Phloem, sieve-element, P-protein, phloem-protein, Drimys
Drimys granadensis (Winteraceae) was chosen for study because of its primitive evolutionary position among angiosperms. Mature sieve elements of the primary phloem of petioles are enucleate and have what we interpret as crystalline P-protein in addition to the more common tubular and fibrillar forms. Companion cells associated with sieve elements retain normal-appearing nuclei and possess bodies of flocculent material within the cytoplasm. The pores connecting mature adjacent sieve elements are of much smaller diameter than those typically encountered in angiosperms. The possession of P-protein and companion cells in Drimys argues for the early evolution of these traits in angiosperm phloem.
Proceedings of the Iowa Academy of Science
©1985 Iowa Academy of Science, Inc.
Dute, Roland R. and Sharkey, Carrie L.
"Phloem of Primitive Angiosperms. III. Phloem of Petioles of Drimys granadensis (Winteraceae),"
Proceedings of the Iowa Academy of Science, 92(3), 104-110.
Available at: https://scholarworks.uni.edu/pias/vol92/iss3/7