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Abstract Detail


DAntonio, Michael [1].

New complexity in arborescent lycopsid cambial dynamics.

The vascular cambium of late Paleozoic arborescent lycopsids is enigmatic and elusive, having never been positively identified in the fossil record. Our understanding of this meristem, therefore, comes almost entirely from wood anatomy, commonly preserved in “coal ball” calcium carbonate concretions. In a seminal paper, Michael Cichan (1985) hypothesized that, as lycopsids produced wood to the inside of the cambium, the cambium itself expanded to keep pace with the wood periphery mainly via broadening of the cambial initials, rather than via multiplicative anticlinal divisions of the cambial initials. This manifested as progressive outwards expansion of wood tracheid diameters within cell files rather than the appearance of new cell files within the wood. This hypothesis is consistent with the majority of the arborescent lycopsid body plan—branches, distal portions of the trunk, and the stigmarian rooting system. However, our understanding of the most proximal portion of lycopsid trunks has only come into focus since the publication of Cichan (1985). Here, I revisit the one known proximal arborescent lycopsid trunk stele, a specimen of Diaphorodendron vasculare that possesses a minute protostele composed of just a handful of primary xylem tracheids surrounded by wood over 1.5 cm thick. In addition to the gradual broadening of existing cambial initials previously identified by Cichan, this specimen also shows that the cambium expanded in circumference in two other ways that involved the creation of new initials as evidenced by new persistent tracheid files in the wood: 1. multiplicative anticlinal divisions, and 2: meristematic activity within patches of interrupted wood. These findings are complementary with those of Cichan (1985) while also expanding the known toolkit of developmental dynamics at the base of the tree, showing that the arborescent lycopsid cambium was more complex than previously thought.

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1 - Stanford University, Geological Sciences, 450 Jane Stanford Way, Building 320, Stanford, CA, 94305, USA

Arborescent lycopsid
Developmental biology

Presentation Type: Poster
Session: P3, Paleobotany Posters
Location: Virtual/Virtual
Date: Wednesday, July 21st, 2021
Time: 5:00 PM(EDT)
Number: P3PB001
Abstract ID:310
Candidate for Awards:None

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