Effects of FC, GA and ABA on the developement of K uptake in germinating radish seeds

Effects of FC, GA3 and ABA on the development of K uptake in germinating radish seeds Germination of Rhaphanus sativus seeds is accompanied in its early phase by a consistent loss to the medium af the main cations. During the first ten hours there is a general efflux . of K+, Na+, Mg2+, C2+ while inn the following period K+ is actively assumed so that at eighteenth hour almost no K+ is detected in the external medium. When seed germination is stimulated by fusicoccin (FC) the development of the capacity of uptake is markedly anticipated .Moreover inhibition of seed germination by abscisic acid (ABA) inhibits the development of K+ uptake. The ABA-induced inhibition is reversed by FC and also, even it to a lower extent, by gibberellic acid GA3. K+ uptake in germinating radish seed depends on energetic metabolism and on protein synthesis Respiratory inhibitors such N, N'-dicydohexylcarbodiimide(DCCD) and salicylhydroxamic acid induced a continuous loss of K from the seed. The presence in the germination medium of inhibitor of RNA and of protein synthesis such as 3'd-adenosine{cordycepin) and ciclohexymide (CHI) inhibits the development of K+ uptake .These data suggest that a FC-sen- sitive, metabolism dependent mechanism of K+ uptake is strictly correlated to the development of the early phase of germination. Preliminary data suggest that a K+ activated ATPase present in plasmalemma preparations is involved in the mechanism of active K+ uptake in the seeds. Lado et al. (Physiol Plantarum 34 ,359 , 1975) showed that FC-induced promotion of germination of dormant seeds is accompanied by marked drop of the pH in the incubation medium, thus 'suggesting that the regulation of a H+/K+ exchange mechanism plays an important role in the process of seed germination.