| Abstract: | Abstract In order to identify phytohormones involved in the initiation and maintenance of galls on the hackberry tree, Celtis occidentalis (Ulmaceae), in the presence of the insect Pachypsylla celtidis (Psyllidae); endogenous levels of cytokinins (CKs) and abscisic acid (ABA) were measured in the tissues of leaves, galls, and larval insects using liquid-chromatography-tandem-mass-spectrometry. The CKs isopentenyl adenine, isopentenyl adenosine, trans-zeatin and cis-zeatin, were extremely concentrated in insect larvae compared to surrounding tissue of leaves and galls. ABA concentrations in the insects were also relatively high at about 3268 pmol?g-1 fresh mass – approximately 25 times higher than in leaves, and 17 times higher than in galls. This represents a novel case of high concentrations of ABA being found in a larval insect. These findings indicate that manipulation of CK and ABA are involved in the initiation and maintenance of hackberry galls in the presence of larval P. celtidis. |
