Changes in the content of indole-3-acetic acid and cytokinins in spruce, fir and oak trees after herbicide treatment

Treatment of spruce, fir and oak trees with herbicides, which may be one of the forest damage inducing agents, caused pronounced changes in the contents and distribution of indole-3-acetic acid (IAA) and cytokinins (CKs) one year after treatment, i.e. at the time of the first microscopically visible damage in treated trees. In Picea pungens IAA content increased in the terminal buds by about 105% and in the apical buds of the first order branches by 220%. The same was true for young sprouts of Abies nordmanniana, while in leaves of oak trees IAA content was decreased by 15% after glyphosate treatment and by 30% after 2,4-dichlorophenoxyacetic acid (2,4-D) treatment. Another striking feature was a significantly decreased content of IAA in the lower parts of roots in Picea pungens (50% of the control), which is accompanied by an increase in IAA content in the middle part of the roots (130%). On the other hand, the IAA content of both sprouts and roots of A. nordmanniana was significantly increased after herbicide treatment. In P. pungens, the content of free cytokinins (sum of zeatin, zeatin riboside, isopentenyladenine and isopentenyladenosine) decreased due to herbicide treatment. The strongest decrease was seen in roots, especially in their upper and middle parts (the average reduction of cytokinin content in roots was 63%). In the above-ground organs the reduction was seen namely for isopentenyladenine and isopentenyladenosine, while the abundance of zeatin riboside was, on the other hand, higher in treated plants. In Quercus robur leaves, the total content of cytokinins also decreased, namely after glyphosate treatment. In consequence of these changes, CK/IAA ratio decreased pronouncedly in all organs of herbicide-treated trees, with the exception of oak leaves treated by 2,4-D.