EFFECT OF FUSICOCCIN ON SUCROSE EXCHANGES BETWEEN A HOST, PELARGONIUM-ZONALE, AND A HIGHER PARASITIC PLANT, CUSCUTA-REFLEXA

The sucrose exchange characteristics at the level of contact between a host, Pelargonium zonale (L.) Aiton, and a parasite, Cuscuta reflexa Roxb., were investigated by studying the effects of fusicoccin (FC). W ith isolated haustoria of Cuscuta, FC stimulated the activity of the p lasma membrane ATPase. This action was established by FC-increased pro ton extrusion, FC-increased O-2 consumption and FC-increased Rb-86 upt ake. Nevertheless, FC strongly inhibited (by 30-50%) sucrose uptake an d strongly enhanced (by 42-47%) sucrose release. These results, which are discussed in relation to the physiology of the association between host and parasite, outline the very special properties of the haustor ium of Cuscuta.