Pelagic growth and colony division of Gloeotrichia echinulata in Lake Erken

Gloeotrichia echinulata colony development was monitored inLake Erken, Sweden and studied in enclosure experiments. Significantcolonial division did not occur in mesh bags, although the abundanceof the pelagic population in the lake increased during the experimentalperiods. On the basis of these findings, it is suggested thatcirculation of G. echinulata to deeper nutrient rich water supportspelagic growth. In support of this, a large part of the buoyantG. echinulata colonies in Lake Erken was found at several metersdepth. In an experiment with nutrient additions, the only treatmentthat favoured G. echinulata development was additions of phosphate,nitrate and iron. Trace element additions had a negative effecton the development of G. echinulata. On the basis of these findings,the nutritional requirements of G. echinulata are discussed.     

The Effect of Ferrous Iron on the Uptake of Manganese by Juncus effusus L.

Juncus effusus L was grown in solution culture at five levelsof ferrous iron The concentration and amount of manganese inthe shoots decreased with increased iron concentration in thesolution, except at the highest iron concentration (128 p pm) where there was a significant increase in manganese concentrationIt is suggested that this increase is due to a chemical interactionin the culture solution The importance of a Fe Mn ratio of twoas a general rule in plant nutrition is questioned Juncus effusus L., iron, manganese, mineral nutrition     

The response of tomato roots (Lycopersicon esculentum Mill.) to iron deficiency stress: alterations in the pattern of protein synthesis

Dicotyledon plants adapt to iron (Fe) deficiency through a seriesof reactions that increase the ability of the plant to assimilateFe and to increase the efficiency of Fe utilization. In an attemptto gain an insight into these adaptive processes, the specificchanges in protein synthesis associated with the onset of theFe deficiency response in tomato roots (Lycopersicon esculentumMill cv. Rutgers) have been investigated. Roots were grown underFe—sufficient and —deficient conditions, and thepattern of protein synthesis was analysed by in vitro translationof root mRNA and by in vivo labelling of root proteins. Polypeptideswere resolved by two—dimensional polyacrylamide gel elec—trophoresis.Seven polypeptides were identified by in vitro translation,whose synthesis was significantly increased during Fe deficiency.The increase was probably specific to Fe deficiency in thatthe polypep—tide synthesis was not increased during phosphatedeficiency stress, was less prominent following prolonged Fedeficiency and was decreased following re—supply of Feto the hydroponic medium. The pattern of in vitro translation of mRNA isolated from Fe—deficientroots was compared to the results obtainedin vivo followingradiolabelling of proteins. In these analyses, eight polypeptideswere identified, tentatively including the seven polypeptidespreviously identified by in vitro translation. All polypeptideswere characterized with regard to molecular mass and pl andtheir localization in the cell, whether being membrane boundor soluble. It is suggested that members of this group of polypeptidesare involved in the response of the root to Fe deficiency: althoughtheir functions remain to be identified. Key words: In vitro protein synthesis, iron, iron deficiency, root, 2-dimensional PAGE     

Sensing Iron--A Whole Plant Approach

Regulatory mechanisms leading to cellular Fe homeostasis wereinvestigated inPlantago (Plantago lanceolata L.) plants grownhydroponically at different temperature regimes either in thepresence or absence of iron. During the experimental periodof 6 d, growth was not affected by Fe availability, but wasdecreased by lowering the root zone temperature (RZT) from 24to 12°C. Cultivating plants at low RZT decreased the reductionactivity for ferric chelates in Fe-deficient plants. In thepresence of iron, the temperature regime did not affect Fe accumulationby root cells, but decreased translocation of Fe to the shoot,and chlorosis of young leaves was observed at suboptimal RZT.Under these conditions root-mediated reduction of ferric chelateswas increased. In cold-treated plants this effect was specificto Fe and could not be evoked by Mn²⁺and Zn ^{+ 2}additions. Supplementingthe medium with the ferrous scavenger ferrozine caused a furtherenhancement in reduction rates, probably due to mobilizationof apoplastic Fe. These results can be explained plausibly ifdifferent sites of Fe sensing are postulated and if it is assumedthat both the absence and presence of iron could be a signalincreasing root reduction activity. Copyright 2000 Annals ofBotany Company Adaptation, iron uptake regulation, ferric reduction, Plantago lanceolata, root zone temperature, whole plant signalling     

Anabolic influences of insulin-like growth factor I and/or growth hormone on the diaphragm of young rats

Lewis, Michael I., Thomas J. LoRusso, and Mario Fournier.Anabolic influences of insulin-like growth factor I and/or growth hormone on the diaphragm of young rats. J. Appl. Physiol. 82(6): 1972-1978, 1997.It iscontroversial whether insulin-like growth factor I (IGF-I), growthhormone (GH), or their combination might enhance body growthand/or tissue anabolism in the well-fed animal with an intactsomatotrophic axis. To assess this further, we studied four groups ofadolescent rats: 1) control (Ctr),2) GH,3) IGF-I, and4) GH/IGF-I. IGF-I was given via anosmotic minipump, whereas GH was injected subcutaneously for a period of 72 h. Diaphragm (Dia) contractile and fatigue properties were determined in vitro. Quantitative histochemical and morphometric analyses were performed on Dia fibers. Total serum IGF-I levels weresignificantly increased in the groups receiving growth factors. Although body weight increased to a greater extent in the animals receiving growth factors, a further synergistic effect was noted in theGH/IGF-I animals compared with either GH or IGF-I groups. Costal Diamass was greater in the groups receiving growth factors. The Dia ofGH/IGF-I animals was more fatigue resistant than the Dia in Ctr. Thecross-sectional area of types IIa and IIx fibers were increased to asimilar extent in all groups receiving growth factors compared withCtr. Succinate dehydrogenase activity of type IIa fibers wassignificantly greater in the GH/IGF-I animals compared with the othergroups. We conclude that the short-term provision of growth factors towell-nourished, normally growing adolescent rats can accelerate bodygrowth and promote selective hypertrophy of predominantly type II Diafibers.

     

Temporal changes in biomass specific photosynthesis during the summer: regulation by environmental factors and the importance of phytoplankton succession

Measurements of phytoplankton photosynthesis vs. irradiance relationships have been made at 3–7 day intervals in Lake Erken (central Sweden) for three years during summer stratification. Both the rate of light-limited (^B) and light-saturated (P_max ^B) photosynthesis per unit chlorophyll a showed distinct and similar temporal trends in each year. Seasonal trends were especially evident for P_max ^B, which increased in value for several weeks following the onset of thermal stratification, and then declined in the presence of the large colonial blue-green alga, Gloeotrichia echinulata. By late summer, when the biomass of G. echinulata had decreased, P_max ^B again rose to its early summer value. The covariation of biomass-specific photosynthesis with the blooming of G. echinulata was the one clear seasonal (week-month) pattern which emerged in each of 3 years. Over short (day-week) time scales, changes in ^B were related to changes in irradiance exposure on the day of sampling. However, the relationship between these two parameters was variable in time, since it was superimposed upon longer term trends controlled by changes in phytoplankton species composition. Increases in G. echinulata biomass corresponded with a deepening of the thermocline, which both increased internal phosphorus loading and the transport of resting G. echinulata colonies into the epilimnion. The timing and magnitude of the yearly G. echinulata bloom was as a result related to the seasonal development of thermal stratification. These results illustrate the importance of seasonal changes in the phytoplankton community as a factor regulating rates of biomass specific photosynthesis, particularly when the successional changes involve species with very different life strategies.     

Thermogravimetric kinetics of corn stalk pretreated by oleaginous fungi Cunninghamella echinulata

The thermogravimetric and composition of corn stalk pretreated by oleaginous fungi Cunninghamella echinulata had been studied in this paper. Results indicated that pretreatment by oleaginous fungi C. echinulata could decrease the activation energy and make the pyrolysis more efficient and energy-saving. By bio-pretreatment, the contents of elements agreed with the weight loss, sugar content, and oil contents, especially the sulfur content was greatly decreased, greatly eliminating the inventory of gas contamination such as the emission of SOx and making the pyrolysis more environmentally friendly. Therefor, corn stalk with sugar pretreated by oleaginous fungi C. echinulata should be a good pyrolysis material to obtain high quality bio-oil.     

Upregulation of gamma-glutamate-cysteine ligase as part of the long-term adaptation process to iron accumulation in neuronal SH-SY5Y cells

Reactive iron is an important prooxidant factor, whereas GSH is a crucial component of a long-term adaptive system that allows cells to function during extended periods of high oxidative stress. In this work, the adaptive response of the GSH system to prolonged iron loads was characterized in human dopaminergic SH-SY5Y neuroblastoma cells. After the initial death of a substantial portion of the cell population, the surviving cells increased their GSH content by up to fivefold. This increase was traced to increased expression of the catalytic and modulatory subunits of -glutamate-cysteine ligase. Under conditions of high iron load, cells maintained a low GSSG content through two mechanisms: 1) GSSG reductase-mediated recycling of GSSG to GSH and 2) multidrug resistant protein 1-mediated extrusion of GSSG. Increased GSH synthesis and low GSSG levels contributed to recover the cell reduction potential from –290 mV at the time of cell death to about –320 mV. These results highlight the fundamental role of GSH homeostasis in the antioxidant response to cellular iron accumulation and provide novel insights into the adaptive mechanisms of neurons subjected to increased iron loads, such as those observed in Parkinson's disease. oxidative stress; glutathione; multidrug resistance protein 1; oxidixed glutathione reductase; neurodegenerative diseases     

The role of thiol compounds in increasing Agrobacterium-mediated transformation of soybean cotyledonary-node cells

Agrobacterium-mediated transformation of soybean cells and the production of fertile transgenic soybean [Glycine max (L.) Merrill] plants using the cotyledonary-node (cot-node) method were improved by amending the solid co-cultivation medium with L-cysteine. The goal of this study was to investigate the role of cysteine and other thiol compounds in increasing the frequency of transformed soybean cot-node cells. The frequency of transformed cells was increased only when L-cysteine was present during co-cultivation of Agrobacterium and cot-node explants. This effect was due to the thiol group since D-cysteine and other thiol compounds also increased the frequency of transformed cells. Copper and iron chelators also increased the frequency of transformed cells, indicating an association with inhibition of polyphenol oxidases and peroxidases. Thiol compounds likely inhibit wound- and pathogen-induced responses, thereby increasing the capacity for Agrobacterium-mediated transformation of soybean cells. The increases in transformed cot-node cells were independent of soybean genotype, Agrobacterium strain, and binary plasmid.     

IAA-oxidase in Impatiens balsamina Affected by GA3 and Tannic Acid

The activity of IAA-oxidase increased in the leaves of Impatiensbalsamina plants receiving inductive photoperiodic cycles andin plants receiving treatments with gibberellic acid (GA₃) and/ortannic acid (TA), even under non-inductive photoperiods; theactivity also increased in the stem receiving inductive photoperiodiccycles (8 h). Treatment with GA₃ and TA mimics the effect ofSD cycles in the development of some isoenzymes of IAA-oxidase.Thus a new isoenzyme at R_f 0.48 developed in the leaves andone at R_f 0.82 developed in both the stem and the leaves ofall plants receiving inductive treatments – photoperiodicor chemical – but not in water-treated controls undernon-inductive photoperiods. Another isoenzyme at R_f 0.68 developedonly in the stems. Flowering, gibberellic acid, IAA oxidase, Impatiens, phenols, photoperiod     

Effects of Exogenous Amino Acids on Iron Uptake in Relation to their Effects on Photoperiodic Flowering in Lemna paucicostata 6746

The flowering of Lemna paucicostata 6746 grown on 14-h photoperiodwas enhanced by the addition of high concentrations of ironto the medium, which also increased the endogenous iron concentration.The addition of asparagine, aspartate, glutamate, -alanine,glycine or serine to the medium also increased the endogenousiron level, resulting in the promotion of flowering. In contrast,the addition of cysteine, cystine, glutamine, arginine, threonineor phenylalanine lowered the endogenous iron level, resultingin the inhibition of flowering. Glycine and asparagine added to the medium during an inductive96-h dark period did not promote iron uptake and had no effecton flowering, but when added during the subsequent 120-h lightperiod, they promoted both iron uptake and flowering response.The increase in the endogenous iron level seems to favor floraldevelopment rather than induction of photoperiodic floweringof Lemna paucicostata 6746. (Received September 8, 1986; Accepted March 31, 1987)     

Cyst production in four species of neritic dinoflagellates

The production of resting cysts in four species of dinoflagellates(Scrippsiella trochoidea, Ensiculifera sp., Alexandrium lusitanicumand Lingulodinium polyedra) was studied in response to severalenvironmental factors of ecological importance (nitrate, phosphate,iron, copper and cyanocobalamin deficiencies, high concentrationsof copper, turbulence, darkness plus concentration. as wellas various media biologically conditioned by dinoflagellates)using unialgal cultures and enrichments of natural populations.Some nutritional deficiencies, mainly phosphorus or nitrogen(in this order), are the most effective inducers of encystment.Among the other deficiencies tested, only iron deficiency wasimportant, affecting only A.lusitanicum. In some cases, biologicalconditioning produced considerable encystment reductions, makingit an important means of competition between species. We suggestthat encystment may be induced in these neritic species by deficienciesin compounds that act as indicators of changes in the hydrographicconditions to which the particular species are adapted.     

Sediment-to-water blue-green algal recruitment in response to alum and environmental factors

The sediment-to-water recruitment of blue-green algae was investigated in a shallow lake following treatment with aluminum sulfate and sodium aluminate to control sediment phosphorus (P) release. A comparison of results from two summers each before and after treatment indicates that the treatment did not universally impact the recruitment of either sporulating or non-sporulating forms of blue-green algae. Blooms of Anabaena, Aphanizomenon, and Coelosphaerium resulted predominantly from growth in the water column following strong recruitment episodes lasting up to two weeks, while Microcystis populations were relatively insensitive to periodically high inputs from recruitment. The development of planktonic populations of Gloeotrichia echinulata, by contrast, were largely dependent on sustained recruitment in response to adequate light and temperature regimes at the sediment surface.The cellular P content of recruited G. echinulata colonies was unaffected by the accumulation of aluminum floc to the lake sediments. Both G. echinulata and C. naegelianum showed elevated levels of cellular P in newly recruited colonies as compared to planktonic colonies, indicating P transport from the sediments to the water column. Total P translocation by blue-green algae was negligible in the absence of a substantial recruitment of G. echinulata. The recruitment of G. echinulata, and hence the magnitude of P translocation, was therefore more responsive to environmental conditions prevalent at the sediments than to direct effects of the treatment itself.     

A New Approach to Understanding the Calcifuge Habit of Plants

Growth rate of the calcifuge plants Carex pilulifera, Deschampsiaflexuosa, Holcus mollis, Luzula pilosa, Nardus stricta, andVeronica officinalis, transplanted into an Ordovician limestonesoil of pH 8, increased by two to three times on addition of5 mol m^-3 of CaHPO₄ compared to untreated conditions. For Galiumsaxatile, however, P treatment was lethal and growth was possibleonly in soil supplied with Fe(III) citrate, which had littleor no effect on growth of the other six species. Phosphate treatmentof the limestone soil greatly increased plant uptake of P, whereasP concentration of shoots from untreated soil was very low andprobably highly deficient, compared to plants of field siteorigin. From this and two other recent studies it is now possibleto conclude that the calcifuge habit of plants, at least underclimatic conditions prevailing in northern Europe, is most oftendue to an inability of such plants to render the native phosphateof limestone soils available to plant uptake. Out of ten calcifugespecies tested, only one exception to this rule was identified.Copyright1994, 1999 Academic Press Carex pilulifera, Deschampsia flexuosa, Galium saxatile, Holcus mollis, Luzula pilosa, Nardus stricta, Veronica officinalis, calcifuge plants, phosphorus, iron, limestone soil, limiting factors     

Possible physiological mechanisms for production of hydrogen peroxide by the ichthyotoxic flagellate Heterosigma akashiwo

Blooms of the toxic red tide phytoplankton Heterosigma akashiwo(Raphidophyceae) are responsible for substantial losses withinthe aquaculture industry. The toxicological mechanisms of H.akashiwoblooms are complex and to date, heavily debated. One putativetype of ichthyotoxin includes the production of reactive oxygenspecies (ROS) that could alter gill structure and function,resulting in asphyxiation. In this study, we investigated thepotential of H.akashiwo to produce extracellular hydrogen peroxide,and have investigated which cellular processes are responsiblefor this production. Within all experiments, H.akashiwo producedsubstantial amounts of hydrogen peroxide (up to 7.6 pmol min^–110⁴ cells^–1), resulting in extracellular concentrationsof ~0.5 µmol l^–1 H₂O₂. Measured rates of hydrogenperoxide production were directly proportional to cell density,but at higher cell densities, accuracy of H₂O₂ detection wasreduced. Whereas light intensity did not alter H₂O₂ production,rates of production were stimulated when temperature was elevated.Hydrogen peroxide production was not only dependent on growthphase, but also was regulated by the availability of iron inthe medium. Reduction of total iron to 1 nmol l^–1 enhancedthe production of H₂O₂ relative to iron replete conditions (10µmol l^–1 iron). From this, we collectively concludethat production of extracellular H₂O₂ by H.akashiwo occurs througha metabolic pathway that is not directly linked to photosynthesis.     

Gloeotrichia echinulata, a colonial cyanobacterium with a unique phosphorus uptake and life strategy

Epilimnetic colonies of Gloeotrichia echinulata were harvestedfrom 200–300 I of water in Lake Erken with filtrationthrough appropriate plankton nets (200 or 70 µm). Phosphateuptake characteristics, phosphorus (P) status and photosynthesisof the colonies were determined twice a week during July andAugust 1991. Phosphate uptake was analysed according to thesimple force- flow relationship of Falkner et al. (Arch. Microbiol.,152, 353–361, 1989). The threshold concentration of Puptake below which uptake ceases for energetic reasons, wasconstantly much higher than the epilimnetic soluble reactivephosphorus (SRP) concentration, so that the planktonic colonieswere unable to acquire any Pin the epilimnion. Neither did organicP seem to be a source of P for planktonic colonies. Gloeotrichiaechinulata has a unique life strategy in comparison to othercommon genera of bloom-forming cynanobacteria. Its P assimilationand growth are completely separated both in time and space;growth is preceded by benthic P assimilation. Epilimnetic growthwas based solely on internally stored P and growth rates fittedthe Droop model well. Depletion of stored P restricts the lengthof the planktonic phase to 15–20 days under ‘optimal’growth conditions. Wind-induced surface drift seemed to be themost important loss factor from the epilimnion. Massive recruitmentof P-rich benthic colonies accounted for two-thirds of totalnet internal P loading observed between mid-July and mid-August(3.8 mg P m^–2 day^–1).     

Response to Waterlogging and Differing Sensitivity to Divalent Iron and Manganese in Clones of Dactylis glomerata L. derived from Well-drained and Poorly-drained Soils

Clonally propagated plants of Dactylis glomerata derived froma well-drained, heavily grazed cliff habitat (clone L) and froman undergrazed poorly-drained soil (clone A) were tested forwaterlogging tolerance in soil-culture. Water-logging did notaffect the two clones differentially, a result, which contrastedstrongly with that of a previous experiment in which simulatedgrazing (clipping to 20 cm) unexpectedly caused clone A to beless tolerant of waterlogging than clone L. Maximum leaf andleaf sheath length was reduced more by water-logging in cloneL than in clone A (P < 0.05). In solution-culture when providedwith factorial combinations of 0.5, 5 and 50 mg dm^–2 ofFe²⁺ and Mn²⁺ the shoot dry weight yield of the dry-soil clonewas reduced more than that of the wet-soil clone by 50 mg Fedm^–3 irrespective of Mn²⁺ concentration (P < 0.01)but the reduction of growth was less at higher Mn²⁺ concentrations.Fifty milligrams of Mn²⁺ dm^–3 reduced the growth of thedry soil clone but increased the growth of the wet soil clonewith Fe²⁺ at 5 mg dm^–2 (P < 0.05). Iron at 0.5 mg dm^–2was suboptimal for shoot growth of both clones at any levelof Mn²⁺ and caused more severe leaf chlorosis in the wet soilclone. Leaf tissue of clone L contained more iron than thatof clone A after waterlogging (P < 0.01) but in solutionculture, though increasing iron from 0.5 to 50 mg dm^–3almost doubled leaf iron content (P < 0.001), the interactionClones x Mn x Fe just failed to reach significance at P <0.05. The manganese content of leaf tissue from the two clonesvaried differently in response to solution manganese (Clonesx Mn P < 0.01), clone A showing a slightly greater increaseof manganese content at high solution concentration. Iron at50 mg dm^–3 suppressed Mn uptake (Mn x Fe, P < 0.001)in both clones. The two clones thus show marked environmentaladaptation to the chemistry of wet and dry soils. Dactylis glomerata, Cocksfoot grass, Orchard grass, waterlogging, iron, manganese, toxicity, deficiency, ecotypes     

Flower-Promoting Effects of Iron and EDDHA in Lemna paucicostata 151

Lemna paucicostata 151 cultured in 1/10 strength M medium containing50 µM FeCl₃ easily flowered in response to short days,although it scarcely flowered under any photoperiod when themedium contained the standard amount of iron (2 µM FeCl₃).The flowering response was accomparied by an increase in theiron content of the plants, which was maximal at pH 5.0. Instandard M medium containing 50 µM FeCl³, this plant didnot flower even though it had a high iron content. Ethylenediamine-di (o-hydroxyphenylacetic acid) (EDDHA) inducedflowering of this strain under continuous light even in theabsence of iron and copper, and its effect was slightly loweredby the presence of iron in the medium. Thus the flower-inducingactivity of EDDHA could not be attributed to the action of ironor copper. EDTA inhibited both the iron uptake and floweringin Fe-rich medium under short-day conditions. (Received May 16, 1986; Accepted July 25, 1986)     

SOME OBSERVATION ON AIR-ION-ENHANCED IRON CHLOROSIS IN BARLEY (HORDEUM VULGARIS) SEEDLINGS

The air ion effects on "active" and "residual" iron distributionin barley seedlings were studied in the course of the developmentof ironchlorosis in an iron-free culture medium. "Active" or"acid soluble" iron plays an important role for chlorophyllbiosynthesis and is extractable with 1.0 N HCl from dried tissues,and "residual" or "acid insoluble" iron does not participatein this chlorophyll formation process and is not extracted with1.0 N HCl. Ions of either charge induced a significant decrease in activeiron content which was associated with a decrease in chlorophyllcontent. Concomitantly, there occurred an increase in both theresidual iron and the cytochrome c fractions. The increase inresidual iron content may involve not only cytochrome c butalso other cytochromes and ironcontaining enzymes as well. Theauthors have proposed a hypothesis that the site of air ionaction in the experiments reported may be the regulatory systemscontrolling iron metabolism in the seed and young seedling.Through this action air ions apparently divert more endogenousfree-state iron to residual iron (consisting of cytochromesand Fe-containing enzymes) than to active iron. Tracer experiments showed that air ions enhanced the uptakeof exogenous iron by early germinating barley seeds. The increasedincorporation of iron was not influenced by light. (Received December 10, 1964; )