Immunofluorescence Localization of β-(1-4)-d-Galactan and Xylans in Tension Wood and Normal Wood Fibres of Leucaena leucocephala

Abstract

The distribution pattern of β-(1-4)-d-galactan and xylans in the fibres of tension wood and normal wood of Leucaena leucocephala was investigated using immunofluorescence microscopy. Light microscopic observation of tension wood fibres revealed that they are characterized by the presence of typical non-lignified, tertiary wall layer. LM-5 labelling of normal fibres showed weak labelling from the cell wall, indicating less concentration of β-(1-4)-d-galactans or masking effect due to co-polymerization of other polymers. Both less substituted (LM-10) and highly substituted (LM-11) xylans found to be distributed more in the secondary wall region, while compound middle lamella showed weak labelling. In tension wood fibres, LM-5 labelling revealed strong signals from tertiary wall layer, indicating that gelatinous layer contains more amount of β-(1-4)-d-galactans. The lignified secondary wall and compound middle lamellae showed weak labelling with LM-5. Labelling of xylans with LM-10 showed intense fluorescence signals from the lignified secondary wall, while gelatinous layer showed weak labelling, indicating less concentration of xylans in the gelatinous layer. In conclusion, in addition to the generalized concept that the G-layer in tension wood fibre is rich in cellulose, our results showed that constitution of pectins and xylans is also different compared to the secondary wall of normal wood fibres.