Understanding photoassimilate allocation into the roots and the release of organic substances from the roots into the rhizosphere is an important prerequisite for characterizing the belowground C input, the spatial and temporal distribution of C, and the interactions between plants and soil microorganisms. Based on
14C phosphor imaging, we visualized the allocation of assimilates into
Lolium perenne roots and estimated the life time of hotspots at the root tips.
Lolium shoots were labeled in a
14CO
2 atmosphere, and herbariums of roots and shoots were prepared 6 h, 2 d, and 11 d after the
14C pulse. The
14C distribution in roots and leaves revealed that pulse labeling does not yield homogeneously labeled plant material. The spatial distribution of assimilate allocation was evaluated based on the
14C specific activity expressed as digital light units (DLU mm
–2) of the imaging plates. Areas with high relative
14C activity were classified as hotspots. Strong
14C hotspots were detected mainly at the root tips already 6 h after the
14C assimilation, and they remained active for at least 2 d. Eleven days after the
14C assimilation, the hotspots at the root tips disappeared and the
14C distribution was much more even than after 6 h or after 2 d.
14C phosphor imaging proved to be a promising tool to visualize the allocation of photoassimilates into the roots and the rhizosphere and can be used to identify hotspots and their dynamics.
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