Formation of Robinetin Crystals in Vessels of Intsia Species

Abstract

Many samples of Intsia spp. contain a few vessels which, throughout their length, possess some elements filled with bright yellow crystals. They serve as a characteristic of the genus. An examination was undertaken to elucidate the mode of formation of these crystals, which have been identified as pure robinetin, and the factors which may control their presence. It was concluded they are formed at pit membranes inside these particular vessels. The non-structural components of fibres, parenchyma and vessels in heartwood differ from each other. Also with the possible exception of the fibres, aberrant cells of each tissue formed different compounds. Heartwood extractives are not transferred directly from the parenchyma to other tissues in all species.

Topochemical investigation on phenolic deposits in the vessels of afzelia (Afzelia spp.) and merbau (Intsia spp.) heartwood

“…The substance in pit membranes (Figure 10 w5x) was also kaempferol-3-rhamnoside, as its spectrum showed the typical maxima at 270 and 350 nm. Accordingly, the hypotheses of Hillis (1996) that synthesis of the deposits in afzelia and merbau is regulated by pit membraneassociated enzymes was confirmed in this study. The extractives (Figure 10 w2x) situated in the S2 of vessels of afzelia are also characterised by absorbance spectra with maxima around 280 nm and slight shoulders at 340 nm owing to the presence of UV-active conjugated double bonds.…”

“…ence of chromophore groups, such as conjugated double bonds, attributed to highly condensed phenolics, as previously described for discoloured beech wood (Koch et al 2003;Koch 2004). It can be confirmed that deposits in the pit membranes are of pure robinetin, as already assumed by Hillis (1996Hillis ( , 1998. It can be confirmed that deposits in the pit membranes are of pure robinetin, as already assumed by Hillis (1996Hillis ( , 1998.…”

“…According to Hillis and Yazaki (1973), robinetin is the main polyphenol of the heartwood of merbau, together with smaller amounts of tri-and tetra-hydroxystilbenes, dihydroxymyricetin, myricetin and naringenin. Hillis (1996) concluded that robinetin is formed from precursors passing through membranes between the vessels and ray and axial parenchyma at the heartwood periphery. The high water solubility of these polymers is responsible for some disadvantageous discolouration, which is manifest as blackish-lined, dark-coloured flecks on the surface that are very difficult to remove.…”

Single-vessel flow measurements indicate scalariform perforation plates confer higher flow resistance than previously estimated

“…Although assumed to be minor, there is a possibility in species with pit membrane remnants (see Table 2) for potential ‘hydrogel’ effects resulting from using pure water rather than an ionic solution for measurements (Zwieniecki, Melcher & Holbrook 2001a). Crystals or other debris could accumulate on scalariform plates under measurement conditions or potentially in vivo (crystals have been observed within vessels (Scurfield & Mitchell 1973; Hillis 1996), resulting in an increased flow resistance. Occlusion of plates might have been responsible for the three statistical outliers in vessel resistivity.…”

Colour changes and morphological performance of impregnated jabon wood using polymerised merbau extractives

“…It is dark reddish-brown. Hillis (1996) mentioned the colour of water soluble material (extractives) from heartwood of Merbau as dark brown. When it infiltrated during impregnation to Jabon wood of cream colour, the colour of the treated Jabon wood (T1 and T2) was in between the colour of the untreated wood and the original colour of Merbau extractives.…”