Effects of AMO‐1618 and B‐995 on Growth and Endogenous Gibberellin Content of Cupressus arizonica seedlings

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Abstract
Soil drenches of 250, 500 or 1000 mg/l of the growth retardants AMO‐1618 or B‐995 effectively reduced dry matter production and stem elongation in young seedlings of Cupressus arizonica Greene. In seedlings treated with AMO‐1618, the acidic, ethyl acetate‐soluble gibberellin‐like substances (GAs), as detected. by bioassay, were reduced to almost undetectable levels. However, the endogenous GA content in seedlings treated with B‐995 were at least 11‐fold greater than in control seedlings and differed as well in chromatographic characteristics, being of a more polar nature than the endogenous GAs of control seedlings. It was concluded that while AMO‐1618 probably acts through interference with GA biosynthesis, B‐995 may act through the interconversion of GAs.