Noninvasive Determination of Phloem Transport Speed with Carbon-14 (14C)
Studying the phloem, through which organic substances are distributed between plant organs, is challenging because of its position deep inside the plant body and its sensitivity to manipulation. The speed of phloem transport can be studied by tracers. Here a protocol for the use of 14C-labeled photoassimilate to measure phloem transport speed is provided. A major advantage of this method is its noninvasiveness, as the isotope is supplied as 14CO2, which is converted in source leaves to 14C-sugars, whose movement is then followed by photomultiplier-based X-ray detectors positioned close to the stem. The same method can be used to determine partitioning among sinks over time and rates of export from sources. The relatively simple handling enables medium throughput experiments under controlled conditions.
Key wordsPhloem transport Carbon allocation Sieve element Isotope Carbon tracing Bremsstrahlung Transport velocity
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