(micronutrient).An element essential to plant and animal nutrition in trace concentration, i.e., minute fractions of 1% (1000 ppm or less). Plants require iron, copper, boron, zinc, manganese, potassium, molybdenum, sodium, and chlorine. Animals require iron, copper, iron, manganese, cobalt, selenium, and potassium. Such elements are also called micronutrients. Do not confuse with tracer.