HR: 1340h
AN: B53A-0980    [Abstracts]
TI: Electric Potential Variations on a Poplar: Beyond Electrokinetic Effects Associated With Sap Flow
AU: Gibert, D
EM: dominique.gibert@univ-rennes1.fr
AF: G{\'e}oscience Rennes (UMR 6118 CNRS/INSU), Universit{\'e} Rennes 1, Rennes, 35000 France
AU: * Le Mou{\"e}l, J
EM: lemouel@ipgp.jussieu.fr
AF: Laboratoire de G{\'e}omagn{\'e}tisme Institut de Physique du Globe, 4 place Jussieu, Paris, 75005 France
AU: Lambs, L
EM: lambs@ecolog.cnrs.fr
AF: Laboratoire dynamique de la biodiversit{\'e}, CNRS, Toulouse, 31000 France
AU: Nicollin, F
EM: florence.nicollin@univ-rennes1.fr
AF: G{\'e}oscience Rennes (UMR 6118 CNRS/INSU), Universit{\'e} Rennes 1, Rennes, 35000 France
AU: Conil, F
EM: frederic.conil@univ-rennes1.fr
AF: G{\'e}oscience Rennes (UMR 6118 CNRS/INSU), Universit{\'e} Rennes 1, Rennes, 35000 France
AU: Perrier, F
EM: frederic.perrier@cea.fr
AF: Laboratoire de G{\'e}omagn{\'e}tisme Institut de Physique du Globe, 4 place Jussieu, Paris, 75005 France
AU: Perrier, F
EM: frederic.perrier@cea.fr
AF: Laboratoire RCE, CEA, Bruyeres-le-Chatel, 91680 France
AB: Electric potential has been monitored since December 2003 in the roots and at two circumferences and one vertical profile in a standing poplar (Populus incognitus). Electric potential is sampled using 5 mm diameter stainless steel rods, inserted 5 mm deep in the cambium, and is referenced to an unpolarizable Petiau electrode installed 80 cm deep in the soil. Various types of signals are observed. Transient signals with long relaxation times affecting some electrodes simultaneously, may be contact potentials triggered by condensation and evaporation. Diurnal variations are observed which present a seasonal variation. During winter, diurnal variations depend on the measurement point, with variable amplitudes and sometimes anticorrelations between electrodes. By contrast, a stable and coherent organization is established in the spring, with larger amplitudes, and lasts during summer. Such signals have been reported previously (Koppan et al., 2000; Morat et al., 1994; Fensom, 1963), have been interpreted as electrokinetic effects associated with sap flow. However, a comparison of the electrical signals with a measurement of the sap flow by a heat flow method, shows that the electrical variation, although clearly correlated to sap flow, is not simply proportional to it. In a living system, electrokinetic effects, in addition to thermoelectrical effects, are probably modified significantly by additional electrochemical effects, such as membrane diffusion potentials, ion active transport by proteins, and action potentials. Such effects have been evidenced in laboratory experiments with plants (e.g., Fromm and Hei, 1998). Electric potential variations in trees may thus reveal mechanisms not accessible by other methods, and maybe reveal new aspects of the physics of living systems. A better understanding of the electrical response of trees to meteorological, chemical or biological forcing may improve the knowledge of transfer processes between the soil and the atmosphere. This is important for the modeling of water and carbon balance in relation to climate change, as well as of the contribution of trees to the migration, retention and dispersion of contaminants. Fensom, D. S., The bioelectric potentials of plants and their functional significance : V. Some daily and seasonal changes in the electrical potential and resistance of living trees, {\it Canadian J. Botany}, {\bf 41}, 831-851, 1963. Fromm, J., and H. Fei, Electrical signaling and gas exchange in maize plants of drying soil, {\it Plant Science}, {\bf 132}, 203-213, 1998. Koppan, A., L. Szarka, and V. Wesztergom, Annual fluctuation in amplitudes of daily variations of electrical signals measured in the trunk of a standing tree, {\it C. R. Acad. Sci. Paris}, {\bf 323}, 559-563, 2000. Morat, P., J.-L. Le Mou{\"e}l, and A. Granier, Electrical potential on a tree. A measurement of the sap flow ?, {\it C. R. Acad. Sci. Paris}, {\bf 317}, 98-101, 1994.
DE: 0400 Biogeosciences
DE: 0614 Biological effects
DE: 0694 Instrumentation and techniques
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting