spruce - New Phytol(1992 120 453^57 Adventitious root...

Unformatted text preview: New Phytol. (1992), 120, 453^57 Adventitious root formation in hypocotyl cuttings of Picea sitchensis (Bong.) Carr. — the influence of plant growth regulators BY C . S E L B Y \ S . J. KENNEDY^ AND B . M . R . HARVEY^ ^Agricultural Botany Research Division, Department of Agriculture for Northern Ireland and The Queen's University of Belfast, Newforge Lane, Belfast, B T9 5PX, U K ^ Greenmount College of Agriculture and Horticulture, 22 Greenmount Road, Antrim BT41 4PU, U K {Received 28 June 1991; accepted 3 December 1991) SU M M A R Y A simple method for the study of adventitious root initiation on Sitka spruce [Picea sitchensis (Bong.) Carr.] hypocotyl cuttings is described and was used to examine the effects of plant growth regulators. Twenty-one-day- old seedlings, grown at a low light intensity (15-20 fimol m~^ s~^) to stimulate hypocotyl elongation, provided easy to handle tissues which were responsive to root inducing treatments. Spontaneous rooting only occurred at a low frequency on untreated cuttings and reliable rooting depended upon auxin treatment. When continuous auxin treatment was used, indole-3-butyric acid (IBA) was more effective than either indole-3-acetic acid (IAA) or 1- naphthaleneacetic acid (NAA), and was optimal between lO""" and 10~* M. Pulse treatments with 10~^ M IBA for as little as 10 min were sufficient to stimulate rooting. All other growth regulators examined were inhibitory to IBA induced rooting. 6-benzylaminopurine (BA) was the most active being inhibitory down to a concentration of 3 X 10"' M when it was applied in a mixture with IBA. Pre-treatment of hypocotyl cuttings with BA prior to auxin treatment demonstrated strong cytokinin 'carry-over' inhibitory effects on rooting. Gibberellic acid Ag (GAg), abscisie acid (ABA) and 2-chloroethyl-phosphoric acid (ethrel) were less potent inhibitors of rooting. Keywords: Picea sitchensis, adventitious roots, auxins, cytokinins. INTRODUCTION Cuttings prepared from young conifer seedlings have frequently been used to study the processes Rooting gymnosperm shoots on tissue culture media involved in root induction (Smith & Thorpe, 1975 a, has been widely recognized to be both difficult to 6; Gronroos & von Arnold, 1987). Similarly, a achieve and unreliable (Minocha 1980; Mott & bioassay employing mung bean seedling cuttings Amerson, 1981; Amerson & Mott, 1982; Bornman, has been widely used to detect rooting factors and 1983; Abo El-Nil, 1987). Spontaneous rooting of cofactors (Bassuk & Howard, 1981;Bassuk, Hunter cultured shoots without the aid of growth regulator & Howard, 1981). In this paper, a simple method for compounds only occurs at low frequencies with studying root induction in Picea sitchensis seedling Picea sitchensis (Webb & Street, 1977; Webb, 1978; hypocotyl tissues is reported and used to investigate John, 1983) and with a wide range of other the influence of exogenous growth regulator com- gymnosperm species (Sommer, Brown & Kormanik, pounds on adventitious rooting.pounds on adventitious rooting....
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