Comparison of Cepa (2-Chloroethyl Phosphonic Acid) Induced Responses in Juvenile Eucalyptus Nitens, E. Globulus and E. Obliqua: A Histochemical and Anatomical Study

Kino veins and/or pockets are a characteristic defect of some Eucalyptus species and have long been recognized as sources of degrade in eucalypt timber. In a comparative study, the course of both histochemical and anatomical responses of three juvenile Eucalyptus species (E. nitens, E. globulus and E. obliqua) to treatment with an ethylene-releasing compound, 2-chloroethyl phosphonic acid (CEPA), were examined. Kino veins were induced in both E. obliqua and E. globulus. The hormone treatment failed to induce kino vein formation in E. nitens. The traumatic parenchyma (that later differentiated into kino veins) was not always derived from the initials of the vascular cambium as reported in previous studies of E. globulus. Instead, the traumatic parenchyma appeared to be produced from the meristematic activity of the inner phloem parenchyma. In addition, kino veins found in 2- to 3-year-old E. globulus were mostly included in the phloem and not in the xylem as generally observed in mature E. globulus.