Spatially Resolved Root Water Uptake Determination Using a Precise Soil Water Sensor

Dusschoten, Dagmar van; Kochs, Johannes; Kuppe, Christian; Sydoruk, V. A.; Couvreur, Valentin; Pflugfelder, Daniel; Postma, J.

doi:10.1104/pp.20.00488

Cited by 13 publications

(11 citation statements)

References 27 publications

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“…We used the recently developed SWaP ( van Dusschoten et al, 2020 ) to continuously scan the profile of the volumetric soil water content ( θ ) which enabled us to derive both U tot and Ψ seq . In principle, the SWaP measurement is based on integrating the pots with the soil columns into a resonator circuit and then determining the resonance frequency which largely depends on θ .…”

Section: Methodsmentioning

confidence: 99%

Stomatal conductance tracks soil-to-leaf hydraulic conductance in faba bean and maize during soil drying

et al. 2022

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Although regulation of stomatal conductance is widely assumed to be the most important plant response to soil drying, the picture is incomplete when hydraulic conductance from soil to the leaf, upstream of the stomata, is not considered. Here, we investigated to what extent soil drying reduces the conductance between soil and leaf, whether this reduction differs between species, how it affects stomatal regulation, and where in the hydraulic pathway it occurs. To this end we non-invasively and continuously measured the total root water uptake rate, soil water potential, leaf water potential, and stomatal conductance of four-week-old, pot-grown maize (Zea mays) and faba bean (Vicia faba) plants during four days of water restriction. In both species, the soil-plant conductance, excluding stomatal conductance, declined exponentially with soil drying and was reduced to 50% above a soil water potential of -0.1 MPa, which is far from the permanent wilting point. This loss of conductance has immediate consequences for leaf water potential and the associated stomatal regulation. Both stomatal conductance and soil-plant conductance declined at a higher rate in faba bean than in maize. Estimations of the water potential at the root surface and an incomplete recovery 22 hours after rewatering indicate that the loss of conductance, at least partly, occurred inside the plants, for example through root suberization or altered aquaporin gene expression. Our findings suggest that differences in the stomatal sensitivity among plant species is partly explained by the sensitivity of root hydraulic conductance to soil drying.

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Section: Methodsmentioning

confidence: 99%

Stomatal conductance tracks soil-to-leaf hydraulic conductance in faba bean and maize during soil drying

et al. 2022

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“…We measured ÛP with a recently developed soil water profiler (SWaP) (van Dusschoten et al 2020). The sensors of the SWaP basically consist of two opposing copper plates (7 × 5 cm 2 ) in a 12 cm high PVC sleeve, shielded with aluminum.…”

Section: Swap Measurement Of ûP Z Imentioning

confidence: 99%

“…Due to its independence of the soil water distribution, U P is better suited than RWU to analyze how well water uptake profiles can be approximated by root length distribution. Recently, a method was introduced to measure U P without actually depending on a uniform soil water distribution, using a highly precise soil water sensor in combination with a fluctuating light intensity (van Dusschoten et al 2020). With this technology, we test the null hypothesis that root water uptake rates per unit root length (A) are constant with depth:…”

Section: Introductionmentioning

confidence: 99%

Shallow roots of different crops have greater water uptake rates per unit length than deep roots in well-watered soil

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Purpose Commonly, root length distributions are used as a first approximation of root water uptake profiles. In this study we want to test the underlying hypothesis of a constant water uptake rate per unit root length over depth. Methods Root water uptake profiles were measured using a novel sensor technology. Root length was measured with MRI and by scanning harvested roots. Experiments were performed with pot-grown barley (Hordeum vulgare), maize (Zea mays), faba bean (Vicia faba), and zucchini (Cucurbita pepo). Results For barley, maize, and faba bean, we found that roots in the top 15 cm had significantly greater water uptake rates per unit length than roots in the bottom 30 cm. For zucchini, the trend was similar but not significant. Therefore, variation of root water uptake rates with depth could be explained only partly (61–71%) by a variation of root length with depth. Conclusion The common approximation of root water uptake profiles by root length distributions relies on constant water uptake rates per unit root length. This hypothesis does not hold in our study, as we found significantly greater water uptake rates per unit length in shallower than in deeper roots. This trend was consistent among species, despite the partly strong variation in physiological parameters. We suggest that this is caused by a decreasing axial transport conductance with depth. This might result in a general underestimation of water uptake rates in shallow soil layers when they are approximated by the root length distribution.

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“…The volumetric soil water content (θ, cm 3 cm − 3 ) was recorded at depths of 1, 10, 50 and 59 cm with frequency domain sensors (EC-5, 0.001 m 3 m − 3 precision; Decagon Devices, USA) (according to Bogena et al (2007), the accuracy is lower, around 1-2% volume, when temperature, electric conductivity and supply voltage effects on the readings are taken into account). The θ was recorded at depths 15, 25 and 34 cm with fixed capacitor sensors, similar to the ones used in the soil water profiler (SWaP, accuracy of 0.002 cm 3 cm − 3 ) described in van Dusschoten et al (2020). A calibration curve for each and one of the sensors was obtained at the same temperature, supply voltage and with the same soil used in our experiments by recording the sensors' readings in soil with known volumetric water content.…”

Section: Soil Columns and Soil Water Isotopic Measurementsmentioning

confidence: 99%

“…Using MRI to monitor root distribution and growth requires careful selection and preparation of the soil (e.g., removal of ferromagnetic particles), and characteristics of the pot (a bigger diameter decreases the signal-to-noise ratio of the images, and thus thin roots are not visible). By comparing root mass and length obtained from MRI and from destructive sampling (e.g., root extraction and scanning) using a particular soil, plant and pot size, we can determine a root-diameter threshold (van Dusschoten et al 2016), differences in root diameter in the soil profile and we can correct θ measurements (van Dusschoten et al 2020). The ten-fold difference between the MRI-and scan-derived RLD profiles could primarily stem from the fact that the average root diameter along the isotopic column was 0.36 ± 0.04 mm, right above the lower detection limit of MRI with the used coil and measurement settings (~ 0.3 mm).…”

Section: Rld Monitoring and Its Role In Rwumentioning

confidence: 99%

Response of a grassland species to dry environmental conditions from water stable isotopic monitoring: no evident shift in root water uptake to wetter soil layers

et al. 2022

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Aims We aimed at assessing the influence of above- and below-ground environmental conditions over the performance of Centaurea jacea L., a drought-resistant grassland forb species. Methods Transpiration rate, CO2 assimilation rate, leaf water potential, instantaneous and intrinsic water use efficiency, temperature, relative humidity, vapor pressure deficit and soil water content in one plant and root length density in four plants, all grown in custom-made columns, were monitored daily for 87 days in the lab. The soil water isotopic composition in eleven depths was recorded daily in a non-destructive manner. The isotopic composition of plant transpiration was inferred from gas chamber measurements. Vertical isotopic gradients in the soil column were created by adding labeled water. Daily root water uptake (RWU) profiles were computed using the multi-source mixing model Stable Isotope Analysis in R (Parnell et al. PLoS ONE 5(3):1–5, 2010). Results RWU occurred mainly in soil layer 0–15 cm, ranging from 79 to 44%, even when water was more easily available in deeper layers. In wet soil, the transpiration rate was driven mainly by vapor pressure deficit and light intensity. Once soil water content was less than 0.12 cm3 cm− 3, the computed canopy conductance declined, which restricted leaf gas exchange. Leaf water potential dropped steeply to around − 3 MPa after soil water content was below 0.10 cm3 cm− 3. Conclusion Our comprehensive data set contributes to a better understanding of the effects of drought on a grassland species and the limits of its acclimation in dry conditions.

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Spatially Resolved Root Water Uptake Determination Using a Precise Soil Water Sensor

Cited by 13 publications

References 27 publications

Stomatal conductance tracks soil-to-leaf hydraulic conductance in faba bean and maize during soil drying

Stomatal conductance tracks soil-to-leaf hydraulic conductance in faba bean and maize during soil drying

Shallow roots of different crops have greater water uptake rates per unit length than deep roots in well-watered soil

Response of a grassland species to dry environmental conditions from water stable isotopic monitoring: no evident shift in root water uptake to wetter soil layers

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