INFLUENCE OF GALLS OF PHANACIS-TARAXACI ON CARBON PARTITIONING WITHINCOMMON DANDELION, TARAXACUM-OFFICINALE

We examined how leaf galls, induced by the cynipid wasp Phanacis tarax aci, influence the partitioning of photoassimilates within the host, t he common dandelion, Taraxacum officinale. Galled and ungalled plants were exposed to (CO2)-C-14 and the labelled photoassimilates accumulat ing within galls and other parts of the host were measured. During the growth phase of the gall they were physiological sinks for photoassim ilates, accumulating 9% to 70% of total carbon produced by the host, d epending upon the number of galls per plant. High levels of C-14 assim ilation in the leaves of galled plants compared to controls, suggest t hat galls actively redirect carbon resources from unattacked leaves of their host plant. This represents a significant drain on the carbon r esources of the host, which increases with the number and size of gall s per plant. Active assimilation of C-14 by the gall is greatest in th e growth phase and is several orders of magnitude lower in the maturat ion phase. This finding is consistent with physiological and anatomica l changes that occur during the two phases of gall development and rep resents a key developmental strategy by cynipids to ensure adequate fo od resources before larval growth begins.