Distribution of growth and proton efflux in gravireactive roots of maize (Zea mays L.).

Roots of Zea mays were maintained in a vertical orhorizontal position and the local elongation rate and H(+) fluxes were measured using Sephadex beads containing a pH indicator. When the roots were kept horizontally, the growth of the lower side was strongly inhibited and that of the upper side slightly stimulated as compared with vertical roots. The H(+) extrusion, which was greatest in the elongation zone, was strongly inhibited on the lower side and slightly stimulated on the upper side as compared with vertical roots.