Cyanide Inhibition of Phloem Transport along the Stolon of<i>Saxifraga sarmentosa</i>L

Abstract

Long thin stolons of Saxifraga were treated with cyanide in both the solution and gaseous forms; the latter was much more effective. Cyanide strongly inhibited the transport of 137Cs and of natural 14C-assimilates. As judged by a variety of approaches, including the use of 14C-cyanide, the inhibition was certainly effective in the sieve tubes themselves. Callose formation did not seem to be promoted. The inhibition was completely reversible, and was never accompanied by a build-up of tracer in, or before, the treated zone; failure to traverse it was not due therefore to membrane damage and consequent leakage. For these reasons the results are held to favour a mechanism of mass flow invoking active pumping in the sieve tubes.