I need to establish where the heartwood ends and where the sapwood begins in certain Amazon trees which have a yellowish to whitish trunk anatomy when in cross section.
Iodide ("IKI") only tells us whether the wood possess starch or not. The presence of starch indicates that the wood is sapwood; however, its absence does not indicate for sure that heartwood is indeed heartwood.
But any other sugestion, from you or someone else, would be very welcome.