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Handbook of Plant Nutrition - chapter 18

18 Selenium Selenium (Se), a beneficial element, is one of the most widely distributed elements on Earth, having an average soil abundance of 0.09 mg kg 1 (1). It is classified as a Group VI A metalloid, having metallic and nonmetallic properties. Selenium was identified in 1818 by the Swedish chemist | CRC_DK2972_Ch018.qxd 7 14 2006 11 59 AM Page 51 18 Selenium Dean A. Kopsell University of Tennessee Knoxville Tennessee David E. Kopsell University of Wisconsin-Platteville Platteville Wisconsin CONTENTS 18.1 The Element Selenium.515 18.1.1 Introduction.515 18.1.2 Selenium Chemistry.516 18.2 Selenium in Plants.517 18.2.1 Introduction.517 18.2.2 Uptake.517 18.2.3 Metabolism.518 18.2.4 Volatilization.520 18.2.5 Phytoremediation .520 18.3 Selenium Toxicity to Plants .521 18.4 Selenium in the Soil .521 18.4.1 Introduction.521 18.4.2 Geological Distribution.522 18.4.3 Selenium Availability in Soils.523 18.5 Selenium in Human and Animal Nutrition.524 18.5.1 Introduction.524 18.5.2 Dietary Forms.524 18.5.3 Metabolism and Form of Selenium.525 18.6 Selenium and Human Health .525 18.6.1 Introduction .525 18.6.2 Selenium Deficiency and Toxicity in Humans.525 18.6.3 Anticarcinogenic Effects of Selenium.526 18.6.4 Importance of Selenium Methylation in Chemopreventive Activity .526 18.7 Selenium Enrichment of Plants.526 18.8 Selenium Tissue Analysis Values of Various Plant Species.543 References.543 18.1 THE ELEMENT SELENIUM 18.1.1 Introduction Selenium Se a beneficial element is one of the most widely distributed elements on Earth having an average soil abundance of 0.09 mg kg 1 1 . It is classified as a Group VI A metalloid having 515 CRC_DK2972_Ch018.qxd 7 14 2006 11 59 AM Page 51 516 Handbook of Plant Nutrition metallic and nonmetallic properties. Selenium was identified in 1818 by the Swedish chemist Jons Jacob Berzelius as an elemental residue during the oxidation of sulfur dioxide from copper pyrites in the production of sulfuric acid 2 . The name selenium originates through its chemical similarities to tellurium Te discovered 35 years earlier. Tellurium had been named after the Earth tellus in Latin so selenium was named for the moon selene in Greek 3 . Although selenium is not considered as an essential plant micronutrient 4 it is essential for maintaining mammalian .