Localization of Nitrate Anion and Vitamin C in Japanese Radish, and the Effect of Fertilization Method on their Contents

Vegetables are important sources of vitamins and minerals; however, they also contain nitrate anion (NO3-), which is a risk factor for vascular diseases and cancer. This study was conducted to investigate the distribution of NO3- and vitamin C (VC) in Japanese radish, which is harvested throughout the year, and the changes in their contents resulting from different fertilization methods. The anatomical distribution of NO and VC differed significantly throughout the Japanese radish. Namely, NO3- in the tip of Japanese radish root was higher than in the end, in all regions of the cortical bundle, the vascular bundle, and the center. On the other hand, the VC content in the end of the root was higher than in the tip in all regions. The content of NO3- in the roots was positively correlated to the amount of nitrogen fertilizer applied during field growth. Treatments with low amounts of basal nitrogen fertilizer resulted in decreased NO3- in the roots. These results suggest that open cultivation with low amounts of basal fertilizer produces good quality Japanese radish containing high levels of VC and low levels of NO3-. (Received Sep. 6, 2012; Accepted Dec. 26, 2012)