Plant regeneration from protoplasts isolated from embryogenic suspension cultured cells of Cinnamomum camphora L.

An efficient and reproducible protocol is described for the regeneration of Cinnamomum camphora protoplasts isolated from cultured embryogenic suspension cells. Maximum protoplast yield (13.1±2.1×10⁶/g FW) and viability (91.8±3.8%) were achieved using a mixture of 3% (w/v) cellulase Onozuka R10 and 3% (w/v) macerozyme Onozuka R10 in 12.7% (w/v) mannitol solution containing 0.12% (w/v) MES, 0.36% (w/v) CaCl₂·2H₂O, and 0.011% (w/v) NaH₂PO₄·2H₂O. First divisions occurred 7–10 days following culture initiation. The highest division frequency (24.6±2.9%) and plating efficiency (6.88±0.8%) were obtained in liquid medium (MS) supplemented with 30 g l^–1 sucrose, 0.7M glucose, 0.1 mg l^–1 NAA, 1.0 mg l^–1 BA, and 1.0 mg l^–1 GA₃. After somatic embryo induction and then shoot induction, the protoplast-derived embryos produced plantlets at an efficiency of 17.5%. Somatic embryos developed into well-rooted plants on MS medium supplemented with 1.0 mg l^–1 3-indole butyric acid (IBA). Regenerated plants that transferred to soil have normal morphology.     

Protein turnover in the attached leaves of non-stressed and stressed barley seedlings

Protein turnover was examined, using tritiated water, in various 2-cm regions of 7-11-d-old, first leaves of barley (Hordeum vulgare). Differences were found between the regions in their protein turnover and their responses to stress. The rate constant for degradation for total protein was the same throughout the leaf and the average half-life (t_1/2) of protein=approx. 220 h. Only in the older regions did a 24-h pulse of³H₂O preferentially label protein with a t_1/2 (90 h) considerably shorter than the t_1/2 for total protein. Soluble protein was degraded faster than insoluble protein and contained an appreciable short-lived protein component observable by short-pulse labelling. The rate of protein synthesis was greatest in the cells of the youngest region and declined as each region aged. The mean rate of protein synthesis over the 4-d period was 4 and 7 nmol h^-1 of amino-N with respect to the regions 1–3 and 7–9 cm from the leaf tip. Seedlings, stressed by adding polyethylene glycol (2.0 MPa) to the roots, showed a marked loss of protein from the older leaf regions with only small losses in the younger regions. Amino acids accumulated in the younger region continuously whereas in the older region little accumulation occurred until day 3 of stress when proline levels increased. Protein synthesis was decreased by between 30% and 50% in all leaf regions. In the region 1–3 cm from the leaf tip, the rate of protein degradation of total protein was enhanced and equalled the rate of degradation of 24-h-pulse-labelled protein which was not itself significantly affected by stress (t_1/2=approx. 90 h). In the region 3–5 cm, the degradation of both 4-d and 24-h-labelled protein was enhanced by stress to rates similar to those found in the region 1–3 cm. This was largely through increases in the degradation of the insoluble protein, but the degradation of soluble protein was also raised. Protein degradation in the region 7–9 cm was not affected by stress.Abbreviations t_1/2 average half-life - PEG polyethylene glycol     

Extractive cultivation of Lactococcus lactis using a polyethylene glycol/MgSO4 · 7H2O aqueous two-phase system to produce nisin

To relieve lactic acid inhibition, an aqueous two-phase system (ATPS) was used to grow Lactococcus lactis. Its composition was 11% (w/v) PEG 20000/3.5% (w/v) MgSO₄ 7H₂O. In this ATPS medium, the cells were completely partitioned in the bottom phase, and lactic acid had the biggest partition coefficient of the eight ATPS media tested. The cell biomass in this medium was 0.64 mg ml^–1, only 60% of that of the control medium, but nisin production (803 IU ml^–1) was enhanced by 33%. The increase in nisin was explained as a result of extraction of lactic acid from the bottom phase to the top one. The changes of tie-line length and phase volume ratio for the identical tie line could affect cell growth and nisin accumulation.     

Enhancement of lactic acid production with ram horn peptone by Lactobacillus casei

Ram horns are a waste material from the meat industry. The use of ram horn peptone (RHP) as a supplement for lactic acid production was investigated using Lactobacillus casei. For this purpose, first, RHP was produced. Ram horns were hydrolysed by treating with acids (3 M H₂SO₄ and 6 M HCl) and neutralizing the solutions to yield ram horn hydrolysate (RHH). The RHH was evaporated to yield RHP. The amounts of protein, nitrogen, ash, some minerals, total sugars, total lipids and amino acids of the RHP were determined and compared with a bacto-tryptone from casein. When the concentrations (1–6% w/v) of the RHP were used in bacterial growth medium as a supplement, 2% RHP (ram horn peptone medium) had a maximum influence on the production of lactic acid by L. casei. The content of lactic acid in the culture broth containing 2% RHP (43 g l^–1) grown for 24 h was 30% higher than that of the control culture broth (33 g l^–1) and 10% higher than that of 2% bacto-tryptone (39 g l^–1). RHP was demonstrated to be a suitable supplement for production of lactic acid. This RHP may prove to be a valuable supplement in fermentation technology.     

Culture medium improvement for Isaria fumosorosea submerged conidia production

Submerged conidia and blastospores of the entomopathogenic fungus Isaria fumosorosea are produced in several liquid culture media. However, yields and the ecological fitness of these propagules vary according to culture media composition. In most culture media, hyphae, blastospores and submerged conidia are white but we found that in some media they develop a brown pigmentation. A dark pigment was extracted from brown-pigmented propagules and analyzed by IR spectroscopy. Adsorption bands coincided to those characteristics of melanins.Hadamard's matrices were employed in order to increase submerged conidia yields and brown pigmentation of fungal propagules. Media containing 20–30 mg/l of FeSO₄·7H₂O and 6–12 mg/l of CuSO₄·5H₂O allowed reaching the highest pigmentation (9 in a hedonic scale). A maximal concentration of submerged conidia of 1.0 (±1.2) × 10¹² cell/l was achieved after 120 h of liquid culture in a improved culture medium, containing 25 ml/l of Polyethylene glycol (MW 200), substance which enhanced submerged conidia production, reducing free mycelia or mycelial pellets formation. In the improved medium, it was estimated that more than 60% of produced biomass corresponded to submerged conidia and blastospores, while in other media, mycelia were the main product (80–97%).     

Hydrogen accumulation by H2-uptake negative strains of Rhizobium

Summary Hydrogen evolution from root nodules has been reported to decrease the efficiency of the nitrogen fixing system. Mutants ofRhizobium meliloti andRhizobium leguminosarum were selected which were deficient in H₂-uptake capacity (Hup^–). The relative efficiency of the nitrogen fixation for both species assessed with C₂H₂ reduction was 0.66.The hydrogen production was monitored using a simple root incubation method. As such, hydrogen production up to 3.83 and 15.57 ml.day^–1.g^–1 plant dry weight were recorded forPisum sativum — Rhizobium leguminosarum 4.20 Hup^– andMedicago sativa — Rhizobium meliloti 1.5 Hup^– respectively. In a closed container (250 ml), hydrogen concentrations up to 20% (v/v) could be reached in the root phase ofMedicago sativa in a time period of 320 hours.     

Medium optimization for a methanol utilizing bacterium based on chemostat theory

Summary In the productions of biomass and vitamin B₁₂ using methanol as the sole carbon source, it is necessary to use a medium in which methanol is the growth limiting substrate. Other inorganic salts should be in slight excess so that the yield of cells and the intracellular content of vitamin B₁₂ do not vary. From basic principles of chemostat culture, a medium was optimized for Pseudomonas AM-1 a methanol utilizing bacterium, for the concentrations of various inorganic salts. This was done in a series of chemostat cultures at a dilution rate of 0.1 h^–1. Optimum amounts of NH₄ ⁺, PO₄ ^3- and Mg²⁺ were estimated from the minimum concentration of the salt at which methanol became growth limiting. The optimum concentrations of Ca²⁺, Fe²⁺, Mn²⁺, and Zn²⁺ as a group were determined in the same way. Cu²⁺, Mo⁶⁺, Co²⁺ and B³⁺ are required at concentrations of g/l and they were not studied as these very low level can be introduced as contaminants from other salts. The optimum medium composition (in g/l) was as follows: (NH₄)₂SO₄, 1.0; H₃PO₄, 75×10^–3; MgSO₄ · 7H₂O, 30×10^–3; CaCl₂ · 2H₂O, 3.3×10^–3; FeSO₄ · 7H₂O, 1.3×10^–3, MnSO₄ · 4H₂O, 0.13×10^–3; ZnSO₄ · 7H₂O, 0.13×10^–3; CuSO₄ · 5H₂O, 40×10^–6; Na₂MoO₄, 40×10^–6; CoCl₂ · 6H₂O, 40×10^–6; H₃BO₃, 30×10^–6 and methanol 4.     

Field energetics of a large carnivorous lizard,Varanus rosenbergi

Summary Field metabolic rates (FMRs; CO₂ production) and water influx rates of Varanus rosenbergi were measured seasonally by means of doubly-labelled water (³H₂ ¹⁸O). Metabolic rates and water influexes were highest in summer (0.18 ml CO₂ g^–1 h^–1 and 17.9 ml H₂O kg^–1 day^–1) and lowest in winter (0.04 ml CO₂ g^–1 h^–1 and 6.5 ml H₂O kg^–1 day^–1). FMRs and water fluxes were intermediate in spring. It is estimated that a 1-kg V. rosenbergi would need to consume 4.7 kg of prey each year to remain in energy balance and that the energy commitment to egg production requires a 40% increase in the food acquisition of a gravid female in late spring and early summer. It is calculated that water influxes in summer are totally provided from food but in other seasons, particularly winter, pulmocutaneous water exchange and/or drinking are significant avenues of water intake.     

The production and utilization of nitric oxide by a new,denitrifying strain of Pseudomonas aeruginosa

When a new strain of Pseudomonas aeruginosa was grown aerobically and then transferred to anaerobic conditions, cells reduced NO ₃ ^– quantitatively to NO ₂ ^– in NO ₃ ^– -respiration. In the absence of nitrate, NO ₂ ^– was immediately reduced to NO or N₂O but not to N₂ indicating that NO ₂ ^– -reductase but not N₂O-reductase was active. The formation of the products NO or N₂O depended on the pH in the medium and the concentration of NO ₂ ^– present. When P. aeruginosa was grown anaerobically for at least three davs N₂O-reductase was also active. Such cells reduced NO to N₂ via N₂O. The new strain generated a H⁺-gradient and grew by reducing N₂O to N₂ but not by converting NO to N₂O. For comparison, Azospirillum brasilense Sp7 showed the same pattern of NO-reduction. In contrast, Paracoccus denitrificans formed 3.5 H⁺/NO during the reduction of NO to N₂O in oxidant pulse experiments but could not grow in the presence of NO. Thus the NO-reduction pattern in P. denitrificans on one side and P. aeruginosa and A. brasilense on the other was very different. The mechanistic implications of such differences are discussed.     

Kinetics of BTEX biodegradation by a coculture of <Emphasis Type="Italic">Pseudomonas putida</Emphasis> and<Emphasis Type="Italic"> Pseudomonas fluorescens</Emphasis> under hypoxic conditions

Pseudomonas putida and Pseudomonas fluorescens present as a coculture were studied for their abilities to degrade benzene, toluene, ethylbenzene, and xylenes (collectively known as BTEX) under various growth conditions. The coculture effectively degraded various concentrations of BTEX as sole carbon sources. However, all BTEX compounds showed substrate inhibition to the bacteria, in terms of specific growth, degradation rate, and cell net yield. Cell growth was completely inhibited at 500mgl^–1 of benzene, 600mgl^–1 of o-xylene, and 1000mgl^–1 of toluene. Without aeration, aerobic biodegradation of BTEX required additional oxygen provided as hydrogen peroxide in the medium. Under hypoxic conditions, however, nitrate could be used as an alternative electron acceptor for BTEX biodegradation when oxygen was limited and denitrification took place in the culture. The carbon mass balance study confirmed that benzene and toluene were completely mineralized to CO₂ and H₂O without producing any identifiable intermediate metabolites.     

Bioconversion of acid-hydrolyzed poplar hemicellulose to acetic acid byClostridium thermoaceticum

Summary Clostridium thermoaceticum was used to ferment carbohydrate released from pretreated oat splet xylan and hemicellulose isolated from hybrid poplar. Hydrolysis with dilute sulfuric acid (2.5% (v/v) for oat spelt xylan and 4.0% (v/v) for poplar hemicellulose) at 100°C for 60 min was found to release the highest concentration of fermentable substrate.C. thermoaceticum, when grown in non-pH controlled batch culture at 55°C under a headspace of 100% CO₂, typically produced 14gl^–1 acetic acid during a 48 h fermentation in medium containing 2% xylose. In fed-batch fermentations this organism was able to produce 42gl^–1 acetic acid after 116h when the concentration of xylose was maintained at approximately 2% and the pH was controlled at 7.0.     

Plant Regeneration Through Somatic Embryogenesis in Leaf Derived Callus of Plumbago Rosea

Regeneration of Plumbago rosea L., a rare medicinal plant, via somatic embryogenesis in callus cultures derived from leaf explants was described. Optimum callus formation was achieved on semi-solid Murashige and Skoog (MS) medium supplemented with 0.25 mg dm^–3 kinetin and 2.0 mg dm^–3 1-naphthaleneacetic acid (NAA). Somatic embryogenesis was achieved upon transferring the 4-week-old callus to a medium containing 1.0 mg dm^–3 kinetic (Kn), 0.5 mg dm^–3 gibberellic acid (GA₃) and 0.1 mg dm^–3 NAA. Embryo maturation and germination was achieved on the half-strength MS basal salts supplemented with 0.01 – 0.25 mg dm^–3 Kn and 2 % (m/v) saccharose. An average of 50 – 60 plantlets were obtained from 150 mg of embryogenic callus within 4 week of subculture. Out of the 50 plantlets about 28 survived in the greenhouse.     

Nickel hyperaccumulation in shoot cultures of Alyssum markgrafii

Shoot cultures of Alyssum markgrafii O.E. Shulz, endemic nickel hyperaccumulating species of central Balkan, were established and maintained on Murashige and Skoog medium supplemented with 0.2 mg dm^–3 benzyladenine (BA). Nickel in form of NiCl₂ . 6 H₂O was supplemented at 22 different concentrations ranging from 0.0001 to 15 mM but none of them was lethal to cultures. High Ni²⁺ concentrations (10 mM or more) arrested shoot growth which, upon transfer to Ni-free medium, commenced via axillary bud proliferation. Shoots that developed from axillary buds through the subculture manifested increased tolerance to Ni²⁺ expressed as shoot elongation. Shoot multiplication and dry biomass production decreased with increase of Ni²⁺ in medium. Only the accumulation of Ni²⁺ in tissues increased with Ni²⁺ content of the medium. Apart from shoot cultures, high Ni²⁺ accumulation was registered in undifferentiated callus cultured on medium with 0.5 mg dm^–3 BA and 0.5 mg dm^–3 naphthylacetic acid. Highest content of accumulated Ni was 2.37 g g^–1 (d.m.) in shoots and 2.65 g g^–1 (d.m.) in callus, both measured on medium with 15 mM Ni²⁺.     

Effect of pH,aeration and sucrose feeding on the invertase activity of intactS. cerevisiae cells grown in sugarcane blackstrap molasses

S. cerevisiae was grown in a blackstrap molasses containing medium in batch and fed-batch cultures. The following parameters were varied: pH (from 4.0 to 6.5), dissolved oxygen (DO) (from 0 to 5.0 mg O₂L^–1) and sucrose feeding rate. When glucose concentration (S) was higher than 0.5 g L^–1 a reduction in the specific invertase activity of intact cells (v) and an oscillatory behavior of v values during fermentation were observed. Both the invertase reduction and the oscillatory behavior of v values could be related to the glucose inhibitory effect on invertase biosynthesis. The best culture conditions for attainingS. cerevisiae cells suitable for invertase production were: temperature=30°C; pH=5.0; DO=3.3 mg O₂L^–1; (S)=0.5 g L^–1 and sucrose added into the fermenter according to the equations: (V–V_o)=t²/16 or (V–V_o)=(V_f–V_o)·(e^0.6t–1)/10.This work was supported by FAPESP     

Characterization of an exopolysaccharide mutant of Nostoc spongiaeforme: Zn2+-sorption and uptake

Exposure of the exopolysaccharide (EPS)-synthesizing cyanobacterium Nostoc spongiaeforme to Zn²⁺ (20 M) transformed the biomass into white debris. However, a few blue–green pin-heads emerged after 2 weeks in the same Zn²⁺-containing medium and formed less mucoid microcolonies (1–2 mm) relative to the protruding colonies (2–4 mm) of the parent strain on nutrient agar. One of such survivors (designated as Zn₂₀) that was stable through 10 successive transfers in Zn²⁺-lacking medium has been adopted for further characterization. The parent strain retained almost 88% of the total EPS synthesized, the rest being released into the ambient medium, while for Zn₂₀, the EPS retained approximated to 74%. Although the Zn²⁺-sensitivity of the mutant was comparable with that of the parent (LD₅₀, 7 M), Zn²⁺ uptake was still 5-fold higher in the former (2 g mg^–1 biomass dry wt., 20 M, external concentration). Also, both the strains showed insignificant difference in Zn²⁺-sorption onto their isolated EPS. The mutant was characterized by having higher cell carbohydrate content (642.8 g mg^–1 dry wt.) than its parent (513.6 g). The X-ray diffraction pattern revealed Zn²⁺ deposition on EPS from the parent mainly as zinc hypophosphite monohydrate [Zn(H₂PO₂)₂·H₂O], whereas there was a lack of distinct peaks in similar samples from Zn₂₀, thus confirming the amorphous nature. There was participation in Zn²⁺ binding of only COO^–, N=O, NO₂, SO₂ groups in the parent while participation of P—O and C=O groups in mutant EPS was evident in IR spectra. The observations suggest that the mutant could be deployed to achieve sustained EPS synthesis, its release and metal sorption/desorption in repeated cycles.     

F420H2 oxidase (FprA) from Methanobrevibacter arboriphilus, a coenzyme F420-dependent enzyme involved in O2 detoxification

Cell suspensions of Methanobrevibacter arboriphilus catalyzed the reduction of O₂ with H₂ at a maximal specific rate of 0.4 U (mol/min) per mg protein with an apparent K _m for O₂ of 30 M. The reaction was not inhibited by cyanide. The oxidase activity was traced back to a coenzyme F₄₂₀-dependent enzyme that was purified to apparent homogeneity and that catalyzed the oxidation of 2 F₄₂₀H₂ with 1 O₂ to 2 F₄₂₀ and 2 H₂O. The apparent K _m for F₄₂₀ was 30 M and that for O₂ was 2 M with a V _max of 240 U/mg at 37°C and pH 7.6, the pH optimum of the oxidase. The enzyme did not use NADH or NADPH as electron donor or H₂O₂ as electron acceptor and was not inhibited by cyanide. The 45-kDa protein, whose gene was cloned and sequenced, contained 1 FMN per mol and harbored a binuclear iron center as indicated by the sequence motif H–X–E–X–D–X₆₂–H–X₁₈–D–X₆₀–H. Sequence comparisons revealed that the F₄₂₀H₂ oxidase from M. arboriphilus is phylogenetically closely related to FprA from Methanothermobacter marburgensis (71% sequence identity), a 45-kDa flavoprotein of hitherto unknown function, and to A-type flavoproteins from bacteria (30–40%), which all have dioxygen reductase activity. With heterologously produced FprA from M. marburgensis it is shown that this protein is also a highly efficient F₄₂₀H₂ oxidase and that it contains 1 FMN and 2 iron atoms. The presence of F₄₂₀H₂ oxidase in methanogenic archaea may explain why some methanogens, e.g., the Methanobrevibacter species in the termite hindgut, cannot only tolerate but thrive under microoxic conditions.Dedicated to Hans Schlegel on the occasion of his 80th birthday.     

Hydrolysis of the amide bond in methionine-containing peptides catalyzed by various palladium(II) complexes: Dependence of the hydrolysis rate on the steric bulk of the catalyst

¹H NMR spectroscopy was applied to study the reactions of cis-[Pd(L)(H₂O)₂]²⁺ complexes (L is en, pic and dpa) with the N-acetylated tripeptides L-methionylglycylglycine, MeCOMet–Gly–Gly, and glycyl–L-methionyl–glycine, MeCOGly–Met–Gly. All reactions were performed in the pH range 2.0–2.5 with equimolar amounts of the cis-[Pd(L)(H₂O)₂]²⁺ complex and the tripeptide at 60 °C. The hydrolytic reactions of the cis-[Pd(en)(H₂O)₂]²⁺, cis-[Pd(pic)(H₂O)₂]²⁺ and cis-[Pd(dpa)(H₂O)₂]²⁺ complexes with MeCOMet–Gly–Gly were regioselective and only the amide bond involving the carboxylic group of methionine was cleaved. However, in the reactions of these three Pd(II) complexes with MeCOGly–Met–Gly, two amide bonds, Met–Gly and MeCO–Gly, were cleaved. From UV–Vis spectrophotometry studies, it was found that the rate-determining step of these hydrolytic reactions is the monodentate coordination of the corresponding Pd(II) complex to the sulfur atom of the methionine side chain. The rate of the cleavage of these amide bonds is dependent on the nature of the bidentate coordinated diamine ligand L (en > pic > dpa). The hydrolytic reaction of cis-[Pd(L)(H₂O)₂]²⁺-type complexes with MeCOMet–Gly–Gly, containing the methionine side chain in the terminal position of the peptide, is regioselective while in the reaction of these Pd(II) complexes with MeCOGly–Met–Gly, none selective cleavage of the peptide occurs. This study contributes to a better understanding of the selective cleavage of methionine-containing peptides employing palladium(II) complexes as catalysts.     

Effect of modulators of cytoskeletal function on desensitization and recovery of PGE2-responsive ovarian adenylate cyclase

Exposure of cultured Graafian follicles to PGE₂ for 20 h resulted in a loss of the cyclic AMP response to fresh hormone. This desensitization was prevented by addition to the medium of D₂O (25–50%) or Li⁺ (0.6 – 6 mM), agents believed to stabilize microtubules, as well as by phalloidin (1.0 – 10 μM), believed to stabilize the polymerized state of actin, in a dose-dependent manner.The spontaneous recovery of responsiveness to PGE₂ upon incubation of refractory follicles for 6 h in hormone-free medium was prevented by addition to the medium of cytochalasin B (CB; 3 μg/ml) or of the actin-binding myosin subfragment HMM S-1 (80 μg/ml) or of anti-actin serum; viz. by agents likely to interfere with microfilament function. D₂O (50%) caused morphological damage to the inner layer of the membrana granulosa and severe depression of protein synthesis. The other drugs used (phalloidin, LiCl and cytochalasin B) had no such effects. Resensitization of refractory follicles was also prevented by cycloheximide (10 μg/ml) and by actinomycin D (10 μg/ml). It is speculated that the recovery process may involve the insertion of a newly synthesized protein, such as PG-receptor, into the membrane by a mechanism dependent on microfilament action.     

Purification and characterization of membrane-bound hydrogenase from Methanosarcina barkeri MS

Hydrogenase was solubilized from the membrane of acetate-grown Methanosarcina barkeri MS and purification was carried out under aerobic conditions. The enzyme was reactivated under reducing conditions in the presence of H₂. The enzyme showed a maximal activity of 120±40 mol H₂ oxidized · min^–1 · min^–1 with methyl viologen as an electron acceptor, a maximal hydrogen production rate of 45±4 mol H₂ · min^–1 · mg^–1 with methyl viologen as electron donor, and an apparent K _m for hydrogen oxidation of 5.6±1.7 M. The molecular weight estimated by gel filtration was 98,000. SDS-PAGE showed the enzyme to consist of two polypeptides of 57,000 and 35,000 present in a 1:1 ratio. The native protein contained 8±2 mol Fe, 8±2 mol S^2–, and 0.5 mol Ni/mol enzyme. Cytochrome b was reduced by hydrogen in a solubilized membrane preparation. The hydrogenase did not couple with autologous F₄₂₀ or ferredoxin, nor with FAD, FMN, or NAD(P)⁺. The physiological function of the membrane-bound hydrogenase in hydrogen consumption is discussed.Abbreviation CoM-S-S-HTP the heterodisulfide of 7-mercaptoheptanoylthrconine phosphate and coenzyme M (mercaptoethanesulfonic acid)     

Effects of glycine on dark-and ligh-induced pulvinar movements and modifications of proton fluxes in the pulvinus of Mimosa pudica during glycine uptake

Glycine (1–50 mM) increases the rate of the dark-induced (scotonastic) movements and decreases the amplitude and the rate of the light-induced (photonastic) movements of the secondary pulvini of Mimosa pudica leaves. The uptake of glycine is accompanied by a long-lasting dose-dependent increase in the alkalinity of the bathing medium of the excised pulvini. The data are in agreement with a H⁺-glycine co-transport mechanism within the pulvinar cells. Fusicoccin (50 M), known to promote H⁺–K⁺ exchange, antagonizes the effects of glycine on the movements and the alkalization of the bathing medium of the excised pulvini. The present results argue for the hypothesis that proton fluxes mediate the scotonastic and photonastic pulvinar movements.Abbreviations Gly glycine - FC fusicoccin - P₁ primary pulvinus - P₂ secondary pulvinus