Do roots mind the gap?
Roots need to be in good contact with the soil to take up water and nutrients. However, when the soil dries and roots shrink, air-filled gaps form at the root-soil interface. Do gaps actually limit the root water uptake, or do they form after water flow in soil is already limiting?
Four white lupins were grown in cylinders of 20 cm height and 8 cm diameter. The dynamics of root and soil structure were recorded using X-ray CT at regular intervals during one drying/wetting cycle. Tensiometers were inserted at 5 and 18 cm depth to measure soil matric potential. Transpiration rate was monitored by continuously weighing the columns and gas exchange measurements.
Transpiration started to decrease at soil matric potential ψ between −5 kPa and −10 kPa. Air-filled gaps appeared along tap roots between ψ = −10 kPa and ψ = −20 kPa. As ψ decreased below −40 kPa, roots further shrank and gaps expanded to 0.1 to 0.35 mm. Gaps around lateral roots were smaller, but a higher resolution is required to estimate their size.
Gaps formed after the transpiration rate decreased. We conclude that gaps are not the cause but a consequence of reduced water availability for lupins.
- Aravena JE, Berli M, Ghezzehei TA, Tyler SW (2011) Effects of root-induced compaction on rhizosphere hydraulic properties - x-ray microtomography imaging and numerical simulations. Environ Sci Technol 45:425–431
- Byrne JM, Pesacreta TC, Fox JA (1977) Development and structure of the vascular connection between the primary and secondary roots of Glycine max (L.) Merr. Am J Bot 64:946–959 CrossRef
- Carbon BA (1973) Diurnal water stress in plants grown on a coarse soil. Aust J Soil Res 24:33–42
- Carminati A, Vetterlein D, Weller U, Vogel H-J, Oswald SE (2009) When roots lose contact. Vadose Zone J 8:805–809 CrossRef
- Carminati A, Moradi A, Vetterlein D, Vontobel P, Lehmann E, Weller U, Vogel H-J, Oswald SE (2010) Dynamics of soil water content in the rhizosphere. Plant Soil 332:163–176 CrossRef
- Carminati A, Schneider CL, Moradi AB, Vetterlein D, Vogel H-J, Hildebrandt A, Weller U, Schüler L, Oswald SE (2011) Rhizosphere increases water availability to roots: a microscopic modelling study. Vadose Zone J 10:1–11 CrossRef
- Czarnes S, Hallett PD, Bengough AG, Young IM (2000) Root- and microbial-derived mucilages affect soil structure and water transport. Eur J Soil Sci 51:435–443 CrossRef
- Draye X, Kim Y, Lobet G, Javaux M (2010) Model-assisted integration of physiological and environmental constraints affecting the dynamic and spatial patterns of root water uptake from soils. J Exp Bot 61:2145–2155 CrossRef
- Faiz S, Weatherley P (1982) Root contraction in transpiring plants. New Phytol 92:333–343 CrossRef
- Garrigues E, Doussan C, Pierret A (2006) Water uptake by plant roots: I-formation and propagation of a water extraction front in mature root systems as evidenced by 2D light transmission imaging. Plant Soil 283:83–98 CrossRef
- Glass RJ, Steenhuis TS, Parlange J-Y (1989) Wetting front instability: 2. Experimental determination of relationships between system parameters and two-dimensional unstable flow field behavior in initially dry porous media. Water Resour Res 25:1195–1207 CrossRef
- Gregory PJ (2006) Roots, rhizosphere and soil: the route to a better understanding of soil science? Eur J Soil Sci 57:2–12 CrossRef
- Hallet PD, Gordon DC, Bengough AG (2003) Plant influence on rhizosphere hydraulic properties: direct measurements using a miniaturized infiltrometer. New Phytol 157:597–603 CrossRef
- Hinsinger P, Bengough AG, Vetterlein D, Young I (2009) Rhizosphere: biophysics, biogeochemistry and ecological relevance. Plant Soil 321:117–152 CrossRef
- Huck MG, Klepper B, Taylor HM (1970) Diurnal variation in root diameter. Plant Physiol 45:529–530 CrossRef
- Moradi AB, Carminati A, Vetterlein D, Vontobel P, Lehmann E, Ulrich W, Hopmans YW, Vogel H-J, Oswald SE (2011) Three-dimensional visualization and quantification of water content in rhizosphere. New Phytol 192:653–663 CrossRef
- Nobel PS, Cui M (1992) Hydraulic conductances of the soil, the root-soil air gap, and the root: changes for desert succulents in drying soil. J Exp Bot 43:319–326 CrossRef
- North GB, Nobel PS (1997) Root-soil contact for the desert succulent Agave deserti in wet and drying soil. New Phytol 135:21–29 CrossRef
- Passioura JB (1980) The transport of water from soil to shoot in wheat seedlings. J Exp Bot 31:333–345 CrossRef
- Read DB, Bengough AG, Gregory PJ, Crawford JW, Robinson D, Scrimgeour CM, Young IM, Zhang K, Zhang X (2003) Plant roots release phospholipid surfactants that modify the physical and chemical properties of soil. New Phytol 157:315–326 CrossRef
- Rudin LI, Osher S, Fatemi E (1992) Nonlinear total variation based noise removal algorithms. Physica D 60:259–268 CrossRef
- Veen BW, Van Noordwijk M, De Willigen P, Boone FR, Kooistra MJ (1992) Root-soil contact of maize, as measured by a thin-section technique. III. Effects on shoot growth, nitrate and water uptake efficiency. Plant Soil 139:131–138 CrossRef
- Vetterlein D, Marschner H, Horn R (1993) Microtensiometer technique for in situ measurements of soil matric potential and root water extraction from a sandy soil. Plant Soil 149:263–273 CrossRef
- Vogel H-J, Weller U, Schlüter S (2010) Quantification of soil structure based on Minkowski functions. Comput Geosci 36:1236–1245 CrossRef
- Whalley WR, Riseley B, Leeds-Harrison PB, Bird NRA, Leech PK (2005) Structural differences between bulk and rhizosphere soil. Eur J Soil Sci 56:353–360 CrossRef
- White RG, Kirkegaard JA (2010) The distribution and abundance of wheat roots in a dense structured subsoil – implications for water uptake. Plant Cell Environ 33:133–148 CrossRef
- Young IM (1995) Variation in moisture contents between bulk soil and the rhizosheath of wheat (Triticum aestivum L. cv. Wembley). New Phytol 130:135–139 CrossRef
- Zwieniecki M, Thompson M, Holbrook N (2003) Understanding the hydraulics of porous pipes: tradeoffs between water uptake and root length utilization. J Plant Growth Regul 21:315–323 CrossRef
- Do roots mind the gap?
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Plant and Soil
Volume 367, Issue 1-2 , pp 651-661
- Cover Date
- Print ISSN
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- Springer Netherlands
- Additional Links
- Root water uptake
- Root-soil contact
- Transpiration rate
- Root shrinkage
- X-ray CT
- Industry Sectors
- Author Affiliations
- 1. Division of Soil Hydrology, Georg-August Universität Göttingen, Büsgenweg 2, 37077, Göttingen, Germany
- 2. Soil Physics Department, Helmholtz Centre for Environmental Research - UFZ, Halle, Germany