The anatomy of the leaf of red pine, Pinus resinosa. I. Nonvascular tissues

Abstract

The general morphology of the secondary needle-leaf of Pinus resinosa and the structure of the dermal and ground tissues are described. An anatomical and ultrastructural study of the mature midregion has shown that the leaf is surrounded by a uniseriate epidermis of dead, thick-walled cells which is subtended by a single layer of living hypodermal cells that contain few recognizable organelles. Plicate mesophyll cells occupy the largest portion of the leaf cross-sectional area. These cells have a thin parietal cytoplasm rich in organelles, surrounding a tannin-filled vacuole. Two resin canals are found in the mesophyll towards the adaxial leaf surface and there may be up to three towards the abaxial surface. The resin canal epithelial cells are living at maturity but their cytoplasm appears metabolically inactive.