tailieunhanh - Handbook of Plant Nutrition - chapter 13

13 Molybdenum Molybdenum was discovered in 1778 by the Swedish chemist, Carl Wilhelm Scheele. However, its importance in biological systems was not established until 1930 when Bortels discovered that molybdenum was essential for the growth of Azotobacter bacteria in a nutrient medium. | 6 6 2006 1 13 PM Page 375 13 Molybden um Russell L. Hamlin Coggins Farms and Produce Lake Park Georgia CONTENTS Historical Information .375 Determination of Function in Plants .376 Nitrogenase .376 Nitrate Reductase .377 Xanthine Dehydrogenase .377 Aldehyde Oxidase .378 Sulfite Oxidase .378 Diagnosis of Molybdenum Status of Deficiency .378 Molybdenum Concentration and Distribution in Plants .379 Analytical Techniques for the Determination of Molybdenum in Plants .382 Assessment of Molybdenum Status of Soils .382 Soil Molybdenum Forms of Molybdenum in Soils .384 Interactions with Phosphorus and Soil Analysis .386 Determination of Total Molybdenum in Soil .386 Determination of Available Molybdenum in Molybdenum Fertilizers .387 Methods of Application .387 Soil Applications .387 Foliar Seed Treatment .388 Crop Response to Applied Molybdenum .388 References .389 HISTORICAL INFORMATION Determination of Essentiality Molybdenum was discovered in 1778 by the Swedish chemist Carl Wilhelm Scheele. However its importance in biological systems was not established until 1930 when Bortels discovered that molybdenum was essential for the growth of Azotobacter bacteria in a nutrient medium 1 . Subsequently 375 6 6 2006 1 13 PM Page 376 376 Handbook of Plant Nutrition in 1936 Steinberg determined that molybdenum was required for the growth of the fungus Aspergillus niger 2 . The essential nature of molybdenum for higher plants was first reported by Arnon and Stout in 1939 3 . In earlier experiments Arnon observed that minute amounts of molybdenum improved the growth of plants in solution culture 4 and that a group of seven heavy metals including .