PRODUCTION OF HYALINE HAIRS BY INTERTIDAL SPECIES OF FUCUS (FUCALES) AND THEIR ROLE IN PHOSPHATE UPTAKE1

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Abstract
A field study to determine the precise times of year at which three intertidal species of Fucus start to produce hyaline hairs and cease producing such hairs was conducted on the Isle of Man, U.K. Hairs were first observed during February, and within 6 days of their initial appearance, all tagged plants of all species at all tidal heights on the shore possessed hairs. Hair production continued until the beginning of October, at which time Fucus plants growing at the lowest stations (+ 3.0 m) had glabrous apical growth. Hair production continued later into the year for plants growing higher on the shore, and it was not until mid‐November that glabrous apical growth was observed in all plants.Phosphate uptake rates of pilose (hairy) and glabrous (hairless) apical sections were measured in November 1988 for F. spiralis L. and in January 1989 for F. spiralis and F. serratus L., at phosphate concentrations ranging from 0.8 μM (ambient seawater) to 9.0 μM. In ambient seawater, pilose plants of F. spiralis removed phosphate 2–3 times faster than glabrous plants, whereas the uptake rates of pilose plants of F. serratus were about 50% greater than those of glabrous plants. The differences between uptake rates of pilose and glabrous plants of both species were smaller or nonsignificant at higher phosphate concentrations. The field and laboratory data are consistent with the hypothesis that hairs are formed in Fucus as a response to increased nutrient demand and that hairs facilitate the uptake of nutrients from seawater at concentrations typical of natural situations.