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One-year-old trees of Pyrus calleryana ‘Bradford’, ‘Aristocrat’ and ‘Redspire’ on ‘OHF 97’ rootstock were treated in a nursery with foliar sprays of Promalin at 750 or 1500 ppm ai or dikegulac-sodium (Atrimmec) at 1440 or 2880 ppm ai in June 1989. Untreated trees of the three pear cultivars averaged less than one branch per tree at the end of the season, while ‘Bradford’ and ‘Aristocrat’ treated with Promalin at either concentration averaged over 10 and ‘Redspire’ averaged 9. Dikegulac promoted branching of all cultivars however, unlike Promalin, reduced tree height and resulted in visibly narrower branching angles.

A study was conducted to determine if exogenously applied indole-3-acetic acid would stimulate symmetric or asymmetric compression wood formation in stems of rooted cuttings of Pseudotsuga menziesii (Mirb.) Franco. Dormant two-year-old rooted cuttings were decapitated one cm below the terminal bud and treated with IAA in lanolin emulsion. Plants treated with IAA at 1 or 10 mg/g concentrations produced up to 25 rows of new xylem cells during the three week treatment period, while control plants produced essentially none. Compression wood formation was greater on the upper (originally adaxial) than on the lower side of the stem. The results support the hypothesis that basal curvature of rooted Douglas-fir cuttings is the result of a system developing a transverse gradient in auxin content in the stem leading to asymmetric compression wood formation.

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