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

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Abstract
An array of three multipliers with BGO-crystals arranged along the petiole has been used to study the movement of 11C-assimilate in Marsilea quadrifolia L. The leaf blades were exposed to a 3–6 min pulse of 11CO2 under continuous light. Data were recorded with 10-s counting intervals and corrected for background, sensitivity of detectors, and 11C-decay. The speed of translocation could be obtained from the time difference between the straight lines of 11C-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 11C-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 11C 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 11C-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.