Rare Earth Elements, Microorganisms, and Control of Plant Diseases

Summary Rare earth elements (REEs) are a group of trace metals relatively abundant in the Earth ’ s crust. REEs are widely dispersed in small concentrations throughout the environment. These elements demonstrate similar physical and chemical properties. REEs have been widely used in various areas of industry, agriculture and medicine. China was the first country to commercially apply REE products as micro-fertilizers or growth simulators in agriculture. Although REEs are not essential for living organisms, they can influence their life processes. Results of recent investigations demonstrate that hormesis commonly occurs in a variety of plants and microorganisms in response to REEs. REEs affect the growth, reproduction and metabolism of microorganisms. Microorganisms are involved in all geochemical cycles of metals. They can produce various organic acids and other substances capable of mobilizing REEs in the soil, thereby promoting their uptake by plants. Metals can be bound by microorganisms through bioadsorption, bioaccumulation, and interactions with metabolic products, which may help in reducing metal leaching and increase their availability to plants. As a result, microorganisms can be used for the revitalization of habitats polluted by metals, primarily water. It was found that REEs can directly and indirectly affect several types of plant pathogens. REEs can control some phytopathogens directly by reducing their growth and virulence in host plants, while also eliciting disease resistance response in plants. The mechanisms by which REEs act against plant diseases result from complex interactions of many biotic and abiotic factors, which indicates the multifaceted nature of this phenomenon. Current evidence confirms that REEs can control pathogens under certain conditions. However, further studies investigating the mechanisms by which REEs control pathogens and performance of individual elements are necessary for their further application.