**Author details**

plants, nutritious solutions, and environmental factors often limit the absorption of K from the nutritious solution in sufficient quantity to optimize the quality attributes mentioned earlier [52]. K is a nutrient particularly required by carbohydrate-producing plants, as it participates in the photosynthetic process, transports carbohydrates from the leaves to the tuber or stalk, and activates the starch synthetase enzyme. In sugarcane, research results have shown a close relationship between the K content in the stems and with the sugar production. In the soybean culture, increased potassium fertilization promotes an increase in the grain protein content and a reduction in the oil content. This one fact can be understood by the participation of K in the process of protein synthesis in the plants. For citrus cultivation, it was observed that the increase of the K content in the leaves increases the size, the production, and the number of fruits. It also increases the vitamin C content and the percentage of acid in the juice, and decreases the con-

64 Potassium - Improvement of Quality in Fruits and Vegetables Through Hydroponic Nutrient Management

centration of soluble solids and the percentage of juice and solids/acid in the fruit.

responsible for the red color of tomato and watermelon [53].

involved in the synthesis of carotenoids and their precursors [54].

(UNIFENAS), encouragement and unconditional support.

**11. Final considerations**

calcium and magnesium.

**Acknowledgements**

The acidity in the tomato and the solids and starch content in the potato are positively correlated with the potassium fertilization, which also affects the composition and quality of strawberry, grape, grapefruit, pistachio, watermelon, and tomato. Generally, K appears to affect acidity, the pH, and carotenoid content. In tomato, the increase of K in the nutritive solution improves the color of the pulp and increases the content of lycopene, which is the carotenoid

Lycopene is not essential for humans and animals, but research shows that it is then beneficial because it has antioxidant properties, which neutralizes free radicals that can cause cell damage. Lycopene is the most sensitive pigment to K deficiency, since K being an essential cofactor for protein synthesis, its deficiency could lead to reduced rates of enzymatic reactions

Potassium presents many important functions in leaf and fruit vegetables, including enzymatic activation, regulation of the osmotic potential of cells, cell expansion, and opening and closing of the stomata, being the nutrient that most affects the quality of leaf and fruit vegetables. Due to potassium performance in several physiological processes, especially in the enzymatic activity, its adequate nutrition is fundamental for the development and quality of the vegetables. The horticulturist should prioritize the use of potassic fertilizers with lower salt content, if possible free of chlorine and containing magnesium and sulfur. However, it is essential to remember that the high potassium content in plants can induce deficiency of

This chapter received financial support from Fundação de Ensino e Tecnologia de Alfenas

Douglas José Marques<sup>1</sup> \*, Hudson Carvalho Bianchini1 , Allan Klynger da Silva Lobato2,3 and Wellington Ferrari da Silva4

\*Address all correspondence to: douglasjmarques81@yahoo.com.br

1 Setor de Olericultura e Experimentação, Universidade José do Rosário Vellano, Alfenas, Brazil

2 Núcleo de Pesquisa Vegetal Básica e Aplicada, Universidade Federal Rural da Amazônia, Paragominas, Brazil

3 Instituto Federal de Muzambinho, Muzambinho, Brazil

4 Departamento de Engenharia Nuclear, Programa de Pós-Graduação em Ciências e Técnicas Nucleares, Universidade Federal de Minas Gerais—UFMG, Belo Horizonte, Brazil
