Inhibition of Tonoplast and Plasma Membrane H$-ATPase Activity in Rice (Oryza sativa L.) Culture Cells by Local Anesthetics

Tonoplast and plasma membrane vesicles were prepared from rice(Oryza sativa L. var. Yuukara) culture cells with step sucrosegradient (30% and 42.9%, w/v) and/or step dextran T-70 gradient(1% and 8%, w/w) to determine the inhibition of tonoplast andplasma membrane AT-Pases by local anesthetics. The degree towhich the anesthetics inhibited these ATPases was of the followingorder: dibucaine>lidocainetetracaine>procaineGABA. Dibucaineranging in concentration from 0.2 nui to 2 mM inhibited tonoplastATPase activity more than plasma membrane ATPase, the half inhibitionsbeing 0.8 and 1.1 mM, respectively. The K_m values of tonoplastand plasma membrane ATPases were not affected by dibucaine,but various values were noted for V_max. Dibucaine inhibitedtonoplast and plasma membrane ATPases solubilized from 0.1%DOC pellet by n-octylglucoside and zwittergent 3–14, respectively.The addition of a phospholipid mixture (asolectin) to solubilizedboth ATPases had no effect on the inhibition by dibucaine. Thus,local anesthetics may act directly on the ATPase moiety withoutlipid mediation. (Received June 15, 1987; Accepted November 13, 1987)     

Isolation of Subunits of Coupling Factor 1 from Maize and Spinach Chloroplasts and Properties of Combinations of Subunits with ATPase Activity

Subunits (, ß, ) and mixtures of subunits ( ß, , ß , ß ) were isolated without denaturationfrom a chloroform extract of chloroplast coupling factor 1 (CF₁)from maize (Zea mays var. Ushiku 5-4) and from spinach by fastprotein liquid chromatography (FPLC), on an anion-exchange columnof Mono-Q in the presence of n-octylglucoside (OG) and on achromatofocusing column of Mono-P. The ß -subunitcomplex (CF¹ ß ) was the minimum unit required forATPase activity, as was confirmed by the reconstituted complexof ß and subunits. An subunit isolated from maizeinhibited the ATPase activity of CF₁ ß from bothmaize and spinach. CF₁ ß was found to contain anOG-dependent Mg²⁺-ATPase. The ATPase activity of CF₁ ß required divalent cations, such as Mg²⁺ or Mn²⁺, for its expressionin the presence of OG; its optimum pH was 8.0 and it was markedlyinhibited by NaN₃. The enzyme hydrolyzed ATP in prefernece toGTP but not CTP, UTP, ADP, AMP or pNPP. Lineweaver-Burk plotsof its activity were curvilinear in the range of 0.6–0.7mM ATP.Mg²⁺. ¹Present address: Department of Biology, School of Education,Waseda University, Shinjuku-ku, Tokyo, 160 Japan. (Received February 15, 1989; Accepted April 20, 1989)     

Uptake of Thallium, a Toxic Heavy-Metal, in the Cyanobacterium Synechococcus R-2 (Anacystis nidulans, S. Leopoliensis) PCC 7942

Uptake of the toxic heavy-metal, thallium, was studied in thecyanobacterium Synechococcus R-2 (PCC 7942) using clinicallyavailable ²⁰¹Tl ⁺. Thallium was found to distribute across theplasmalemma passively, and so the accumulation ratio of theion ([Tl⁺]_i/[Tl⁺]_o) could be used to calculate the apparentmembrane potential (­_i,o) of the cells (^ETI⁺_i,o = ­_i,o).The permeability of the plasmalemma to TI⁺ (^PTI⁺ 1 to 5 nms^–1)is higher than that of K⁺. Valinomycin does not increase thepermeability of TI⁺. Transient changes in the ­_i,o of cells,because of electrogenic transport of ions, could be detectedfrom its effects upon the uptake rate of TI⁺. HCO^–₃ hyperpolarizedSynechococcus cells, whereas NH⁺₄, CH₃NH⁺, and K⁺ led to depolarization.The use of TI⁺ as a reporter of ­_i,o has some inherent limitations.Tl⁺ is toxic at very low concentrations (inhibitory effectsare apparent after about 6 h at concentrations as low as 1 mmolm^–3). The rate of equilibration is slow (t_1/25 to 20 min).Equilibration of TI⁺ takes about 2 h, which limits its valueas a membrane potential probe. Large amounts of TI⁺ bind tothe surface of the cells making the method impracticable formeasuring accumulation ratios of less than about 10 (­_i,o)values smaller than about –60 mV). Cultures continuouslyexposed to Tl⁺ (10 mmol m^–3) eventually become TI⁺ resistantby actively extruding TI⁺ (µTI⁺_i,o= –3±0.2kJ mol^–1) and so thallium cannot be used as a ­_i,oprobe in such cells. (Received October 28, 1997; Accepted August 31, 1998)     

Purification by Affinity Chromatography of {alpha}-Amylase--A Main Amylase in Cotyledons of Germinating Vigna mungo Seeds

In Vigna mungo cotyledons, the -amylase activity increased markedlyduring germination at 27°C in the dark, while the activityof other amylases was very low. The -amylase was purified from4-day-old cotyledons by affinity chromatography on epoxyactivatedSepharose 6B substituted with rß-cyclodextrin andby column chromatography on Bio-Gel P-200. Gel filtration andpolyacrylamide gel electrophoresis showed that the enzyme existsmostly as a monomer (43,000 daltons), but partially aggregatesto form dimer, trimer and further multimers. Ca²⁺ protectedthe -amylase against heat inactivation. Incubation of the enzymewith 5 mM EDTA or dialysis against 10 mM EDTA resulted in a50–90% loss of activity. The inactivation was partiallyreversed by the addition of Ca²⁺. Other properties, such asthe amino acid composition, K_m value, pH optimum and activationenergy were similar to those of other plant -amylases. (Received May 6, 1981; Accepted June 22, 1981)     

Variation in Natural Abundance of 15N among Plant Parts and in 15N/14N Fractionation during N2 Fixation in the Legume-Rhizobia Symbiotic System

Sixteen legumes were grown in N-free media so that N was suppliedentirely by symbiotic N₂ fixation. The plant tissues were analyzedfor natural ¹⁵N abundance (expressed as ¹⁵N per mil relativeto air N₂) with a ratio mass spectrometer. The nodules of desmodium,centro, siratro, soybean and winged bean showed high enrichmentin ¹⁵N (+9), while red clover showed slight enrichment (+2).The nodules of 9 other forage legumes (Townsville stylo, whiteclover, alsike clover, common vetch, Chinese milk vetch, senna,alfalfa, ladino clover, and hairy vetch) showed little enrichmentin ¹⁵N. In all the legumes investigated, particularly in the ureide-transportingplants such as desmodium, centro, siratro, soybean, winged beanand field bean, the ¹⁵N value of the shoots was negative (–3.2).The ¹⁵N value of the shoots in winged bean and field bean variedby about 1 depending on the Rhizobium strains used. The isotopicmass balance of 13 legumes indicated that isotopic fractionationoccurs during N₂ fixation by the legume-rhizobia symbiosis witha preference for ¹⁴N over ¹⁵N, resulting in a ¹⁵N value of –0.2to –2 in the whole plant. The results indicate that ¹⁵N/¹⁴N isotopic discrimination witha preference for the lighter atom may occur in both N₂ fixationand export of fixed N from nodules. ¹Present address: Department of Soils and Fertilizers, NationalAgriculture Research Center, Kannondai, Tsukuba, Ibaraki 305,Japan. (Received October 8, 1985; Accepted April 7, 1986)     

An NTP-Binding Protein That Cross with a Ras-Specific Antibody in the Myceia of Neurospora crassa

A Ras-related NTP-binding protein was partially purified froma membrane fraction derived from the mycelia of Neurospora crassa.[-³²P]ATP and [-³²P]GTP were incubated with mem brane and solublefractions which were then irradiated with UV light to inducecrosslinking of tightly bound nucleotides. After SDS-polyacrylamidegel electrophoresis, blotting onto a nitrocellulose filter andautoradiography it was apparent that most of the proteins thatbound [-³²P]-GTP also bound [-³²P]ATP. Pretreatment of the membranefraction with Ras-specific antibody effectively blocked thebinding of [-³²P]ATP and [-³²P]GTP to several ATP-GTP-bindingproteins. The band of a protein with a molecular weight of 26kDa on the SDS-polyacrylamide gel cross-reacted strongly withthe Ras-specific antibody. The protein was extracted from thegel and further purified by repeated gel electrophoresis. Thepurified protein bound [-³²P]ATP, [-³²P]-GTP, [-³²P]CTP and[-³²P]UTP at 1.6x10^– M and was autophosphorylated in thepresence of [-³²P]ATP and [-³²P]GTP at 1.7x10 M. Pretreatmentof the protein with Ras-specific antibody partially blockedthe autophosphorylation in the presence of these nucleotides.The binding of [-³²P]ATP to the NTP-binding protein was blockedby addition of ATP at 10^–4–10^–3 M. ATP ata concentration of 10^–4 M prevented the binding of [-³²P]to a greater extent than did GTP at the same concentration.Binding of [-³²P]CTP and [-³²P]UTP to the protein was also observed. (Received October 7, 1991; Accepted July 14, 1992)     

Pumpkin (Cucurbita sp.) seed globulin III. Comparison of subunit structures among seed globulins of various Cucurbita species and characterization of peptide components

Various Cucurbita seed globulins showed patterns similar toone another on SDS-gel electrophoresis, and ß bandsfor unreduced globulins and , ', and ' bands for reduced ones.On gel electrophoresis in 6 M urea, reduced globulin gave twoacidic and two basic bands. These corresponded to and ' chainsand ₁ and ₂ chains, respectively, identified by two-dimensionalurea-SDS gel electrophoresis. The compositions of the and ßsubunits were proposed. (Received September 8, 1977; )     

Effects of Gibberellins and Prohexadione on the Activities of Oryzain and {alpha}-Amylase in Rice Seeds

Oryzains, cysteine proteinases of rice seeds, are induced byGA₃ in germinating rice seeds [Abe et al. (1987) Agric. Biol.Chem. 51: 1509]. The effects of GA₁, GA₃, GA₄, GA₉, and GA₂₀on the production of oryzain and -amylase were investigatedin embryoless half- and whole-seeds of rice (cv. Nipponbare).When gibberellins (GAs) were incubated with embryoless half-seeds,GA₁, GA₃ and GA₄ induced oryzain and -amylase, but GA₉, andGA₂₀ did not. GA₉ and GAM induced oryzain and -amylase productionin whole seeds, but this production was inhibited by the simultaneousapplication of prohexadione, an inhibitor of 2ß- and3ß-hydroxylation of GAs. Prohexadione did not inhibitthe activities of oryzain and -amylase induced by GA₁. Theseresults suggest that GAs possessing the 3ß-hydroxylgroup induce activities of oryzain and -amylase in rice seedsand that GA₉ and GA₂₀ have activity only after they are convertedmetabolically to active GAs, probably GA₄ and GA₁, respectively.GA₁, was more active than GA₄ in both half seeds and wholeseeds incubation. Oryzain and -amylase activities induced byGA₄ were significantly inhibited in the presence of 10^–4M prohexadione. This suggests that the conversion of GA₁, toGA₄ (13-hydroxylation) might be inhibited at a high dose ofprohexadione in whole seeds. ⁴Present address: Institute of Food Development, Kyung Hee University,Suwon 449-701, Korea     

Pumpkin (Cucurbita sp.) seed globulin V. Proteolytic activities involved in globulin degradation in ungerminated seeds

Two proteolytic activities I and II involved in the globulindegradation were detected in pumpkin seeds. Activity I, hydrolyzing and ß subunits of the globulin to form F_ß,was found in both dry seeds and cycloheximide-treated cotyledons,and decreased during germination. Activity II, hydrolyzing F_ßto produce small peptides and amino acids, was not observedin dry seeds but found in cycloheximide-treated cotyledons,increased up to 4 days, and gradually decreased during germination. Activity I gave limited hydrolytic products from the globulinand the chain, but not from F_ß, the chain and some animal proteins. It was inhibitedby EDTA. On the other hand, activity II hydrolyzed F_ßand the chain faster than the globulin, the chain and some animal proteins. It was inhibitedby EDTA and p-chloromer-curibenzoate, and activated by ß-mercaptoethanol,dithiothreitol and CoCl₂. Optimum pH's were at about 6.8 andat 6.0 to 6.8 for activities I and II, respectively. The degradation process of the globulin can be divided intotwo steps: the first step is the conversion of globulin to F_ßand the second step, F_ß to small peptides and aminoacids. (Received November 9, 1979; )     

A Rapid and Sensitive Method for Determination of Relative Specificity of RuBisCO from Various Species by Anion-Exchange Chromatography

A rapid and sensitive method to determine the relative specificity() of ribulose 1,5-bisphosphate carboxylase/oxygenase (RuBisCO)using anion-exchange chromatography is described. We employedthe open gas system for the reaction of RuBisCO to get the mostreliable CO₂ and O₂ concentrations in the reaction mixture.3-Phosphoglycerate and 2-phosphoglycolate which were formedin the RuBisCO reaction were completely separated and directlymeasured with anion-exchange chromatography without using radioisotopes.The determination of the value was accomplished in 3 h. The values of RuBisCO enzymes from higher land plants were between90 and 96, and those from bacteria including cyanobacteriumwere close to 45. These values were in agreement with previouslyreported values. The enzyme of the red macroalga Porphyra yezoensisexhibited a value of over 140, as expected from the reportedvalue of the enzyme from the red microalga Porphyridium cruenteum.RuBisCO from the green macroalga Ulva pertusa had a value closeto 70 and similar to that of the enzyme from the green microalgaChlamydomonas reinhardtii. ⁴On leave from Research and Development Center, Unitika Ltd.,23 Kozakura, Uji, Kyoto, 611 Japan. ⁵Present address: Nara Institute of Science and Technology,8916-5 Takayama-Cho, Ikoma, Nara, 630-01 Japan     

An {alpha}-Glucan from Suspension-Cultured Rice Cells

An -glucan was isolated from 11-day-old suspension-culturedrice cells by extraction with hot Na-phosphate buffer (pH 6.8).The -glucan had []_D=+234? (C = 0.14, in water) and its averagemolecular weight was estimated to be about 1.4 ? 10⁴, basedon elution characteristics on acalibrated Sepharose CL-6B column.Upon partial acid hydrolysis, the -glucan gave mainly malto-oligosaccharides.The maximum absorption of the iodine complex of the -glucanin the presence of Na₂SO₄ was at 470 nm. The results of hydrolysisby , ß- and iso-amylases and methylation analysisindicated that the isolated -glucan is a highly branched polysaccharidewith an average chain length of 9. The exterior and interiorchain lengths of the -glucan were calculated to be 5 and 3,respectively. (Received July 23, 1986; Accepted February 7, 1987)     

Pumpkin (Cucurbita sp.) seed globulin IV. Terminal sequences of the acidic and basic peptide chains and identification of a pyroglutamyl peptide chain

Pumpkin seed globulin is composed of heterogeneous polypeptidechains, acidic and chains and basic ₁ and ₂ chains (12). This study showed that the basicchains had similar N-terminal sequences, Gly-Leu-Asp-Glu-Thr-Ile-for the ₁ chain and Gly-Leu-Glu-Glu-Thr-Ile- for ₂. On the contrary,the N-terminal sequences of the acidic and chains were dissimilar, Ile-Gln-Gly-Tyr- for the chain and no N-terminal residue for the chain, according to routine terminal analysis. Pyrrolidonylpeptidase digestion of the chain and its thermolysin digestion followed by Edman degradationsrevealed that the N-terminal sequence of the chain was < Glu-Ile-Glu-Gln-Gln-Glu-Pro(Trp,Ser)-. The N-terminal sequences and the C-terminal residuesindicated that the acidic and chains were more heterogeneous than the basic ₁ and ₂ chains.A preliminary study on the degradation of storage globulin isalso presented. (Received November 9, 1979; )     

Nucleoside Triphosphate(NTP)-Binding Proteins and Endogenous ADP-ribosyl Transferase in Neurospora crassa

Nucleoside triphosphate(NTP)-binding proteins were detectedin the crude extract of mycelia of Neurospora crassa, whichwas treated with 1% Lubrol PX and fractionated by gel filtration.Protein fractions showing the capacity to bind [³⁵S]ATPS or[³⁵S]GTPS were designated as AGN1 to 6. The binding of [³⁵S]ATPSor [³⁵S]GTPS was prevented in the presence of 0.1 mM ATP orGTP except that in fractions AGN1 and 2, the presence of GTPstimulated the binding of [³⁵S] ATPS to ATP(NTP)-binding proteins.ATP or GTP was 1 to 2 orders of magnitude more effective thanCTP or UTP in preventing the binding of [³⁵S]GTPS in AGN1, 2and 5. Among these fractions AGN1, 2, 5 and 6 showed activityto hydrolyze 1 nM [–³²P]ATP or [–³²P]GTP. NTP-bindingproteins bound with [³⁵S]ATPS or [³⁵S]GTPS had lower apparentmolecular weights than the same proteins without bound nucleotide.Proteins bound with [³⁵S]ATPS or [³⁵S]GTPS and those [³²P]ADP-ribosylatedby endogenous ADP-ribosyl transferase in each fraction wereanalyzed by SDS-PAGE. About 20 species of ATP or ATP-GTP-bindingproteins were detected, several of which were ADP-ribosylated.The binding of [³⁵S]ATPS or [³⁵S]GTPS to NTP-binding proteinswas confirmed by the comparison of non-boiled and boiled samplesimmediately before loading to SDS-PAGE. ATP, GTP, CTP or UTPat the concentration of 0.1 mM effectively removed [³³S]ATPSor [³⁵S]GTPS bound to NTP-binding proteins. (Received December 10, 1990; Accepted April 18, 1991)     

Regulation of sexual agglutinability in Saccharomyces cerevisiae of {alpha} and {alpha} types by sex-specific factors produced by their respective opposite mating types

The sexual agglutinability of haploid cells of heterothallicSaccharomyces cerevisiae was repressed when they were culturedin the absence of easily fermentable sugars, such as glucoseand mannose. The repression was reversed by the action of hormone-likesubstances of the opposite mating types. The substance producedby mating type cells was identical to subtsance-I which isknown to induce sexual agglutinability of inducible matingtype cells. The mating type cells produce a new hormone-likesubstance which induces or enhances sexual agglutinability of mating type cells. A crude fraction of the mating type-specific substance ( substance-I)was obtained by passing the culture filtrate of mating typecells through Amberlite CG-50 (H⁺ form), followed by elutionwith 1.5 M ammonia. ² On leave from Osaka City University. (Received December 25, 1975; )     

A Transient Stimulation of Net Photosynthesis of Rye Leaves by {alpha}-Hydroxy-2-pyridinemethanesulphonic Acid ({alpha}-HPMS) due to Inhibition of Photorespiratory CO2 Release

The effects of -hydroxy-2-pyridinemethanesulphonic acid (-HPMS)upon net photosynthesis (P_n, the CO₂ compensation point (),post-lower illumination burst of CO₂ (PLIB) and post-lower temperatureburst of CO₂ (PLTB) in detached rye (Secale cereale L.) leaveswere investigated. At low concentrations ( 0.5 mol m^–3),-HPMS initially stimulated P_n and decreased the magnitude ofboth PLIB and PLTB. The decreased at all concentrations of-HPMS (0.05–5.0 mol m^–3. The effects of -HPMS onP_n and were time-dependent and, after a few minutes, the P_nwas inhibited while values increased considerably. At a higherconcentration (5.0 mol m ^–3), the transient effects of-HPMS were shorter () or not observed at all (P_n. Both PLIBand PLTB, when expressed in relation to P_n, increased at higherlevels of this compound. Similar data with respect to the effectsof -HPMS on PLIB and PLTB were found for leaves of dandelion(Taraxacum officinale L.). The results suggest that -HPMS may stimulate P_n by inhibitingphotorespiration, as originally suggested by Zelitch (1966),but only at low concentrations and over a short time span. Thedecrease of PLIB and PLTB values at low -HPMS levels is consistentwith these processes being a residual activity of the glycolatepathway. Key words: CO₂ compensation point, -hydroxy-2-pyridinemethanesulphonic acid, photorespiration, photosynthesis     

Biosynthetic mechanism of glycolate in Chromatium III. Effects of {alpha}-hydroxy-2-pyridinemethanesulfonate, glycidate and cyanide on glycolate excretion

Effects of -hydroxy-2-pyridinemethanesulfonate (-HPMS), 2,3-epoxypropionate(glycidate), and cyanide on the photosynthetic activities ofChromatiumwere studied. -HPMS stimulated photosynthetic CO₂fixation in the bacterial cells in both N₂ and O₂ environments.The formation and subsequent excretion of both glycolate andglycine in the O₂ atmosphere were markedly enhanced by -HPMS.In contrast to a recent report by Zelitch [Arch. Biochem. Biophys.163: 367–377 (1974) ] that glycidate specifically inhibitsglycolate formation in tobacco leaf disks, we found that ithad no influence on CO₂ fixation by Chromatium in either N₂or O₂ atmosphere, and that the synthesis and extracellular excretionof glycolate were markedly stimulated by glycidate treatment.Cyanide (0.01–1 mM) exerted a marked inhibitory effecton photosynthetic CO₂ fixation in N². In O₂ atmosphere, photosynthesiswas stimulated by 0.01 mM cyanide, and inhibited by it abovethis level. Both the incorporation of ¹⁴CO₂ into glycolate andthe total synthesis of glycolate in the light were also enhancedby 0.01 mM cyanide, and strongly inhibited above that concentration. ¹This is paper XXXVI in the series "Structure and Function ofChloroplast Proteins," and the research supported in part bygrants from the Ministry of Education of Japan (No. 111912),the Toray Science Foundation (Tokyo) and the Naito Science Foundation(Tokyo). (Received May 31, 1976; )     

Purification and properties of soluble cytochrome b-560 from spinach leaves

A b-type cytochrome having an -band at 560 nm was isolated fromspinach leaves (Spinacia oleracea). A method is described forpreparing this cytochrome, cytochrome b-560 (spinach), in apurified state. The cytochrome has, in its reduced state, absorption bands at560 nm (), 530 nm (ß) and 427 nm (); and in the oxidizedstate at 562 nm (), 529 nm (ß) and 417 nm (). Thepyridine ferro-haemochrome prepared from cytochrome b-560 hadan -band at 556.5 nm, indicating the protohaem-nature of theprosthetic group. The cytochrome has an oxidation-reduction potential (E'⁰) of+0.13V at pH 7.0, as measured using the ferri-ferro oxalate system. The cytochrome is rapidly reduced on illumination with red orfar-red light in the presence of spinach chloroplasts and isoxidized at a slower rate in the dark. This photoreduction isinhibited by 1x10^–6 M 3-(3,4-dichlorophenyl)-1,1-dimethylurea(DCMU). The molecular weight of the cytochrome is 30,000 asestimated by the dextran gel filtration method. (Received December 3, 1971; )     

Fractionation of Nitrogen Isotopes during the Uptake and Assimilation of Ammonia by Plants

Two varieties (Nihonbare and Koshihikari) of rice plants (Oryzasativa L.) were grown hydro-ponically with two levels (20 and100 mg N liter ^–1) of ammonia. Variations in levels ofnatural abundance of ¹⁵N (¹⁵N) were analyzed in the ammoniaand organic nitrogen of shoots and roots, as well as in theammonia in the culture solution. There was substantial fractionationof nitrogen isotopes during the uptake of ammonia. When plantsabsorbed a large proportion of ammonia from a solution witha low concentration, less negative ¹⁵N values in plants andhigh positive ¹⁵N values in the ammonia remaining in solutionwere observed. The reverse was found when a smaller fractionof ammonia was absorbed from a solution with a higher concentrationof ammonia. The ^l5N values of ammonia in shoots and roots werehigher than in the respective constituent organic nitrogen,suggesting the fractionation of nitrogen isotopes during theassimilation of ammonia. Wild-type and mutant cells of the cyanobacterium(blue-green alga) Synechococcus PCC 7942 were grown in nitrate-or ammonia-containing medium as the source of nitrogen. Fractionationof nitrogen isotopes during the uptake of nitrate was limited,whereas that during the uptake of ammonia was considerable. ¹ In this report, the term ammonia refers indiscriminately toboth NH₃ or NH₄⁺. (Received June 13, 1991; Accepted September 12, 1991)     

Effects of blue light deficiency on acclimation of light energy partitioning in PSII and CO2 assimilation capacity to high irradiance in spinach leaves

Blue light effects on the acclimation of energy partitioningcharacteristics in PSII and CO₂ assimilation capacity in spinachto high growth irradiance were investigated. Plants were grownhydroponically in different light treatments that were a combinationof two light qualities and two irradiances, i.e. white lightand blue-deficient light at photosynthetic photon flux densities(PPFDs) of 100 and 500 µmol m^–2 s^–1. The CO₂assimilation rate, the quantum efficiency of PSII (PSII) andthermal dissipation activity / in young, fully expanded leaves were measured under 1,600 µmol m^–2 s^–1white light. The CO₂ assimilation rate and PSII were higher,while / was lower in plants grown under high irradiancethan in plants grown under low irradiance. These responses wereobserved irrespective of the presence or absence of blue lightduring growth. The extent of the increase in the CO₂ assimilationrate and PSII and the decrease in / by high growth irradiance was smaller under blue light-deficient conditions. These resultsindicate that blue light helps to boost the acclimation responsesof energy partitioning in PSII and CO₂ assimilation to highirradiance. Similarly, leaf N, Cyt f and Chl contents per unitleaf area increased by high growth irradiance, and the extentof the increment in leaf N, Cyt f and Chl was smaller underblue light-deficient conditions. Regression analysis showedthat the differences in energy partitioning in PSII and CO₂assimilation between plants grown under high white light andhigh blue-deficient light were closely related to the differencein leaf N.     

An electrophysiological study of the membrane in aplanospore-like cell of Boergesenia forbesii

Membrane potential and resistance, each of which was the sumof those of the plasmalemma and tonoplast, measured in the coenocyticthallus of Boergesenia forbesii were 6.7 mv inside positiveand 2.8 k.cm², respectively. Protoplasm squeezed from the thallus into artificial sea water(ASW) formed numerous spherical bodies, which are termed aplanospore-likecells (simply "spores"). The following electrical propertiesof the "spores" 20–40 hr after squeezing were obtained:potential difference (p.d.) across plasmalemma (E_co) was –66mv (– means inside negative), plasmalemma resistance 665cm², p.d. across the tonoplast (E_vc) +73 mv, and tonoplast resistance2.6 k.cm². Tenfold increase in external [K⁺] caused +45 mv changein E_co and +17 mv in E_vc. The plasmalemma was entirely depolarizedin Ca⁺⁺-free ASW or ASW containing Triton X-100. When the "spore" was immersed in potassium-rich (277 mil) ASW,E_co was almost zero and the tonoplast showed two states (I andII, E_ve about +70 mv and +20 mv, respectively). E_vc went backand forth between the two states spontaneously or when a smallcurrent was applied. In most cases oscillatory changes in E^vcoccurred after the lapse of a long time in the K+-rich sea water.Membrane resistances in states I and II were 5 and 9 k.cm²,respectively. (Received July 11, 1977; )