Cryoanalytical studies of freezing damage and recovery in Fucus vesiculosus (Phaeophyceae)

Receptacles of Fucus vesiculosus L, were examined using cryoscanning electr on microscopy of rapidly frozen, hydrated tissue to avoid extraction and co llapse of the extracellular matrix (ECM) and provide new structural informa tion. The pore of the conceptacle was occluded by the tightly appressed tip s of the paraphyses, These were embedded in copious ECM within the concepta cle, The ECM inside the conceptacle and in the medulla differed markedly in texture and with respect to the distribution of S and Cl, as revealed by e nergy-dispersive X-ray microanalysis. High levels of S were restricted to t he conceptacle's ECM, whereas the ECM in the medulla was always S poor and Cl rich. Receptacles frozen naturally at low tide during the winter of 1998 showed extensive damage in the medulla, and this likely accounts for the c essation of reproduction during the winter on the Maine shore. The damaged receptacles recovered and resumed growth during the spring, and they releas ed gametes by May, Abscission of the overwintered receptacles was observed in June to July, coincident with the formation of new receptacles at the ti ps of newly grown portions of the fronds.