Dennis Robert Hoagland (April 2, 1884 – September 5, 1949) was an American chemist and plant and soil scientist working in the fields of plant nutrition, soil chemistry, agricultural chemistry, biochemistry, and physiology. He was Professor of Plant Nutrition at the University of California at Berkeley from 1927 until his death in 1949.
Dennis Hoagland is commonly known for discovering the active transport of electrolytes in plant cells, using innovative model systems under controlled experimental conditions, such as solution culture.
Hoagland was able to show that various plant diseases are caused by a lack of trace elements such as zinc and established their importance for plant nutrition and development.
He pioneered research into the interactions between plant and soil by establishing soil pH and the importance of soil solution, temperature and light for plant growth.
Hoagland and his associates formulated an artificial, complete inorganic nutrient medium, universally known as Hoagland solution, that continues to be used worldwide for culturing plants hydroponically.
Biography
Private life
Dennis Hoagland was the son of Charles Breckinridge Hoagland (1859 – 1934) and Lillian May Hoagland (1863 – 1951). He spent his first eight years in Golden and during his later childhood he lived in Denver. He attended the Denver public schools and in 1903 entered Stanford University. In 1920, Dennis R. Hoagland married Jessie A. Smiley. She died suddenly of pneumonia in 1933. He was left with the responsibility of bringing up three young boys named Robert Charles, Albert Smiley, and Charles Rightmire.
Career
Hoagland graduated from Stanford University (1907) with a major in chemistry. In 1908 he became an instructor and assistant in the Laboratory of Animal Nutrition at the University of California at Berkeley, an institution with which he would be associated for the remainder of his life. There he worked in the fields of animal nutrition and biochemistry. In 1910 he was appointed assistant chemist in the Food and Drug Administration of the U.S. Department of Agriculture until 1912 (Schmidt and Hoagland, 1912, 1919), when he entered the graduate school in the Department of Agricultural Chemistry with Elmer McCollum at the University of Wisconsin, receiving his master's degree in 1913 (McCollum and Hoagland, 1913). In the fall of that year he became assistant professor of agricultural chemistry and in 1922 associate professor of plant nutrition at Berkeley.
Hoagland was a founder of the Annual Review of Biochemistry and a proponent of the Annual Review of Plant Physiology and the Annual Review of Medicine which first appeared in 1950, after his death.
Work
Brief overview
During World War I, Hoagland tried to substitute the lack of imports of potassium-based fertilizers from the German Empire to the United States with plant extracts from brown algae, inspired by the ability of giant kelp to absorb elements from seawater selectively and to accumulate potassium and iodide many times in excess of the concentrations found in seawater (Hoagland, 1915). Based on these findings he investigated the ability of plants to absorb salts against a concentration gradient and discovered the dependence of nutrient absorption and translocation on metabolic energy. Innovative model systems and techniques, used under rigidly controlled experimental conditions, thus enabled the identification and isolation of individual variables in the measurement of plant-specific parameters (Hoagland, Hibbard, and Davis, 1926).
During his systematic research, mainly by solution culture technique, and inspired by a principle of Julius von Sachs and the work of Wilhelm Knop, he developed the basic formula for the Hoagland solution, whose composition was originally patterned after the displaced soil solution obtained from certain soils of high productivity (Hoagland, 1919)1. His research also led to new discoveries on the need and function of trace elements required by living cells, thus establishing the essentiality of molybdenum for the growth of tomato plants, for example (Arnon and Hoagland, 1940; Hoagland, 1945). Hoagland was able to show that various plant diseases are caused by a lack of trace elements such as zinc (Hoagland, Chandler, and Hibbard, 1931, ff.), and that boron, manganese, zinc, and copper are indispensable for normal plant growth (Hoagland, 1937).