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In phloem transport, whether protoplasmic activity participates in assisting sap flow in sieve element-companion cell complcx hils long been in debate. The prcsent investigation assumcd microfilament (MF) and microtubule (MT), the two constituents of the protoplasmic cytoskeleton, as motive force, and employed germinating pea seedling suspended in moist chamber as experinental material: thc seed being the source; the elongating root, the sink.14C-labeled sucrose was added to the seed as indicator. The amount of sap transported from source to sink was measured by the increase in root elongation. The transport phloem was within the cylinder of the peclcd root in thc middle. The exposed cylinder was treated with MF inhibitor (cytochalasin B), or microtubule inhibitor (amiphosmethyl). Results showed that the sap influx into the elongating root. and the14C activity as well, was reduced by abut one half in treatrrrent with cytochaliisin B, and much less by amiphos-methyl treatment. Similar effect was shown in clcctrical impulse Ireatnimt, which scems to disrupt the MF and MT configuration.