Plants determine whether an element is essential based on their own physiological and developmental needs. Elements in plant tissues are classified as essential  and non-essential . According to the required amount, essential nutrients are divided into macronutrients — nitrogen (N), phosphorus (P), and potassium (K); secondary nutrients — sulfur (S), calcium (Ca), and magnesium (Mg); and micronutrients — boron (B), iron (Fe), copper (Cu), zinc (Zn), manganese (Mn), molybdenum

I. Introduction In orchards, zinc deficiency in citrus trees can lead to chlorotic spots on leaves, slow growth of new shoots, fruit...