Resin-Secretory Structures of Boswellianeglecta (Burseraceae) in Borana Administrative Zone, Southern Ethiopia

Abstract

Boswellia neglecta is a small tree that produces commercially important oleo-resin known as frankincense. This frankincense has been used for varied purposes, and it is a source of income for rural households in southern and south-eastern Ethiopia. Despite the long history of using this species, knowledge on bark anatomy and resin-secretory structures is lacking. In this study, anatomical description of the bark including network and distribution of resin secretory structures were determined; relationship between bark thickness, and axial resin canal characteristics with tree DBH of B. neglecta were assessed in dry deciduous woodlands Borana Administrative Zone, Ethiopia. Twenty-one sampled trees were raandomly selected for this study. The network of resin-secretory structure was investigated from tangential, radial and transversal sections of bark samples using light microscopy. The average density, diameter and total area of axial resin canals were determined from transversal sections of 42 bark samples. The results revealed that the inner bark axial and radial resin canals occurred and that they are interconnected by radial resin canals. Whereas, in the wood, there were no any resin secretory structures. On average, density of functional-axial resin canals is low, reaching 0.33 mm-2. Inner bark thickness linearly increases with tree diameter, but resin canal density was not varying across the inner bark. The total area of axial resin canals was highly significant (p<0.001) positively related to the DBH. The findings of the study will thus lead to new advances in our insights and knowledge on the resin secretory structures of B. neglecta. However, further research is required to introduce new tapping technology for a sustainable resin production.