Study and relationship between ions, whether essential or not, and their biochemical indicators with the aim of early and effective detection of possible deficiency and/or toxicity states, particularly in horticultural plants. Another essential aspect of this line of research is how alterations in the ionic status of the plants could influence the production and nutritional quality of plant products intended for human consumption. Finally, the role played by some ionic elements termed beneficial is analysed, for example, selenium and iodine, in nutrition, physiology and the agricultural characteristics of the plants.