Mass spectrometric analysis of gas exchange by the diatom Thalassiosira weisflogii grown under 12 : L/D cycles indicates that mitochondrial respiration is highest in light, averaging 54 µ mol O 2 (mg Chl a ) −1 h while gross photosynthesis was 162 . In dark, consumption slowly decreased to minimum 29 mol(mg at end scotophase. When cells were poised DIC (dissolved inorganic carbon) compensation point light (DIC concentration where net equals zero), only slightly higher than dark. Adding...

The assimilation of nitrogen by N-limited microalgae has profound effects on respiratory and photosynthetic metabolism. addition inorganic causes a rapid increase in the rate amino acid synthesis, which increases requirements for keto-acids. This results large demand tricarboxylic cycle intermediates. To meet this demand, activity increases, resulting high rates CO 2 release during photosynthesis. Tricarboxylic reductant, produced ammonium assimilation, is oxidized via mitochondrial...

This study explored the long-term impacts of a pulse disturbance triclosan on five nontarget green algae in Lake Erie. Comprehensive analyses were performed using multiple physiological end points at community and subcellular scales. The toxic mechanism wide range concentrations was analyzed. diverse sensitivity species complex interrelationships among revealed. results showed taxonomic groups key issue for difference. High doses caused irreversible damage algae, environmentally relevant...

This study investigated the toxicity of triclosan to green microalga Chlorococcum sp. under multiple environmental stressors. The interactions between and stressors were explored through full two-way factorial, synchrotron-based Fourier transform infrared spectromicroscopy principal component analyses. Phosphorus concentration, pH * phosphorus temperature NaCl concentration most statistically significant factors exposure. variation those would have a huge impact on biophysiological...

Mass spectrometric analysis shows that assimilation of inorganic nitrogen (NH(4) (+), NO(2) (-), NO(3) (-)) by N-limited cells Selenastrum minutum (Naeg.) Collins results in a stimulation tricarboxylic acid cycle (TCA cycle) CO(2) release both the light and dark. In previous study we have shown TCA reductant generated during NH(4) (+) is oxidized via cytochrome electron transport chain, resulting an increase respiratory O(2) consumption photosynthesis (HG Weger, DG Birch, IR Elrifi, DH...

The rate of respiratory O2 consumption by Chlamydomonas reinhardtii cell suspensions was greater after a period photosynthesis than in the preceding dark period. This "light-enhanced respiration" (LEDR) function both duration illumination and photon fluence rate. Mass spectrometric measurements gas exchange indicated that gross increased during photosynthesis, whereas CO2 production decreased rate-dependent manner. postillumination provided good measure light. LEDR substantially presence...

Mass spectrometric analysis of O(2) and CO(2) exchange in the green alga Selenastrum minutum (Naeg. Collins) provides evidence for occurrence mitochondrial respiration light. Stimulation amino acid synthesis by addition NH(4)Cl resulted nearly a 250% increase rate TCA cycle efflux both light dark. Ammonium caused similar cyanide sensitive consumption Anaerobiosis inhibited release NH(4)Cl. These results indicated that cytochrome pathway electron transport chain was operative responsible...

A model which predicts total photosynthetic electron flow from a linear regression of the relationship between corrected steady-state quantum yield and nonphotochemical quenching (E Weis, JA Berry [1987] Biochem Biophys Acta 894: 198-208) was formulated for N-limited cells green alga Selenastrum minutum. Unlike other models based on net CO(2) fixation, our is measured as gross O(2) evolution. This allowed prediction water to both fixation NO(3) (-)/NO(2) (-) reduction. The equation...

ABSTRACT Imposition of low, but above freezing, temperatures resulted in a gradual increase the cold hardiness western red cedar seedlings. This was associated with decrease maximum rates photosynthetic CO 2 fixation and O evolution, changes chlorophyll fluorescence transients which indicated that photoinhibition had occurred. Maximum declined approximately 40% during hardening. The leaves changed colour from green to red‐brown hardening process. change due synthesis large amounts carotenoid...

Interactions between growth temperature and measurement were examined for their effects on white spruce [ Picea glauca (Moench) Voss] root respiration. Total dark respiration rates increased with unaffected by temperature. Partitioning of respiratory electron flow the cytochrome alternative pathways was also The proportion mediated pathway constant at temperatures 4°C 18°C, but higher temperatures. Changes in activity paralleled changes capacity, almost fully engaged all Roots grown low...

The effects of ammonium assimilation on photosynthetic carbon fixation and O(2) exchange were examined in two species N-limited green algae, Chlorella pyrenoidosa Selenastrum minutum. Under light-saturating conditions, resulted a suppression by S. minutum but not C. pyrenoidosa. These different responses are due to relationships between cellular ribulose bisphosphate (RuBP) concentration the RuBP binding site density carboxylase/oxygenase (Rubisco). In both species, decrease concentration....

Abstract Twenty species/isolates of cyanobacteria and green algae were isolated from cyanobacterial bloom samples in lakes associated with the upper Qu'Appelle River drainage system southern Saskatchewan, Canada. Three amoebae species ( Cochliopodium sp., Vannella sp. Vermamoeba vermiformis ) also one these samples, subjected to grazing assays determine which or could potentially serve as a food source. Amoeba rates quantified based on diameter plaque after 12 days agar plate assays, by...

Iron acquisition from various ferric chelates and colloids was studied using iron‐limited cells of Anabaena flos‐aquae (Lyng.) Brèb UTEX 1444, a cyanobacterial strain that produces high levels siderophores under iron limitation. Various chelators greatly varying affinity for Fe 3+ (HEDTA, EDDHA, desferrioxamine mesylate, HBED, 8‐hydroxyquinoline) were assayed the degree by cells. uptake rates (measured graphite furnace atomic absorption spectrometry) varied approximately inversely with...

Four species of green algae (Chlorella kessleri Fott et Novakova, Chlorococcum macrostigmatum Starr, Haematococcus lacustris [Girod-Chantrans] Rostaf., Stichococcus bacillaris Nag.) were grown in iron-limited chemostats and under phosphate limitation iron (nutrient) sufficiency. For all four species, steady-state culture density declined with decreasing degree (increasing growth rate), whereas chl per cell or biovolume increased. Plasma membrane ferric chelate reductase activity was enhanced...

Inhibitor titration curves and discrimination against (18)O(2) by mitochondrial respiration in three strains of green algae (Selenastrum minutum [Naeg.] Collins, two Chlamydomonas reinhardtii Dangeard) with differing respiratory capabilities were determined. Discrimination for cytochrome pathway ranged from 19.89 to 20.43%. alternative wild-type C. (measured the presence KCN) was 25.46%, while values a oxidase deficient mutant 24.24 24.96%. In absence KCN, not engaged reinhardtii, only algal...

The basis for the negative correlation between seed number and size was experimentally investigated in a natural population of Clintonia borealis. Clones this species vary significantly estimated self‐compatibility (ratio set with selfing to that outcrossing) appears affect seeds individual flowers each. be largely self‐compatible more per flower than incompatible ones under pollination. However, naturally pollinated clones smaller those clones, significance relationship removed by holding...

The assimilation of ammonium by the N-limited green alga Selenastrum minutum results in suppression photosynthetic electron flow from H(2)O to CO(2) (6, 7, 18). In this study, are presented which describe correponding change steady-state chlorophyll a fluorescence. addition resulted transient decline fluorescence followed marked increase. Fluorescence did not return control levels until added had been assimilated. Analysis transients showed that rapid increase nonphotochemical quenching...

Nitrogen-limited cells of Selenastrum minutum (Naeg.) Collins are able to assimilate NH(4) (+) in the dark under anaerobic conditions. Addition results a threefold increase tricarboxylic acid cycle (TCAC) CO(2) efflux and an eightfold rate anaplerotic carbon fixation via phosphoenolpyruvate carboxylase. Both these observations consistent with increased TCAC flow supply intermediates for amino biosynthesis. H(14)CO(3) (-) assimilating incorporation radiolabel into alpha-carboxyl glutamic...

N,N′-di(2-hydroxybenzoyl)-ethylenediamine-N,N′-diacetic acid (HBED) is a very strong Fe 3+ chelator. Strategy I vascular plants, which use reductive system for iron acquisition, similar to many green algae, are able access from HBED (R.L. Chaney. 1988. J. Plant Nutr. 11: 1033–1050). However, iron-limited cells of the alga Chlamydomonas reinhardtii Dangeard were unable present as –HBED. In contrast, chelated with hydroxyethylethylenediaminetriacetic (HEDTA; weaker chelator) was rapidly taken...

Iron acquisition by iron-limited cyanobacteria is typically considered to be mediated mainly siderophores, iron-chelating molecules released into the environment. In this set of experiments, iron uptake cells cyanobacterium Anabaena flos-aquae (L.) Bory was investigated in resuspended siderophore-free medium. Removal siderophores decreased iron-uptake rates ∼60% compared siderophore-replete conditions; however, substantial remained. absence Fe(III) much more rapid from a weaker synthetic...