Ultrastructural Identification of Suberin in Bark

Bark is composed of three layers an inner bark or phloem, a periderm layer, and an outer bark or rhytidome (110). Each of these layers can vary widely in appearance and thickness depending upon the tree, its age, and environmental conditions. The periderm layer consists of three cell types. The phellogen is the meristem that produces the phelloderm, a parenchymatous layer of cells produced internally, and the phellem, which is formed on the external side. The phellem cells are the cork cells that lay down a layer of suberin over the primary cell wall and seal off the cell, leading to eventual cell death. The anatomy of cork cells in bark has been reviewed by several authors (71, 73, 195, 295, 301, 312, 315, 320, 339, 344, 386, 432, 489, 490), and many of the woody plants whose periderm lay- 

Genus/species Microscopy method Comment(s) Reference(s) 

Agathis australis LM Crystals in phelloderm cell walls 69 

Libocedrus bidwillii LM Thin-walled phellem cells 68 

Abies balsamea LM, TEM Lamellar suberin in phellem cell walls 140, 142, 154, 452 

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