Haworth, Matthew , McElwain, Jennifer .
A revision of "xeromorphic" plant cuticle characters as indicators of palaeo-environmental aridity.
“Xeromorphic” plant cuticle features are commonly used in palaeobotany to indicate plant growth in an arid environment. However, many supposedly xeromorphic adaptations such as thick cuticle, sunken stomata, stomatal wax plugs, stomatal and epidermal papillae and epidermal trichomes are often found in extant plants growing in environments where water availability is not restricting to growth. In the light of the revised ecological functions of these “xeromorphic” adaptations it is necessary to revisit many of the palaeo-environmental interpretations based upon plant fossils possessing these cuticle features. We intend to focus this paper / talk on the role of stomatal papillae, using the extinct Cretaceous conifer Pseudofrenelopsis as a case example. The function of stomatal papillae is unknown, yet these waxy lobes overhanging the stomatal pit are often interpreted in palaeobotanical literature as xeromorphic adaptations, presumably serving some anti-transpirant role. We intend to highlight evidence from extant species to show that stomatal papillae are not adaptations to environmental aridity, but instead are most commonly found in plants growing in moist or high precipitation environments, where their role appears to be to prevent blockage of the stomatal pore and so maintain gas exchange. Pseudofrenelopsis is a classic example of a fossil conifer generally considered to indicate extreme environmental aridity due to its cuticular features. However, this interpretation is becoming increasingly difficult to reconcile not only with evidence from extant conifers but also with that of stratigraphic and climate modelling studies.
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1 - University College Dublin, School of Biology and Environmental Science, UCD Science Centre West, University College Dublin, Belfield, Dublin, Co. Dublin, D4, Ireland
Presentation Type: Oral Paper:Papers for Sections
Location: Williford A/Hilton
Date: Wednesday, July 11th, 2007
Time: 11:00 AM