Summary
Exudate can be obtained from incisions made in the bark of the stem of actively growing Ricinus plants. 14C-labelled assimilates from a fed leaf are rapidly detected in the exudate. This movement was both acropetal and basipetal from the fed leaf, at rates of over 100 cm h-1. Estimated rates within intact plants were 80–84 cm h-1.
In contrast with xylem sap obtained from the same plant, the exudate obtained had an alkaline pH (8.2), a high dry matter content (10–12.5%), high sugar content (8–10%) which was predominantly sucrose; high potassium content (60–80 mM) and low calcium content (0.5–1.0 mM).
It is concluded, on the basis of the present evidence, that the exudate is a true sample of the sieve tube sap undergoing translocation.
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Hall, S.M., Baker, D.A. & Milburn, J.A. Phloem transport of 14C-labelled assimilates in Ricinus . Planta 100, 200–207 (1971). https://doi.org/10.1007/BF00387036
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DOI: https://doi.org/10.1007/BF00387036