Translocation profiles of (11)C-assimilates in the petiole of Marsilea quadrifolia L.

An array of three multipliers with BGO-crystals arranged along the petiole has been used to study the movement of (11)C-assimilate in Marsilea quadrifolia L. The leaf blades were exposed to a 3-6 min pulse of (11)CO2 under continuous light. Data were recorded with 10-s counting intervals and corrected for background, sensitivity of detectors, and (11)C-decay. The speed of translocation could be obtained from the time difference between the straight lines of (11)C-increase monitored at different positions along the petiole. The speed was within the range of 60 to 150 cm h(-1). Cutting as well as cold treatment at definite locations on the petiole led to an immediate stop of (11)C-movement. Both inhibition and-in the case of chilling-restoration of translocation were detectable within minutes. When the assimilation chamber was flushed with nitrogen gas, the normal increase of (11)C at the monitored sites slowed down which, after prolonged N2-treatment, even resulted in a decrease. With a time-delay down the petiole, replacement of N2 by an air-stream led to complete restoration of the (11)C-slope. These and similar shortterm effects on translocation could not be detected by former methods. This technique is also useful in with species other than Marsilea qu., which was chosen as a test plant because of the anatomical 'simplicity' of its petiole.