Bernard, Stephanie M , StClair, Sam , Placella, Sarah , Salve, Rohit , Brodie, Eoin L , Firestone, Mary K , Torn, Margaret S , Ackerly, David D. , Andersen, Gary L .
A molecular analysis of plant response to long-term changes in water availability in an annual grassland.
Further knowledge of plant response to environmental modifications is required to improve our understanding and potentially predict the broader effects of global climate change over terrestrial ecosystems. To gain a mechanistic understanding of a grassland ecosystem's response to global climate change from the level of gene expression to the whole ecosystem function, we designed an experimental setup that allowed precise control of precipitation regimes and collection of plant samples (leaf and root) at specific soil moisture values. A. barbata plants (an annual grass dominant in many California grasslands) were grown in monoculture or in mixed communities including additional grass and forbs species. The plants, grown on natural soil, were submitted to three precipitation regimes (low, ambient and high) dispensed in several cycles of watering and drought periods. Under these growing conditions the plants were exposed to long-term (several months) changes in water availability, which are similar to field conditions. Analysis of leaf samples collected at peak physiology and during the drought period indicated that ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) mRNA levels tended to be higher in plants grown under ambient conditions compared to those exposed to low or high precipitation treatments. However, the changes in Rubisco transcript abundance did not always relate to changes in leaf level photosynthesis. The mRNA levels for genes involved in nitrogen metabolism such as glutamine synthetase and nitrate reductase were correlated to some measures of soil water and nitrogen availability. Overall, results collected from the first season suggested that under low precipitation treatments plants were subjected to a mild water stress while under high precipitation the soil was depleted in nitrogen.
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1 - Lawrence Berkeley National Laboratory, Earth Sciences Division, One Cyclotron Road, Berkeley, CA, 94720, USA
2 - UC Berkeley, Integrative BIology
3 - UC Berkeley, ESPM
Presentation Type: Plant Biology Abstract
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM