Production of growth centers in lignotubers1

Species with lignotubers exhibit crown enlargements. In addition, many shoots and roots occur on surfaces of lignotubers. For lignotubers to form enlargements with many shoots and roots on their surfaces, they must produce many growth centers derived from the original vascular cambium. These growth centers arise from fragmented cambia and then remain within the lignotubers. In the present study, numbers and orientations of growth centers were determined within three species of lignotubers. Lignotubers were sawed in transverse and longitudinal slices to locate growth centers within the tissues. Lignotubers of Heteromeles arbutifolia and Frangula californica exhibited more vertically aligned growth centers with extensive shoot lobes while lignotubers of Eucalyptus nicholii exhibited a wider variety of orientations of growth centers. Lignotubers of H. arbutifolia and F. californica had 20 and 11 growth centers and more vertically aligned growth centers with extensive shoot lobes while lignotubers of E. nicholii had nearly 60 growth centers with fewer lobes.