Role of aquaporin activity in regulating deep and shallow root hydraulic conductance during extreme drought

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2014-05-30

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Key message Deep root hydraulic conductance is upregulated during severe drought and is associated with upregulation in aquaporin activity. In 2011, Texas experienced the worst single-year drought in its recorded history and, based on tree-ring data, likely its worst in the past millennium. In the Edwards Plateau of Texas, rainfall was 58 % lower and the mean daily maximum temperatures were >5 °C higher than long-term means in June through September, resulting in extensive tree mortality. To better understand the balance of deep and shallow root functioning for water supply, we measured root hydraulic conductance (KR) in deep (~20 m) and shallow (5-10 cm) roots of Quercus fusiformis at four time points in the field in 2011. Deep roots of Q. fusiformis obtained water from a perennial underground (18-20 m) stream that was present even during the drought. As the drought progressed, deep root KR increased 2.6-fold from early season values and shallow root KR decreased by 50 % between April and September. Inhibitor studies revealed that aquaporin contribution to KR increased in deep roots and decreased in shallow roots as the drought progressed. Deep root aquaporin activity was upregulated during peak drought, likely driven by increased summer evaporative demand and the need to compensate for declining shallow root KR. A whole-tree hydraulic transport model predicted that trees with greater proportions of deep roots would have as much as five times greater transpiration during drought periods and could sustain transpiration during droughts without experiencing total hydraulic failure. Our results suggest that trees shift their dependence on deep roots versus shallow roots during drought periods, and that upregulation of aquaporin activity accounts for at least part of this increase. © 2014 Springer-Verlag Berlin Heidelberg.

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10.1007/s00468-014-1036-8

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Johnson, Daniel M, Mark E Sherrard, Jean-Christophe Domec and Robert B Jackson (2014). Role of aquaporin activity in regulating deep and shallow root hydraulic conductance during extreme drought. Trees. 10.1007/s00468-014-1036-8 Retrieved from https://hdl.handle.net/10161/10634.

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Domec

Jean Christophe Domec

Visiting Professor in the Nicholas School of the Environment

Bordeaux Sciences Agro in FRANCE (primary appointment)

Discovery of knowledge in Plant water relations, ecosystem ecology and ecohydrology, with special focus on: - Long-distance water transport under future climate; - Drought tolerance and avoidance; - Patterns of changes in structural and functional traits within individual plants. My goal as a researcher is to improve the fundamental science understanding of how plants and terrestrial ecosystems respond to climate changes, and to provide tree breeders with policy-relevant information. I have carried out research on interactions between soil water and plant water use in contrasting ecosystems, in cooperation with scientists at Bordeaux Sciences Agro in FRANCE (primary appointment), Duke University, Oregon State University, and the USDA Forest Service, Southern Global Change Program, recently renamed EFETAC (Eastern Forest Environmental Threat Assessment Center).


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