**4. Potassium nutrition and quality of seeds and seedlings**

The attention to adequate potassium nutrition must occur from the acquisition of seeds because nutritional status of mother plant affects not only the final yield of crop but also the quality of seeds produced. For example, Marrush et al. [40] found that K deficiency benefits a high incidence of premature germination, in other words, viviparity in bell pepper plants (*Capsicum annum* L. cv. "California wonder").

In hydroponic crops, nitrogen is mainly supplied as nitrate (NO3−). For leafy vegetables, the accumulation of NO3− is a concern for humans, especially for children, it can be harmful to health, depending on the amount consumed in the diet [52]. Thus, the inclusion of ammoniacal N can promote a significant increase in productivity and contribute to growing demand for safer foods. However, several factors may alter the availability of ammonium

) to plants and increase their rate of absorption by plants, which may lead to phyto-

are very similar in relation to valence and ionic radius, in addition to being

Potassium Nutrition in Fruits and Vegetables and Food Safety through Hydroponic System

was possible to maintain plant productivity, increasing the K concentration

+ , since 29

[54]. In addition,

and a low concen-

+

http://dx.doi.org/10.5772/intechopen.71742

+

Potassium nutrition is efficient in minimizing the phytotoxic effects of excess NH<sup>4</sup>

uptake and thereby mitigate the phytotoxic effects of excess NH<sup>4</sup>

affected, compared to plants cultivated with a high concentration of NH<sup>4</sup>

lower incidence of diseases, and increased quality of product harvested.

**6. Potassium and post-harvest nutrition of vegetables**

absorbed by the same carrier. Thus, increased K concentration may inhibit or even decrease

Hernandez-Gomez et al. [55] verified that the cultivation of peppers with high concentra-

of nutrient solution, which resulted in adequate K contents in the plant tissue. Also, in this study, the water relations, the photosynthetic rate, and the stomatal conductance were not

K plays a very important role in the mitigation of biotic stresses to which plants are susceptible, since it participates in the synthesis of high-molecular-weight compounds such as proteins, starch, and cellulose, reducing the accumulation of soluble sugars, organic acids, and amides, of which pathogens are fed [3]. In this context, Perrenoud [56] gathered a series of studies where the incidence of pests and diseases was reduced as a function of nutrition with K and diverse cultures. However, there are important relationships of K with other nutrients, and an adequate K/N ratio in plant tissue may be responsible for increased productivity,

For example, Adams and Massey [57], in order to maximize productivity, fruit quality, and greater resistance to diseases in tomato, suggest a K/N ratio of 1.2/1 in vegetative stage and 2.5/1 in reproductive stage. Another important factor to consider is the nutrient concentrations, which must be adjusted, depending on several factors. This way, Nam et al. [58] demonstrated a concentration of K in strawberry; this element was responsible for a higher productivity, but was not the same that bring results about lower incidence of diseases, which

Potassium is present in plant cells in cationic form K and plays an important role in the physiological activity of plants. In addition to metabolic functions of K in photosynthetic metabolism, enzyme activation, protein synthesis, osmotic regulation, and stomatal movement [59], K has a close relationship with post-harvest quality of vegetables, because post-harvest parameters such as fruit size, soluble solids, lycopene, and vitamin C concentration are influ-

indicates that in conditions of high productivity, the quality of food can be affected.

(NH4 +

NH4 +

toxicity [53].

K and NH4

tions of NH4

tration of K.

+

+

enced by this nutrient.

Consequently, the deficiency of K in mother plant, during the phenological stage of seed formation, may decrease the germination rate of harvested seeds [41]. However, the seeds of plants well-nourished with K may present the germination rate due to the accompanying ion of the source of K used, because of a negative correlation between germination percentage and concentration of Cl in sweet pepper seeds [42].

In relation to the production of *Brassica oleracea* seedlings, Zhang et al. [43] have demonstrated that although it depends on a relationship with other nutrients, the enrichment of substrate with K provides more vigorous seedlings. However, there is little research to verify if investment in seedling production is offset by the final productivity of plant in the field.
