Enhanced accumulation of starch and total carbohydrates in alginate-immobilized Chlorella spp. induced by Azospirillum brasilense: II. Heterotrophic conditions

The effect of the bacterium Azospirillum brasilense jointly immobilized with Chlorella vulgaris or C. sorokiniana in alginate beads on total carbohydrates and starch was studied under dark and heterotrophic conditions for 144h in synthetic growth medium supplemented with either d-glucose or Na-acetate as carbon sources. In all treatments, enhanced total carbohydrates and starch content per culture and per cell was obtained after 24h; only jointly immobilized C. vulgaris growing on d-glucose significantly increased total carbohydrates and starch content after 96h. Enhanced accumulation of carbohydrate and starch under jointly immobilized conditions was variable with time of sampling and substrate used. Similar results occurred when the microalgae was immobilized alone. In both microalgae growing on either carbon sources, the bacterium promoted accumulation of carbohydrates and starch; when the microalgae were immobilized alone, they used the carbon sources for cell multiplication. In jointly immobilized conditions with Chlorella spp., affinity to carbon source and volumetric productivity and yield were higher than when Chlorella spp. were immobilized alone; however, the growth rate was higher in microalgae immobilized alone. This study demonstrates that under heterotrophic conditions, A. brasilense promotes the accumulation of carbohydrates in two strains Chlorella spp. under certain time-substrate combinations, producing mainly starch. As such, this bacterium is a biological factor that can change the composition of compounds in microalgae in dark, heterotrophic conditions.     

The fine structure of autotrophic and heterotrophic cells of Chlorella vulgaris (Emerson strain)

Cells of the Emerson strain of Chlorella vulgaris become verymuch enlarged when cultured heterotrophically. The ultrastructureof these giant cells has been examined and compared with thatof cells cultured autotrophically. The chief area of differenceis within the chloroplast where there is a massive accumulationof starch and little or no synthesis of lamellae under heterotrophicconditions. Synthesis of cell wall material is apparently possibleunder heterotrophic conditions but the production of the variouscellular organelles does not keep pace with the increase incell volume. (Received August 12, 1968; )     

Heterotrophic Growth of Two Strains of the Acido-Thermophilic Red Alga Galdieria sulphuraria

The acido-and thermophilic red alga Galdieria sulphuraria (Galdieri)Merola grows under mixo- and heterotrophic conditions on 27different sugars and sugar alcohols as sole carbon source. Weseparated two strains from an isolate originally collected atMt. Lawu (Indonesia). These strains are indistinguishable ingrowth and pigmentation under autotrophic conditions. However,under heterotrophic conditions, strain 074 W lost most of itspigments whereas strain 074 G stayed green on all substratestested. Strain 074 G had the highest pigment content when grownon sugar alcohols. Usually the alga exhibited a short lag-phasefollowed by logarithmic growth. However, when transferred fromauto- to heterotrophic conditions a lag-period of about 45 dayswas observed with the sugar alcohol dulcitol. Similarly, longlag-periods were also noticed for strain 074 G grown on D-mannitoland for strain 074 W grown on D-ribose. The length of the lag-phaseis a function of the length of the previous culture under autotrophicconditions. This enormous versatility in the heterotrophic growthof Galdieria sulphuraria presents an ideal system to study themetabolism of rare sugars and sugar alcohols. (Received November 21, 1994; Accepted March 9, 1995)     

The Effect of Glucose on Cell Division in Chlorella vulgaris, Beijerinck (Emerson Strain)

Cell division in cultures of the Emerson strain of Chlorellavulgaris is markedly inhibited following inoculation into aglucose medium under conditions which are sub-optimal for autotrophicgrowth. Dry-weight accumulation is not inhibited and the resultis the production of cells considerably larger than those occurringin a glucose-free medium. The more closely the conditions ofculture approach those which are saturating for autotrophicgrowth, the less pronounced is the glucose effect. Evidenceis presented which suggests that the heterotrophic utilizationof glucose may be the dominant form of nutrition during theglucose-induced inhibition of cell division. It is suggestedthat the difference in response to glucose recorded under variousconditions of culture may be a reflection of the extent of glucosesuppression of photosynthesis under the various conditions.The possibility is discussed that the light requirement forcell division shown by this strain may be linked with photosynthesis.     

Ultrastructural Modifications of Plastids and Starch Metabolism during the Microsporogenesis of Ophrys lutea (Orchidaceae)

Ultrastructure of plastids has been studied throughout microsporogenesisof Ophrys lutea Cav. (Orchidaceae). A typical dedifferentiation/redifferentiationcycle of plastids was observed. At prophase I, plastids of pre-meiocytesgradually lost starch and separated the meiocytes through cytomicticchannels. At meiosis, plastids dedifferentiated to protoplastsand redifferentiated in young microspores. During pollen grainformation and maturation a cycle of starch accumulation/degradationoccurred; the mature pollen grain is starchless. Results arediscussed in terms of genetic inheritance following haploidnuclear state and in terms of carbohydrate metabolism. Plastids, starch, microsporogenesis, ultrastructure, Ophrys lutea, Orchidaceae     

The Effect of Low Temperature upon Starch, Sucrose and Fructan Synthesis in Leaves

Measurements on plants in a temperature gradient tunnel showthat diurnal accumulation of starch in illuminated leaves wasgreatly reduced at temperatures below 8 °C, whereas sucrosesynthesis was less affected under similar conditions. High chillingsensitivity for leaf starch accumulation was observed in a numberof chilling resistant temperate species. Enzymes of sucroseand fructan metabolism from mature leaves of Lolium temulentumwere less strongly inhibited at low temperatures than enzymesinvolved in starch synthesis. These results are discussed inrelation to carbon partitioning in species which grow and aremetabolically active at chilling temperatures. Lolium temulentum, starch, sucrose, fructan, temperature, enzyme activity, carbon partitioning     

Changes of Starch Localization within the Chloroplast Induced by Changes in CO2 Concentration during Growth of Chlamydomonas reinhardtii: Independent Regulation of Pyrenoid Starch and Stroma Starch

To understand the physiological function of the pyrenoid, aprotein complex in algal chloroplast stroma with surroundingstarch sheaths, the effects of environmental conditions on thepyrenoid and pyrenoid starch were investigated in the unicellulargreen alga Chlamydomonas reinhardtii. Pyrenoid starch was rapidlyaccumulated within 5 hours when the extracellular CO₂ concentrationwas lowered from 4% to ordinary air level (0.04%). Startingwith high-CO₂ grown cells containing well-developed stroma starchgranules, degradation of stroma starch and accumulation of pyrenoidstarch were observed in parallel during the adaptation to lowCO₂ condition. This pyrenoid-starch accumulation was light dependentand completely inhibited by DCMU. The starch relocalizationprocess was reversible, but the breakdown of pyrenoid starchwas slower than its accumulation. The time courses of accumulation(or degradation) of starch around the pyrenoid paralleled increases(or decreases) in carbonic anhydrase (EC 4.2.1.1 [EC] ) activity,and the pyrenoid starch accumulation is thought to be one ofthe adaptation phenomena to CO₂ concentration. When nitrogenassimilation was inhibited, stroma starch and total starch contentincreased, while that of pyrenoid starch decreased. These resultsindicate that the synthesis and degradation of the two formsof starch were regulated independently by the environmentalconditions. ADP-glucose starch synthase (EC 2.4.1.21 [EC] ) activitywas detected at a physiological level, but the change of starchlocalization could not be explained by total starch synthaseactivity nor by starch-degrading enzyme activities. We assumethat starch metabolism around the pyrenoid is regulated independentlyfrom that in other stromal spaces. (Received May 16, 1988; Accepted July 17, 1988)     

Seed Development in a Shrunken Endosperm Barley Mutant

Seg8 is one of eight barley (Hordeum vulgare L.) mutants whoseendosperm development is affected by the maternal plant genotype.This study was initiated to determine the nature and onset ofabnormal development to provide a basis for further studiesaimed at understanding the mechanism of genetic control. Seeddevelopment and synthesis and accumulation of reserve substanceswere compared between seg8 and its normal counterpart, cv. Klages.Light microscopic examination showed that the mutant phenotypeappeared as early as 4 d after anthesis (DAA), and seg8 graindry weight was significantly lower than cv. Klages by 8 DAA.Grain cell number was significantly lower in seg8 by 8 DAA,indicating an early termination of cell division. The mutanthad a lower starch concentration and higher sucrose concentration,also evident at 8 DAA. Rates of [¹⁴C]sucrose incorporation intostarch in excised half seeds were similar in both genotypesat 2 and 4 DAA, but at 8 and 12 DAA seg8 had a lower rate. Totalprotein concentration was not significantly different betweenthe two genotypes throughout endosperm development. These resultsindicate that the mutation affects cell division and starchaccumulation prior to 8 DAA. It is not known if the reductionin starch biosynthesis and accumulation results from a reducedcapacity for starch or a defect in starch biosynthesis. Hordeum vulgare L., barley, shrunken endosperm mutant, endosperm development, starch, protein, endosperm cell number     

Root Respiration and Carbohydrate Status of Two Wheat Genotypes in Response to Hypoxia

To investigate root respiration and carbohydrate status in relationto waterlogging or hypoxia tolerance, root respiration rateand concentrations of soluble sugars in leaves and roots weredetermined for two wheat (Triticum aestivum L.) genotypes differingin waterlogging-tolerance under hypoxia (5% O₂) and subsequentresumption of full aeration. Root and shoot growth were reducedby hypoxia to a larger extent for waterlogging-sensitive Coker9835. Root respiration or oxygen consumption rate declined withhypoxia, but recovered after 7 d of resumption of aeration.Respiration rate was greater for sensitive Coker 9835 than fortolerant Jackson within 8 d after hypoxia. The concentrationsof sucrose, glucose and fructose decreased in leaves for bothgenotypes under hypoxia. The concentration of these sugars inroots, however, increased under hypoxia, to a greater degreefor Jackson. An increase in the ratio of root sugar concentrationto shoot sugar concentration was found for Jackson under hypoxicconditions, suggesting that a large amount of carbohydrate waspartitioned to roots under hypoxia. The results indicated thatroot carbohydrate supply was not a limiting factor for rootgrowth and respiration under hypoxia. Plant tolerance to waterloggingof hypoxia appeared to be associated with low root respirationor oxygen consumption rate and high sugar accumulation underhypoxic conditions.Copyright 1995, 1999 Academic Press Oxygen consumption rate, sugar accumulation, Triticum aestivum L., waterlogging tolerance     

Starch Accumulation and Photosynthetic Activity in Primary Leaves of Bean (Phaseolus vulgaris L.)

The effects of starch accumulation on photosynthesis and chloroplastultrastructure were studied in primary leaves of bean (Phaseolusvulgaris L. cv. Bulgarian). De-topping the shoot above the primaryleaf node, caused over an 8-day period, a considerable increasein the photosynthetic activity of the primary leaves, despitethe fact that a large quantity of starch had accumulated intheir chloroplasts. The accumulation of starch was greater inthe chloroplasts of spongy cells in comparison with that ofthe palisade cells. Initiation of starch grains was observedmainly in the peripheral part of the chloroplast, distant fromthe cell wall. As a result, most of the starch was accumulatedclose to the inner part of the cell, leaving a considerablemass of the chloroplast near the cell wall free of starch. Theaccumulation of starch was accompanied by the destruction, deformationand disorientation of grana and thylakoids. It is concludedthat the accumulation of starch is not inevitably a limitingfactor in photosynthesis and the results cast doubt on the hypothesisthat starch accumulation or dissipation is the main factor involvedin the regulation of photosynthesis. Phaseolus vulgaris L, bean, photosynthesis, starch accumulation, chloroplast ultrastructure     

Changes of Starch and Sorbitol in Leaves Before and After Removal of Fruits from Peach Trees

Changes in contents of nonstructural carbohydrates in leaves,as well as some characteristics of leaves before and after fruitremoval, were investigated in potted peach (Prunus persica L.)trees. Leaf area and dry mass per unit leaf area (SLW) at thefruit-maturation stage decreased with increasing numbers ofpeaches per tree, whereas the chlorophyll content per unit areain leaves of fruiting trees increased. The chlorophyll contentdecreased more rapidly upon removal of fruit than that in leavesof fruiting trees. The starch content per unit dry mass in leavesof fruiting trees at the fruit-maturation stage was lower thanthat in leaves of non-fruiting trees. Starch accumulated significantlyin leaves within 1 d of removal of fruit during the fruit-maturationstage and continued to increase thereafter. The accumulationof starch after removal of fruit occurred more rapidly thanthe decrease in chlorophyll content. Reducing and non-reducingsugars (total sugars) per unit dry mass in the leaves were higherin fruiting trees than in non-fruiting trees. After fruit removal,the total sugar content of leaves increased temporarily andthen gradually decreased. The sorbitol content per unit freshmass in leaves of fruiting trees during the fruit-maturationstage was slightly higher than that in leaves of non-fruitingtrees. One day after removal of fruit, the sorbitol contentincreased in parallel with the accumulation of starch and remainedhigh. The sucrose content of leaves did not change markedlyupon removal of fruit. Prunus persica L.; peach leaves; nonstructural carbohydrate; starch and sorbitol; fruit removal     

Studies in Stomatal Behaviour: II. THE ROLE OF STARCH IN THE LIGHT RESPONSE OF STOMATA

The relationship between starch-content and aperture in thestomata of Pelargonium has been investigated by a quantitativetechnique. Heath's suggestion of an inherent diurnal rhythmin starch-content is confirmed, and the light effect which hasbeen the subject of previous contradictory reports is foundto be dependent on external humidity. When humidity is high,light (which in these experiments is confounded with reducedC0₂-content) causes a striking reduction in stomatal starch;when humidity is low, light has no effect on starch, but itseffect on aperture is unchanged. No evidence for any dependenceof aperture on carbohydrate status was obtained, and it is suggestedthat the function of carbohydrate changes in stomata is, asearlier suggested by Kisselew, the amplifying and stabilizingof changes primarily controlled by other factors.     

Seasonal Concentrations of Non-structural Carbohydrates of Five Actinidia Species in Fruit, Leaf and Fine Root Tissue

To characterize seasonal patterns of carbohydrate concentrationsin Actinidia species from different natural habitats, leaf,fruit and fine root tissue samples from five species (A. arguta,A. deliciosa, A. chinensis, A. polygama and A. eriantha) werecollected over one season, and analysed for fructose, glucose,sucrose, myo -inositol and starch concentrations. Sucrose andstarch peaked in leaf tissue around flowering time. In fruit,hexose sugars and/or myo -inositol transiently increased earlyin development. Starch accumulated in fruit of all species,beginning sooner after anthesis in A. arguta and A. polygamathan in the other species. Sucrose accumulation coincided withonset of net starch degradation in A. arguta but was delayedin the other species. At final fruit sampling, concentrationsof glucose and fructose were greater than sucrose in all speciesexceptA. arguta . myo -Inositol concentrations constituted >10%of total sugars for most of the season in leaf and fruit tissuesof all species except A. polygama. Fine roots of A. arguta andA. polygama contained significantly more starch and sucrosefor most of the year than those of the other species. Observeddifferences in seasonal carbohydrate patterns may reflect differentnatural habitats, with A. arguta and A. polygama growing naturallyin colder climates than the other species. Transient accumulationof sugars in fruit during early stages of development has beenconsidered to act as primary osmoticum for cell expansion. However,the presence of only low sugar concentrations in A. erianthaquestions this hypothesis. Copyright 2000 Annals of Botany Company Actinidia arguta, Actinidia deliciosa, Actinidia chinensis, Actinidia eriantha,Actinidia polygama , kiwifruit, carbohydrates, fruit, leaves, fine roots, seasonal     

Simulation of water-bloom formation in the cyanobacterium Microcystis aeruginosa

A mechanism for buoyancy increases in the cyanobacterium Microcystisaeruginosa and the associated formation of surface water-bloomsis presented. The mechanism is based on considering a responsetime in the rate of carbohydrate accumulation. When irradianceincreases, the Microcystis cells may require time to increasetheir rate of carbohydrate accumulation. If irradiance decreasesbefore adjustment, the maximum rate of carbohydrate accumulationis not reached. Colony buoyancy increases during mixing whenthe time scales of the light fluctuations are shorter than theresponse time. To examine the mechanism, a model of Microcystisbuoyancy that incorporates the response time has been coupledwith a hydrodynamics model that simulates mixing. The modelwas applied to a shallow lake to show that a prolonged episodeof intense mixing caused the simulated Microcystis coloniesto become excessively buoyant. Once the mixing subsided, thecolonies accumulated at the surface. Decreases in carbohydratewere reduced in large colonies as their size afforded buoyancyforces that could readily overcome the entraining forces ofthe mixing.     

Enhanced accumulation of starch and total carbohydrates in alginate-immobilized Chlorella spp. induced by Azospirillum brasilense: I. Autotrophic conditions

The effect of the microalgae-growth promoting bacterium Azospirillum brasilense on accumulation of total carbohydrates and starch in two species of Chlorella (Chlorella vulgaris and Chlorella sorokiniana), when the bacterium and each microalga were jointly immobilized in alginate beads was studied under autotrophic conditions for 144h in synthetic medium. The interaction of the bacterium with the microalgae enhanced accumulation of total carbohydrate and starch. Cells of Chlorella accumulated the highest amounts of carbohydrate after incubation for 24h. Yet, this did not coincide with the highest affinity and volumetric productivity measured in these cultures. However, after incubation for 72h, mainly in jointly immobilized treatments of both microalgae species, the cultures reached their highest total carbohydrate content (mainly as starch) and also the highest affinity and volumetric productivity. These results demonstrate the potential of A. brasilense to affect carbohydrates and starch accumulation in Chlorella spp. when both microorganisms are co-cultured, which can be an important tool for applications of microalgae.     

Physiology and Ultrastructure of an Oxygen-resistant Chlorella Mutant under Heterotrophic Conditions

The oxygen-resistant strain of Chlorella sorokiniana (Shihira and Krauss), distinguished by its ability to grow autotrophically under high partial pressures of oxygen, was studied and partially characterized in heterotrophic culture. Ultrastructural analysis of glucose-grown oxygen-resistant strain and wild type cells reveals that osmiophilic deposits (possibly polyphosphate) are present only in wild type, while oxygen-resistant strain apparently contains increased amounts of starch and endoplasmic reticulum. Of major physiological significance are the observations that: (a) oxygen-resistant strain requires 6 to 8 days to completely adapt to dark, heterotrophic conditions, whereas wild type acclimates in 1 day; (b) oxygen-resistant strain is resistant to high oxygen tension only when grown on glucose, but not on acetate; and (c) the respiratory rate, but not the photosynthetic rate, of heterotrophic oxygen-resistant strain is abnormal compared to wild type.     

Influence of Carbon Dioxide Concentration on Growth, Carbohydrate Content, Translocation and Photosynthesis of White Clover

White clover ramets were grown at various carbon dioxide concentrations(200, 350 and 1000 µl 1^–1), defoliated and regrownat the same concentrations. Morphological characteristics, dryweights and non-structural carbohydrate contents of plant organs,diurnal variation of sugar and starch content of leaves, translocationof assimilates and photosynthesis were determined. Carbon dioxide concentration influenced the dry weights, butnot the number and size of the plant organs. However, defoliationof plants at low carbon dioxide concentration resulted in decreasedleaf size and stolon length. Carbon dioxide concentration influencedthe content and diurnal variation of starch and sugar in theleaves. Starch was accumulated at medium carbon dioxide concentrationand sugar at a higher concentration when the storage capacityfor starch seemed to be exceeded. Starch was preferentiallyaccumulated in the first and sugar in the second half of thelight period. Translocation was decreased during the periodsof accumulation. Sugar accumulation in the leaves seemed tobe a consequence of the imbalance between sink and source, whereasstarch accumulation seemed to follow an in-built diurnal pattern.Accumulation of both starch and sugar during the photoperiodwas followed by degradation and export during the dark period.Decreased dark export occurred at low carbon dioxide concentrationwhen neither starch nor sugar was accumulated during the photoperiod. Carbon dioxide, white clover, Trifolium repens L., growth, carbohydrates, starch, sugar, translocation, photosynthesis     

Seasonal Changes of the Metabolites in the Leaves, Bark and Xylem Tissues of Olive Tree (Olea europaea. L) II. Carbohydrates

Seasonal changes of starch and soluble carbohydrates in leaves,bark and xylem tissues of olive tree were examined during acomplete annual cycle. Leaf starch and soluble carbohydrateswere detected at high levels during the spring and autumn metabolicallyactive periods. The low level of leaf starch in combinationwith the drastic reduction of soluble carbohydrates and mannitol,defined the summer period of the low metabolic state of thetree. The low leaf starch level in conjunction with the risensoluble carbohydrate levels in leaves in winter were associatedwith cold acclimation processes. The bark and xylem tissueswere performing as starch deposition sites, and differencesin the extent of starch accumulation in these tissues were detectedduring the seasons. The starch fluctuations in bark and xylemwere discussed in relation to the translocation of metabolitesand other physiological processes. Mannitol, the most abundantleaf carbohydrate, was examined in relation to the reducingsugars exported to the bark. The bark mannitol was examinedin conjunction with the sucrose, glucose and starch levels inthe maturing bark tissues and was correlated to the low wintertemperatures. During the winter there was a drastic reductionof mannitol circulation from the bark to xylem. Olive tree, Olea europaea, L, carbohydrates     

Properties of Phosphoenolpyruvate Carboxylase and Carbohydrate Accumulation in the C3-CAM Intermediate Sedum telephium L. Grown Under Different Light and Watering Regimes

A comparison of the activity and properties of the enzyme phosphoenolpyruvatecarboxylase (PEPC) was made for plants of Sedum telephium L.grown under low (70 µmol m^–2 s^–1) or high(500µmol m^–2 s^–1) PPFD and subjected to varyingdegrees of water stress. Under well-watered conditions onlyplants grown under high PPFD accumulated titratable acidityovernight and the extractable activity of PEPC was almost 2-foldhigher in these plants than in plants grown under low PPFD.Increasing drought stress resulted in a substantial increasein the activity of PEPC extracted both during the light anddark periods and a decrease in the sensitivity to inhibitionby malic acid. The magnitude of these changes was determinedby the severity and duration of drought and by light intensity.A comparison of the kinetic properties of PEPC from severelydroughted plants revealed that plants droughted under high PPFDhad a lower K_m for PEP than plants under low PPFD. Additionof 2·0 mol m^–3 malate resulted in an increase inthe K_m for PEP, with plants draughted under low PPFD havinga significantly higher K_m in the presence of malic acid comparedto those under high _PPFD. Response to the activator glc-6-P,which lowered the K_m for PEP, also varied between plants grownunder the two light regimes. Under well-watered conditions PEPCextracted from plants under high PPFD was more sensitive toactivation by glc-6-P than those under low PPFD. After the severedrought treatment, however, the K_m for PEP in the presence ofglc-6-P was similar for enzyme extracted from plants grown underboth light regimes. Soluble sugars and starch were depletedovernight and were both possible sources of substrate for PEPC.With increasing drought, however, the depletion of starch relativeto soluble sugars increased under both light regimes. The propertiesof PEPC and the characteristics of carbohydrate accumulation/depletionare discussed in relation to the regulation of CAM in S. telephiumgrown under different light and watering regimes. Key words: PEP carboxylase, CAM, carbohydrates, Sedum telephium     

Changes of Carbohydrates in Pepper (Capsicum annuum L.) Flowers in Relation to Their Abscission Under Different Shading Regimes

Abscission of pepper flowers is enhanced under conditions oflow light and high temperature. Our study shows that pepperflowers accumulate assimilates, particularly in the ovary, duringthe day time, and accumulate starch, which is then metabolizedin the subsequent dark period. With the exception of the petals,the ovary contains the highest total amounts of sugars and starch,compared with other flower parts and contains the highest totalactivity, as well as activity calculated on fresh mass basis,of sucrose synthase, in accordance with the role of this enzymein starch biosynthesis. Low light intensity or leaf removaldecreased sugar accumulation in the flower and subsequentlycaused flower abscission. The threshold of light intensity fordaily sugar accumulation in the sink leaves was much lower thanin flowers, resulting in higher daytime accumulation of sugarsin the sink leaves than in the adjacent flower buds under anylight intensity, suggesting a competition for assimilates betweenthese organs. Flowers of bell pepper cv. ‘Maor’and ‘899’ (sensitive to abscission) accumulatedless soluble sugars and starch under shade than the flowersof bell pepper cv. ‘Mazurka’ and of paprika cv.‘Lehava’ (less sensitive). The results suggest thatthe flower capacity to accumulate sugars and starch during theday is an important factor in determining flower retention andfruit set. Pepper; Capsicum annuum L.; abscission; shading; pepper flowers; ovary; leaves; sugars; starch; acid invertase; sucrose synthase