A novel non-invasive optical method for quantitative visualization of pH dynamics in the rhizosphere of plants.

A novel optical method for non-invasive, quantitative and high-resolution imaging of spatial and temporal pH dynamics in soils mediated by plant roots is introduced. This method overcomes present limitations of measurement of pH, mainly short-term and punctiform measurements, by recording long-term dynamics of the micro-pattern of pH in the root-soil interface without disturbance of the biological and physico-chemical conditions. Juncus effusus L., rooting in a permanently flooded rhizotron, was selected as the test organism for qualifying the technique. The measurements showed pronounced diurnal variations of pH along the roots, particularly along the elongation zone. Diurnal oscillation of pH caused by the roots reached up to 0.5 units. Long-term records at 4 s intervals over more than 8 weeks revealed considerable spatial and temporal patterns of pH dynamics in the rhizosphere of about 10% of the pH scale (pH 7.0-8.5). The measured data were validated by the use of pH electrodes. Concomitantly measured oxygen concentration showed hypoxic conditions around root tips (10-70 micromol O2 L-1) and almost anoxic conditions (0.9 micromol O2 L-1) in the bulk soil. The present study qualifies this novel pH-sensing technique as a powerful analytical tool for quantitative visualization of undisturbed bioprocess dynamics.

[1]  P. M. Neumann,et al.  The Spatially Variable Inhibition by Water Deficit of Maize Root Growth Correlates with Altered Profiles of Proton Flux and Cell Wall pH1 , 2004, Plant Physiology.

[2]  V. Römheld,et al.  In vivo Measurement of Root-induced pH Changes at the Soil-Root Interface: Effect of Plant Species and Nitrogen Source , 1983 .

[3]  L. Bogorad,et al.  Light-induced, Dark-reversible Absorbance Changes in Roots, Other Organs, and Cell-free Preparations. , 1978, Plant physiology.

[4]  Tian C. Zhang,et al.  Applications of Microelectrode Techniques To Measure pH and Oxidation−Reduction Potential in Rhizosphere Soil , 1999 .

[5]  P. Nye.  Changes of pH across the rhizosphere induced by roots , 1981, Plant and Soil.

[6]  A. V. Van Bruggen,et al.  Moving Waves of Bacterial Populations and Total Organic Carbon along Roots of Wheat , 1999, Microbial Ecology.

[7]  H. Johnson,et al.  A comparison of 'traditional' and multimedia information systems development practices , 2003, Inf. Softw. Technol..

[8]  L. Jaffe,et al.  Natural H Currents Traverse Growing Roots and Root Hairs of Barley (Hordeum vulgare L.). , 1979, Plant physiology.

[9]  K. Abromeit.  Music Received , 2023, Notes.

[10]  R. Miller,et al.  Chemical and microbiological properties , 1982 .

[11]  Ulrich Schurr,et al.  Effect of Soil pH on Growth and Cation Deposition in the Root Tip of Zea mays L. , 2000, Journal of Plant Growth Regulation.

[12]  A. Bloom,et al.  A comparison of NH4+ and NO3– net fluxes along roots of rice and maize , 1998 .

[13]  W. H. Patrick,et al.  Redox Range with Minimum Nitrous Oxide and Methane Production in a Rice Soil under Different pH , 2003 .

[14]  T. Adhya,et al.  Effect of continuous and alternate water regimes on methane efflux from rice under greenhouse conditions , 1997, Biology and Fertility of Soils.

[15]  Peter Frenzel,et al.  CH4 emission from a hollow-ridge complex in a raised bog: The role of CH4 production and oxidation , 2000 .

[16]  L. Voesenek,et al.  Changes in growth, porosity, and radial oxygen loss from adventitious roots of selected mono‐ and dicotyledonous wetland species with contrasting types of aerenchyma , 2000 .

[17]  Christian Huber,et al.  Dual Lifetime Referencing (DLR) — a New Scheme for Converting Fluorescence Intensity into a Frequency-Domain or Time-Domain Information , 2001 .

[18]  P Kuschk,et al.  Influence of the redox condition dynamics on the removal efficiency of a laboratory-scale constructed wetland. , 2005, Water research.

[19]  S. Jarvis,et al.  Rates of hydrogen ion efflux by nodulated legumes grown in flowing solution culture with continuous pH monitoring and adjustment , 1985 .

[20]  G. Kirk,et al.  Root-induced iron oxidation and pH changes in the lowland rice rhizosphere. , 1994, The New phytologist.

[21]  Hans Rudolf Christen,et al.  Grundlagen der Allgemeinen und anorganischen Chemie , 1969 .

[22]  W. Peters.  Growth rate gradients and extracellular pH in roots: how to control an explosion. , 2004, The New phytologist.

[23]  N. Revsbech,et al.  Use of an Oxygen-Insensitive Microscale Biosensor for Methane To Measure Methane Concentration Profiles in a Rice Paddy , 1998, Applied and Environmental Microbiology.

[24]  B. Jaillard,et al.  pH mapping in transparent gel using color indicator videodensitometry , 1996, Plant and Soil.

[25]  W. Silk,et al.  A mathematical model for pH patterns in the rhizospheres of growth zones , 1999 .

[26]  David L. Valentine,et al.  Biogeochemistry and microbial ecology of methane oxidation in anoxic environments: a review , 2002, Antonie van Leeuwenhoek.

[27]  N. Revsbech,et al.  Microsensor analysis of oxygen and pH in the rice rhizosphere under field and laboratory conditions , 1999, Biology and Fertility of Soils.

[28]  Simplified measurement of soil pH using an agar-contact technique , 1990, Plant and Soil.

[29]  H. Cypionka,et al.  Life at the oxic-anoxic interface: microbial activities and adaptations. , 2000, FEMS microbiology reviews.

[30]  P. Lea,et al.  The Biochemistry, Molecular Biology, and Genetic Manipulation of Primary Ammonia Assimilation , 2002 .

[31]  Peter J. Gregory,et al.  New approaches to studying chemical and physical changes in the rhizosphere: an overview , 1999, Plant and Soil.

[32]  W. H. Patrick,et al.  Methane and Nitrous Oxide Emissions from a Rice Field in Relation to Soil Redox and Microbiological Processes , 2000 .

[33]  A. Bloom,et al.  Root Development and Absorption of Ammonium and Nitrate from the Rhizosphere , 2002, Journal of Plant Growth Regulation.

[34]  Z. Rengel,et al.  Measurements of H+ fluxes and concentrations in the rhizosphere. , 2003 .

[35]  G. Kirk,et al.  The potential for nitrification and nitrate uptake in the rhizosphere of wetland plants: a modelling study. , 2005, Annals of botany.

[36]  H. Flessa,et al.  pH values and redox potentials in microsites of the rhizosphere , 1989 .

[37]  Peter B Reich,et al.  The impact of material used for minirhizotron tubes for root research. , 2003, The New phytologist.

[38]  T. Colmer.  Long-distance transport of gases in plants: a perspective on internal aeration and radial oxygen loss from roots , 2003 .

[39]  Benoît Jaillard,et al.  Origins of root-mediated pH changes in the rhizosphere and their responses to environmental constraints: A review , 2004, Plant and Soil.

[40]  William Ussler,et al.  Methane dynamics across a tidally flooded riverbank margin , 1995 .

[41]  H. Marschner.  Mineral Nutrition of Higher Plants , 1988 .

[42]  B. Sorrell.  Effect of external oxygen demand on radial oxygen loss by Juncus roots in titanium citrate solutions , 1999 .

[43]  Peter J. Gregory,et al.  Rhizosphere geometry and heterogeneity arising from root-mediated physical and chemical processes. , 2005, The New phytologist.

[44]  A. Vermoesen,et al.  Nitrous oxide and methane emissions from different soil suspensions: effect of soil redox status , 2001, Biology and Fertility of Soils.

[45]  C. Foyer,et al.  Photosynthetic Nitrogen Assimilation and Associated Carbon and Respiratory Metabolism , 2002, Advances in Photosynthesis and Respiration.

[46]  I Klimant,et al.  Dual lifetime referencing as applied to a chloride optical sensor. , 2001, Analytical chemistry.

[47]  P. Roger,et al.  Production, oxidation, emission and consumption of methane by soils: A review , 2001 .

[48]  C. Foyer,et al.  Photosynthetic nitrogen assimilation: inter-pathway control and signaling , 2002 .

[49]  Guy J. D. Kirk,et al.  The Biogeochemistry of Submerged Soils , 2004 .

[50]  M. Iijima,et al.  Regulation of rhizosphere acidification by photosynthetic activity in cowpea (Vigna unguiculata L. walp.) seedlings. , 2002, Annals of botany.

[51]  H. Bock.  Grundlagen der allgemeinen und anorganischen Chemie. Von H. R. Christen. Verlag Sauerländer, Aarau/Otto Salle Verlag, Frankfurt/Main 1968. 1. Aufl., 576 S., 220 mehrfarb. Abb., Linson sfrs. 56,—/ DM 52,— , 1969 .

[52]  R. Wassmann,et al.  The role of rice plants in regulating mechanisms of methane missions , 2000, Biology and Fertility of Soils.

[53]  A. Bezbaruah,et al.  pH, redox, and oxygen microprofiles in rhizosphere of bulrush (Scirpus validus) in a constructed wetland treating municipal wastewater , 2004, Biotechnology and bioengineering.

[54]  P. Kopittke,et al.  Effect of Mn deficiency and legume inoculation on rhizosphere pH in highly alkaline soils , 2004, Plant and Soil.

[55]  A. Bloom,et al.  Ammonium, nitrate, and proton fluxes along the maize root , 1998 .

[56]  I. Mendelssohn,et al.  Fate of oxygen losses from Typha domingensis (Typhaceae) and Cladium jamaicense (Cyperaceae) and consequences for root metabolism. , 2000, American journal of botany.