Light Induced Polarity of Redox Reactions in Leaves of Elodea canadensis Michx

This paper reports that extracellular reductase activity in leaves of Elodea canadensis, hitherto never associated with polar processes thought to be involved in bicarbonate utilization, also shows a very marked polarity in light. The effect of ferricyanide, applied to the lower side of illuminated leaves, was a depolarization of the membrane electrical potential of up to 110 millivolts, while no depolarization was induced when ferricyanide was applied to the upper side. In the dark ferricyanide induced a depolarization when applied to either the upper or to the lower side of the leaf. Staining with tetrazolium salts, specific indicators for reductase activity, resulted in the formation of a precipitate on the lower side of the leaf when illuminated and on both sides in the dark. The precipitate was only located along the plasmalemma.     

Photosynthesis In Elodea canadensis Michx: Four-Carbon Acid Synthesis

Experiments to determine the early labeled photosynthetic products in Elodea canadensis show that after 2 seconds of exposure to NaH¹⁴CO₃, 45% of the ¹⁴C incorporated is located in malate and aspartate. Phosphoglyceric acid and sugars account for 27% of the label during similar exposures. Equivalent amounts of organic acids and C₃ cycle products are present after 8 seconds. Four-carbon acids remain relatively unchanged throughout the first 45 seconds of exposure, while sugars increase in a linear fashion. Enzyme assays indicate that ribulose diphosphate and phosphoenolpyruvate carboxylase enzymes are present in a ratio of approximately 2:1. It appears that E. canadensis is able to synthesize significant amounts of four-carbon acids via β-carboxylation and this may play a role in maintaining a pH favorable for carboxylation in aquatic plants.     

Cyanide-Resistant Respiration in Neurospora crassa

Cell respiration in wild type and poky was studied as part of a long-term investigation of cyanide-resistant respiration in Neurospora. Respiration in wild type proceeds via a cytochrome chain which is similar to that of higher organisms; it is sensitive to antimycin A or cyanide. Poky, on the other hand, respires by means of two alternative oxidase systems. One of these is analogous to the wild-type cytochrome chain in that it can be inhibited by antimycin A or cyanide; this system accounts for as much as 15% of the respiration of poky f(-) and 34% of the respiration of poky f(+). The second oxidase system is unaffected by antimycin A or cyanide at concentrations which inhibit the cytochrome chain maximally. It can, however, be specifically inhibited by salicyl hydroxamic acid. The cyanide-resistant oxidase is not exclusive to poky, but is also present in small quantities in wild type grown under ordinary circumstances. These quantities may be greatly increased (as much as 20-fold) by growing wild type in the presence of antimycin A, cyanide, or chloramphenicol.     

Cyanide-Resistant Respiration in Relation to Fruit Respiratory Climacteric

Changes in respiratory rate and the effects of respiratory inhibitorson respiration were determined in apple (Malus sylvestris cv. Delicious) and red pepper (Capsicum fructescens) fruits dusting different stages of development and ripening.The results showed that there was an abrupt rise in respiration daring ripening inapple fruit, but the respiration of the red pepper declined continuously throughout theripening period. Thus the apple is climacteric and the red pepper is non-climacteric fruit. The respiration of apple fruit was sensitive to KCN (1 mM) during the period ofdevelopment but changed to CLAM-sensitive and CN-resistant during preclimactericand climacteric phases, indicating that a diversion of respiratory pathways from the cy-tochrome path to the alternative path has occurred. The respiration of the red pepperfruit was CN-sensitive thoughout the whole period of fruit ripening, suggesting thatthe operation of the CN-resistant path was insignificant. Slices from climacteric apple fruits developed induced .respiration after aging, bothKCN and CLAM (1 mM) inhibited the induced respiratic considerably. However, slices from red pepper fruits showed no evidence of induced respiration after aging. Slices from climacteric apple fruits infiltrated with 3 mM CLAM before aging, reducedthe peak of the induced respiration by about 30%, indicating that the development ofinduced respiration was suppressed by the presence of CLAM. The above results indicated that the: climacteric fruits were characterized by diversion of traffic from the cytochrome path to the alternative path during ripening andby the development of induced respiration after slicing and aging. While in nonclimacteric fruits no .diversion of electron transport path was observed during ripening andno induced respiration occurred after aging. Although both the eytochrome and alternative pathways were present in the tissue of red pepper fruits, the alternative pathwas not operating except when the cytochrome path was blocked or was saturated by electron flow.     

Spread of Elodea canadensis in Lake Baikal

In Lake Baikal Elodea canadensis Michx. was first observed at the end of the 1970's.Suggestions have been made as to the bringing of E. canadensis to Baikal by aquarists or by transport vehicles and transport together with fishes taken from lakes of the Urals where mass development of the plant was observed at the beginning of the present century. The spread of E. canadensis along Lake Baikal must be due to navigation, but natural factors also affect its spread.The quantitative biomass development of E. canadensis in various areas of the lake is reviewed, and discussed in relation to historical aspects of spread and regulation by environmental factors.The fast spread of E. canadensis, its high competitive quality and metabolic capacities for purifying sewage waters deserve attention.Expansion of E. canadensis may be referred to as a catastrophic phenomenon. Its effect has now covered practically the whole perimeter of Lake Baikal.     

Spread of Elodea canadensis in Lake Baikal

Elodea canadensis Michx. was first observed in Lake Baikal at the end of the 70's. E. canadensis was probably introduced to Baikal by aquarists or by transport vehicles and transport together with fishes taken from lakes of the Urals, where mass development of the plant was observed at the beginning of the present century. The spread of E. canadensis along lake Baikal may be due to navigation, but natural factors also affect its spread.The fast spread of E. canadensis, its high competitive quality and metabolic properties for purifying sewage waters are of interest.The expansion of E. canadensis may be considered a catastrophic phenomenon; its effect now covers practically the whole perimeter of Lake Baikal.     

Cyanide-Resistant Respiration of a Neurospora crassa Membrane Mutant

Choline starvation of the Neurospora crassa chol-1 mutant leads to a decrease in respiration through the cytochrome chain and a concomitant induction of the alternate oxidase.     

Calcium-mediated enhancement of copper tolerance in Elodea canadensis

The alleviative effects of exogenous calcium on copper phytotoxicity were investigated in Elodea canadensis plants. There was a significant accumulation of Cu in the plants after their exposure to 0.01 mM Cu accompanied by many symptoms of toxicity. Increased uptake of Cu severely reduced content of photosynthetic pigments, soluble proteins, and free proline. The total antioxidant capacity (T-AOC), reduced glutathione (GSH), and non-protein thiol (NP-SH) were severely suppressed in Cu-stressed plants resulting in a rapid increase in content of superoxide anion (O₂ ^·?), hydrogen peroxide, lipid peroxidation, and cell death. Simultaneous application of Ca markedly increased the content of photosynthetic pigments, soluble proteins, free proline, T-AOC, GSH, and NP-SH, and reduced oxidative damage as indicated by lowered content of MDA, O₂ ^·?, and H₂O₂; and decreased cell death. Furthermore, application of Ca reduced Cu uptake and effectively reversed the Cu-induced nutrient imbalance.     

Arsenic species uptake and translocation in Elodea canadensis

Abstract

The capacity of Elodea canadensis to phytofiltrate arsenic species from water was evaluated. Plants were adapted to tap water and supplemented with 15 and 250?µg L^?1 of As. Inorganic arsenic species (As III, As V), and organic arsenic compounds: monomethylarsonate (MMA) and dimethylarsinate (DMA) were analyzed. Sampling was carried out at different times after exposure in culture water and plant organs. Plants exposed to 15?µg L^?1 of As concentration showed no significant difference on As concentration (95% confidence level) in their organs compared to controls. When plants were exposed to 250?µg L^?1 of As concentration, a significant increase of As concentration in plant organs was observed. After 1?h exposure, plants reduce 63.16% the As concentration in the culture water, with a bioaccumulation factor (BF) of 4.3. Under these conditions, E. canadensis accumulate As V in roots and do not translocate it to stems (transfer factor <1). MMA was determined in stems and leaves. E. canadensis effectively phytofiltrate As from tap water of a city located in an arsenic endemic area from concentrations of 36?µg L^?1 to undetectable levels (10?ng L^?1).     

Light-Induced Polar pH Changes in Leaves of Elodea canadensis: I. Effects of Carbon Concentration and Light Intensity

Leaves of the submerged aquatic Elodea canadensis Michx. exhibit a light induced polar pH reaction. In this study, the effects of light intensity and dissolved inorganic carbon concentration on this polar reaction were examined. At a light intensity of 100 watts per square meter the leaf showed a polar pH response when the dissolved inorganic carbon concentration was less than about 1 millimolar. The polar reaction was suppressed at a higher dissolved inorganic carbon concentration. This suppression was not due to the buffering capacity of bicarbonate. Because another weak acid, acetate, did not inhibit the polarity, but even had a small stimulatory effect, the effect of bicarbonate is also not due to acidification of the cytoplasm. The suppression of the polar reaction by CO₂/HCO₃⁻ was relieved when the light intensity was increased. Apparently there is competition for product(s) of the photosynthetic light reactions between processes generating the polar reaction and the carbon fixation reactions. The possibility that the redox state of the cell regulates the generation of the polar reaction is discussed.     

Cyanide-Resistant Respiration in Suspension Cultured Cells of Nicotiana glutinosa L

The respiration of dark-grown Nicotiana glutinosa L. cells in liquid suspension culture was found to be highly cyanide resistant and salicylhydroxamic acid (SHAM) sensitive, indicative of an active alternative respiratory pathway. This was especially true during the lag and logarithmic phases of the 14-day growth cycle. Mitochondria isolated from logarithmically growing cells exhibited active oxidation of malate, succinate, and exogenous NADH. Oxidation of all three substrates had an optimum pH of 6.5 and all were highly resistant to inhibited by cyanide and sensitive to SHAM. Respiratory control was exhibited by all three substrates but only if SHAM was present to block the alternative pathway and divert electrons to the phosphorylating cytochrome pathway. The cyanide-resistant oxidation of exogenous NADH has previously only been associated with Arum spadix mitochondria. Coemergence during evolution of the alternative respiratory pathway and the exogenous NADH dehydrogenase in plant mitochondria as a possible mechanism for removal of cytoplasmic NADH is proposed. Evidence is presented which suggests that mitochondrial assays should be performed at pH 6.5.     

Copper and zinc in Elodea canadensis from rivers with various pollution levels

The anthropogenic impact of xenobiotics contributes to environmental risk for the aquatic environment and thus, must be controlled. Elodea canadensis, a cosmopolitan aquatic macrophyte with an important role in the ecology of many littoral zones, may provide an integrated record of pollution. Therefore, it was interesting to investigate the accumulation of Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn in this species and in water and bottom sediments collected from rivers with various levels of contamination. Of these rivers one control and one polluted was selected for the collection of E. canadensis for an experiment to compare the ability of this species to accumulate Cu and Zn. These elements were supplemented at concentrations (mg L⁻¹) of 0.01, 0.02, 0.03, 0.05, 0.08 and 0.14 as CuSO₄·5H₂O, and 0.4, 0.6, 0.9, 1.4, 2.03 and 3.04 as ZnSO₄·7H₂O and in a mixture containing (mg L⁻¹) 0.01Cu + 0.4Zn, 0.02Cu + 0.6Zn, 0.03Cu + 0.9Zn, 0.05Cu + 1.4Zn, 0.08Cu + 2.03Zn and 0.14Cu + 3.04Zn. After the experiment, E. canadensis from the polluted river contained significantly higher Cu and Zn concentrations when applied separately and also significantly higher Cu and Zn concentrations when applied as a mixture compared to the control river. These higher concentrations in E. canadensis from the polluted river were found in all combinations in the experiment. Thus, E. canadensis habituated in polluted sites to the exposure, and long-term influence of elevated metal levels appeared to be better adapted, and it also exhibited a higher increase in biomass than plants from the control river in all the experimental Cu and Zn solutions. Younger leaves of E. canadensis were more resistant to the effects of Cu and Zn than older leaves. Both Cu and Zn negatively affected the cell structure of older leaves, although the influence of Cu on plasma membrane integrity and chloroplast distribution was stronger than that of Zn. The influence of the Cu + Zn mixture on E. canadensis resulted in less pronounced cell disintegration than the influence of Cu added separately.The explanation of differences in the E. canadensis biomass increase and metal concentrations under the binary Cu and Zn impact needs further examination.     

Extension Growth in Primary Cell Walls with Special Reference to Elodea canadensis

A quantitative study of distribution of perforations in thecellulose frame-work of longitudinal walls of cortical parenchymashows that their number and spacing change in an orderly manneras the tissue grow. These perforations are considered to bepit-fields, not primarily concerned with cell-wall growth, sincethey do nto occur in walls adjacent to intercellular spaces.The data are discussed in relation to the general problem ofcell extension, and are interpreted as showing that cell-wallgrowth is intersusceptive throughout; tip-growth does not occur.     

Distribution of Plasma Membrane H+-ATPase and Polar Current Patterns in Leaves and Stems of Elodea canadensis*

The proton pumping ATPase in the plasma membrane of Elodea canadensis is believed to play a major role in inorganic carbon acquisition. To investigate potentially different carbon uptake strategies within the same plant, plasma membrane H⁺-ATPase distribution and polar current patterns were investigated in Elodea leaves and stems. Specific activity of plasma membrane H⁺-ATPase in leaf microsomal fractions was tenfold higher than in stem derived microsomes. Probing western blots with a monoclonal antibody specific for plasma membrane H⁺-ATPase, yielded strongly visible double bands at 100 kDa in leaf microsome preparations, whereas little antigen was detected in analogous stem microsome preparations. Using the same plasma membrane H⁺-ATPase specific antibody on tissue sections, the enzyme was found almost exclusively localized at the border of cells at the lower leaf surface. A positive ion current leaving the lower leaf surface was measured, using a vibrating probe device. Part of this current entered the upper leaf surface and part of it the internodes of the stem. The experimental results support the view, that Elodea leaves have different means of inorganic carbon uptake than stem internodes.     

Cyanide-Resistant Root Respiration and Tap Root Formation in Two Subspecies of Hypochaeris radicata

Root respiration of the tap root forming species Hypochaeris radicata L. was measured during tap root formation. A comparison was made of two subspecies: H. radicata L. ssp. radicata L., a subspecies from relatively rich soils, and H. radicata L. ssp. ericetorum Van Soest, a subspecies from poor acidic soils. Root respiration was high and to a large extent inhibited by hydroxamic acid (SHAM) before the start of the tap root formation, indicating a high activity of an alternative non-phosphorylative electron transport chain. The rate of root respiration was much lower and less sensitive to SHAM when a considerable tap root was present. However, root respiration was also cyanide-resistant when a tap root was present, indicating that the alternative pathway was still present. A decreased rate of root respiration coincided with an increase of the content of storage carbohydrates, mainly in the tap root. The level of reducing sugars was constant throughout the experimental period, and it was concluded that the activity of the alternative oxidative pathway was significant in oxidation of sugars that could not be utilized for purposes like energy production, the formation of intermediates for growth or for storage. Root respiration decreased after the formation of a tap root. This decrease could neither be attributed to a gradual disappearance of the alternative chain, nor to a decreased level of reducing sugars. No differences in respiratory metabolism between the two subspecies have been observed, suggesting that a high activity of the alternative oxidative pathway is not significant in adaptation of the present two subspecies to relatively nutrient-rich or poor soils.     

Light-Induced Polar pH Changes in Leaves of Elodea canadensis: II. Effects of Ferricyanide: Evidence for Modulation by the Redox State of the Cytoplasm

The effect of an extracellular electron acceptor, ferricyanide, on the light-induced polar leaf pH changes of the submerged angiosperm Elodea canadensis in light and in darkness was determined. The rate of transmembrane ferricyanide reduction was stimulated by increased light intensity and was inhibited by inorganic carbon, indicating that changes in the redox state of the chloroplast were reflected at the plasma membrane. The addition of ferricyanide inhibited the light-induced polar leaf pH reaction. This effect could be balanced by increasing the light intensity. In the dark, the acidification induced by ferricyanide was not influenced by diethylstilbestrol at concentrations that completely inhibited the polar leaf pH changes. This indicates that the ferricyanide-induced H⁺ extrusion and the H⁺ transport during the polar reaction were mediated by different mechanisms.     

Population genetics of the invasive water weed Elodea canadensis in Finnish waterways

Invasions of exotic species often involve a rapid evolutionary change in the introduced populations. Elodea canadensis is an invasive aquatic weed native to North America. Our aims were to reveal the evolutionary consequences of invasion to the population genetic structure of the presumably clonal E. canadensis in Finland and to test the hypothesis that the whole Finnish population originates from the first introduction of the species. We used ten polymorphic microsatellite markers to analyze the genetic characteristics of seven introduced E. canadensis populations in Finland. Despite the species' totally asexual mode of reproduction in Finland, two to five alleles per locus were detected in Finnish populations, and the expected heterozygosities varied between 0.19 and 0.37. The majority of variation was found within populations. Except for one, all pairwise values of population differentiation (F _ST) were significant, indicating restricted gene flow among the Finnish populations. In addition, a Bayesian analysis of population structure revealed the presence of regional population structuring. Genetic analyses indicate that E. canadensis could have been introduced to Finland multiple times. However, the amount of genetic variation and regional clustering detected could also be explained by post-establishment evolution, and based on this study it is not possible to exclude one introduction event followed by rapid evolution. We also tested the usability of the microsatellite markers for native North American samples in order to compare the within-population genetic characteristics of introduced and native populations. However, in native populations only four microsatellite markers amplified reliably, indicating sequence variation within primer-binding regions and, thus, genetic differentiation among populations of E. canadensis.     

Further Study on the Involvement of Cyanide-Resistant Respiration in the Germination of Cocklebur Seeds

The effect of propyl-gallate (PG) and benzohydroxamic acid (BHAM),inhibitors of cyanide-resistant, alternative respiration path(AP), on germination were examined using after-ripened upperand lower cocklebur (Xanthium pennsylvanicum Wallr.) seeds pre-soakedat 23?C for various periods. Germination was strongly suppressedby PG or BHAM at concentration above 2 mM. However, germinationwas enhanced by low concentrations of PG or BHAM (0.25 or 0.5mM) which reduced some portions of AP operation. Similarly,the high temperature-induced germination of pre-soaked upperseeds was promoted by the same low concentration range of PGor BHAM, in which PG and BHAM were effective only when appliedat the start of high temperature incubation. The inhibitionof germination by C₂H₄ at high temperature occurred only whenseeds were exposed to C₂H₄ during the earlier period of hightemperature incubation, and delayed application tended to promotetheir germination, although most of germinated seeds did notexhibit the normal germination behaviour of predominant radicleprotrusion. If the upper seeds had been subjected to a short-timepre-soaking, the inhibition of high temperature-induced germinationby C₂H₄ was prevented by the low concentrations of PG or BHAM,although the germination restored was mostly an abnormal, predominantlycotyldonary growth, suggesting that the germination inhibitionby C₂H₄ may be involved in some step of axial growth or in thegrowth of some specific axial zone. The lower concentrationsof PG or BHAM were promotive to the axial growth even at 33?C.Based on these results, the involvement of AP in cocklebur seedgerminaton is discussed in relation to the differential growthof axial and cotyledonary tissues. (Received May 2, 1986; Accepted October 27, 1986)     

Mutants of the Phytopathogenic FungusMagnaporthe griseaDeficient in Alternative, Cyanide-Resistant, Respiration

The phytopathogenic fungusMagnaporthe griseahas a cyanide-resistant respiratory pathway. The fungicide SSF-126 ((E)-2-methoxyimino-N-methyl-2-(2-phenoxyphenyl) acetamide) blocks the cytochrome electron transport ofM. griseaand induces the alternative respiratory pathway. Twelve mutants ofM. griseamore susceptible to SSF-126 than wild type were identified afterN-methyl-N′-nitro-N-nitrosoguanidine mutagenesis. Five mutants retained a reduced alternative respiration activity, and seven mutants lacked alternative pathway activity. A monoclonal antibody against the maize alternative oxidase cross-reacted against a 40-kDa mitochondrial protein ofM. grisea,indicating that the 40-kDa protein is an alternative oxidase. Immunoblot analysis indicated that the seven completely deficient mutants grouped into two classes: four mutants produced the 40-kDa proteins while the other three mutants failed to produce the functional protein.