EFFECTS OF METHYLXANTHINES ON SEISMONASTIC REACTION, PROTON FLUX, MEMBRANE-POTENTIAL, RESPIRATION AND CALCIUM-UPTAKE IN MOTOR CELLS OF MIMOSA-PUDICA PULVINUS

Methylxanthines (theophylline, aminophylline, caffeine) inhibit the se ismonastic reaction of primary pulvini of Mimosa pudica leaves, showin g that these compounds act on rapid turgor variations and the concomit ant ion migrations. Compared with theophylline, aminophylline is more effective and caffeine is less effective in triggering the inhibitory effect. These compounds alter H+-ATPase activity as a rapid dose-depen dent proton influx was noted about 4 min after application, indicating that an early impact may be at the plasmalemma. However, they have al most no effect on the motor cell membrane potential. Moreover, the com pounds hinder the calcium transport. Not all of these inhibitory effec ts are mediated through an action on general cell metabolism since res piration was not affected even by rather long treatment (about 2 h).