Naturally-occurring growth regulators in leaf washings of Picea sitchensis (Bong.) Carr and Betula pendula Roth.

Leaf washings were collected during and immediately after periods of rainfall ('natural') from Picea sitchensis (Bong.) Carr and Betula pendula Roth., growing in the field. They contained acidic and non-acidic ethyl acetate-soluble growth regulating factors, including a gibberellin-like compound and an inhibitor resembling abscisic acid (ABA). Similar ranges of growth regulators were obtained when needles of Picea sitchensis were intermittently sprayed with a fine water mist ('artificial') in glasshouse conditions, greater amounts of an ABA-like compound occurring per unit volume of spray when intervals between spray applications were shortened.