Tyloses in fossil plants: New data from a Mississippian tree, with a review of previous records

ABSTRACT

Tyloses are protoplasmic swellings of parenchyma cells into the lumen of adjacent conducting cells. They develop as part of the heartwood formation process, or in response to embolism or pathogen infection. Here, we report the oldest fossil evidence to date of tylosis formation that occurs in permineralized wood of the (pro)gymnosperm Dameria hueberi from the Tournaisian (lower Mississippian, ca. 350 Ma) of Australia. Different developmental stages of tylosis formation are recognizable that range from small bubble-like protrusions to dense tyloses entirely filling the lumen of the conducting cells. The trigger for the development of tyloses in D. hueberi remains unknown. A survey of the fossil record of tyloses shows their occurrence in most groups of vascular plants since the Carboniferous. Future research in this field will screen even older (Devonian) fossils for evidence of tyloses and aim to understand the roles these structures have had in plant–pathogen interactions and plant hydraulic properties in the past.

KEYWORDS:

• Paleobotany
• Carboniferous
• plant
• anatomy
• embolism
• xylem
• plant–pathogen interactions

Acknowledgments

We are indebted to John Talent (Sydney) and the late Ruth Mawson, who led the two field trips in NE Queensland during which the specimens of Dameria hueberi were collected, as well as to the managers of ‘Dosey Springs’ for granting access to the Montgomery Dam area during these field trips. We thank Muriel Demaret (Liège) for the initial loan of the Bouxharmont material illustrated in Figure 5A and 5C. We also thank the organizers of this special issue for inviting us to contribute, and we appreciate the insightful comments and suggestions of Zhuo Feng (Nanjing) and two anonymous reviewers. AMAP (botAny and Modelling of Plant Architecture and vegetation) is a joint research unit that associates Montpellier University, CNRS (UMR 5120), CIRAD (UMR51), INRAe (UMR931), and IRD (UR123).

Authors’ Contribution statement

ALD: conceptualization; investigation; visualization; writing – original draft, review and editing. CJH: investigation; visualization; writing – review and editing. JG: investigation; visualization; writing – review and editing. BMB: investigation; writing – review and editing. MK: investigation; writing – review and editing.

Data availability

Digital data: full resolution original files of the images used in Figures 2 and 3 are available open-access in Figshare at https://doi.org/10.6084/m9.figshare.c.5869925.

Non-digital data: consists of thin-sections and mounted acetate peels of fossil plants. For Dameria hueberi the specimens and slides are deposited in the Collections de Paléobotanique, Université de Montpellier, under specimen numbers MOD2 and MOD5. For Zygopteris/Etapteris the material is deposited in the Collections of the University of Illinois, Urbana-Champaign, under specimen numbers UI 3457 and UI 22655. For Ankyropteris corrugata two specimens are illustrated: one from Bouxharmont, Belgium, collections of the University of Liège, specimen number BX 336, and one from Burnley, England, Collections de Paléobotanique, Université de Montpellier, specimen number B 309. For Protopitys buchiana the material is deposited in the Collections de Paléobotanique, Université de Montpellier, under specimen number BOU 1500.

Slide/peel numbers and repositories for all illustrated specimens are available at 10.6084/m9.figshare.c.5869925.

Disclosure statement

No potential conflict of interest was reported by the author(s).