Multiple shoot production from seedling explants of slash pine (Pinus elliottii, Engelm.).

Hypocotylary explants obtained from 30- to 40-day-old slash pine (Pinus elliottii, Engelm.) seedlings treated with 6-benzylaminopurine produced multiple buds that eventually elongated into axillary shoots. The explants were pulse treated (45-s dip) with 6-benzylaminopurine (22.2, 111, 222 µM) plus a control and cultured on three different basal media containing activated charcoal (0.5% w/v). Hormonal concentration and basal medium were compared for the number and size of axillary shoots induced after 12 and 29 days. The greatest number of axillary shoots was produced by explants that were pulse treated with 111 µM 6-benzylaminopurine and cultured on Gresshoff and Doy medium. The axillary shoots were fewer in number per explant than shoots previously reported resulting from hormonally induced advantitious buds of slash pine, but the axillary shoots developed more rapidly.

Plantlet regeneration from mature zygotic embryos of eastern white pine (Pinus strobus L.).

Plants were regenerated from whole embryo explants obtained from eastern white pine (Pinus strobus L.) seeds. Embryos were surgically removed and axenically cultured to induce buds in vitro on a modified Murashige and Skoog medium containing various concentrations of 6-benzylaminopurine. Embryos remained on bud induction medium for 21 days and then were transferred to the same basal medium without 6-benzylaminopurine to promote bud development and subsequent shoot elongation. The medium containing 10 µM 6-benzylaminopurine induced the greatest number of shoots per embryo. Rooting was achieved by direct transfer of the shoots to a non-sterile artificial soil mixture followed by multiple treatments with 15 nM 1-naphthaleneacetic acid. Regenerated seedlings are currently growing under greenhouse conditions.