EFFECTS OF DICHLOROBENZONITRILE ON THE FORMATION OF CELL-WALL APPOSITIONS (PLUGS) IN INTERNODAL CELLS OF CHARA-CORALLINA KLEIN EX WILLD, EM RDW AND NITELLA-FLEXILIS (L) AG

The effect of dichlorobenzonitrile (DCB), an inhibitor of cellulose synthesis, on the formation of local cell wall appositions (plugs) was studied in internodal cells of the Characeae Chara corallina Klein ex. Willd, em. R. D. W. and Nitella flexilis (L.) Ag. DCB significantly reduces size and number of fibrillar, membrane-free plugs induced by 6 x 10(-2) M CaCl2. Formation of these plugs leads to an increase in the cellulose content which is abolished in the presence of DCB. Plugs formed during treatment with DCB have a less regular structure, but membrane recycling appears not to be disturbed. Cells are able to recover from DCB treatment and normal plugs are then formed. DCB has only minor effects on size, number and structure of amorphous, membrane-containing plugs induced by chlortetracycline (CTC) although their callose content is significantly enhanced. The data confirm that fibrillar plugs consist mainly of crystalline cellulose and that this polysaccharide does not play any role in the formation of amorphous plugs.