126:696-706. Plant Physiol. Water can be contaminated by … 84:329-332. The Arabidopsis CCH gene, highly homologous to the yeast ATX1 (Himelblau et al., 1998) has been the most extensively studied of the three Cu chaperones in plants (Mira et al., 2001a,b). Sequestration may also be in the apoplast, or in specialized cells such as epidermal cells and trichomes. In contrast, phytochelatins (PC) are a family of enzymatically-synthetized cysteine-rich peptides. Biol. [ Links ], Belouchi A, Cellier M, Kwan T, Saini HS, Leroux G, Gros P (1995) The macrophage-specific membrane protein Nramp controlling natural resistance to infections in mice has homologues expressed in the root system of plants. [ Links ], Wintz H, Vulpe C (2002) Plant copper chaperones. High soil copper levels can occur as a result of excessive use of copper containing fungicides and industrial activity (such as mining). These are some questions of fundamental importance in plant biology, which underlie an area of research that is emerging now that the necessary molecular tools are available. A possible direct interaction between Cu and Ca at the oxidizing side of PSII was also shown in vitro (Sabat, 1996) and in vivo (Maksymiec and Baszynski, 1999). In fact the mechanisms that contribute to Cu homeostasis are just beginning to be elucidated in higher plants since Cu ions are essential components of a variety of enzymes, transcription factors and other proteins. Blackie Academic and Professional, London. Heavy metal ATPases have been classified as type 1B ATPases and, together with the closely related type 1A ATPases (which are thought to be involved in K+ transport), they are considered to constitute a monophyletic group (Palmgren et al., 1998). Phytogenous chronic poisoning is seen after ingestion of plants, such as subterranean clover (Trifolium subterraneum), that produce a mineral imbalance and result in excessive copper retention. Physiol. Deficiency of copper can lead to increased susceptibility to diseases like ergot, which can cause significant yield loss in small grains. The LCHII antenna complex and D1 protein of the PSII reaction center are not affected even at these elevated Cu concentrations (Yruela et al., 2000). 271:27408-27415. Copper (Cu) is an essential metal for human, animals and plants, although it is also potentially toxic above supra-optimal levels. 35:295-304. Biochemistry 39:5413-5421. We use cookies to help provide and enhance our service and tailor content and ads. [ Links ], Hirayama T, Kieber JJ, Hirayama N, Kogan M, Guzman P, Nourizadeh S, Alonso JM, Dailey WP, Dancis A, Ecker JR (1999) Responsive-to-antagonist1, a Menkes/Wilson disease-related copper transporter, is required for ethylene signaling in Arabidopsis. [ Links ], Burda K, Kruk J, Schmid GH, Strzalka K (2003) Inhibition of oxygen evolution in photosystem II by Cu(II) ions is associated with oxidation of cytochrome b559. Since PCs can form complexes with Cu it may be possible that PC-Cu complexes are not sequestered in the vacuole (Cobbet and Goldsbrough, 2002). [ Links ], Sadmann G, Böger P (1980) Copper-mediated lipid peroxidation processes in photosynthetic membranes. HMA5 and HMA8 (PAA2) are the most similar in sequence to HMA7 (RAN1) and HMA6 (PAA1), respectively (Baxter et al., 2003), however their precise functions have not been described. Four members of this family HMA5, HMA6 (PAA1), HMA7 (RAN1) and HMA8 (PAA2) are the most closely related to the Cu/Ag subclass. Biophys. These studies indicated that Cyt b559 is affected after PSII centers are photoinhibited and that the HP form of Cyt b559 is more sensitive to the toxic Cu action than the LP form under photoinhibitory conditions (Bernal et al., 2004). Biochem. This finding could suggest the possibility of subgroups that may vary in their substrate specificity, although this remains to be demonstrated. [ Links ], Gupta M, Cuypers A, Vangronsveld J, Clijsters H (1999) Copper affects the enzymes of the ascorbate-glutathione cycle and its related metabolites in the roots of Phaseolus vulgaris. Chem. Copper toxicity also can produce oxidative stress in plants. Cu acts as a structural element in regulatory proteins and participates in photosynthetic electron transport, mitochondrial respiration, oxidative stress responses, cell wall metabolism and hormone signaling (for a review see Marschner, 1995; Raven et al., 1999). [ Links ], Jasiewicz C (1981) The effect of copper and application of different forms of nitrogen on some physiological indices of maize. Copper (Cu)‐containing fungicides and bactericides are used extensively for disease control on staked tomatoes (Lycopersicon esculentum Mill.) The leaves may also be twisted or malformed and show chlorosis or even necrosis (Marschner, 1995). At concentrations above those required for optimal growth Cu was shown to inhibit growth and to interfere with important cellular processes such as photosynthesis and respiration (Marschner, 1995; Prasad and Strzalka, 1999). The remaining four type 1B ATPases in Arabidopsis thaliana HMA1, HMA2, HMA3 and HMA4 are most closely related to the divalent cation transporters from prokaryotes and have no apparent counterparts in non-plant eukaryotes. Although the mineral nutrition of higher plants is of fundamental importance to agriculture and human health, many basic questions remain unanswered, particularly in relation to the accumulation of essential heavy metals. Acta Agraria et Silvestria Agraria 20:95-106. However, recently rapid progress has been made, particularly with the application of the knowledge of transport processes in yeast to other eukaryote organisms (Eide, 1998; Nelson, 1999). Photochem. Biochem. [ Links ], Bernal M, Roncel M, Ortega JM, Picorel R, Yruela I (2004) Copper effect on cytochrome b559 of photosystem II under photoinhibitory conditions. © 2020 Elsevier Ltd. All rights reserved. Copper is an essential metal for normal plant growth and development, although it is also potentially toxic. Plant Physiol. (2004) observed that excess Cu activated mitogen-activated protein kinases (MAPKs) suggesting that MAPK pathways are activated in response to excess Cu. Membrane transport systems are likely to play a central role in these processes. COPPER TOXICITY IN PLANTS Although copper is an essential micronutrient, excess of copper might be toxic to plants. HMA7 (RAN1) was identified in a genetic screen for plants with an unusual response to the ethylene antagonist trans-cyclooctene, underscoring the critical role of Cu in the ethylene-signaling pathway (Hirayama et al., 1999). 164:195-202. Plant Physiol. Plant Sci. Copper Toxicity Copper toxicosis occurs following the ingestion and accumulation of excessive amounts of copper in the liver. [ Links ], Shioi Y, Tamai H, Sasa T (1978a) Effects of copper on photosynthetic electron transport systems in spinach chloroplasts. Plants growing in soil that has too much copper may develop … 126:1519-1526. [ Links ], Pätsikkä E, Aro E-M, Tyystjärvi E (1998) Increase in the quantum yield of photoinhibition contributes to copper toxicity in vivo. Prog. Králova et al. In: Prasad MNV, Hagemeyer J (eds), Heavy metal stress in plants: from molecules to ecosystems, pp.73-97. Copper participates in numerous physiological processes and is an essential cofactor for many metalloproteins, however, problems arise when excess copper is present in cells. Free Radic. Finally, COPT4 represents a third group showing high level expression in roots that lacks Met-residues and motifs essential for Ctr1-mediated high-affinity Cu transport. However, our knowledge of the transport processes for heavy metals across plant membranes at the molecular level is still rudimentary in most cases. Putative target sequences to the chloroplast and the secretory pathway have been predicted for COPT3 and COPT5, respectively. Its participation in root elongation and pollen development has been also described (Sancenón et al., 2004). Review Heavy metals toxicity in plants: An overview on the role of glutathione and phytochelatins in heavy metal stress tolerance of plants S.K. The redox properties that make Cu an essential element also contribute to its inherent toxicity. 279:15348-15355. Annu. Opin. Nutr. Copper (Cu) toxicity in plants may lead to iron (Fe), zinc (Zn) and manganese (Mn) deficiencies. 41:548-555. Such strategies must prevent accumulation of the metal in the freely reactive form (metal detoxification pathways) and ensure proper delivery of this element to target metalloproteins. J. In: Terry N, Banuelos G (eds), Phytoremediation of contaminated soil and water, pp.235-250. [ Links ], Stauber JL, Florence TM (1987) Mechanism of toxicity of ionic copper and copper complexes to algae. Soc. [ Links ], Curie C, Alonso JM, Le Jean M, Ecker JR, Briat JF (2000) Involvement of Nramp 1 from Arabidopsis thaliana in iron transport. [ Links ], Henriques FS (1989) Effects of copper deficiency on the photosynthetic apparatus of sugar beet (Beta vulgaris L.) J. 33:1085-1092. It plays an important physiological role in Cu acquisition and accumulation since it is required for growth under Cu limiting conditions. The mechanism of Cu toxicity on photosynthetic electron transport has been extensively studied in vitro and it was found that PSII (figure 1) is a more sensitive site to Cu toxicity (for review see Droppa and Horváth, 1990; Barón et al., 1995) than photosystem I (PSI) (Ouzounidou et al., 1997). P-type Cu transporting ATPases are thought to be important not only in obtaining sufficient amounts of heavy metal ions for essential cell functions but also in preventing accumulations of these ions to toxic levels. Plant Physiol. Cu deficiency was found to reduce photosystem I (PSI) electron transport due to decreased formation of plastocyanin (Baszynski et al., 1978; Shikanai et al., 2003) which is the major target site of Cu deficiency in photosynthesis. Biochim. Academic Press, London. Plant Cell Environ. Since HMA8 (PAA2) shows similarity to PacS transporter from cyanobacteria and has a chloroplast transit sequence it has been suggested that it could be involved in Cu transport through the thylakoid membrane (Pilon et al., unpublished data). In: Raskin I, Ensley BD (eds), Phytoremediation of toxic metals using plants to clean up the environment, pp.231-246. 132:708-713. As a consequence of such modifications, alteration of PSII membrane fluidity was found (Quartacci et al., 2000). Photoinhibition is a universal cost factor decreasing the overall yield of photosynthesis, and both in vitro ( Mohanty et al., 1989 ; Yruela et al., 1996b ) and in vivo evidence (this study) suggests that excess copper speeds up photoinhibition. Sequence comparisons generally group the type 1B ATPases into two further classes: i) those transporting monovalent cations, Cu/Ag and ii) those transporting divalent cations, Cd/Pb/Zn/Co (Axelsen and Palmgren, 2001; Cobbet et al., 2003). ScienceDirect ® is a registered trademark of Elsevier B.V. ScienceDirect ® is a registered trademark of Elsevier B.V. Copper bioavailability, uptake, toxicity and tolerance in plants: A comprehensive review. Chem. Z. Pflanzenphysiol. 18:4361-4371. Cu-deficient plants show a change in the expression of a series of genes and activation of morphological changes such as in root and leaf architecture. The data of partial sequences and expressed sequence tags obtained suggest these ATPases occur in a variety of plant species. http://www.scielo.br/ Copper is an essential metal for normal plant growth and development, although is also potentially toxic. Annu. The first one, COPT1 was identified by the ability of its cDNA to functionally complement a Saccharomyces cerevisiae mutant defective in high-affinity Cu uptake (Kampfenkel et al., 1995). Plant Physiol. 129:1251-1260. Copper participates in numerous physiological processes and … 118:441-69. Email: yruela@eead.csic.es. J. Biol. [ Links ], Cobbet CS, Hussain D, Haydon MJ (2003) Structural and functional relationships between type 1B heavy metal transporting P-type ATPases in Arabidopsis. [ Links ], Jegerschöld C, MacMillan F, Lubitz W, Rutherford AW (1999) Effects of copper and zinc ions on photosystem II studied by EPR spectroscopy. Biogeochemical behaviour of Cu in soil-plant-human system was précised. Biochemistry 35:9469-9474. Photobiol. Paa1 mutants have a high chlorophyll fluorescence phenotype arising from impaired photosynthetic electron transport apparently because of a deficiency in holoplastocyanin (Shikanai et al., 2003). 53:1-11. Curr. Photosynth. J. Solioz and Vulpe (1996) defined the heavy metal P-type ATPases as CPx-ATPases because they share the common feature of a conserved intramembranous cysteine-proline-cysteine, cysteine-proline-histidine or cysteine-proline-serine motif (CPx motif) which is thought to function in heavy metal transduction. 45:127-134. Acta 1365:37-45. Plant. J. Participa de vários processos fisiológicos, sendo co-fator essencial para muitas metaloproteínas; no entanto, aparecem problemas quando o cobre está presente em excesso nas células. Biochim. A possible role of metal transporters and chaperones in phytoremediation (defined as the use of green plants to remove pollutants from the environment or to render them harmless) has been proposed. Science 284:2148-2152. Baszynski and Kruppa (1995) proposed that those processes induced by Cu could involve either the destruction of the oxygen-evolving complex polypeptide composition or the interaction with ions necessary for proper functioning of the complex such as Mn, Ca and Cl. Thus, these proteins prevent inappropriate Cu interaction with other cellular components. [ Links ], De Vos CHR, Schat H, De Waal MAM, Voojis R, Ernst WHO (1991) Increased resistance to copper-induced damage of the root cell plasmalemma in copper tolerant Silene cucubalus. 35:11-15. [ Links ], Kaiser BN, Moreau S, Castelli J, Thomson R, Lambert A, Bogliolo S, Puppo A, Day DA (2003) The soybean NRAMP homologue, GmDMT1 is a symbiotic divalent metal transporter capable of ferrous iron transport. 49:643-668. 113:142-150. Crit. 1). [ Links ], Maksymiec W, Baszynski T (1999) The role of Ca2+ ions in modulating changes induced in bean plants by an excess of Cu2+ ions. In plants, investigations of the N-ramp family have been largely restricted to rice (Oryza sativa) where three N-ramp gene homologues have been identified, OsNramp1, OsNaramp2 and a partial length of OsNramp3 (Belouchi et al., 1995, 1997). Plant Physiol. Chem. Some authors (Schröder et al., 1994, Arellano et al., 1995) suggested that the electron flow from Tyrz to P680+ is blocked at toxic Cu concentrations. The CCS gene, homolog of the yeast LY7 gene, has been identified in tomato (Lycopersicon esculentum; LeCCS) (Zhu et al., 2000), Arabidopsis thaliana (Wintz and Vulpe, 2002), and potato (Solanum tuberosum; StCCS) (Trindade et al., 2003). [ Links ], Samson G, Morissette JC, Popovic R (1988) Copper quenching of the variable fluorescence in Dunaliella tertiolecta. (1994) and Sersen et al. [ Links ], Prasad MNV, Strzalka K (1999) Impact of heavy metals on photosynthesis. J. Biol. Chem. Rev. Acta 891:75-84        [ Links ], Droppa M, Horváth G (1990) The role of copper in photosynthesis. For this purpose, plants –like all other organisms- have homeostatic mechanisms to maintain the correct concentrations of essential metal ions. Physiol. Plant Physiol. Copper is required for many enzymatic activities in plants and for chlorophyll and seed production. Plant Physiol. Plant Physiol. [ Links ], Stohs SJ, Bagchi D (1995) Oxidative mechanisms in the toxicity of metal ions. Copper Toxicity is a build up of stored bio-unavailable copper in the body. 84:1-5. The mechanisms developed in the acquisition of essential heavy metal micronutrients have not been clearly defined although a number of genes have now been identified which encode potential transporters. Z. Naturforsch. Liming may be beneficial, as copper becomes less available to plantsat high pH. 19:273-280. We also delimits the Cu accretion in food crops and allied health perils from soils encompassing less or high Cu quantity. 219:1-14. Phytogenous and hepatogenous factors influence secondary chronic copper poisoning. plants, so when sheep consume molybdenum-containing plants at proper levels, they are less likely to develop copper toxicity. [ Links ], Balandin T, Castresana C (2002) AtCOX17, an Arabidopsis homolog of the yeast copper chaperone COX17. Evidence that Cu impairs the function of the oxidizing side were also reported (Cedeño-Maldonado and Swader, 1972; Vierke and Struckmeier, 1977; Shioi et al., 1978a,b; Bohner et al., 1980; Samuelsson and Öquist, 1980). Springer-Verlag, Berlin. [ Links ], Yruela I, Alfonso M, Barón M, Picorel R (2000) Copper effect on the protein composition of photosystem II. 33:227-233. 117-138. [ Links ], Drazkiewicz M, Skórzynska-Polit E, Krupa Z (2003) Response of the ascorbate-glutathione cycle to excess copper in Arabidopsis thaliana (L.). At the cellular level, specific transporters are presumably responsible for the uptake and secretion of metal ions, and there may be additional transporters that allow sequestration into organelles. 347:749-755. (2002) to explain the severe effects caused by the presence of high Cu concentrations during photoinhibition in vivo. 109:1141-1149. The plant hormone ethylene is an important signal in many abiotic stress situations but also in plant pathogen interaction. (2003) have designated these as HMA1 to HMA8 although three of them, HMA6, HMA7 and HMA8, had previous designations, PAA1, RAN1 and PAA2, respectively. Copper toxicity was damaging to plant roots, with symptoms ranging from disruption of the root cuticle and reduced root hair proliferation, to severe deformation of root structure. 7:500-505. [ Links ], Palmgren MG, Axelsen KB (1998) Evolution of P-type ATPases. Plant Cell Physiol. Copper chaperones: The Cu chaperones belong to a new family of cytosolic, soluble, low-molecular-weight metal-receptor proteins named metallochaperones, and are involved in the intracellular trafficking of metal ions. Trans. Biochim. Aqua (aryloxiacetato)copper (II) complexes. Finally, an overview of various techniques involved in the reclamation and restoration of Cu-contaminated soils has been provided. Plant. 17:177-191. This review gives a briefly overview of the current understanding of the more important features concerning copper toxicity and tolerance in plants, and brings information of recent findings on copper trafficking including copper detoxification factors, copper transporters and copper chaperones. [ Links ], Yruela I, Montoya G, Picorel R (1992) The inhibitory mechanism of Cu on the photosystem II electron transport from higher plants. Plant Physiol. [ Links ], De Vos CHR, Vonk MJ, Voojis R, Schat H (1992) Glutathione depletion due to copper-induced phytochelatin synthesis causes oxidative stress in Silene cucubalus. 109:871-878. The first one, including COPT1 and COPT2, displays the more high-affinity Cu transporter features. Plant. [ Links ], Belouchi A, Kwan T, Gros P (1997) Cloning and characterization of the OsNramp family from Oryza sativa, a new family of membrane proteins possibly implicated in the transport of metal ions. Centro de Ciências e Tecnologias Agropecuárias, https://doi.org/10.1590/S1677-04202005000100012. 20:291-310. Despite their role in Cu homeostasis, neither CCH nor RAN1 are induced by Cu treatment, indicating that they might be more important in helping cells cope with Cu deficit than Cu excess. The brain, a secondary location. 117:619-627. Res. In plants, three different members of the Cu chaperone family, CCH, COX17 and CCS, have been identified and characterized at different levels. A different proposal was given by Pätsikkä et al. Thus, these transporters and chaperones could be involved in the overall strategy of heavy metal tolerance. How plants detect and respond to deficiencies in Cu and other essential micronutrients is still obscure. [ Links ], Zhu H, Shipp E, Sanchez RJ, Liba A, Stine JE, Hart PJ, Gralla EB, Nersissian AM, Valentine JS (2000) Cobalt(2+) binding to human and tomato copper chaperone for superoxide dismutase: implications for the metal ion transfer mechanism. Chlorophyll fluorescence measurements. Plant Biol. Plant. Function, structure, and mechanism of action. [ Links ], Puig S, Thiele DJ (2002) Molecular mechanisms of copper uptake and distribution. J. Exp. Copper Toxicity in Plants Although soil rarely produces excessive amounts of copper on its own, copper toxicity can occur from the repeated use of fungicides that contain copper. The COPT1 transporter allows the entrance of Cu into cells (Kampfenkel et al., 1995; Sancenón et al., 2003). J. Biol. Biochemical studies using membrane vesicles indicate that the substrate for 1B heavy-metal-transporting P-type ATPases is Cu(I) rather than Cu(II) (Voskoboinik et al., 2002). (2003) found that high Cu concentrations, apart from the inhibition of oxygen evolution, changed the initial S-state distribution of the oxygen-evolving complex, oxidized both the LP and the HP forms of Cyt b559, and enhanced the formation of the Chlz+ radical. These mechanisms appear to be involved primarily in avoiding the accumulation of toxic concentrations at sensitive sites within the cell preventing the damaging effects rather than developing proteins that can resist the heavy metal effects. 135:453-458. [ Links ], Hirayama T, Alonso JM (2000) Ethylene captures a metal! In particular, the interaction of metal chaperones with transporters deserves attention since this may have important implications for sequestration of metals within intracellular stores. 304:825-830. (2001) showed that some mycorrhizal species protect Pinus sylvestris against Cu toxicity extracellularly, although the amount of Cu retained by different fungi vary considerably. Copper (Cu) is an essential element for humans and plants when present in lesser amount, while in excessive amounts it exerts detrimental effects. [ Links ], Wang H, Shan X-q, Wen B, Zhang S, Wang Z-j (2004) Responses of antioxidative enzymes to accumulation of copper in a copper hyperaccumulator of Commoelina communis. There are still no indications of how they may be regulated in higher plants, but this could occur potentially at the transcriptional level (control on initiation rates, mRNA stability, differential mRNA splicing) or at the post translational level (targeting, stability). Physiol. The ascorbate-glutathione cycle has been reported to be involved in response to excess Cu (Gupta et al., 1999; Drazkiewicz et al., 2003). According to the relationship between POD activity and copper content, the toxic critical value was set at 26 mg Cuper kg dry matter (DM) in roots and 21 mg Cuper kg DM in the 3rd-leaf. Subsequently, two Arabidopsis genes were identified (Alonso et al., 1999) which show similarity to Nramps. Esta revisão descreve, brevemente, o atual conhecimento sobre as principais características da toxicidade e tolerância de plantas ao cobre, assim como as recentes descobertas sobre o transporte de cobre, incluindo fatores de destoxificação, transportadores e chaperonas de cobre. CRC Press LLC. 70:947-957. Thus, both Cu chelation and Cu pumping activity are likely to be required not only for Cu-uptake but also for other processes. Since copper is both an essential cofactor and a toxic element, involving a complex network of metal trafficking pathways, different strategies have evolved in plants to appropriately regulate its homeostasis as a function of the environmental copper level. 90:175-179. However, a clear role of PCs in Cu detoxification has not been shown. Marques et al. Plant Physiol. 51c:179-184. Consequently, Cu chaperones bind and deliver Cu ions to intracellular compartments and insert the Cu into the active sites of specific partners, the Cu-dependent enzymes. Physiol. Physiol. Plant Physiol. Since adding excess Fe in the hydroponic growth medium reduced Cu toxicity symptoms a competition between Cu and Fe uptake mechanisms at the root level was proposed. 129:1852-1857. Plant Physiol. [ Links ], Ouzounidou G, Moustakas M, Strasser RJ (1997) Sites of action of copper in the photosynthetic apparatus of maize leaves: kinetic analysis of chlorophyll fluorescence, oxygen evolution, absorption changes and thermal dissipation as monitored by photoacoustic signals. Microcystins and copper commonly co-exist in the natural environment, but their combined toxicity remains unclear, especially in terrestrial plants. Organic acids excreted by plants can facilitate metal uptake, but these molecules can also inhibit metal acquisition by forming a complex with it outside the root so that it is not taken up. The ratio of copper to molybdenum in the total diet of sheep should be 6-to-1 [ Links ], Arellano JB, Lázaro JJ, López-Gorgé J, Barón M (1995) The donor side of PSII as the copper-inhibitory binding site. Os mecanismos envolvidos na aquisição desse micronutriente essencial não foram claramente definidos, apesar de vários genes que codificam para transportadores de cobre terem sido recentemente identificados. 24:81-90. Both the acceptor and the donor sides of PSII were suggested as the main targets of Cu toxic action. J. Biol. This role is explained by the fact that ethylene receptors are Cu-dependent proteins (Rodríguez et al., 1999; Hiramaya and Alonso, 2000). Sci. The first CPx-ATPase reported in plants was PAA1 (P-type ATPase of Arabidopsis 1) from Arabidopsis thaliana (Tabata et al., 1997). Contam. High levels of CCH expression were found in stems of this plant. [ Links ], Mohanty N, Vass I, Demeter S (1989) Copper toxicity affects photosystem II electron transport at the secondary quinone acceptor QB. Physiol. Biophys. Physiol. [ Links ], Samuelsson G, Öquist G (1980) Effects of copper chloride on photosynthetic electron transport and chlorophyll-protein complexes of Spinacea oleracea. J. Biol. EMBO J. Plant. Under physiological conditions Cu exists as Cu2+ and Cu+. These findings suggest an indirect role in Cu transport (Sancenón et al., 2004). The critical free Cu concentration in nutrient media (below which Cu deficiency occurs) ranges from 10-14 to 10-16 M. Plants usually find a variable supply of Cu in the soil since typically soil solution concentrations range from 10-6 to 10-9 M, but plants may still need to solubilize and reduce the metal. Plant Biol. 26:695-708. J. [ Links ], Barón M, López-Gorgé J, Lachica M, Sadmann G (1992) Changes in carotenoids and fatty acids in photosysyem II of Cu-deficient pea plants. 50:698-701. The most apparent effect of Cu toxicity on PSII is the inhibition of oxygen evolution accompanied by quenching of variable fluorescence (Hsu and Lee, 1988; Samson et al., 1988; Mohanty et al., 1989). Alonso JM, Hirayama T, Roamn G, Nourizadeh S, Ecker JR (1999) EIN2, a bifunctional transducer of ethylene and stress response in Arabidopsis. Plants grown in the presence of high levels of Cu normally show reduced biomass and chlorotic symptoms. Heavyapplications of P fertilisers may reduce the availability of excess copper tothe plants. [ Links ], Hall JL (2002) Cellular mechanisms for heavy metal detoxification and tolerance. Birth control pills, copper IUDs, vegetarian diets, copper piping, and estrogen are just Thus HMA7 (RAN1) is involved in ethylene signaling by transporting Cu to the secretory pathway, where it is required for the formation of functional ethylene receptors (Woeste and Kieber, 2000).