Functional anatomy and clonal multiplication of Melaleuca alternifolia cheel. in the Central Queensland region

Study examines the extent to which some environmental parameters influence oil yield in the newly established tea tree oil industry.. Young oil glands of Melaleuca alternifolia possessed a densely cytoplasmic epidermal lining, and cell fragments were observed in mature glands indicating a lysigenous mode of formation. The glands were capped by modified epidermal cells. Oil was observed to pass through these cells when the leaf was subjected to vacuum. The yield and composition of tea tree oil was recorded over a 48 hour period and showed no significant variation. Short term (8 days) water stress did not affect oil yield or composition. Further, varying nitrogen and phosphorous nutrition and light levels over a three month period did not influence oil gland density or oil yield from leaves formed under the imposed conditions. The lack of a diurnal variation in oil content, together with observations of the mode of formation and development of the gland and effects of environmental conditions on oil gland density and oil yield, support the concept of a one way developmental pathway for oil gland formation and oil content. Thus the oil yield of a leaf should be determined by the growth conditions prevailing at the time of leaf expansion, gland formation and oil synthesis. Oil gland initials were first apparent in immature leaves (c.node 3) within shoot apical growth of Melaleuca alternifolia. Glands continued to form, while density per unit area decreased, as the leaf expanded. Under the growth conditions employed, a maximum number of ca. 550 glands was reached as the leaf matured at node 12. Variation in the number of glands present in the most recently fully expanded leaf was less within a plant than between plants of the same seed source, indicating a genetic component to oil gland density. Micropropagation of M. alternifolia Cheel. (tea tree) was achieved using nodal explants from mature trees. A culture procedure involving nodes sourced from 1.5 to 3 cm fromthe shoot tip, cultured into a shoot induction medium of MS basal salts supplemented with 1 mg.L-¹6-benzylaminopurine and 60 mM sucrose for 12 weeks, followed by subculturing for root induction on medium containing MS basal salts, 60 mM sucrose and 0.1 or 1 M indole acetic acid for 8 weeks, is recommended. A comparison of the source of explant material and the form of cytokinin and mineralised nitrogen on the production of multiple shoots per node was made. Further, an investigation of the effect of shoot induction treatment, the age of plant used for explants and the value of the presence of charcoal, sucrose and light on subsequent root formation in plantlets is reported