Mineral composition in the holdfast of three brown algae of the genus Laminaria

The mineral (Na, K, Ca, Mg, Fe, Mn and Zn) contents in the holdfast of three brown algae of the genus Laminaria were determined to compare with those in frond and stipe. The wild and cultivated kelps of Laminaria japonica, L. ochotensis, and L. diabolica were used as samples. The K content was markedly high (11.76-14.91 g/100 g dry weight) in the holdfast of cultivated L. japonica; the K/Na ratio (3.88-5.18) of the holdfast was greater than those of frond and stipe as well as the reported values of frond (1.0-2.2). The content of Ca in the holdfasts of these three species was also higher than those in frond and stipe. The content of Mn showed the same tendency. This is the first report showing that the holdfast of L. japonica and L. diabolica is rich in minerals, especially K.