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A novel non‐invasive optical method for quantitative visualization of pH dynamics in the rhizosphere of plants
Author(s) -
BLOSSFELD STEPHAN,
GANSERT DIRK
Publication year - 2007
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1111/j.1365-3040.2006.01616.x
Subject(s) - rhizosphere , chemistry , soil water , dynamics (music) , ph indicator , soil ph , biological system , botany , environmental chemistry , soil science , environmental science , biology , genetics , physics , bacteria , acoustics
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 µ mol O 2 L −1 ) and almost anoxic conditions (0.9 µ mol O 2 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.