**Author details**

diet. Consequently, eating food with low potassium content is an effective way to limit the potassium intake. On the other hand, limiting the amount of salt used is a more effective way of reducing sodium intake than concentrating only on eating foods with low sodium content. We conclude that the benefits of reducing the intake of potassium are greater than the risks of

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

The increase in glucose content in frilly lettuce and spinach for osmoregulation during potassium restriction treatment supports our hypothesis and resulted in elevated ascorbic acid levels (**Table 8**). A significant association between glucose content and ascorbic acid content in tomato under a salt stress condition has been previously reported [24]. It was reported that exogenous glucose treatment increased the ascorbic acid content in rice roots [25]. The increase in ascorbic acid content by potassium restriction was accompanied by an increase in GHLD activity (**Table 8**). Previous studies showed that ascorbic acid accumulates when GHDL is upregulated [26, 27]. Therefore, the increase in ascorbic acid content observed in this study may be attributable to the accumulation of the ascorbate matrix and the upregulation of

Glucose content and GLDH activity did not change with potassium restriction in green lettuce, although the level of ascorbic acid increased (**Table 8**). These findings suggest that an indicator induced an increase in the level of metabolites from glucose to ascorbic acid. It was reported that ascorbic acid content increased when exogenous galactonolactone was introduced [25]. In wheat, ascorbic acid contents change without increasing its GHDL activity [28]. These results support the results that ascorbic acid content increased without changes in

Glucose content increased with potassium restriction in red reef lettuce, although GLDH activity and ascorbic acid content remained the same. These results suggest that glucose is also used by other metabolic systems such as the glycolytic pathway and the synthesis path-

In this chapter, the author demonstrated a cultivation method to reduce the potassium content in leafy vegetables without causing significant potassium deficiency symptoms. Potassium content was also successfully reduced in tomatoes, with no significant change in the fresh weight per fruit, although the total yield was reduced. Furthermore, the author showed the changes of minerals and the ascorbic acid content and the mechanism. These results will con-

This study was partially supported by the Core Research for Evolutionary Science and Technology project, Japan Science and Technology Agency (Grant number JPMJCR15O4).

tribute to an improvement in the dietary quality of dialysis patients.

increasing the intake of sodium.

GHDL during potassium restriction.

glucose levels and GLDH activity.

ways for cellulose and starch.

**4. Conclusion**

**Acknowledgements**

Ogawa Atsushi1,2\*

\*Address all correspondence to: 111111@akita-pu.ac.jp

1 Department of Biological Production, Akita Prefectural University, Akita Japan

2 Japan Science and Technology Agency (JST), Project Core Research for Science and Technology (CREST), Saitama, Japan
