Mechanical-chemical induction of balsam from Liquidambar excelsa trees

Rasamala (Liquidambar excelsa (Noronha) Oken) is an endemic plant in Indonesia. Apart from its use as wood, Rasamala also produces an exudate, known as balsam. Rasamala balsam has the potential to be a substitute for other true balsams derived from Altingiaceae, namely Storax. However, local communities have not used Rasamala balsam to its full potential owing to a lack of knowledge about the tapping method and processing. Therefore, an easy and efficient induction method for plant exudates is required to boost productivity. The use of exogenous hormones as stimulants and less damaging tapping techniques for plant stems requires further investigation. In this study, mechanical and chemical inductions were conducted using 0.1%, 1%, 2%, 5%, and 10% (w/w) methyl jasmonate and ethephon as stimuli. These chemical compounds were applied to young twigs without incision (TW), by incision (TI), to branches perforated with an electric bore (BB), and by incision (BI). After exogenous application for 21 days, Rasamala balsam exuded in all induction techniques, except for the TW treatment. BI treatment showed the highest effective induction, as indicated by the highest balsam exudation. Furthermore, methyl jasmonate was a better chemical stimulant than ethephon. In addition, the induced balsam Rasamala exudate showed a physical characteristic of a clear, thick, sticky colorless to white liquid with a distinctive balsamic odor.