Photoorganotrophic growth of a blue-green alga, Anabaena variabilis

By training Anabaena variabilis in the presence of glucose andcasamino acids, the cells became proliferable without a supplyof CO₂. Their growth under these conditions was not affectedby CMU and their growth rates were linearly proportional tothe light intensity, inferring that this growth was independentof photosystem II action and its nutritional mode was of photoorganotrophicnature. The process of transition to this nutritional mode includedat least two consecutive stages: relief from the susceptibilityto organic substances which initially evoked arrest of cellgrowth, followed by the shift of cellular metabolism to organotrophy.In cells grown photoorganotrophically, the contents of phycobilinpigments decreased to nearly one-fifth as much as that of lithotrophicallygrown cells with concomitant degradation of the activity ofphotosynthetic oxygen evolution, while the chlorophyll contentsremained less altered. Accompanying these results, the activityfor incorporating external amino acids into cellular proteinswas enhanced several hundred times. Neither in the dark norin anaerobiosis was this organotrophic growth permitted butwhen light too dim to support lithotrophic growth was supplied,the organotrophic growth was affected at a slow but discerniblerate. (Received August 2, 1974; )     

Electron donor-specificity observed in photosystem I reactions of membrane fragments of the blue-green alga Anabaena variabilis and the higher plant Spinacea oleracea

Electron donating activities of plastocyanins and c-type cytochromesof various organisms for photosystem I reactions were studiedwith membrane fragments of the blue-green alga Anabaena variabilisand the higher plant Spinacea oleracea. In the Anabaena photosystem I reaction, basic but not acidicplastocyanin and c-type cytochromes acted as efficient electrondonors, while only acidic redox proteins were active in thespinach photosystem I reaction. The selective reactivity ofredox proteins in the two photosystem I reactions was observedwith both plastocyanin (or cytochrome) limited and saturatedconditions. These data support our previous observation that photosystemI of blue-green algae differs from those of other green plantswith respect to specificity to the proteinous electron donor(1). (Received August 17, 1971; )     

Organic Acid Exudation by Wild Herbs in Response to Elevated Al Concentrations

In acidic soils, monomeric aluminium (Al³⁺) can reach levelsthat are toxic to plants, thus preventing many species fromgrowing there. Organic acids chelate Al and render it non-toxic.It has been shown that exudation of organic acids by Al-tolerantcrops increases their tolerance to Al. We have extended thisobservation to wild plants by comparing the ability of ten herbsto exude organic acids in response to elevated Al levels. Wehypothesized that exudation of organic acids was related tothe ability of plants to grow on Al-rich soils. Two grasseswere grown in rhizotrons in soils with 41 and 63 µM reactiveAl. Organic acids were sampled from root tips connected to anintact plant-root system.Deschampsia flexuosa (L.) Trin. exudedmore malic acid when grown in the soil with the highest Al content.Five forbs and five grasses were also exposed to three Al levels(0, 25 and 75 µM) in a hydroponic system.Rumex acetosellaL. and Viscaria vulgaris Bernh. increased exudation of oxalicacid and Galium saxatile auct. non L. and Veronica officinalisL. increased exudation of citric acid in response to elevatedAl. The distribution of the forbs in the field as describedby soil pH was negatively related to the amount of organic acidsexuded in response to Al. In contrast, none of the grasses exudedhigher amounts of organic acids with increasing Al concentrationin the hydroponic experiment. Copyright 2001 Annals of BotanyCompany Citrate, malate, aluminium detoxification, rhizotron, hydroponics, rhizosphere, Carex pilulifera,Deschampsia flexuosa , Festuca gigantea, Galium saxatile, Geum urbanum, Holcus mollis,Milium effusum , Rumex acetosella, Veronica officinalis, Viscaria vulgaris     

Sample preservation for determination of organic compounds: microwave versus freeze-drying

In search of a reliable drying method, which might be used evenunder field conditions, microwave drying was compared to freeze-dryingof plant material. Leaves of Ananas comosus and Avicennia germinansas well as buds and phloem of Acer pseudoplatanus were usedand checked for one or more of the following substances: sugars,sugar alcohols, organic and amino acids, total nitrogen, andglycinebetaine. With most samples good agreement was achieved between the twodrying methods. Only in the case of the Ananas comosus leaves,which exhibited low pH and high water content, did appreciabledifferences occur in organic and amino acids. Besides that,sucrose was the compound most susceptible to alterations, whichwas especially evident when leaves of Sambucus nigra were driedin the two different compartments (condenser compartment, dryingbell jar) of the freeze-dryer in use. For Ananas comosus leaf samples it was shown that microwavingcan also be used prior to extraction of tissue sap. Key words: Microwave, freeze-drying, drying method, tissue sap, organic solutes     

Studies on the Hill reaction of membrane fragments of blue-green algae V. A correlation between the solubilization of a photochemically active chromoprotein (ACP) and the inactivation of photosystem II activity in membrane fragments of Anabaena cylindrica

The relationship between a photochemically active chromoprotein(ACP) (cf. ref. 1) and photosystem II was investigated withmembrane fragments of Anabaena cylindrica, A. variabilis andP. boryaman. ACP was solubilized from membrane fragments of A. cylindricabut not from those of A. variabilis or P. boryanum, when themembrane fragments had been incubated in a dilute buffer andhad lost their Hill or photosystem II activity. In A. cylindrica,ACP-solubilization always occurred, independent of photosystemII inactivation, on incubation of the membrane fragments inmedia without PEG. However, the amount of ACP solubilizationaccompanying photosystem II inactivation was twice that withoutphotosystem II inactivation. The increase in ACP solubilizationaccompanying photosystem II inactivation. The kinetics resembledthose for the decrease in 695 nm fluorescence emitted by membranefragments at — 196?C (cf. 2). The ACP solubilized independent of photosystem II inactivationwas assumed to have been released during disruption of intactcells in the preparation of membrane fragments. The slow ACPsolubilization upon the inactivation of photosystem II was attributedto the pigment being bound to membranes. We assume that thephoto-reactive component of ACP, P690 (cf. 3, 4), is releasedfrom the membranes during photosystem II inactivation, and thatP690 is a component of photosystem II which emits the 695 nmfluorescence at — 196?C. (Received March 22, 1974; )     

Further investigation of the light-induced cytochrome b-559 reaction in membrane fragments of the blue-green alga Anabaena variabilis

Oxidation-reduction reactions of the low redox potential cytochromeb-559 were studied for membrane fragments of the blue-greenalga Anabaena variabilis. Cytochrome photooxidation was observableat room temperature when the membrane fragments had been preincubatedat room temperature in the dark. A CCCP addition (10^–4M) strongly enhanced the reaction. Oxidation consisted of a DCMU-sensitive and an insensitive reaction.The former depended on actinic illumination of short wavelength.The latter showed a dependency on longer wavelength light. Theformer was assumed to be induced by the action of photosystemII and the latter by that of photosystem I. The photosystem II oxidation was small before preincubation,and was enhanced by added DPIP or Ferro. This was interpretedas photosystem II action inducing oxidation as well as reduction;reduction being inactivated during dark incubation or beingsuppressed by added redox reagents which compete for electronacceptance from photosystem II so that oxidation was apparentlyenhanced. The oxidationreduction reactions of this cytochromewith low redox potential were assumed to be almost identicalwith those of the high redox potential form, at least in themembrane fragments of Anabaena variabilis. (Received June 8, 1975; )     

Storage of Pollen Grains in Organic Solvents: Effect of Organic Solvents on Leaching of Phospholipids and its Relationship to Pollen Viability

In vitro germinability and membrane integrity (as revealed bythe fluorochromatic reaction (FCR) test) of pollen grains ofCrotalaria retusa L. stored in various organic solvents forsix months at –20±2 °C were studied and correlatedwith leaching of lipids, phospholipids, sugars and free aminoacids from pollen grains into organic solvents during storage.Pollen grains stored in organic solvents with low dielectricconstants (a measure of their non-polar nature), such as hexane,cyclohexane and diethyl ether, showed high scores for germinationand FCR and very little leaching of phospholipids, sugars andamino acids. Pollen grains stored in solvents with high dielectricconstants (a measure of their polar nature) such as isopropanoland methanol did not show germination or positive FCR scores,but showed extensive leaching of phospholipids, sugars and freeamino acids. The viability of pollen grains stored in organicsolvents seems to be determined largely by the effect of theorganic solvents on pollen phospholipid composition, which inturn affects membrane integrity and consequently pollen viability. Crotalaria retusa, organic solvents, pollen storage, viability, phospholipids     

Carotenoids and fatty alcohols as non-ionic hydrophobic inhibitors of photochemical activities of chioroplasts

Carotenoids and fatty alcohols were added to intact spinachchloroplasts in suspension, and the effects of these reagentson the absorption spectrum and photochemical activities of chloroplastswere examined. The addition of lutein, ß-caroteneand neoxanthin transformed a chlorophyll a form (C684) havingan absorption maximum at 684 nm into C666, and the activityof photosystem II decreased parallel with this transformation.The activity of photosystem I was completely unaffected by theeffect of added carotenoids, whereas both cyclic and non-cyclicphotophosphorylations were inhibited by the additions. Theseeffects were reproducibly observed only with a "petroleum ether-soluble"fraction of each carotenoid, monomeric and less polymerizedforms, which are soluble in petroleum ether at –25°C;the "insoluble" fraction of more polymerized forms was ineffective.Comparative experiments with lutein, DCMU and CCCP as inhibitorsand the dependence of inhibition on light intensity suggestedthat the site of inhibition by carotenoids is on the water sideof photosystem II between its reaction center and the CCCP-inhibitingsite. Fatty alcohols with carbon atoms between 8 and 12 producedstronger but less specific effects on the spectrum and activities.At low concentrations the uncoupling of photophosphorylationoccurred and, in a middle concentration range, the activityof photosystem II decreased with the transformation of C684into C666 and with a change in carotenoid bands. At higher concentrations,where the enhanced activity of photosystem I decreased froma maximum to zero, the red band of chlorophyll a further changedin a complex manner and the absorption around 503 nm decreased.We, thus, deduced that C684 and some endogeneous carotenoidsare associated with photosystem II on its water side and thatadded carotenoids and fatty alcohols at lower concentrationschange their states, resulting in the inhibition of this photosystem. (Received December 20, 1971; )     

Effects of Far-red Light on the Labelling of Acyl Lipids during the Greening of Barley (Hordeum vulgare)

Etiolated Hordeum vulgare (barley) Plants were greened underwhite light or far-red (> 700 nm) light. Exposure to far-redlight inhibited chlorophyll synthesis (especially chlorophyllb) and the development of photosystem II which were seen whengreening took place under white light. Primary leaves were detachedand the labelling of their acyl lipids from [¹⁴C]acetate wasstudied under white light or far-red light illumination. Greeningwith far-red light caused a reduction in the radiolabellingof polyunsaturated fatty acids and diacylgalactosylglycerol.Total fatty acid labelling rates were unaffected. Phosphatidylethanolamine,which was normally poorly labelled, accounted for up to 15 percent of the total radioactivity in acyl moieties of lipids inleaves greened with far-red light. The results are discussedin connection with the role that acyl lipids may play in normalthylakoid structure and function. Hordeum vulgare, barley, acyl lipids, white light, far-red light, chloroplasts, thylakoids     

Sites of electron donation by alkylhydroquinones in the electron transport chain of spinach chloroplasts

Alkyl derivatives of p-hydroquinones were examined as electrondonors for the electron transport chain in spinach chloroplasts.Hydrophobic hydroquinones with long side chains donate relativelymore electrons to photosystem 1, while hydrophilic hydroquinoneand methylhydroquinone donate electrons specifically to photosystem2. ¹On leave; Research Laboratories, Fuji Photo Film Co., Ltd.,Asaka, Saitama. (Received March 2, 1973; )     

Immunological Quantification of Proteins Related to Light-Harvesting Chlorophyll a/b Protein Complexes of the Two Photosystems in Rice Mutants Totally and Partially Deficient in Chlorophyll b

Ten rice chlorina mutants of Type I, which totally lack chlorophyllb and hence are unable to synthesize light-harvesting chlorophylla/b protein complexes of photosystem II (LHC-II), containedmRNA for proteins related to LHC-II. Immunoblotting with anantiserum, which had been raised against the 24 and 25 kDa apoproteinsof LHC-II and found to cross-react with the 26 kDa protein ofLHC-II and the 20 and 21 kDa apoproteins of light-harvestingchlorophyll a/b protein complexes of photosystem I (LHC-I),revealed that all the five proteins related to LHC-Iand LHC-IIwere present in reduced amounts in the Type I mutants. ThreeType HA mutants, which have a chlorophyll a/b ratio of 10, weremore abundant in the apoproteins, while three Type IIB mutantswith the ratio of 15 were heterogeneous in terms of the apoproteincontent. All the chlorina mutants contained less P700 comparedwith the wild type rice, but were relatively more abundant inthe LHC-I proteins than the LHC-II proteins. The results showthat all the rice chlorina strains are mutants of chlorophyllb synthesis and the deficiency of chlorophyll b differentlyaffects accumulation of the apoproteins of LHC-I and LHC-II.To balance light absorption between the two photosystem, lossof LHC-II is partly counter-balanced by a decrease in the numberof PSI complexes in the mutants. (Received January 21, 1988; Accepted April 28, 1988)     

Functional development of photosystems I and II in dark-grown pine seedlings

Green plastids prepared from seedlings of Pinus silvestris harvestedafter three weeks of growth in the dark, without exposure tolight, catalyzed photoreductions of methyl viologen and nicotinamide-adeninedinucleotide phosphate, and cyclic photophosphory-lation withN-methylphenazonium methosulfate, but could not catalyze thephotoreduction of 2,4-dichlorophenol indophenol in the absenceand presence of diphenylcarbazide. In dark-grown seedlings ofPinus silvestris, functional photosystem I developed with noexposure to light, but no photosystem II activity was abserved. (Received August 22, 1973; )     

Studies on cytochromes in photosynthetic electron transport system II. Participation of photosystem I in the light-induced oxidation-reduction of cytochrome b559 in spinach chloroplasts

The role of photosystem I in the photooxidation-reduction reactionsof cytochrome b₅₅₉ was elucidated by studying the effects ofelectron acceptors and inhibitors of photosystem I on reactionsof the cytochrome in spinach chloroplasts. We concluded thatthe cytochrome is photoreduced through photosystem I and, inthe presence of DCMU and ferrocyanide, is photooxidized by photosystemI. (Received December 20, 1972; )     

Contents of Cytochromes, Quinones and Reaction Centers of Photosystems I and II in a Cyanobacterium Synechococcus sp.

The contents of photosystem I and photosystem II reaction centers,cytochrome c-553, cytochrome c-550, cytochrome f, cytochromeb-559, cytochrome b-563, plastoquinone and vitamin K₁ in thecyanobacterium Synechococcus sp. were determined. About threephotosystem I reaction centers were present for each photosystemII reaction center. The amounts of cytochromes functioning betweenthe two photosystems were approximately half those of the photosystemI reaction center. Plastocyanin was not detected, while plastoquinoneand vitamin K₁ were present in excess of other electron carriersand reaction centers. The results indicate the importance ofplastoquinone and cytochrome c-553 for cooperation of the tworeaction centers through electron transport. ¹Present address: Toray Basic Research Laboratory, 1111 Tebiro,Kamakura, Kanagawa 248, Japan. (Received June 17, 1982; Accepted January 17, 1983)     

Direct Evaluation of Effects of Fatty-Acid Unsaturation on the Thermal Properties of Photosynthetic Activities, as Studied by Mutation and Transformation of Synechocystis PCC6803

Glycerolipids of thylakoid membranes isolated from the cyanobacteriumSynechocystis PCC6803 contained high levels of dienoic and trienoicC₁₈ fatty acids, in addition to saturated C₁₆ and monoenoicC₁₈ fatty acids. A mutant (Fadl2) of this cyanobacterium wasdefective in the desaturation of C₁₈ fatty acids at the ¹² position,and its thylakoid membranes lacked trienoic acids and containeda very reduced level of dienoic acids. A derivative strain ofFadl2 (Fadl2/desA), which had been transformed with a gene fordesaturation at the ¹² position, fully recovered the abilityto desaturate the fatty acids in the glycerolipids of thylakoidmembranes. The thermal properties of the photosynthetic activitiesof the mutant and the transformant were compared with thoseof the wild-type strain. Despite great diversity in the extentof unsaturation of fatty acids between the wild-type, Fadl2,and Fad12/desA strains, no significant differences were foundeither in the temperature dependence of photosynthesis or inthe heat stability of photosynthetic, photosystem II and photosystemI activities. These results demonstrate that the trienoic fattyacids and, probably, the dienoic acids of the lipids in thethylakoid membrane do not affect the thermal properties of theabove-mentioned activities of photosynthesis. ³Permanent address: Institute of Plant Physiology, BiologicalResearch Center of Hungarian Academy of Sciences, H-6701 Szeged,P.O. Box 521, Hungary (Received August 9, 1990; Accepted December 7, 1990)     

Exposure of the Cyanobacterium Synechocystis PCC6803 to Salt Stress Induces Concerted Changes in Respiration and Photosynthesis

In order to survive and to grow in the presence of a high salinity(550 mM NaCl) Synechocystis PCC6803 increases its energeticcapacity. The salt-induced increase of electron transport ratesinvolves both cytochrome c oxidase and photosystem I. In contrast,electron transport rates measured through complexes I plus IIIof the respiratory chain, or through the photosystem II pluscytochrome b₆f complexes of the photosynthetic chain, do notshow appreciable changes. The time at which changes in electrontransport rates occur in the photosystem I and cytochrome coxidase complexes after the onset of salt stress indicates similaritiesin the adaptation of dark respiration and (cyclic) photosyntheticelectron flow. Given an increase of whole cell respiration andof PSI cyclic electron flow larger than the neosynthesis ofcytochrome aa3 and PSI reaction centers would predict, it appearsthat both adaptations require more than just synthesis of thesetwo complexes. (Received April 12, 1993; Accepted August 10, 1993)     

Chloroplast development in 4-thiouridine-cultured radish seedlings III. Photochemical activities in isolated plastids

Accumulation of chlorophyll, development of photosystem I andII activities and contents of chloroplastic components wereinvestigated in greening radish seedlings germinated and grownwith 4-thiouridine (4SU). The development of photosystem I activityprior to that of photosystem II was observed also in the 4SU-culturedgreening radish cotyledons in which chlorophyll accumulationwas inhibited up to 60–80% of that of the control. Photochemicalactivities expressed on a plastid protein basis decreased withthe increase of 4SU in the culture medium. In contrast to ferredoxinand ferredoxin-NADP reductase, which were present in significantamounts in the treated cotyledons, chloroplastic cytochromes(f, b₅₅₉ and b₆ decreased in the plastids from 4SU-culturedcotyledons. These results suggest that 4SU interferes in partwith protein synthesis in plastids and thereby with chloroplastdevelopment. (Received December 4, 1979; )     

Light-induced Changes of the Electrical Potential in Chloroplasts Associated with the Activity of Photosystem I and Photosystem II

The electric potential changes induced by flashing and continuouslight were measured with microcapillary electrodes in isolatedwhole chloroplasts of Peperomia inetallica. In continuous lightthe chloroplast electrical potential rose in two phases. Theinitial rapid phase coincided in extent with the flash-inducedpotential and was insensitive to the electron transfer inhibitorDBMIB. The subsequent phase was relatively slow (20–30ms) and was inhibited by DBMIB. Electron acceptors of photosystemII (p-phenylendiamine, p-benzoquinone) added to DBMIB-treatedchloroplasts produced a suppression of the flash-induced responseand a considerable increase in the steady level of the potentialin the light. The electrical potential associated with the activityof photosystem II rose in continuous light much more slowlythan that associated with the activity of photosystem I aloneor the activities of both photosystems. Illumination of chloroplastswith successive flashes at a repetition rate 5 Hz in the presenceof oxaloacetate, a terminal acceptor of photosystem I, was accompaniedwith a gradual decline of the flash-induced potential. The specificrole of two photosystems in the light-induced H⁺ transport andthe electrogenesis across the chloroplast thylakoid membranesis discussed.     

Changes in the Organic Acid Content of some Cultivated Plants Induced by Mineral Ion Deficiency

Four plant species (Zea mays, Lolium italicum, Phaseolus vulgaris,and Pisum sativum) were grown either with full nutrient supplyor with calcium, potassium, or nitrogen deficiency. After 4–6weeks the shoots were analysed for their content of K⁺, Ca²⁺,Mg²⁺, and Na⁺, of total anions, and of organic acids. The qualitativepattern of organic acid components, characteristic of each species,remained, with few exceptions, unchanged by deficiency treatments.Striking differences were detected in the total acid contentand in the quantities of the respective main organic acid components,especially in potassium-deficient plants. These changes showedstrong correlations with alterations of cation excess and demonstratethat aconitate in Zea mays, malonate in Phaseolus vulgaris,and citrate in Pisum sativum contribute to charge balance.