INVITRO SHOOT MULTIPLICATION OF EASTERN WHITE CEDAR (THUJA-OCCIDENTALIS)

A protocol for clonal propagation of eastern white cedar (Thuja occide ntalis L.) was enhanced by optimizing the shoot multiplication stage u sing unbranched in vitro-produced shoots. This was achieved by careful selection of different medium components. An optimum range of 10 to 1 4 axillary shoots was obtained when shoots were cultured on half-stren gth Quiorin and LePoivre medium containing 10 muM filter-sterilized ze atin for 3 wk. Transfer of the treated shoots to cytokinin-free medium containing 0.05% activated charcoal improved both the number and qual ity of the axillary shoots produced. Maximum axillary bud induction wa s also accomplished when shoots were pulsed in 1 mM liquid, filter-ste rilized zeatin for 3 h, and then transferred to half-strength Quiorin and LePoivre, charcoal-containing medium. Inclusion of 4% sucrose impr oved the number of axillary shoots obtained. Half strength of the majo r salts produced an optimum response. Shoots obtained from different c ultures (1 to 5 yr old) responded similarly to the applied cytokinin; however, newly induced shoots (4 mo. old) gave a significantly higher response.