Inhibiting peach-tree growth with abscisic acid, hinokitiol and tropolone applied to partially ringed bark strips.

The dwarfing effects of growth inhibitors [abscisic acid (ABA), hinokitiol and tropolone] applied to a connecting bark strip on a partially ringed trunk were evaluated using 2-year-old peach trees. A 2 cm strip of bark was removed from the circumference of the trunk, leaving a 2 mm-wide connecting bark band to which aqueous solutions of the chemicals were applied. Positive correlations were found between bark regeneration and tree growth. High concentrations of tropolone and hinokitiol retarded both bark regeneration and shoot growth. Tropolone at 500 µg ml^-1 and 1,000 µg ml^-1 completely inhibited bark regeneration, even resulting in tree-death similar to complete ringing. Regenerated bark at 1,000 µg ml^-1 ABA was half that in the partially ringed water control, and regeneration was completely inhibited at 2,000 µg ml^-1 ABA. Root weight was also reduced in accordance with the decline in bark regeneration. These results indicate that tree growth can be controlled by chemically modifying bark regeneration, or by translocation to the shoots of partially ringed trees. The cost of chemicals will be less than that of whole-tree sprays for growth inhibition. [ABSTRACT FROM AUTHOR]