Effect of some inhibitors on kanamycin formation byStreptomyces kanamyceticus

The formation of kanamyein is markedly inhibited by mercuric chloride, sodium iodoacetate, 2,4-dinitrophenol, sodium arsenite and sodium azide particularly when these are added at the start of fermentation. Less inhibition of kanamyein synthesis is observed in case of sodium 5,5-diethylbarbiturate, malonic acid, sodium arsenate and sodium fluoride. Inhibition of kanamycin synthesis is associated with growth inhibition in case of 2,4-dinitrophenol, sodium arsenite and sodium azide. Bacitracin and D-cycloserine have a stimulatory effect on kanamycin synthesis with slight inhibition of cellular growth. This stimulation might be due to accumulation of cell wall intermediates — aminosugar and sugar — which are shunted to the pathway of kanamycin synthesis. Penicillin lowers kanamycin synthesis by 65 percent as compared with 19 percent reduction of cellular growth. Chloramphenicol has a stimulatory effect at lower concentration (20 μg/ml), when it is added at 24 h of fermentation. At higher concentration (60 (μg/ml) chloramphenicol shows marked inhibition of both cellular growth and antibiotic biosynthesis.     

Endogenous light-on rhythm in respiration of a long-day duckweed, Lemna gibba G3 II. On basic and rhythmic components of the rhythm

Effects of respiratory substrates (glucose, malate, citrateand pyruvate) and inhibitors (fluoride, iodoacetate, azide andDNP) on the O₂-uptake rhythm in a long-day duckweed,Lemna gibbaG3 in continuous light period were examined. Rates of O₂-uptake at the starting point (6 hr after the beginningof a continuous light period) and at the time of the first peakof the rhythm (18 hr after the beginning of a continuous lightperiod) were equally increased by exogenous substrates. Sensitivityof respiration to fluoride or iodoacetate was almost the sameat the 6th and 18th hr. The O₂-uptake (at the 6th, 18th, 30thand 42nd hr) was increased by DNP by the same amount. Azideat lower concentrations than 5X10^–4 M did not affect O₂-uptakeat the 6th hr, but inhibited uptake at the 18th hr. In the presenceof 5 X 10^–4 M of azide the rates of O₂-uptake at the 18th,30th or 42nd hr were down to the rate at the 6th hr, which wasinsensitive to azide. These results suggest that the O₂-uptakerhythm consists of two components, i.e. the basic respirationwhich is promoted by exogenous substrate, sensitive to DNP andinsensitive to azide; and rhythmic respiration, which is sensitiveto azide, but is not influenced by exogenous substrate and DNP. (Received February 19, 1971; )     

Penetration of naphthaleneacetic acid into pear (Pyrus communis L.) leaves

The penetration of naphthaleneacetic acid (NAA) into pear (Pyruscommunis L. cv. Bartlett) leaves as influenced by selected treatingsolution and environmental factors was studied under definedand controlled conditions. Penetration through the adaxial leafsurface was linear with time, whereas, movement through theabaxial surface was rapid initially and then the rate diminishedwith time. Penetration through both leaf surfaces was proportionalto external concentration and was temperature dependent. MoreNAA penetrated at pH values below than above the pK_a. Light(1000 ft-c) stimulated NAA penetration. The light enhanced penetrationof NAA was depressed by 3-tert-butyl-5-chloro-6-methyluracil,3-(p-chlorophenyl)-1,1-dimethylurea, phenylmercuric acetate,2,4-dinitrophenol, carbonylcyanide m-chlorophenylhydrazone andcarbonylcyanide p-trifluoromethoxyphenylhydrazone. We concludedthat NAA penetration was controlled by both physical and metabolicfactors. ¹ Journal Article No. 5725 from the Michigan Agricultural ExperimentStation. This investigation was supported-in-part by NIH TrainingGrant No. 5 TOI GM 00246 from General Medical Sciences, PublicHealth Service Grant CC 00246 from the National CommunicableDisease Center, Atlanta, Georgia, and Food and Drug AdministrationGrant FD 00223. ² Present address: Department of Plant & Soil Sciences,University of Massachusetts, Amherst, Massachusetts, 01002. (Received November 9, 1971; )     

Studies on Foliar Penetration: VII. FACTORS CONTROLLING THE PENETRATION OF CHLORIDE IONS INTO THE LEAVES OF PHASEOLUS VULGARIS

The pattern of penetration of chloride ions into the abaxialsurfaces of the primary leaves of Phaseolus vulgaris has severalfeatures in common with those previously recorded for 2,4-dichlorophenoxyaceticacid (2,4-D), 2,2-dichloropropionic acid (dalapon), and 4-amino-3,5,6-trichloropicolinicacid (picloram). In the dark the rate of entry of chloride ionsup to 24 h is constant, but in the light entry is at first slowand then more rapid. This acceleration does not occur at lowtemperature or when the tissue is treated with 3-(3,4-dichlorophenyl)-l,l-dimethylureaor phenylmercuric chloride. Neither does it take place at theadaxial surface or when the leaves are more mature. The most distinguishing feature of the pattern of penetrationof chloride ions is its dependence on external pH. In darknessentry is unaffected by changes in pH but in the light the rateof entry is increased as the pH falls, but this response isrestricted to young leaves. No binding of chloride seems tooccur within the tissue. These findings support the view that penetration of the abaxialsurface in young leaves of Phaseolus is largely determined bya membrane system. This system decreases in importance as theleaf matures and the overlying cuticle thickens. At the adaxialsurface the thicker cuticle is seemingly a major barrier topenetration even in very young leaves.     

Studies on Foliar Penetration: VI. FACTORS CONTROLLING THE PENETRATION OF 4-AMINO-3,5,6-TRI-CHLOROPICOLINIC ACID (PICLORAM) INTO THE LEAVES OF PHASEOLUS VULGARIS

The evaluation of the factors controlling the penetration of4-amino-3,5,6-trichloropicounic acid (picloram), containing¹⁴C in the carboxyl group, into leaves of Phaseolus vulgarisis complicated by the ability of the leaf tissue to decarboxylatethe compound rapidly. The degradation system becomes fully activatedonly after some hours following treatment with picloram whilethe capacity for decarboxylation declines with the age of theleaf. When allowance for decarboxylation is made, the pattern of penetrationfor picloram resembles in particular that of 2,2-dichloropropionicacid (dalapon). At the abaxial surface penetration continuesover 24 h at a fairly constant rate but in light, which enhancespenetration, a ‘surge’occurs between the secondand sixth hour. Raising the external concentration promotespenetration and in light entry is directly proportional to concentrationup to at least 2.5 x 10^–l M. The response to varying lightintensity resembles that of dalapon rather than 2,4-D. Evenlow intensities promote penetration; the effect is maximal atabout 10 000 lx at the abaxial surface but continues at leastup to 20 000 lx at the adaxial surface. Penetration is retarded at 4°C but the decarboxylation systemremains functional. In light, but not in darkness, penetrationis strikingly reduced by 3-(3,4-dichlorophenyl)-l,l-dimethylurea(DCMU). Raising the external pH from 4.2 to 7.2 retards entry. It is concluded that the factors which determine the penetrationof picloram into Phaseolus leaves also control the entry ofa wide range of organic compounds and inorganic ions.     

The Effect of Arsenate and Other Inhibitors on Early Events during the Germination of Lettuce Seeds (Lactuca sativa L.)

The effect of arsenate, arsenite, 2,4-dinitrophenol, and anaerobiosis on early events in seed germination was investigated using both intact and punched seeds of lettuce (Lactuca sativa L.). It was found that punching the seed removes penetration barriers to the entrance of inhibitors without an undue loss of germination or light responses. The kinetics of the action of germination inhibitors were established by 2-hour pulse experiments. Arsenate and 2, 4-dinitrophenol have very different kinetics. The inhibition of germination in punched seeds by arsenate given in conjunction with phosphate compared with the lack of inhibition of arsenate plus phosphate on the growing seedling, suggest a distinct metabolic change in the germinating embryo at some time between the onset of germination and subsequent seedling growth.     

Effect of inhibitors of energy metabolism and protein synthesis on the process of neutral red segregation in frog erythrocytes

Effects of inhibitors of energy metabolism and protein synthesis on Neutral red segregation in frog erythrocytes were studied. Inhibitors of both glycolysis and respiration significantly reduced formation of segregation zones. This influence was most striking with antimycin A, rotenone and cyanide. This indicates that intact respiratory pathways may play an important part in the process of Neutral red segregation. Such uncouplers as FCCP (carbonyl cyanide p-trifluoromethoxyphenylhydrazone) and 2,4-dinitrophenol (DNP) as well as inhibitors of oxidative phosphorylation (arsenate and azide) are also very effective in inhibiting the Neutral red segregation at low concentrations. The effects of these uncouplers and of olygomycin suggest an important role of ATP as an energy source for the segregation process. An inhibitor of protein synthesis, such as cycloheximide, produces some reduction in segregation zones formation. Trapping of Neutral red by protonation could readily explain the high level of this dye accumulation in nucleated erythrocytes. The fact that low concentrations of FCCP and DNP inhibit the process of segregation brings a supporting evidence for the possibility of the ATP-driven proton pump involved in Neutral red segregation.     

The Uptake of Growth Substances: X. THE ACCUMULATION OF PHENOXYACETIC ACID AND 2,4-DICHLOROPHENOXYACETIC ACID BY SEGMENTS OF AVENA MESOCOTYL

Segments of Avena mesocotyl were placed in buffered solutionsof phenoxyacetic acid (POA) or 2,4-dichlorophebnoxyacetic acid(2,4-D), containing carbon-14 in the carboxyl group, and thequantities of radioactivity taken up by the tissues measured.With freshly cut segments in solutions of 2,4-D there is accumulationof carbon-14, but the course of uptake is interrupted by a temporaryphase when some of the accumulated 2,4-D is released to theexternal solution. If after cutting the segments are first pretreatedby placing them for about 15 h in buffer, and then transferredto 2,4-D, there is progressive accumulation with no phase ofnet loss. Pretreated segments absorb greater quantities of either 2,4-Dor POA than freshly excised tissues. Following pretreatmentin buffer the course of uptake of POA is linear but for 2,4-Dthe course is curvilinear. However, after pretreatment withnon-radioactive 2,4-D the subsequent rate of uptake of radioactive2,4-D is constant over long periods. The uptake of radioactive2,4-D is largely independent of the concentration of non-radioactive2,4-D given during pretreatment. When segments which have absorbed 2,4-D-1-¹⁴C are transferredto buffer, a relatively small proportion of the carbon-14, the‘mobile fraction’, is released. The amount releasedfollowing different periods of uptake is constant whereas thelevel of non-mobile carbon-14, the ‘residual fraction’,rises progressively in step with accumulation. The uptake of POA and 2,4-D is accompained by the formationwithin the tissues of other radioactive substances. It is concludedthat the residual fraction is composed, at least in part, ofthese metabolic products and that accumulation and metabolicconversion are inter-connected. Dinitrophenol (DNP) slowly and progressively depresses the uptakeof POA whereas the uptake of 2,4-D is very rapidly arrested.However, after about 2 h, in the continued presence of DNP,uptake of 2,4-D restarts but the rate never attains that ofthe control. These divergent effects of DNP indicate that POAand 2,4-D are accumulated by different pathways.     

Calcification in the Green Alga Halimeda: IV. THE ACTION OF METABOLIC INHIBITORS ON PHOTOSYNTHESIS AND CALCIFICATION

The effects of a number of metabolic inhibitors on calcificationand photosynthesis in Halimeda tuna, H. discoidea, and H. macrolobaare described. The inhibitors used are CCCP, DNP, DCMU, azide,cyanide, chloramphenicol, cycloheximide, and Diamox. The effectsof these inhibitors, although complex, are consistent with ourmodel of calcification in Halimeda. Inhibition of photosyntheticCO₂ uptake inhibits calcification as does stimulation of respiratoryCO₂ evolution (i.e. uncoupling). There is also indirect evidencefor the presence of a possible light stimulated H⁺ efflux whichinhibits calcification. The observed calcification rate is thereforethe result of a number of factors which affect the concentrationof CO^–and the pH in the intercellular space of the Halimedathallus. The results obtained with the carbonic anhydrase inhibitor Diamoxprovide further evidence for the effective separation of theintercellular space from the external medium by the appressedperipheral utricles.     

Anoxic Seed Germination of Erythrina caffra: Ethanol Fermentation and Response to Metabolic Inhibitors

Erythrina caffra seeds were shown to be true anaerobic germinators.They exhibit a Pasteur effect, high alcohol dehydrogenase activityand produce high levels of ethanol under anoxia, in which situationgermination starts to be suppressed by as little as 0.1% externallyapplied ethanol. Toxic levels of ethanol production appear tobe prevented by a decrease in the rate of ethanol accumulation.Carbon monoxide does not inhibit germination. Cyanide, SHAM,iodoacetate, pyrazole, and 4-methylpyrazole are more inhibitoryto anoxic than aerobic germination whereas azide, arsenate,and fluoride inhibit both. Azide, pyrazole, 4-methylpyrazoleand a low concentration of cyanide and SHAM tend to stimulateethanol production in air. At 10 mol m^–3, 4-methylpyrazolestimulates anaerobic ethanol production. At higher concentrationsthis compound and all other inhibitors used suppress anaerobicethanol production initially. Inhibition of ethanol productionby 10 mol m^–3 cyanide is paralleled by an accumulationof acetaldehyde. Azide and cyanide appear to exert their inhibitoryeffect at different loci. Key words: Erythrina caffra, anoxic germination, fermentation, metabolic inhibitors     

Short-term Measurements of the Cytoplasmic pH of Chara corallina Derived from the Intracellular Equilibration of 5,5-Dimethyloxazolidine-2,4-Dione (DMO)

Smith, F. A. 1986. Short-term measurements of the cytoplasmicpH of Chara corallina derived from the intracellular equilibrationof 5,5-dimethyloxazolidine-2,4-dione (DMO).—J. exp. Bot.37: 1733–1745. Measurements of the time-course of influx of ¹⁴C-labelled 5,5-dimethyloxazolidine-2,4-dione(DMO) into the cytoplasm and vacuole of internodal cells ofChara corallina, and of efflux of DMO into non-radioactive solutions,have shown that exchange of DMO across the tonoplast is veryrapid compared with exchange across the plasma membrane. Thishas made possible calculations of cytoplasmic pH from distributionof DMO between cytoplasm and vacuole over short periods (5 or10 min) even when intracellular DMO is not at flux equilibriumwith external DMO. Using this new method, estimates have beenmade of the rates and magnitude of: (i) acidification of thecytoplasm caused by acidic growth regulators (IAA and NAA) andby metabolic inhibitors (azide, DNP, CCCP and DCMU), and (ii)alkalinization caused by uptake of ammonium and methylammoniumions. The potential application of the method to future studiesof membrane transport in charophyte cells is assessed. Key words: Charophyles, cytoplasmic pH.     

Induction of DNA synthesis and callus formation from tuber tissue of Jerusalem artichoke by 2,4-dichlorophenoxyacetic acid

Cellus induction was observed from Jerusalem artichoke tubertissue on a synthetic medium containing 2,4-D at 10^–6,10^–5 (optimum conc.) and 10^–4 M. The first DNA synthesis(thymidine incorporation) was observed only at 2,4-D concentrationsof 10^–5 to 10^–4M. In 10^–5 M 2,4-D treatedtissue, DNA synthesis increased after a 20 hr lag and reacheda maximum at 36 hr, after which it decreased. Actinomycin Dand 8-aza-guanine; inhibitors of RNA synthesis, inhibited DNAsynthesis completely. 2,4-D caused the characteristic changesin RNA and protein syntheses. In comparison with the control,RNA and protein syntheses were first repressed then inducedbefore the peak of DNA synthesis. Treatment with cycloheximide(10^–4M) for one hour before inoculation inhibited proteinsynthesis completely for 12 hr; consequently DNA synthesis wasalso delayed. The results suggest that RNA and protein synthesesneeded for callus induction are regulated by 2,4-D in the firstDNA synthesis. (Received July 19, 1973; )     

The Uptake of Growth Substances: VIII. ACCUMULATION OF CHLORINATED BENZOIC ACIDS BY AVENA SEGMENTS: A POSSIBLE MECHANISM FOR THE TRANSIENT PHASE OF ACCUMULATION

If segments from the mesocotyls of Avena sativa are first keptin buffer then the initial rates of uptake of radioactive 2,3,6-trichlorobenzoicacid (2,3,6-TCBA) and 2,4- and 2,5-dichlorobenzoic acids (2,4-DCBAand 2,5-DCBA) are less than those of freshly excised segments.No such effect of pretreatment is found for benzoic acid orfor 2-chlorobenzoic acid (2-CBA). Uptake of 2,3,6-TCBA normallybecomes negative between two and six hours after excision, andthis phase of net loss is prevented by the addition of streptomycin,which also offsets the decline in the rates of uptake of 2,5-DCBAand 2,4-DCBA. In contrast, streptomycin inhibits accumulationof 2-CBA. From a comparison of these results with similar andprior findings for substituted phenoxyacetic acids, it is concludedthat the initial uptake of 2,3,6-TCBA, 2,5-DCBA, and 2,4-DCBAis governed by an unstable accumulatory system (Type 1), whosebreakdown can result either in a phase of net loss during thecourse of uptake, or in a decline in uptake following pretreatment. Net loss of 2,3,6-TCBA is also prevented by synthalin (decamethylenediguanidine dihydrochloride), cetyl trimethyl ammonium bromide(CTAB) and by 2,3,5-triiodobenzoic acid (TIBA). During pretreatment,the presence of streptomycin, synthalin or TIBA prevents a fallin the subsequent uptake of 2,3,6-TCBA, while the addition ofCTAB causes a dramatic increase in uptake. We have proposed for Type 1 accumulation a biochemical mechanismcapable of accounting for the unstable nature of the accumulationand for the protective action of the compounds with cationicnitrogen groups, such as streptomycin, synthalin, and CTAB.     

The Uptake of Growth Substances: VI. A COMPARATIVE STUDY OF THE FACTORS DETERMINING THE PATTERNS OF UPTAKE OF PHENOXYACETIC ACID AND 2,4,5-TRICHOLOROPHEN-OXYACETIC ACID, WEAK AND STRONG AUXINS, BY GOSSYPIUM TISSUES2

Using segments of etiolated hypocotyls of Gossypium, a comparativestudy has been made of the processes which determine the patternsof uptake of a very weak auxin, phenoxyacetic acid (POA), anda very powerful one, 2,4,5-trichlorophenoxyacetic acid (2,4,5-T). When segments are placed in solutions of POA-1-¹⁴C, a continuousincrease in the radioactivity of the tissues is accompaniedby the formation of radioactive metabolities which can be separatedfrom POA by techniques of paper chromatography. At the sametime there is a progressive increase in the amount of radio-activitywhich cannot be removed by transferring the tissues to buffer.Uptake is inhibited by low temperature, anaerobiosis, 2,4-dinitrophenol,and iodoacetate. It is concluded that the accumulation of POAinvolves its metabolic conversion to products which do not readilydiffuse out into the external medium. With 2,4,5-T-1-¹⁴C the radioactivity of the segments at firstincreases rapidly but this is followed after two hours by aphase of rapid decrease. No radioactive metoabolites can bedetected by paper chromatography and all of the ¹⁴C taken upcan be rapidly removed by transfer to buffer. The magnitudeof the decrease in radioctivity during the second phase of uptakeis balanced by a release to the medium of a matched amount ofradioactive 2,4,5-T. Uptake of 2,4,5-T is somewhat less sensitiveto temperature and anaerobiosis than uptake of POA and is bycontrast only slightly inhibited by 2,4-dinitrophenol and iodoacetate. Pretreatment of segments in buffer markedly alters the patternof uptake of 2,4,5-T but not that of POA. It reduces both theamount of 2,4,5-T initially taken up and the amount subsequentlyreleased to the medium. In addition, both net loss of radioactivityduring the course of uptake of 2,4,5-T and the reduction inthe extent of uptake following pretreatment are both arrestedby adding streptomycin, but not by the addition of pencillinor chloramphenicol. It is concluded that the uptake of 2,4,5-T involves reversibleaccumulation by a process whose efficiency decreases with time:the most likely systems are a metabolically linked mechanismfor the active transport across a membrane or reversible adsorptionon specific binding sites.     

ON THE NATURE OF MOSS OXALIC ACID OXIDASE

Moss oxalic acid oxidase freed from catalase by boiling is stronglyinhibited by the "metal-complexing" compounds such as thiocyanate,azide, diethyldithiocarbamate, and hydrosulfite. Inactivatedby dialysis against thiocyanate or azide, the enzyme can bereactivated to a considerable extent by the addition of ferricsalt, cytochrome-c or hemoglobin, not by other metal ions, suchas Cu²⁺, Zn²⁺ , Mn²⁺, and Fe²⁺. Nitrate, chlorate, monoiodoacetate,and iodide also act as strong inhibitors towards moss oxalicacid oxidase. Some enzyme fractions which were obtained by the sodium sulfateprecipitation method were stimulated by Fe³⁺, but not by cytochrome-cor by other metallic ions. This stimulation was inhibited bythiocyanate, azide and monoiodoacetate. ¹ Present address: Biological Institute, University of Toyama,Toyama     

Characteristics of Transport of L-Leucine and Glycine in Pea Protoplasts

The uptake of L-leucine and glycine into pea protoplasts wasstudied under various conditions. The uptake of both L-leucineand glycine was pH dependent with the optimal pH being 4.0 and5.0 for L-leucine and glycine, respectively. A kinetic studyof L-leucine uptake showed that uptake is multiphasic; K_m valuesof different phases were 1.1 mol m^–3, 33.3 mol m^–3and 100 mol m³. A similar analysis for glycine at a concentrationrange of 0.1–10 mol m^–3 also showed a multiphasictransport system for it. The uptake of L-leucine at lower concentrations(between0.1–2.0 mol m^–3) was energy dependent, since arsenate,azide, dinitrophenol and iodoacetate inhibited the uptake. However,the uptake of L-leucine was not inhibited by ouabain at anyconcentration of L-leucine employed. The uptake of glycine wasnot inhibited by any of these inhibitors suggesting that glycineuptake was not mediated by an active process. Key words: Pea protoplast, L-Leucine, Glycine transport, Active transport, Mediated transport     

PROMOTION OF PERITHECIAL INITIALS IN MONACROSPORIUM DOEDYCOIDES BY 6–METHYL PURINE

The promotion of perithecial initials in the imperfect fungus Monacrosporium doedycoides is enhanced by the addition of the RNA synthesis inhibitor 6-methyl purine (6-MP). The addition of two other RNA inhibitors (8-azaguanine and actinomycin-D) causes the promotion of initials but not at the magnitude observed with 6-MP. Application of a protein synthesis inhibitor (cycloheximide), a base analog (5-fluorouracil), or an amino acid analog (p-fluorophenyl-alanine) are not promotive on initial formation and can be inhibitory. The apparent cause for the promotion of perithecial initials in the imperfect fungus is that sexual structures are inhibited by mRNA's synthesized by the organism and the addition of 6-MP prohibits their synthesis.     

L-Leucine Transport in Isolated Protoplasts of Vinca Suspension Culture: Characterization of Uptake

The uptake of L-leucine into Vinca protoplasts was studied undervarious conditions. The uptake was highly pH-dependent, withthe optimal pH between 3.0 and 4.0. The uptake was also energydependent, since azide, 2,4-dinitrophenol (DNP), carbonyl cyanidem-chlorophenyl hydrazone (CCCP), and iodoacetate inhibited theuptake. Oligomycin, N,N'-dicycIohexyI carbodiimide (DCCD) andvanadate, but not ouabain, inhibited the uptake, suggestingthat ATPase for H⁺ electrogenic extrusion was necessary to theuptake of L-leucine. The uptake showed stereospecificity, butwas partially inhibited by other L-amino acids. A kinetic studyof the uptake showed that the uptake was multiphasic with threesaturable phases and one unsaturable phase which occurred atconcentrations of L-leucine over 1 mM. The K_m values of thethree affinity sites were 1.4 x 10^–3 M, 1.3 x 10^–4M, 4.3 x 10^–5 M; the maximum velocity values were 3.3x 10^–8, 4.5 x 10^–9, 1.8 x 10_–9 mol/10 min/4x 10⁶ cells. (Received April 18, 1981; Accepted August 25, 1981)     

Mechanism of L-Lysine Transport by Pea Protoplasts

Dureja, I., Guha-Mukherjee, S. and Prasad, R. 1986. Mechanismof L-lysine transport by pea protoplasts.—J. exp. Bot.37: 549–555. L-Lysine uptake was studied in pea protoplasts to characterizethe transport process. The uptake was pH dependent with optimumat pH 5?8. A kinetic analysis of uptake showed that L-lyslneuptake was biphasic. The respiratory inhibitors, sodium arsenate,azide, iodoacetate and 2, 4, dinitrophenol, inhibited the uptakeof L-lysine at a final concentration of 0?1 mol m^–3 suggestingit to be mediated in part by an active process. Competitiveinhibition of L-lysine uptake by only L-arglnine and of L-leucineand glycine uptake by several amino acids indicated that L-lysineuptake occurs via a specific system whereas the uptake of L-leucineand glycine was mediated through a relatively non-specific permease. Key words: Pea protoplasts, L-lysine transport, active transport, specific system