Induction of tyloses in Eucalyptus globulus 'chips'

Cambial stem chips containing intact cambium between xylem and phloem, or w ith the phloem layer removed, were cut from the main stem axis of four-year -old Eucalyptus globulus during the winter and grown under controlled envir onmental conditions for seven weeks on fully defined culture media. Light m icroscopy revealed that tyloses were induced in sapwood vessels in the regi on adjacent to the cambium within these stem chips. When incubated in autoc laved double-distilled water (control medium) tyloses were produced in 3.7% and 4.7% of vessels in chips with the phloem layer intact and removed, res pectively. When non-hormonal ingredients were included, tyloses developed i n 69.5% and 76.1% of vessels in chips with the phloem layer intact and remo ved, respectively. Addition of 1.0 mg l(-1) of l-naphthalene acetic acid (N AA, a synthetic auxin) to the medium had a slight, but significant, inhibit ory effect on tylosis formation.