The distribution of acidic and esterified pectin in cambium, developing xylem and mature xylem of Pinus sylvestris

Homogalacturonans with low and high degree of methyl esterification have been immuno-localised in the cambium, differentiating xylem and mature xylem of Finns sylvestris, by monoclonal antibodies JIM5 and JIM7. In the unlignified cambial tissue the antibodies revealed a similar distribution for acidic and esterified pectin in the compound middle lamella, ray cell walls and pit membranes. In the lignified xylem tissue, pectin was also found in the compound middle lamella, although dominantly in the methylesterified form. Lignification seemed to coincide with a decrease in the presence of acidic pectin in the compound middle lamella. Both antibodies indicated labelling in pit membranes and ray cell walls in partially and fully lignified wood fibres.