Fig. 3.

Populus trees expressing Atetr1-1 have reduced sensitivity to ethylene applied locally to the stem. (A) Ethylene (2 ppm) was applied for 14 days by a flow-through cuvette to a restricted stem section of approximately 2-m-tall trees. (B and C) Ethylene stimulated cambial growth and wood formation in the wild type. (D and E) This response was reduced by the expression of the dominant-negative mutant allele Atetr1-1. Horizontal lines indicate the position of the cuvette (63 mm long). The experiment was performed on 3 independent trees of each genotype (wild-type, 35S::etr1-1 lines 1E and 3A). The picture shows a typical response from wild-type and ethylene-insensitive trees. The arrows indicate the approximate position after which wood was formed under the influence of ethylene. Field of width of transverse cross sections is 2 mm.