Investigations on copper deficiency in plants

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Abstract
A water-culture technique has been described which makes it possible to determine with precision the effects on plant growth resulting from the absence of traces of the various heavy metals.The essential nature of copper for plant growth has been confirmed, and the quantitative data presented show that the addition of traces of copper to a nutrient solution leads to increases of growth of the order of 200–1200%.The characteristic symptoms produced by growing oats, peas, wheat, Wimmera rye-grass, Phalaris, flax, tomato, subterranean clover, and lucerne in nutrient solutions devoid of copper are described. Copper becomes necessary for normal healthy growth at an early seedling stage and is required so long as active growth is proceeding. Optimum growth of oats was obtained throughout a wide range of copper concentration in the nutrient solution.Oats grown in a copper-free nutrient solution until the development of acute deficiency symptoms recovered and completed their normal life cycle on the addition of sufficient copper to the solution.The copper content of oats at various stages of growth has been determined. The proportion of copper in the dry matter of the plant was greatest in the young stages and rapidly decreased as growth proceeded.The copper content of mature oat plants showing symptoms of copper deficiency was less than 1·0 mg. per kg. whether grown in nutrient solution or obtained from copper-deficient soils. Oats which ceased growth from copper deficiency at an earlier stage of development contained a relatively greater amount of copper in their dry matter.