INFLUENCE OF MINERALS ON CYTOPLASMIC STREAMING IN ROOT HAIRS OF INTACT WHEAT SEEDLINGS (TRITICUM-AESTIVUM L)

The calcium dependency of the cytoplasmic streaming of wheat root hair s was demonstrated by adding the Ca-Ionophore A 23187. Within three mi nutes the streaming velocity was decreased dramactically. The influenc e of ammonium on the cytoplasmic streaming is highly pH-dependent. Whi le at a pH of 9.0 an inhibitory effect was observed even at low ammoni um concentrations (0.5 mM) no effect could be measured at a pH of 6.5. Nitrate, independently of medium pH had no effect on the cytoplasmic streaming. The same is true for aluminium. It is suggested that at pH 9 ammonium permiates the plasmalemma as NH3. Due to higher cytoplasmic pH (similar to 7.5), NH3 is protonated leading to an increase in cyto plasmic pH. Ammonium may displace sorbed calcium leading to an increas e in the free cytoplasmic calcium responsible for the cessation of the streaming. Alternative explanations are discussed.