PREPARATION AND INITIATION OF GROWTH IN AXIAL ORGANS OF GERMINATING QUIESCENT SEEDS .2. INITIATION OF ACID GROWTH IN THE AXIAL ORGANS OF BROAD BEAN-SEEDS

In the axial organs of imbibing and germinating bean seeds (Vicia faba var. minor L.) the phenomenon of acid growth was studied during early cell elongation. Radicle emergence was preceded by proton extrusion t o ambient solution. Acid buffer promoted the initiation of cell elonga tion and radicle protrusion. Acidification of the ambient solution and initiation of cell elongation were inhibited by diethylstilbestrol an d ortho-vanadate, but stimulated by fusicoccin. The conclusion was dra wn that the initiation of cell elongation, which follows the pattern o f acid growth, was preceded by activation of plasmalemma H+-ATPase occ urring at the threshold (68%) water content in axial organs. Protons e xtruded by ATPase into cell was enhanced the plasticity of cell walls, thus facilitating the initiation of cell elongation.