Secondary growth in Vertebraria roots from the Late Permian of Antarctica: a change in developmental timing

• Published in: International Journal of Plant Sciences
• Main Authors: Decombeix, Anne-Laure, Taylor, Edith L, Taylor, Thomas N.
• Other Authors: Department of Ecology and Evolutionary Biology, University of Kansas, University of Kansas Lawrence (KU), Department of Ecology and Evolutionary Biology, university of Kansas
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2009
• Subjects: [SDU.STU.PG]Sciences of the Universe [physics]/Earth Sciences/Paleontology; [SDV.BV.BOT]Life Sciences [q-bio]/Vegetal Biology/Botanics; Transantarctic Mountains; Antarc*; Antarctica
• Online Access: https://hal.archives-ouvertes.fr/hal-00657525; https://hal.archives-ouvertes.fr/hal-00657525/document; https://hal.archives-ouvertes.fr/hal-00657525/file/2009_ALD%20ELT%20TNT_IJPS.pdf; https://doi.org/10.1086/597784

International audience Permineralized Vertebraria roots from the late Permian of the Central Transantarctic Mountains, Antarctica, are investigated to understand the unusual vascular anatomy of the genus. The specimens range from ;1mm to several centimeters in diameter and illustrate all the stages of secondary growth. Our observations confirm previous hypotheses on the development of these roots and suggest that their unique anatomy is the result of a change in developmental timing. Vertebraria is characterized by a vascular cambium that remains discontinuous through several growth seasons, leading to the formation of lacunae alternating in cross section with wedges of secondary vascular tissues. The bifacial nature of the cambium is confirmed by the presence of well-developed secondary phloem composed of longitudinally elongated cells and uniseriate parenchymatous rays. In some of the largest specimens, a continuous vascular cylinder is formed by the differentiation of cambium from parenchymatous cells bordering the lacunae. The new specimens provide additional information on the secondary xylem anatomy and vascular connection to lateral roots.