Apoplastic transport of ions in the motor organ of Samanea.

Turgor-mediated leaf movements of the legume Samanea saman are associated with the migration of K(+) and Cl(-) between opposing sides of the motor organs (pulvini). We have investigated the pathway of this ion migration by localizing K(+) and Cl(-) within the secondary pulvinus at various times during leaf movements. Ion distributions in freeze-dried cryosections of pulvini were determined by scanning electron microscopy/x-ray microanalysis. The results indicate that the apoplast is a major pathway for the migration of K(+) and Cl(-) within the pulvinus.