| Abstract: | The inhibition of phloem translocation caused by electric- andcold-shock was studied by macro- and microautoradiography inmature leaves of maize (Zea mays L.). In addition, both typesof stimulation triggered action potentials with amplitudes ofmore than 50 mV which were transmitted without diminution insieve tubes with velocities of 3-5 cm s-1. By utilizing X-raymicroanalysis ion concentrations of sieve tubes were measuredin non-stimulated and stimulated leaves. It was shown that potassiumand chloride diminished about 3-fold after stimulation whilethe amount of cytoplasmic calcium may have increased. Thesedisplacements lead to the conclusion that calcium influx aswell as potassium and chloride efflux are involved in the propagationof action potentials. A possible relationship between electricsignalling and the reduction of phloem translocation is discussed. Key words: Action potential, electric and cooling stimuli, energy-dispersive X-ray microanalysis, ion shifts, phloem translocation |
