A SYSTEM FOR REPEATABLE FORMATION OF ELONGATING ADVENTITIOUS BUDS IN NORWAY SPRUCE TISSUE-CULTURES

Seedlings of Norway spruce (Picea abies L. KARST.) were induced with c ytokinin combinations to form adventitious buds. A repeatable inductio n and formation of elongating buds was obtained via an induction cycle with cytokinins showing low bud-inducing capacity (zeatin, kinetin, 2 iP), followed by subculture periods on media without plant growth regu lators. Newly formed adventitious buds could be induced again without loosing their ability for elongation. One of the most effective phytoh ormone combinations for induction of elongating buds was 0.5 zeatin 0.05 kinetin (mg l-1) for 3 weeks. Zeatin in a concentration range (0. 1 mg l-1 to 0.2 mg l-1) stimulated the shoot elonglation of preexistin g terminal meristems in adventitious buds used for repeated cytokinin induction. 2iP promoted shoot formation and elongation in a concentrat ion range from 0.1 mg l-1 to 0.5 mg l-1 depending on the explant type (adventitious bud/shoot) used.