PARENT SESSION
Poster Session 1: Photosynthesis and Water Relations
Monday, August 8, 5:00 PM - 6:30 PM, Exhibit Hall 220 A-E, Level 2, Palais des congrès de Montréal
Aquaporin-mediated changes in deep tree root hydraulic conductivity studied in central Texas caves.
McElrone, Andrew*,1, Pockman, William 2, Bichler, Justin1, Jackson, Robert 3, 1 Department of Biology, Philadelphia, PA, USA2 Department of Biology, Albuquerque, NM, USA3 Nicholas School of the Environment and Department of Biology, Durham, NC, USA
ABSTRACT- Deep roots can contribute substantially to whole tree water use through uptake of reliable water resources. Despite their importance, we lack knowledge of deep root physiology due to limited access for in situ measurements. We used a cave system on the Edwards Plateau in central Texas to access deep tree roots, which utilize a perennial underground stream at ~20 meters depth. Stem and tap root sap flow, water potential (
), and fine-root hydraulic conductivity (Lp) were measured on Bumelia lanuginosa and Quercus fusiformis to characterize the response of these species to changes in environmental conditions. Sap flow and water potential data in deep roots closely tracked similar changes in stem sap flow for both tree species. Deep root Lp calculated from these measurements cycled diurnally with peaks corresponding to the greatest daily canopy water demand. During repeated whole-tree shade treatments on B. lanuginosa, 50-75% reductions in stem sap flow corresponded with reductions in calculated Lp of deep roots. Field studies using aquaporin (water-channel) chemical inhibitors on fine roots of both species revealed aquaporin activity that corresponded with calculated changes in deep root Lp. Low values of fine root Lp were correlated with decreased aquaporin activity during periods of low canopy water demand under shading treatments or cloudy weather. Such adjustments would reduce flow resistance in deep roots and may maintain deep water use as environmental conditions change throughout the season.
Key words: Deep roots, aquaporins, root hydraulic conductivity, caves