Effects of nitrogen form and concentration on the distribution of ions within cucumber fruits

The objective of this study was to determine the influence of nitrogen concentration and the ratio of NO3 to NH4 on the distribution of inorganic elements within the tissues of cucumber fruit grown on rockwool. Nitrogen was supplied at three N concentrations and four ratios of NO3 to NH4. Increases in the total nitrogen concentration within the nutrient medium significantly increased the NO3 content of all the fruit tissues. but this effect was most pronounced in the skin. neck and apical region. The concentration of K, Ca. Mg and NO3 in all rcgions of the fruit was higher when NO, constituted 75% or more of the total N in the nutrient medium, but was reduced by increasing concentrations of NH4. The Mn content of the tissue in the central region of the fruit was reduced by NH4 ions, whereas the Cu content of this tissue increased. No significant effect of N form on the B, Fe, Zn content of fruits was detected. In contrast, the B content of the apical tissue and the Zn content of the skin declined significantly with increasing N level. The highest concentrations of K and NO were found in the neck and skin tissues, whereas the highest concentrations of Mn and Cu were observed only in the fruit skin. Mg concentrations were lowest in the tissues of the fruit neck, while B concentrations were highest in tissues near to the site of style abscissior. (C) 2002 Elsevier Science B.V. All rights reserved.