Sprecher
Beschreibung
Extensive work has been done on modelling plant hydraulics incorporating all organ parts of extant plants. However, these approaches have only initially been applied to extinct plants, yet as whole-plant concepts are exceptionally rare in the fossil record. During the last decades, some studies attempted to create a conductivity model for the medullosans based on the dimensions and interconnectivity of the tracheids in the secondary tissue only. The medullosans were key elements of late Paleozoic tropical ecosystems. They exhibited large and complex fronds that could reach several meters in length, attached to slender stems with a complex dissected stele and numerous vascular bundles, pointing to a great water conductivity potential. We apply innovative modelling approaches to detailed architectural and anatomical reconstructions of specimens from the Chemnitz Fossil Forest (early Permian), both at tissue and cellular scales. The hydraulic model encompasses the stem and frond vascular systems including their interface.
Preliminary results show that the peripheral vasculature (PVS) in Medullosa stellata conducted 98% of the stem water, whereas the pith vascular strands (CAS) conducted only 2%. This result supports our previous hypothesis that the function of the CAS was to supply the stem apex and leaf primordia with water, whereas the PVS mainly supplied the active fronds. This result represents a first step towards assessing the hydraulic functioning of the extinct medullosans to better understand their macroevolutionary history, including radiation and extinction patterns.