Stomatal index responses of Agrostis canina to CO₂ and sulphur dioxide: implications for palaeo‐[CO₂] using the stomatal proxy

• Published in: The New phytologist Vol. 188; no. 3; pp. 845 - 855
• Main Authors: Haworth, Matthew, Gallagher, Angela, Elliott‐Kingston, Caroline, Raschi, Antonio, Marandola, Danilo, McElwain, Jennifer C
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.11.2010; John Wiley & Sons; Wiley Subscription Services, Inc
• Subjects: Agrostis - anatomy & histology; Agrostis canina; Atmospherics; Carbon dioxide; Carbon Dioxide - analysis; Carbon Dioxide - pharmacology; CO2; Fossils; Fumigation; Gases; Greenhouses; History, Ancient; Hydrogen sulfide; Hydrogen Sulfide - analysis; Hydrogen Sulfide - pharmacology; Hydrogen sulphide; Italy; Leaves; palaeo‐[CO2]; Plant growth; Plant Stomata - drug effects; Plants; Population growth; Reduction; Stomata; stomatal index; Sulfur; Sulfur dioxide; Sulfur Dioxide - analysis; Sulfur Dioxide - pharmacology; Sulphides; Sulphur; Sulphur dioxide; sulphur dioxide (SO2); Tanneries; Vegetal fossils; Volcanic activity; Volcanic Eruptions - analysis; Volcanic gases; Volcanism; Italy
• ISSN: 0028-646X; 1469-8137
• DOI: 10.1111/j.1469-8137.2010.03403.x

• Stomatal index values of fossil plants are widely used in reconstructing palaeo‐[CO₂]. This depends upon the assumption that the stomatal index is determined by the atmospheric concentration of CO₂ ([CO₂]). This study investigates whether fumigation with, and resistance to, sulphur dioxide (SO₂) induces a reduction in the stomatal index that may affect stomatal reconstructions of palaeo‐[CO₂] coinciding with episodes of global‐scale volcanism. • Agrostis canina from Mefite di Ansanto, Italy, grow in atmospheres of elevated‐[CO₂], SO₂ and hydrogen sulphide (H₂S). Mefite A. canina were compared with a control population in a ‘common‐garden' experiment and a controlled‐environment study under elevated‐[CO₂] and SO₂ fumigation. • In A. canina, resistance to toxic volcanic gases is not associated with reduced stomatal index, and fumigation with SO₂ does not cause a decrease in stomatal initiation. The two populations of A. canina analyzed in this study exhibit different stomatal index-[CO₂] ‘responses', with control plants showing a reduction in stomatal index and Mefite plants showing no response. • Stomatal reconstructions of palaeo‐[CO₂] during past episodes of global‐scale volcanism probably reflect atmospheric [CO₂] and not [SO₂]. The lack of a reduction in the stomatal index in response to elevated [CO₂] in the Mefite plants, suggests that resistance to toxic gases and/or long‐term growth at high [CO₂] reduces, or negates, sensitivity of the stomatal index-[CO₂] relationship, or that stomatal index-[CO₂] in the Mefite plants is attuned to [CO₂] fluctuations at much higher concentrations.