Plant Materials. The bulk of the mature leaf tissue collected from a 26-year-old single
individual rubber tree grown in an outdoor field at the Department of Biology, Faculty of
Science, Khon Kaen University was used for comparison. Mature leaves sampled from
nine accessions of rubber tree from Sakon Nakhon, Loei and Khon Kaen provinces and
seventeen species of tropical plant plants from Khon Kaen province were also conducted
to confirm the effectiveness of the protocol.