Dielectric-Gravimetric Measurements onFucus vesiculosusandAscophyllum nodosumDuring Dehydration

Samples of the marine algae Fucus vesiculosus and Ascophyllum nodosum were dehydrated between plates of a condenser so that simultaneous measurements of dielectric properties and rate of water loss could be made. During the desiccation process, both the evaporation rate and the dielectric properties become zero at a critical hydration Hc, indicating that for H <Hc, the residual water must be in a tightly bound state. The absolute values of Hc, depend on the nature of the sample, but they are in the range 0·1–0·3, well above the hydration limit for active ion uptake (H=0·02). It is concluded that, in these fucoids, living cells are maintained in the hydration region where water is in the bound state only.