Root water uptake under heterogeneous soil moisture conditions: an experimental study for unraveling compensatory root w
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Root water uptake under heterogeneous soil moisture conditions: an experimental study for unraveling compensatory root water uptake and hydraulic redistribution Anooja Thomas & Brijesh Kumar Yadav
& Jiří Šimůnek
Received: 23 June 2020 / Accepted: 7 October 2020 # Springer Nature Switzerland AG 2020
Abstract Aims Plant roots often encounter heterogeneity in soil water content and respond by compensating water uptake from wet zones to cope with the transpiration demand. Simultaneously, plants may also exhibit rootmediated hydraulic redistribution from wet to dry zones. Experiments were conducted to simultaneously monitor compensated root water uptake and hydraulic redistribution in the vadose zone. Methods Vertical and horizontal split-root lysimeters were used to hydraulically isolate maize roots under altering soil water conditions. Compensated root water uptake and root-mediated hydraulic redistribution were monitored by continuous measurement of water content in the lysimeter compartments. Results Soil water heterogeneity and limited soil water availability were found to accelerate the root water uptake from moist region to compensate the reduced water
availability in dry zone. However, no measurable root mediated hydraulic redistribution was observed in short term basis, despite high water potential gradient in the root zone of both lysimeters. The night-time transpiration and xylem refilling processes seem to override the hydraulic redistribution on a diurnal basis in our experiment. Conclusions Our study shows that compensated root water uptakeplays a major role in meeting the transpiration demand. In contrast, the role of root mediated hydraulic redistribution is found to benegligible in maize plant. Keywords Compensatory root water uptake . Hydraulic redistribution . Split-root lysimeter . Night-time transpiration . Xylem refilling
Introduction Responsible Editor: Rafael S. Oliveira Electronic supplementary material The online version of this article (https://doi.org/10.1007/s11104-020-04738-3) contains supplementary material, which is available to authorized users. A. Thomas : B. K. Yadav (*) Department of Hydrology, Indian Institute of Technology Roorkee, Roorkee 247667, India e-mail: [email protected] e-mail: [email protected] A. Thomas : J. Šimůnek Department of Environmental Sciences, University of California Riverside, Riverside, CA 92521, USA
Water uptake by plant roots is often regulated by endogenous factors such as root-shoot biomass and growth stage, as well as by external factors including soil water content, nutrient availability, and prevailing weather conditions (Albasha et al. 2015). The soil water content in the root zone is often heterogeneously distributed due to multiple factors such as soil type, irrigation/rainfall variability, non-uniform root distribution, and dynamic root water uptake patterns (Doussan et al. 2006; Yadav and Mathur 2008; Dara et al. 2015). Therefore, plants often deploy compensated root water uptake (hereafter referred to as CRWU) (Green and
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