The influence of dinitrophenol on phloem transport along the stolon of Saxifraga sarmentosa.

Dinitrophenol in concentrations of 5×10(-3) M applied to the centre 30 cm of 60-70 cm stolons of Saxifraga produces a strong and reversible inhibition of the phloem transport of (137)Cs or (14)C-assimilates. There is every reason to believe that this effect is localised in the sieve tubes; callose formation does not occur. This evidence is very difficult to reconcile with the Münch hypothesis; it seems on the contrary to demand a theory of active pumping.