Journal
NEW PHYTOLOGIST
Volume 194, Issue 1, Pages 63-69Publisher
WILEY
DOI: 10.1111/j.1469-8137.2011.04025.x
Keywords
carbon isotopes; ci; ca; interannual variation; Juniperus; last glacial period; low CO2; tree rings
Categories
Funding
- National Science Foundation (NSF) CAREER [0746822]
- National Science Foundation (NSF) PECASE
- Wohlgemuth Faculty
- NSF C-CHANGE IGERT [0801522]
- Madison and Lila Self Graduate Fellowship at KU
- Direct For Education and Human Resources
- Division Of Graduate Education [0801522] Funding Source: National Science Foundation
- Division Of Integrative Organismal Systems
- Direct For Biological Sciences [0746822] Funding Source: National Science Foundation
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While studies of modern plants indicate negative responses to low [CO2] that occurred during the last glacial period, studies with glacial plant material that incorporate evolutionary responses are rare. In this study, physiological responses to changing [CO2] were compared between glacial (La Brea tar pits) and modern Juniperus trees from southern California. Carbon isotopes were measured on annual rings of glacial and modern Juniperus. The intercellular : atmospheric [CO2] ratio (ci/ca) and intercellular [CO2] (ci) were then calculated on an annual basis and compared through geologic time. Juniperus showed constant mean ci/ca between the last glacial period and modern times, spanning 50 000 yr. Interannual variation in physiology was greatly dampened during the last glacial period relative to the present, indicating constraints of low [CO2] that reduced responses to other climatic factors. Furthermore, glacial Juniperus exhibited low ci that rarely occurs in modern trees, further suggesting limiting [CO2] in glacial plants. This study provides some of the first direct evidence that glacial plants remained near their lower carbon limit until the beginning of the glacialinterglacial transition. Our results also suggest that environmental factors that dominate carbon-uptake physiology vary across geologic time, resulting in major alterations in physiological response patterns through time.
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