Lignotuber bud development in Eucalyptus cinerea (F. Muell. ex benth)

Lignotuber anatomy and patterns of accessory bud development were studied i n the cotyledonary nodes of Eucalyptus cinerea, a lignotuber-forming eucaly pt species widely grown for the cut foliage market. Plants were greenhouse- grown from seed. Observations were made of both natural growth patterns and of the responses to a single defoliation event involving the removal of al l main and lateral stems above node 4 at 17 wk of age. Examinations mere ma de by light microscopy of serial sections and by direct observations in the greenhouse. Lignotuber initiation was visible by 9 wk and was preceded by the development of two accessory buds within each cotyledonary axil, one ad axial and one abaxial to the naked bud. By 22 wk, lignotubers were well dev eloped, and the number of accessory buds per cotyledonary axil had increase d. These buds developed adventitiously within the lignotuber cortex and als o within strands of parenchyma tissue radiating out from the center of the lignotuber. This central area contained the naked bud that had been engulfe d during lignotuber development. Pruning stimulated both accessory bud deve lopment and shoot growth from the lignotuber with 17.3 +/- 6.8 buds stimula ted following pruning, compared with 9.0 +/- 1.0 in the unpruned seedlings.