Functional organization of the bark of Hevea brasiliensis (rubber tree): a structural and histoenzymological study.

Summary The secondary phloem of Hevea brasiliensis presents a repetitive organization in which alternate bands of laticifers, parenchyma cells and sieve tubes occur. The majority of the laticiferous vessel rings are located outside the conducting phloem zone. Radial transport through phloem rays thus appears to be essential in providing the laticifers with those metabolites needed for the biosynthesis of rubber. Enhanced respiratory and phosphatase activities are frequently detectable within ray cells.