A physiological study of boron deficiency in plants

Abstract

does not appear. First page follows. Introduction Problems relating to the nutrition of plants have assumed an increasing importance since it is now evident that the so-called micronutrients play an important role not only in the physiology of the plants but often of animals which feed upon them. True, most soils contain these elements, but soils are known in which the amounts necessary for healthy plant growth fall below the critical level. It is a matter of record that the systems of farming in California which expanded horticulture in the latter part of the nineteenth and early twentieth centuries were for a time highly successful, but eventually in certain districts the fruit and vegetable crops were affected with hitherto unknown maladies unrelated to attacks of plant-disease organisms or of insects. The new maladies were termed “dieback,” “yellow leaf,” “sour sap,” “little-leaf,” “mottle-leaf,” “cork spot,” “decline,” and others, all of which connoted a general lack of vitality and fruitfulness. In an attempt to remedy the condition, soil amendments which included a wide range of materials were applied to orchards and fields, sometimes with success, but often contrariwise. When conventional methods of treatment failed to ameliorate the situation, it became apparent that new studies must be undertaken to ascertain the underlying causes of the unexplained crop failures. The problems were investigated from various angles; often false starts were made, but eventually it was discovered that small amounts of the micronutrients could overcome the unthrifty condition of some of the trees. An extensive series of experiments has demonstrated that the application of small quantities of manganese, or iron, or boron, or zinc can often restore unhealthy plants to vigor. Usually the salts of these elements are applied directly to the tree, but in vegetable growing they are applied to the soil.