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Symptoms of copper deficiency in nurseries trees (A) with formation of gum pockets in new branches (details in B) resulting from tissue breakdown and sap leakage, and in young trees in the field (C and D) showing long and vigorous twigs that grow tortuous.

Symptoms of copper deficiency in nurseries trees (A) with formation of gum pockets in new branches (details in B) resulting from tissue breakdown and sap leakage, and in young trees in the field (C and D) showing long and vigorous twigs that grow tortuous.

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Copper (Cu) deficiency affects young citrus trees mostly when fertilized with high nitrogen (N) rates and under reduced foliar applications of Cu-based fungicides. On the other hand, trees are prone to Cu toxicity resulting from excessive applications of fungicides to control foliar and fruit diseases in the orchards. Despite Cu present in pesticid...

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Context 1
... deficiency has been verified by the appearance of visual symptoms (Mattos Junior et al., 2005), which in nursery trees are characterized by the formation of gum pockets in new branches resulted from tissue breaking down and consequent sap leakage from the xylem and phloem vessels (Figure 2A and 2B). Under severe Cu deficiency, die-back of stems is observed in trees, of which the Westin, a vigorous sweet orange variety, exhibits such problem more frequently in the field (Quaggio & Piza Junior, 2001). ...
Context 2
... severe Cu deficiency, die-back of stems is observed in trees, of which the Westin, a vigorous sweet orange variety, exhibits such problem more frequently in the field (Quaggio & Piza Junior, 2001). In non-bearing trees, these symptoms are characterized by the growth of branches that curve in "S" shape, leaf blades excessively developed and protruding veins on the underside (Figures 2C and 2D). These observations suggest that growth limitations occur and consequently potential maximum production of trees is affected. ...

Citations

... Moreover, extensive and overuse of copper (Cu) based agrochemicals, including fertilizers, herbicides, fungicides, and insecticides, have resulted in soil Cu contamination (Fan et al., 2011;Tomas Schoffer et al., 2020;Triantafyllidis et al., 2020;Mir et al., 2021). For example, soil in the Florida Indian River area contained up to 400 mg Cu kg − 1 soil because of excessive utilization of Cu-based fungicides in an effort to prevent or control citrus diseases (Fan et al., 2011;Hippler et al., 2017), which is beyond the permissible limits introduced by the European Union (50-140 mg kg − 1 ) and FAO (36-75 mg kg − 1 ) (Onyedikachi et al., 2018;Ahmad et al., 2021). Cu that has built up in soil cannot be degraded chemically or biologically and thus jeopardizes food security and the environment. ...
... The occurrence of a positive interaction between these two elements was due to the fact that Cu has a strong affinity with the nitrogen atom of the amino group, indicating that soluble nitrogen compounds, such as amino acids, act as Cu carriers in the xylem and phloem (Huang et al. 2021). On the other hand, in citrus, the exaggerated supply of N caused Cu deficiency (Hippler et al. 2017;Huang et al. 2021). With the exception of the biological fixation of legumes, no results were found to explain the increase in N concentration as a result of the increase in Cu levels. ...
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In plants, several chemical elements are found in different concentrations and formulations. Some of these elements influence each other, either through positive stimulation or inhibition. This study evaluated the correlation between nutrient contents and production components of Jatropha (Jatropha curcas L.). The experiment was conducted at the Federal University of Viçosa-MG, Brazil. A randomized block design with four replications was used. The treatments consisted of six Jatropha clones transplanted 4.5 years ago, from the municipalities of Janaúba and Bomfim, in Minas Gerais, Brazil. Yield was determined by harvesting the ripe and dried fruits, and the oil and protein contents in the grains were obtained by nuclear magnetic resonance. To determine nutrient contents, leaves were collected when the plants were in flowering, with yellow fruits and when the fruits were dry. There was a significant and negative association between grain yield and Mg content. Regarding foliar nutrient contents, the positive (r) significant correlations were between the following pairs: (N and S, r=0.554); (N and Cu, r=0.460); (P and Ca, r=0.420); (K and Zn, r=0.511); (K and Cu, r=0.506); (Ca and Mg, r=0.603); (Zn and Fe, r=0.662); (Zn and Mn, r=0.795); (Zn and Cu, r=0.574); (Fe and Mn, r=0.528) and (Mn and Cu, r=0.479); and the negative ones were between: (K and Ca, r=-0.596); (K and Mg, r=-0.673); (Mg and Cu, r=-0.506). Therefore, it was possible to prove the existence of nutritional interaction between some elements, as well as the effects on grain yields. This research will serve as a basis for studies to recommend fertilizer doses, plant improvement through nutritional efficiency, and studies in the area of biochemistry.
... Cu ions are cofactors in many enzymes, e.g., cytochrome c oxidase, Cu/Zn superoxide dismutase (SOD), amine oxidase, polyphenol oxidase, plastocyanin and laccase [19]. Cu deficiency disturbs metabolism, reduces stress resistance, damages enzyme systems and, in effect, reduces yields [20]. At high concentrations in tissues, Cu inhibits plant growth, disturbs photosynthetic electron transport and causes chlorosis, necrosis and dwarfism [21,22]. ...
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Different content of Zn in the soil and organic fertilization can affect micronutrient uptake by plants. A pot experiment was carried out to determine the impact of increasing Zn application rates, i.e., 200, 400 and 600 Zn mg·kg−1, in combination with bovine and chicken manures and mushroom substrate on Cu and Ni content, uptake and bioaccumulation factor in cocksfoot (Dactylis glomerata L.). Control objects without Zn and organic fertilizers and after application of only different Zn doses and only organic fertilizers were also tested. Application of Zn at 400 and 600 mg·kg−1 significantly decreased the content, uptake and value of bioaccumulation factor of Cu in the grass. Different Zn doses were not found to influence the content and bioaccumulation factor of Ni in cocksfoot, but application at 200 Zn mg·kg−1 increased Ni uptake. Chicken manure increased the content and bioaccumulation factor of Cu and Ni in the test plant, and all the organic fertilizers increased their uptake. Cocksfoot showed no tendency to excessive bioaccumulation of Cu and Ni.
... The occurrence of Cu deficiency in citrus plants has been suggested in newly planted and young orchards in soils with low levels of available nutrient, as well as in the production of seedlings in nurseries, in which the use of organic substrates favors the specific adsorption of this metal and limits root absorption (Mattos Jr. et al. 2010Hippler et al. 2017). ...
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Aims Copper (Cu) is essential for enzymatic systems, electron transport during photosynthesis, and lignin synthesis, affecting plant metabolism and growth. Cu deficiency is observed in young tree orchards, possibly induced by interaction with other mineral nutrients, although visual symptoms are not easily characterized. This study evaluated the induction of Cu deficiency in citrus, due to high nitrogen (N) fertilization, based on the assessment of biochemical parameters, gas exchange, and anatomy of plant tissues. Methods Valencia orange trees were submitted to levels of Cu supply via fertigation in addition to foliar spraying (control without Cu or with 2.4 g plant⁻¹ of Cu), and N (medium = 8.6 or high = 25.9 g plant⁻¹ of N) for 210 days. Results Plants well supplied with Cu exhibited higher electron transport rate, net CO2 assimilation, transpiration, and stomatal conductance, in comparison to the control without Cu. Those grown with high N exhibited greater electron transport rate compared to medium N. Plants without Cu and high N supply exhibited the lowest nitrate reductase activity, whereas plants fertilized with Cu and high N exhibited the greatest increase in the activity of this enzyme, in addition to the highest levels of total free amino acids. Furthermore, plants without Cu and high N exhibited the lowest Cu/Zn-SOD II isoform activity. Loose parenchyma structures of leaves and branches were associated with visual symptoms of Cu deficiency. Conclusion Plant responses demonstrated how Cu deficiency is induced in citrus trees by excess N, thus highlighting the importance of establishing best nutrient management for sustainable fruit production. Graphical Abstract
... It was estimated that 1-2 kg ha −1 year −1 of Cu and As and 5-9 kg ha −1 year −1 of Zn and Pb entered the soils under fruit production due to the repeated spraying of chemicals [66][67][68]. Fungicides with high Cu contents are currently used for citrus disease prevention in the United State [69]. Thirty years old citrus grove soil was reported to contain 200-300 mg kg −1 extractable Cu, which is 10-15 times higher than that in non-citrus soils [70]. ...
... It was estimated that 1-2 kg ha −1 year −1 of Cu and As and 5-9 kg ha −1 year −1 of Zn and Pb entered the soils under fruit production due to the repeated spraying of chemicals [66][67][68]. Fungicides with high Cu contents are currently used for citrus disease prevention in the United State [69]. Thirty years old citrus grove soil was reported to contain 200-300 mg kg −1 extractable Cu, which is 10-15 times higher than that in non-citrus soils [70]. ...
Article
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Soil pollution caused by potentially toxic metals has become a worldwide environmental issue. Geogenic processes and anthropogenic activities are two important sources of soil pollution. Soils may inherit toxic metals from parent materials; however, soil pollution mostly results from industrial and agricultural activities. Contamination by metals can be indicated by the changes in chemical, biochemical, and microbial properties of soils and plant responses. The total concentration of toxic metals in soil is still the most widely used indicator for risk assessment although extractable amounts have been reported to be more closely related to plant uptake. Several models have been proposed for assessing soil contamination by toxic metals, but none of them are commonly accepted for application to a wide range of soils. This review paper highlights how toxic metal contamination negatively affects soil and environmental quality, impacts food quality and security, and poses a threat to human health. Further research is needed to not only improve soil contamination diagnosis, modeling, and regulatory standards but also for remediation efficiency.
... Copper nutrition is critical in citrus development. Its deficiency is commonly associated with rapid growth in non-bearing trees following periods of high nitrogen fertilizer usage, and this leads to distorted leaf and twig growth and visual leaf chlorosis (Yruela, 2009; Hippler et al., 2017). Cu is poorly mobile in the phloem. ...
... Cu is poorly mobile in the phloem. Its application is recommended during periods of new vegetative growth (Marschner, 2012;Hippler et al., 2017) and should be regularly applied as foliar and ground fertilizer (Hippler et al., 2018). Cu is an important cofactor for many enzymes such as superoxide dismutase, amino oxidase, laccase, blue copper protein, and plastocyanin, but it also plays an important role for the transcription of protein trafficking machinery and oxidative phosphorylation (Yruela, 2005(Yruela, , 2009. ...
... Applications that increase Cu uptake in citrus could therefore be deemed valuable for agronomic purposes. Cu as a phytosanitary application has been used in the control of pathogens for many years (Russell, 2005;Hippler et al., 2017) and is considered a potent antimicrobial element (Vincent et al., 2018). The Cu portion of MFA may have contributed to the stabilization of HLB DI. ...
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Huanglongbing (HLB) is considered the most destructive disease in Citrus production and threatens the future of the industry. Microbial-derived defense elicitors have gained recognition for their role in plant defense priming. This work assessed a 5% (V/V) microbial fermentation application (MFA) and its role in the elicitation of defense responses in HLB-infected Citrus sinensis trees following a foliar application with a pump sprayer. Using a PCR detection method, HLB infection levels were monitored in healthy and infected trees for 20months. Nutrient analysis assessed N, P, K, Ca, Mg, Mn, Zn, Fe, B, and Cu concentrations in the trees. MFA significantly increased Cu concentrations in treated trees and resulted in the stabilization of disease index (DI) in infected trees. Initial real-time qPCR analysis of defense-associated genes showed a significant increase in pathogenesis-related protein 2 (PR2) and phenylalanine ammonia lyase (PAL) gene expression in healthy and HLB-infected trees in response to MFA. Gene expression of PR2 and PAL peaked 6h post-microbial fermentation application during an 8-h sampling period. A transcriptomic assessment using GeneChip microarray of the hour 6 samples revealed differential expression of 565 genes when MFA was applied to healthy trees and 909 genes when applied infected citrus trees when compared to their respective controls. There were 403 uniquely differentially expressed genes in response to MFA following an intersectional analysis of both healthy and infected citrus trees. The transcriptomic analysis revealed that several genes associated with plant development, growth, and defense were upregulated in response to MFA, including multiple PR genes, lignin formation genes, ROS-related genes, hormone synthases, and hormone regulators. This study provides further evidence that MFA may play an important role as a plant elicitor in an integrated pest management strategy in citrus and other agronomically important crops.
... In this regard, the fruit set is considered one most important indices of improved response fruit yield; [30,31] reported that fruit set and yield in citrus were significantly influenced by Zn fertilization. In addition, Cu deficiency is common in citrus trees that do not bear fruits during the first years after orchard establishment because of the increase in plant vigor through the application of high levels of nitrogen-containing fertilizers [32][33][34][35]. Zinc, on the other hand, is required for the production of auxin, the plant hormone responsible for cell elongation and growth [36]. ...
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The goal of this study was to examine how to improve the vegetative growth, nutritional status, productivity, and fruit quality of Washington navel orange trees by examining the effect of foliar application of ZnSO4 (0, 300, and 600 mg/L) solutions in combination with CuSO4 (0, 200, and 400 mg/L) solutions on Washington navel orange trees, which were 11 years old and grown in clay loam soil with a surface irrigation system. The results showed that all the investigated measurements responded specifically to each investigated factor. ZnSO4 elicited a stronger and more effective response than CuSO4. Nonetheless, the response varied only slightly or moderately from one measurement to the next. In terms of the interaction effect between ZnSO4 and CuSO4 concentrations, the effect of each investigated factor was directly reflected in its combinations, with ZnSO4 (600 mg/L) and CuSO4 (200 and 400 mg/L) being the most effective for the majority of the measurements under consideration. When the highest level of ZnSO4 was combined with the highest level of CuSO4, the highest values for the various vegetative growth parameters shoot length and diameter, number of leaves per shoot, leaf area, and total assimilation area per shoot were obtained. As a result, the nutritional status (the highest total leaf chlorophyll and leaf mineral contents) was significantly coupled with the treatment of 600 mg/L ZnSO4 in combination with 400 mg/L CuSO4. Moreover, the combinations of the highest ZnSO4 concentration (600 mg/L) and CuSO4 concentration (400 mg/L) exhibited the greatest statistical values of the measurements of fruiting aspects as well as fruit quality. Consequently, it can be recommended that using 600 mg/L ZnSO4 in combination with 400 mg/L CuSO4 as a foliar spray on monthly basis during the period from March to July could be safely recommended under similar environmental conditions and horticulture practices adopted in the present experiment.
... The wide use of Cu fungicides to control diseases is commonplace in citrus groves as in many other crops (Hippler et al. 2017;Fan et al. 2011). Kelepertzis (2014) observed soil metal accumulation due to agricultural practices mainly in citrus soils rather than other permanent crops. ...
... Usually, a large amount of Cu foliar is sprayed reaching soil by leaf run off (Fan et al. 2011). Li et al. (2005) reported high Cu concentrations in older apple orchards compared with younger ones, similarly to those observed in vineyards (Brunetto et al. 2014;Miotto et al. 2017;Hummes et al. 2019) and in citrus by Hippler et al. (2017). Also, the interpretation of our results based on previous studies, which reported that optimum available Cu in citrus orchards range from 2 to 6 mg kg −1 soil (Mattos-Jr et al. 2012;Li et al. 2015), showed that in 21.0% of tested soils, the levels of Cu DTPA were high to excessive (> 6 mg kg −1 ), pointing out that 94% of them belong to old (58.8%) and younger (35.2%) citrus groves. ...
Article
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Citrus fruits are cultivated in more than 100 countries around the world. The main citrus fruit–producing counties are Brazil, China, and the USA although the whole Mediterranean region ranks first worldwide. In Greece, citrus occupy an area of about 40.000 ha, representing 43% of total fruit crops. Soil quality is affected by long-term citrus cultivation. Soil organic matter is depleted in long-term citrus cultivation, in contrast to nutrients that seemed to increase in the following descending order: POlsen > Naecxh > NO3-N > Kecxh > Caecxh > Mgecxh due to usual management practices. To evaluate the environmental impact due to broad use of Cu fungicides in long-term citrus cultivation, Cu total fraction and DTPA-extractable in agricultural soil were determined. Soil contamination rate was evaluated via proper indices of different sensitivities on their calculations. In particular, 22% of samples in older orchards were highly polluted based on the single-factor pollution index (PI). The index geo-accumulation index (Igeo) presented hysteresis in comparison with PI, which was more sensitive, comprehensive, and reliable, able to describe better the pollution classification of citrus soils. The calculation of monomial potential ecological risk for Cu showed that in older citrus groves, the average value was 11.8, while the max value was 49.8 indicating moderate ecological risk suggesting the negative environmental impact of intensive citrus cultivation. These results denote the need to preserve soil fertility and prevent potential toxic element accumulation due to long-term cultivation management practices, aiming to achieve soil sustainability and food security in National or Euro-Mediterranean scale.
... On the other hand, B and Cu toxicities are increasingly found under specific growing conditions. This is the case in arid and semiarid regions where B accumulates in the root soil layer or because of the uneven application of B fertilizers (Papadakis et al., 2003;Bell and Dell, 2008), but also in areas where Cu accumulates in the soil due to Cu deposition as a result of foliar application of pesticides (Fan et al., 2011;Hippler et al., 2017a). Copper-induced stress damages to plants is minimized with the supply of N or Ca by enhancing the antioxidant system, while maintaining photosynthesis (Hippler et al., 2018b). ...