Induction of Tyloses in Eucalyptus Globulus 'chips'

Cambial stem chips containing intact cambium between xylem and phloem, or with the phloem layer removed, were cut from the main stem axis of four-year-old Eucalyptus globulus during the winter and grown under controlled environmental conditions for seven weeks on fully defined culture media . Light microscopy revealed that tyloses were induced in sapwood vessels in the region adjacent to the cambium within these stem chips. When incubated in autoclaved 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, respectively. When non-hormonal ingredients were included, tyloses developed in 69.5% and 76.1% of vessels in chips with the phloem layer intact and removed, respectively. Addition of 1.0 mg l -1 of l-naphthalene acetic acid (NAA, a synthetic auxin) to the medium had a slight, but significant, inhibitory effect on tylosis formation.