Despite the fact that micronutrients are required in very low concentrations
by plants, they are as essential for plant metabolism and growth as macronutrients.
Foliar analysis is a valuable tool in order to detect micronutrient deficiencies before
macroscopic symptoms appear in plants; for that purpose, critical micronutrient
concentrations have been established. Other diagnostic tools used to assess
micronutrient deficiencies are soil analysis, plant-growth response (in annual plants),
and visual observation of symptoms. Recently, more and more biochemical indicators,
as early detectors of micronutrient deficiencies, are used. Fertilization (soil or foliar
application) should be included in the cultivation program in order to improve the low
nutritional status of plants. However, before fertilization, it is absolutely necessary to
have a deep knowledge of the physiological roles of the necessary micronutrients for
normal plant growth. So, the physiological roles of micronutrients, as well as some
critical deficiency concentrations in soils and plants, are presented in detail and fully
discussed in this chapter.
Keywords: Critical concentrations, foliar deficiency symptoms, micronutrient
deficiency, micronutrient sufficiency, plant growth, plant metabolism,
physiological roles.
