Transportprozesse in Vallisneria-Blättern und die Wirkung von Kinetin und Kolchizin: II. Symplastischer Transport von α-Aminoisobuttersäure in Vallisneria-Blättern und die Wirkung von Kinetin

Abstract

Summary The symplastic transport of α-aminoisobutyric acid (AIB) in leaves of Vallisneria spiralis L. has been studied. The following results are obtained: 1. A transport path through the free space (apoplastic translocation) can be excluded. 2. The transport of 14C-AIB through the leaf is not affected if 12C-AIB is applied to the middle zone to be passed by 14C-AIB. Neither the accumulation in the middle zone nor the transport towards the rest of the leaf is decreased. Since 12C-AIB has been applied in a concentration range saturating the uptake process, it should compete with the 14C-transport, if this transport includes efflux and re-absorption. 3. The symplastic transport is blocked after heat killing of a short zone of the leaf strip and it is decreased when AIB is transported through a zone of plasmolyzed cells. 4. The velocity of symplastic transport is higher than one would expect by a simple diffusion mechanism. 5. Transport of AlB through short leaf strips does not show polarity. AIB applied to the middle part moves in apical as well as in basal direction with comparable velocity. 6. The directed symplastic transport of AIB induced by kinetin is characterized by the fact that kinetin applied to a leaf area not identical with the uptake zone creates an attraction centre for the accumulation of AIB; the optimal concentration of kinetin is 1μM under our experimental conditions; the symplastic transport is decreased after application of kinetin to the zone of uptake of AIB or to the whole leaf strip; if both ends of the leaf strip were treated with kinetin the directed transport of AIB applied in the middle part of the leaf strip takes place simultaneously in opposite directions.