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RESEARCH ARTICLE

Selenium desorption in tropical soils by sulfate and phosphate, and selenium biofortification of Mombaça grass under increasing rates of phosphate fertilisation

Maria Jéssica Vieira dos Santos A , Josimar Henrique de Lima Lessa A , Mateus Belisário de Assis A , Jéssica Francisco Raymundo A , Bruno Teixeira Ribeiro A , Luiz Roberto Guimarães Guilherme A and Guilherme Lopes https://orcid.org/0000-0002-7898-798X A B
+ Author Affiliations
- Author Affiliations

A Department of Soil Science, School of Agriculture, Federal University of Lavras, Lavras, MG 37200-900, Brazil.

B Corresponding author. Email: guilherme.lopes@ufla.br

Crop and Pasture Science - https://doi.org/10.1071/CP21059
Submitted: 28 January 2021  Accepted: 23 July 2021   Published online: 18 October 2021

Abstract

Selenium (Se) is essential for animals and humans, and studies assessing the influence of sulfur (S) and phosphorus (P) on Se availability and biofortification in tropical soils are required. This study evaluated the adsorption of selenate (SeVI) and selenite (SeIV) in two oxidic soils with contrasting soil texture and assessed effects of phosphate and sulfate as competitive anions on Se desorption. The study also examined Se biofortification of Panicum maximum cv. Mombaça grown in Se-treated clayey soil under increasing rates of P fertilisation. In the laboratory, different Se concentrations were added to soils for adsorption studies (0, 1, 2, 4 mg L–1 for SeVI and 0, 4, 8, 16 mg L–1 for SeIV), with Se desorption performed by adding different concentrations of P (0, 2.18, 4.36, 10.90, 21.90 mg L–1) or S (0, 3.75, 7.5, 15, 30 mg L–1). Mombaça grass was grown in pots for 43 days in the clayey soil fertilised with SeVI and increasing P rates. Selenium adsorption varied depending on Se speciation, Se rate and soil texture, with SeIV showing greater adsorption than SeVI. In general, amounts of SeVI desorbed increased with increasing addition of P and (mainly) S. However, only P had a positive effect for releasing SeIV from soils. At all SeVI rates added in the clayey soil, Se contents in the shoot dry matter of Mombaça grass increased with increasing P fertilisation rate, agreeing with the desorption results. Further studies combining desorption with biofortification data are recommended for assessing the influence of P in sandy clay loam tropical soils.

Keywords: biofortification, selenium speciation, Se sorption, Se availability, competitive anions, pasture, phosphate, sulfate, tropical soils.


References

Araújo SN (2019) Estratégias de aplicação de selênio para biofortificação do feijoeiro comum e seus efeitos residuais no capim Mombaça. MSc Dissertation, Federal University of Lavras, Lavras, MG, Brazil.

Araujo AM, Lessa JHL, Ferreira LA, Guilherme LRG, Lopes G (2018) Soil management and ionic strength on selenate retention in oxidic soils. Ciência e Agrotecnologia 42, 395–407.
Soil management and ionic strength on selenate retention in oxidic soils.Crossref | GoogleScholarGoogle Scholar |

Araujo AM, Lessa JHL, Lima FRD, Raymundo JF, Curi N, Guilherme LRG, Lopes G (2020a) Adsorption of selenite in tropical soils as affected by soil management, ionic strength, and soil properties. Journal of Soil Science and Plant Nutrition 20, 139–148.
Adsorption of selenite in tropical soils as affected by soil management, ionic strength, and soil properties.Crossref | GoogleScholarGoogle Scholar |

Araujo AM, Lessa JHL, Chanavat LG, Curi N, Guilherme LRG, Lopes G (2020b) How sulfate content and soil depth affect the adsorption/desorption of selenate and selenite in tropical soils? Revista Brasileira de Ciência do Solo 44, e0200087
How sulfate content and soil depth affect the adsorption/desorption of selenate and selenite in tropical soils?Crossref | GoogleScholarGoogle Scholar |

Bahia Filho AFC (1974) Fósforo em Latossolos do estado de Minas Gerais: intensidade, capacidade e quantidade de fósforo, fósforo ‘disponıvel’ e crescimento vegetal. PhD Thesis, Federal University of Viçosa, Viçosa, MG, Brazil.

Benedetti MM, Curi N, Sparovek G, Filho AC, Silva SHG (2011) Updated Brazilian’s georeferenced soil database: an improvement for international scientific information exchanging. In ‘Principles, application and assessment in soil science’. (Ed. EBO Güngör) pp. 307–330. (InTech: Rijeka, Croatia)

Boldrin PF, Faquin V, Ramos SJ, Boldrin KVF, Ávila FW, Guilherme LRG (2013) Soil and foliar application of selenium in rice biofortification. Journal of Food Composition and Analysis 31, 238–244.
Soil and foliar application of selenium in rice biofortification.Crossref | GoogleScholarGoogle Scholar |

Broadley M, Brown P, Cakmak I, Man JF, Rengel Z, Zhao F, et al. (2012) Beneficial elements. In ‘Marschner’s mineral nutrition of higher plants’. 3rd edn. pp. 249–269. (Academic Press: Cambridge, MA, USA)

Carvalho GS, Oliveira JR, Curi N, Schulze DG, Marques JJ (2019) Selenium and mercury in Brazilian Cerrado soils and their relationships with physical and chemical soil characteristics. Chemosphere 218, 412–415.
Selenium and mercury in Brazilian Cerrado soils and their relationships with physical and chemical soil characteristics.Crossref | GoogleScholarGoogle Scholar | 30476773PubMed |

Cominetti C, Bortoli MC, Garrido AB, Cozzolino SMF (2012) Brazilian nut consumption improves selenium status and glutathione peroxidase activity and reduces atherogenic risk in obese women. Nutrition Research 32, 403–407.
Brazilian nut consumption improves selenium status and glutathione peroxidase activity and reduces atherogenic risk in obese women.Crossref | GoogleScholarGoogle Scholar | 22749175PubMed |

Di Gregorio S, Lampis S, Malorgio F, Petruzzelli G, Pezzarossa B, Vallini G (2006) Brassica juncea can improve selenite and selenate abatement in selenium contaminated soils through the aid of its rhizospheric bacterial population. Plant and Soil 285, 233–244.
Brassica juncea can improve selenite and selenate abatement in selenium contaminated soils through the aid of its rhizospheric bacterial population.Crossref | GoogleScholarGoogle Scholar |

Eich-Greatorex S, Krogstad T, Sogn TA (2010) Effect of phosphorus status of the soil on selenium availability. Journal of Plant Nutrition and Soil Science 173, 337–344.
Effect of phosphorus status of the soil on selenium availability.Crossref | GoogleScholarGoogle Scholar |

Faria LA (2009) Levantamento sobre selênio em solos e plantas do estado de São Paulo e sua aplicação em plantas forrageiras. PhD Thesis, University of São Paulo, São Paulo, SP, Brazil.

Ferreira DF (2011) Sisvar: a computer statistical analysis system. Ciência e Agrotecnologia 35, 1039–1042.
Sisvar: a computer statistical analysis system.Crossref | GoogleScholarGoogle Scholar |

Fordyce FM (2007) Selenium geochemistry and health. Ambio 36, 94–97.
Selenium geochemistry and health.Crossref | GoogleScholarGoogle Scholar |

Fordyce FM (2013) Selenium deficiency and toxicity in the environment. In ‘Essentials of medical geology’. (Springer: Dordrecht, The Netherlands) 10.1007/978-94-007-4375-5_16

Freitas FP, Fonseca DM, Braz TGS, Martuscello JA, Santos MER (2012) Forage yield and nutritive value of Tanzania grass under nitrogen supplies and plant densities. Revista Brasileira de Zootecnia 41, 864–872.
Forage yield and nutritive value of Tanzania grass under nitrogen supplies and plant densities.Crossref | GoogleScholarGoogle Scholar |

Furlani AMC (2004) Nutrição mineral. In ‘Fisiologia vegetal’. pp. 40–75. (Guanabara Koogan: Rio de Janeiro)

Gabos MB, Alleoni LRF, Abreu CA (2014) Background levels of selenium in some selected Brazilian tropical soils. Journal of Geochemical Exploration 145, 35–39.
Background levels of selenium in some selected Brazilian tropical soils.Crossref | GoogleScholarGoogle Scholar |

Galić L, Vinkovié T, Ravnjak B, Loncarić Z (2021) Agronomic biofortification of significant cereal crops with selenium: a review. Agronomy 11, 1015
Agronomic biofortification of significant cereal crops with selenium: a review.Crossref | GoogleScholarGoogle Scholar |

Goh KH, Lim TT (2004) Geochemistry of inorganic arsenic and selenium in a tropical soil: effect of reaction time, pH and competitive anions on arsenic and selenium adsorption. Chemosphere 55, 849–859.
Geochemistry of inorganic arsenic and selenium in a tropical soil: effect of reaction time, pH and competitive anions on arsenic and selenium adsorption.Crossref | GoogleScholarGoogle Scholar | 15041289PubMed |

González-Morales S, Labrada-Pérez F, Leija-Martinez P, Medrano-Macías J, Dávila-Rangel IE, Juárez-Maldonado A, Rivas-Martinez EN, Benavides-Mendoza A (2017) Selenium and sulfur to produce Allium functional crops. Molecules 22, 558
Selenium and sulfur to produce Allium functional crops.Crossref | GoogleScholarGoogle Scholar |

Hossain A, Skalicky M, Brestic M, Maitra S, Sarkar S, Ahmad Z, Vemuri H, Garai S, Mondal M, Bhatt R, Kumar P, Banerjee P, Saha S, Islam T, Laing AM (2021) Selenium biofortification: roles, mechanisms, responses and prospects. Molecules 26, 881
Selenium biofortification: roles, mechanisms, responses and prospects.Crossref | GoogleScholarGoogle Scholar | 33562416PubMed |

Huo B, He J, Shen X (2020) Effects of selenium-deprived habitat on the immune index and antioxidant capacity of Przewalski’s gazelle. Biological Trace Element Research 198, 149–156.
Effects of selenium-deprived habitat on the immune index and antioxidant capacity of Przewalski’s gazelle.Crossref | GoogleScholarGoogle Scholar | 32040847PubMed |

Irfan M, Aziz T, Xu M (2020) Phosphorus (P) use efficiency in rice is linked to tissue-specific biomass and P allocation patterns. Natural Resources 10, 4278

Lanza MGDB, Silva VM, Montanha GS, Lavres J, Carvalho HWP, Reis AR (2021) Assessment of selenium spatial distribution using μ-XRF in cowpea (Vigna unguiculata (L.) Walp.) plants: integration of physiological and biochemical responses. Ecotoxicology and Environmental Safety 207, 111216
Assessment of selenium spatial distribution using μ-XRF in cowpea (Vigna unguiculata (L.) Walp.) plants: integration of physiological and biochemical responses.Crossref | GoogleScholarGoogle Scholar | 32916525PubMed |

Lara TS, Lessa JHL, Souza KRD, Corguinha APB, Martins FAD, Lopes G, Guilherme LRG (2019) Selenium biofortification of wheat grain via foliar application and its effect on plant metabolism. Journal of Food Composition and Analysis 81, 10–18.
Selenium biofortification of wheat grain via foliar application and its effect on plant metabolism.Crossref | GoogleScholarGoogle Scholar |

Lessa JHL, Araujo AM, Silva GNT, Guilherme LRG, Lopes G (2016) Adsorption–desorption reactions of selenium (VI) in tropical cultivated and uncultivated soils under Cerrado biome. Chemosphere 164, 271–277.
Adsorption–desorption reactions of selenium (VI) in tropical cultivated and uncultivated soils under Cerrado biome.Crossref | GoogleScholarGoogle Scholar |

Lessa JHL, Raymundo JF, Corguinha APB, Martins FAD, Araujo AM, Santiago FEM, Carvalho HWP, Guilherme LRG, Lopes G (2020) Strategies for applying selenium for biofortification of rice in tropical soils and their effect on element accumulation and distribution in grains. Journal of Cereal Science 96, 103125
Strategies for applying selenium for biofortification of rice in tropical soils and their effect on element accumulation and distribution in grains.Crossref | GoogleScholarGoogle Scholar |

Li Z, Liang D, Peng Q, Cui Z, Huang J, Lin Z (2017) Interaction between selenium and soil organic matter and its impact on soil selenium bioavailability: a review. Geoderma 295, 69–79.
Interaction between selenium and soil organic matter and its impact on soil selenium bioavailability: a review.Crossref | GoogleScholarGoogle Scholar |

Li H, Liu X, Wassie M, Chen L (2020) Selenium supplementation alleviates cadmium induced damages in tall fescue through modulating antioxidant system, photosynthesis efficiency, and gene expression. Environmental Science and Pollution Research International 27, 9490–9502.
Selenium supplementation alleviates cadmium induced damages in tall fescue through modulating antioxidant system, photosynthesis efficiency, and gene expression.Crossref | GoogleScholarGoogle Scholar | 31919821PubMed |

Liu X, Zhao Z, Duan B, Hu C, Zhao X, Guo Z (2015) Effect of applied sulfur on the uptake by wheat of selenium applied as selenite. Plant and Soil 386, 35–45.
Effect of applied sulfur on the uptake by wheat of selenium applied as selenite.Crossref | GoogleScholarGoogle Scholar |

Liu X, Yang Y, Deng X, Li M (2017) Effects of sulfur and sulfate on selenium uptake and quality of seeds in rapeseed (Brassica napus L.) treated with selenite and selenate. Environmental and Experimental Botany 135, 13–20.
Effects of sulfur and sulfate on selenium uptake and quality of seeds in rapeseed (Brassica napus L.) treated with selenite and selenate.Crossref | GoogleScholarGoogle Scholar |

Lopes AS, Guilherme LRG, Ramos SJ (2012) The saga of the agricultural development of the Brazilian Cerrado. IPI 60th Anniversary. e-ifc No. 32, pp. 29–57. International Potash Institute, Zug, Switzerland. Available at: https://www.ipipotash.org/publications/eifc-261 (accessed 9 September 2021)

Lopes G, Ávila FW, Guilherme LRG (2017) Selenium behavior in the soil environment and its implication for human health. Ciência e Agrotecnologia 41, 605–615.
Selenium behavior in the soil environment and its implication for human health.Crossref | GoogleScholarGoogle Scholar |

Malavolta E (1981) ‘Manual de química agrícola, adubos e adubações,’ 3rd edn. (Editora agronômica Ceres: São Paulo, SP, Brazil)

Martinez RAS (2013) Biofortificação agronômica da soja com selênio. PhD Thesis, Federal University of Lavras, MG, Brazil.

Matos RP, Lima VMP, Windmöller CC, Nascentes CC (2017) Correlation between the natural levels of selenium and soil physicochemical characteristics from the Jequitinhonha Valley (MG), Brazil. Journal of Geochemical Exploration 172, 195–202.
Correlation between the natural levels of selenium and soil physicochemical characteristics from the Jequitinhonha Valley (MG), Brazil.Crossref | GoogleScholarGoogle Scholar |

Mehra OP, Jackson ML (1958) Iron oxide removal from soils and clays by a dithionite-citrate system buffered with sodium bicarbonate. Clays and Clay Minerals 7, 317–327.
Iron oxide removal from soils and clays by a dithionite-citrate system buffered with sodium bicarbonate.Crossref | GoogleScholarGoogle Scholar |

Nakamaru YM, Sekine K (2008) Sorption behavior of selenium and antimony in soils as a function of phosphate ion concentration. Soil Science and Plant Nutrition 54, 332–341.
Sorption behavior of selenium and antimony in soils as a function of phosphate ion concentration.Crossref | GoogleScholarGoogle Scholar |

Nakamaru Y, Tagami K, Uchida S (2006) Effect of phosphate addition on the sorption-desorption reaction of selenium in Japanese agricultural soils. Chemosphere 63, 109–115.
Effect of phosphate addition on the sorption-desorption reaction of selenium in Japanese agricultural soils.Crossref | GoogleScholarGoogle Scholar | 16376408PubMed |

Natasha Shahid M, Niazi NK, Khalid S, Murtaza B, Bibi I, Rashid MI (2018) A critical review of selenium biogeochemical behavior in soil-plant system with an inference to human health. Environmental Pollution 234, 915–934.
A critical review of selenium biogeochemical behavior in soil-plant system with an inference to human health.Crossref | GoogleScholarGoogle Scholar |

National Institutes of Health (2021) Selenium: fact sheet for health professionals. Office of Dietary Supplements, National Institutes of Health, Bethesda, MD, USA. Available at: https://ods.od.nih.gov/factsheets/Selenium-HealthProfessional/#h3 (accessed 22 March 2021)

Oliveira KD, França TN, Nogueira VA, Peixoto PV (2007) Enfermidades associadas à intoxicação por selênio em animais. Pesquisa Veterinaria Brasileira 27, 125–136.
Enfermidades associadas à intoxicação por selênio em animais.Crossref | GoogleScholarGoogle Scholar |

Ramkissoon C, Degryse F, Silva RC, Baird R, Young SD, Bailey EH, McLaughlin MJ (2019) Improving the efficacy of selenium fertilizers for wheat biofortifcation. Scientific Reports 9, 19520
Improving the efficacy of selenium fertilizers for wheat biofortifcation.Crossref | GoogleScholarGoogle Scholar | 31863023PubMed |

Ramos SJ, Ávila FW, Boldrin PF, Pereira FJ, Castro EM, Faquin V, Reis AR, Guilherme LRG (2012) Response of brachiaria grass to selenium forms applied in a tropical soil. Plant, Soil and Environment 58, 521–527.
Response of brachiaria grass to selenium forms applied in a tropical soil.Crossref | GoogleScholarGoogle Scholar |

Rayman M (2012) Selenium and human health. Lancet 379, 1256–1268.
Selenium and human health.Crossref | GoogleScholarGoogle Scholar | 22381456PubMed |

Reis HPG, Barcelos JPQ, Silva VM, Santos EF, Tavanti RFR, Putti FF, Young SD, Broadley MR, White PJ, Reis AR (2020) Agronomic biofortification with selenium impacts storage proteins in grains of upland rice. Journal of the Science of Food and Agriculture 100, 1990–1997.
Agronomic biofortification with selenium impacts storage proteins in grains of upland rice.Crossref | GoogleScholarGoogle Scholar | 31849063PubMed |

Ribeiro AC, Guimarães PTG, Alvarez VVH (Eds) (1999) ‘Recomendação para o uso de corretivos e fertilizantes em Minas Gerais: 5. Aproximação.’ (Comissão de Fertilidade do solo do Estado de Minas Gerais: Viçosa, MG, Brazil)

Saha U, Fayiga A, Sonon L (2017) Selenium in the soil-plant environment: a review. International Journal of Applied Agricultural Science 3, 1–18.
Selenium in the soil-plant environment: a review.Crossref | GoogleScholarGoogle Scholar |

Santos JZL, Furtini Neto AE, Resende AV, Carneiro LF, Curi N, Moretti BS (2011) Resposta do feijoeiro à adubação fosfatada em solos de Cerrado com diferentes históricos de uso. Revista Brasileira de Ciência do Solo 35, 193–202.
Resposta do feijoeiro à adubação fosfatada em solos de Cerrado com diferentes históricos de uso.Crossref | GoogleScholarGoogle Scholar |

Sarwar N, Akhtar M, Kamran MA, Imran M, Riaz MA, Kamran K, Hussain S (2020) Selenium biofortifcation in food crops: key mechanisms and future perspectives. Journal of Food Composition and Analysis 93, 103615
Selenium biofortifcation in food crops: key mechanisms and future perspectives.Crossref | GoogleScholarGoogle Scholar |

Schiavon M, Nardi S, Vecchia FD, Ertani A (2020) Selenium biofortification in the 21st century: status and challenges for healthy human nutrition. Plant and Soil 453, 245–270.
Selenium biofortification in the 21st century: status and challenges for healthy human nutrition.Crossref | GoogleScholarGoogle Scholar |

Schomburg L (2017) Dietary selenium and human health. Nutrients 9, 1–22.

Schwertmann U (1973) Use of oxalate for Fe extraction from soils. Canadian Journal of Soil Science 53, 244–246.
Use of oxalate for Fe extraction from soils.Crossref | GoogleScholarGoogle Scholar |

Snyder MM, Um W (2014) Adsorption mechanisms and transport behavior between selenate and selenite on different sorbents. International Journal of Waste Resources 4, 1–8.

Söderlund M, Virkanen J, Holgersson S, Lehto J (2016) Sorption and speciation of selenium in boreal forest soil. Journal of Environmental Radioactivity 164, 220–231.
Sorption and speciation of selenium in boreal forest soil.Crossref | GoogleScholarGoogle Scholar | 27521902PubMed |

Soil Survey Staff (2014) ‘Keys to Soil Taxonomy.’ 12th edn. (U.S. Department of Agriculture, Natural Resources Conservation Service: Washington, DC)

Sposito G (2008) ‘The chemistry of soils.’ (Oxford University Press: Oxford, UK)

Stroud J, Broadley MR, Foot I, Fairweather-Tait S, Hart DJ, Hurst R, Knott P, Mowat H, Norman K, Scott P, Tucker M, White PJ, McGrath SP, Zhao FJ (2010) Soil factors affecting selenium concentration in wheat grain and the fate and speciation of Se fertilisers applied to soil. Plant and Soil 332, 19–30.
Soil factors affecting selenium concentration in wheat grain and the fate and speciation of Se fertilisers applied to soil.Crossref | GoogleScholarGoogle Scholar |

Teixeira PC, Donagemma GK, Fontana A, Teixeira WG (2017) ‘Manual de métodos de análise de solo.’ (Empresa Brasileira de Pesquisa Agropecuária (EMBRAPA), Ministério da Agricultura, Pecuária e Abastecimento: Brasilia, DF)

USEPA (2007) Method 3051 A: micro- wave assisted acid digestion of sediments sludges, soils and oils. In ‘Sw-846 test methods for evaluation of solid waste physical and chemical methods’. pp. 1–30. (Office of Solid Waste, United States Environmental Protection Agency: Washington, DC) Available at: https://www.epa.gov/sites/production/files/2015-12/documents/3051a.pdf (accessed 12 September 2021)

Vega Ravello R, Oliveira C, Lessa J, Vilas Boas LV, Castro EM, Guilherme LRG, Lopes G (2021) Selenium application influenced selenium biofortification and physiological traits in water-deficit common bean plants. Crop & Pasture Science
Selenium application influenced selenium biofortification and physiological traits in water-deficit common bean plants.Crossref | GoogleScholarGoogle Scholar |

Violante A, Cozzolino V, Perelomov L, Caporale AG, Pigna M (2010) Mobility and bioavailability of heavy metals and metalloids in soil environments. Journal of Soil Science and Plant Nutrition 10, 268–292.
Mobility and bioavailability of heavy metals and metalloids in soil environments.Crossref | GoogleScholarGoogle Scholar |

Wang D, Zhou F, Yang W, Peng Q, Man N, Liang D (2017) Selenate redistribution during aging in different Chinese soils and the dominant influential factors. Chemosphere 182, 284–292.
Selenate redistribution during aging in different Chinese soils and the dominant influential factors.Crossref | GoogleScholarGoogle Scholar | 28500973PubMed |

Winkel LH, Vriens B, Jones GD, Schneider LS, Pilon-Smits E, Bañuelos GS (2015) Selenium cycling across soil-plant-atmosphere interfaces: a critical review. Nutrients 7, 4199–4239.
Selenium cycling across soil-plant-atmosphere interfaces: a critical review.Crossref | GoogleScholarGoogle Scholar | 26035246PubMed |

Withers PJA, Rodrigues M, Soltanghesi A, Carvalho TS, Guilherme LRG, Benites VM, Gatiboni LC, Sousa DMG, Nunes RS, Rosolem CA, Andreote FD, Oliveira Júnior A, Coutinho ELM, Pavinato PS (2018) Transitions to sustainable management of phosphorus in Brazilian agriculture. Scientific Reports 8, 2537
Transitions to sustainable management of phosphorus in Brazilian agriculture.Crossref | GoogleScholarGoogle Scholar | 29416090PubMed |

Zhang D, Dong T, Ye J, Hou Z (2017) Selenium accumulation in wheat (Triticum aestivum L.) as affected by coapplication of either selenite or selenate with phosphorus. Soil Science and Plant Nutrition 63, 37–44.
Selenium accumulation in wheat (Triticum aestivum L.) as affected by coapplication of either selenite or selenate with phosphorus.Crossref | GoogleScholarGoogle Scholar |

Zhang J, Taylor EW, Bennett K, Saad R, Rayman MP (2020) Association between regional selenium status and reported outcome of COVID-19 cases in China. The American Journal of Clinical Nutrition 111, 1297–1299.
Association between regional selenium status and reported outcome of COVID-19 cases in China.Crossref | GoogleScholarGoogle Scholar | 32342979PubMed |