Chelation in the Absorption and Translocation of Mineral Elements

Abstract

Naturall y occurring chelates of heavy metals are probably important sources of these elements in the soil and undoubtedly this is the primary form in which they are absorbed and translocated in plants. The use of synthetic chelates as nutrient sources for agricultural plants has developed within the past 10 years. Following the development of practical applica­ tions for synthetic che1ates in agriculture in 1952, research has been stimu­ lated toward synthesizing new chelates and studying their properties. Be­ cause these new compounds can be made with a wide range of properties they are being used not only as agricultural sources of heav y metals but more important as tools to advance our knowledge about mechanisms of up­ take and translocation of these elements in plants. Wallace (1) reported in 1956 that about 200 papers had been written concerning the use of che­ lates in soil and plant nutrition. Since that time several hundred other stud ies have been published. This doe s not include the thous ands of papers written on the analytical uses of chelates, their synthesis, chemical prop­ erties and industrial Uses. A number of books have been written that COver various phases of chelation and the readers are referred to these for defi­ nitions and a broader scope of the subject (2 to 5). Many of the papers written on chelates in plant nutrition are contro­ versial. In some cases, apparently correct observations were made but lack of general information precluded drawing conclusions. In others, lack of replication and thoroughness of study has undoubtedly caused misinterpre­ tation of observations. Only a relatively few of the published papers will be cited in this review. However, an effort will be made to COver what this reviewer believes to be the pertinent