pollinated progenies of 4 trees from Idaho, 100 trees from 5 localities represented in a provenance trial, and 76 trees from four full-sib families of F1intervarietal crosses allowed assessment of biosynthetic pathways, geographic variation, and modes of inheritance. Hypothetical biosynthetic pathways, derived from the cooccurrence of terpenes implied that the variation in 17 monoterpenes could be represented by three or four biogenetic pathways. As a result, geographic variation between the coastal and Rocky Mountain varieties can be described by the relative percentages of β-pinene, the terpinene–sabinene group of terpenes, the camphene group, and perhaps limonene. An abrupt reduction in the production of the camphene group occurs in going from interior to coastal populations. Moreover, patterns of segregation within four full-sib intervarietal hybrid families suggested that production of high relative percentages of the camphene group was governed by a single dominant gene. The dominant allele is characteristic of the Rocky Mountain variety, but isolated occurrences were also found on dry sites in coastal British Columbia. The recessive allele occurs far into the range of the Rocky Mountain variety. The coastal variety is characterized by the synthesis of relatively large amounts of β-pinene and the terpinene–sabinene group and their mode of inheritance is quantitative. Although concentrations of these terpenes decline towards the Rocky Mountains, genes controlling high amounts occur in populations of Idaho and western Montana. The variation in β-pinene and terpenes of the terpinene–sabinene group does not appear to be clinal. Trees with 5–10% ocimene are predominant in eastern Oregon. This terpene was found only in less than 1% amounts in trees from the coastal region and Montana and was practically absent in a provenance from Arizona. Hence it may serve to differentiate Rocky Mountain populations.

ISSN:0008-4026    

DOI:10.1139/b80-067

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Because of their structure and active metabolic state, pollen grains are vulnerable to any agent in thein vitrogermination medium. Surfactants are used in biological systems to reduce surface tension but are also known to produce subtle biochemical effects. This study investigated the effect of three nonionic surfactants on the germination characteristics of pollen grains from three pollen source genotypes. Pollen grains from three single cross hybrids (Wf9 × H55, K64 × K55, Ky228 × Ky226) were cultured on an artificial medium (15% sucrose, 0.6% bacto-agar, 0.03% calcium nitrate, 0.01% boric acid) supplemented with all possible combinations of three concentrations (10, 100, 1000 ppm, v/v) of the following surfactants: (i) Tween 80 (polyoxyethylene sorbitan monooleate); (ii) X-114 (alkyl phenoxypolyethoxy ethanol); and (iii) commercial sticker spreader (alkyl olefin aromatic polymers). A control containing no supplement was included. Over all genotypes, increasing concentrations of Tween 80 had the least effect on the germination characteristics measured (germination and ruptured percent, pollen tube length at 1, 2, and 3 h after inoculation) and X-114 had the greatest effect with no germination found above 10 ppm. For most of the germination characteristics, highly significant pollen source genotype X concentration interactions were found for each surfactant. The direction and magnitude of the surfactant effects depended on the surfactant, its concentration, the germination characteristic involved, and the pollen source genotype.

ISSN:0008-4026    

DOI:10.1139/b80-068

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Phaeococcus exophialae, a black yeast, is examined by electron microscopy. In addition to previously reported yeast and hyphal growth forms, the fungus is observed to produce sterile aerial strands. Presence of a dialysis membrane barrier on the culture medium surface appears to be conducive to the development of the strands. Other factors controlling the production of the erect structures are not known. The strands are compared and contrasted with synnemata.

ISSN:0008-4026    

DOI:10.1139/b80-069

出版商:NRC Research Press    

年代:1980

数据来源: NRC