P. Couchat

CEA Cadarache

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Gérard Lascève

CEA Cadarache

P. Moutonnet

International Atomic Energy Agency

Michel Puard

Centre de Coopération Internationale en Recherche Agronomique pour le Développement

J.F. Bois

Centre d'Écologie Fonctionnelle et Évolutive

Florent Brissaud

Centre National de la Recherche Scientifique

Alain Vavasseur

Commissariat à l'Énergie Atomique et aux Énergies Alternatives

Damien Picard

Centre National de la Recherche Scientifique

Bao Gui Zhang

China Agricultural University

J. Ramodiharilafy

CEA Cadarache

J.P. Volat

Cooperative Institutions

Commissariat à l'Énergie Atomique et aux Énergies Alternatives

CEA Cadarache

Centre National de la Recherche Scientifique

Centre de Coopération Internationale en Recherche Agronomique pour le Développement

China Agricultural University

CEA Grenoble

Laboratoire de Mathématiques

Gouvernance, Risque, Environnement, Développement

Shanghai Jiao Tong University

Ruijin Hospital

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Données préliminaires sur la transpiration du riz pluvial, variété IRAT 13, soumis àune carence hydrique

Plant and Soil (1980)

Damien Picard P. Couchat P. Moutonnet

Rice plant

Plant production

Water Stress

10.1007/bf02211699

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Citations (2)

The measurement of thermal neutron constants of the soil; application to the calibration of neutron moisture gauges and to the pedological study of soil

Natl. Bur. Stand. (U.S.), Spec. Publ.; (United States) (1975)

P. Couchat C. Carre J. Marcesse Jinn-Hsuan Ho

The neutronic method for measuring the water content of soils is more and more used by agronomists, hydrogeologists and pedologists. On the other hand the studies on the phenomena of slowing down and diffusion process have shown a narrow relation between the thermal absorption (..sigma../sub a/) and diffusion (..sigma../sub d/) constants and the thermal flux developed in the soil around a fast neutron source like Am-Be. Then, the authors present two original applications of the direct measurement of ..sigma../sub a/ and ..sigma../sub d/. The method described consists in the measurement, in a cube of graphite with an Am-Be source in the middle, on one side of the perturbation of the thermal flux, obtained by the introduction of 300 g of soil, and on the other side of the transmitted thermal flux measured through the same sample of soil, on a side of the cube. After calibrating the device, these two parameters give ..sigma../sub a/ and ..sigma../sub d/ which are easily introduced in the calibration equation of neutron moisture gauge. also these two values are useful for the pedologists because ..sigma../sub d/ is connected to clay content in the soil and ..sigma../sub a/ is connected to the type of clay bymore » the way of rare earth contents.« less

Sigma

Neutron probe

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Citations (18)

Importance de l'oxygénation des racines du riz (Oryza sativa) en culture inondée

L'Agronomie Tropicale (1975) (1986)

Michel Puard P. Couchat Gérard Lascève

L'oxygenation du systeme racinaire est un element essentiel du bon fonctionnement de la plante. En milieu inonde, la presence d'une lame d'eau entre le milieu air et le milieu sol diminue notablement l'aeration de la rhizosphere. L'experience realisee confirme que le riz possede la capacite de prelever de l'oxygene dans l'atmosphere, puis de le transporter au niveau racinaire. De plus, une variabilite importante de la capacite d'oxygenation des racines suivant l'origine genetique du materiel etudie a ete mise en evidence. La comparaison du riz a d'autres plantes cultivees montre qu'il existe une relation entre la capacite de transport vers les racines et l'aptitude a supporter l'inondation

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A Study of Strontium-90 Movement in a Sandy Soil

Soil Science Society of America Journal (1980)

P. Couchat Florent Brissaud J. P. Gayraud

Different methods were used to describe 90Sr movement in a Montpellier sandy soil at a pore water velocity of about 0.1 cm/sec. Shaking tests showed that the adsorption and the desorption of 90Sr on this soil material may be considered as instantaneous and that the equilibrium adsorption-desorption relation was hysteretic. However adsorption-desorption data obtained from material balance calculations on effluent data from soil columns did not agree with those obtained from shaking tests. This difference was confirmed by comparison of measured breakthrough curves for 90Sr and tritiated water with those calculated using equilibrium isotherms obtained from shaking tests. Equilibrium adsorption-desorption isotherms obtained from fitting of experimental breakthrough curves by a S/360 CSMP simulation model agreed well with the experimental data derived from the material balance method. The results show that isotherms from shaking tests overestimate the effect of 90Sr adsorption-desorption during transport. The hysteresis effect was less pronounced in the data obtained by the material balance method and it was shown that an approximating, linear, nonhysteretic adsorption-desorption isotherm adequately described for practical purposes, the leaching of 90Sr in the sandy soil.

Hysteresis

Material balance

10.2136/sssaj1980.03615995004400010002x

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Citations (8)

Modification anatomique induites dans les racines seminales de riz (Oryza sativa) par les conditions de culture

L'Agronomie Tropicale (1975) (1986)

Michel Puard P. Couchat J Bossy

Le riz est une plante cultivee soit dans des sols inondes (riz aquatique), soit dans des sols exondes, alimentes par la pluie (riz pluvial). Les aleas climatiques ou les sequences topographiques des sols peuvent amener des alternances d'inondation et de secheresse. Les auteurs ont tente de voir, par une analyse au microscope electronique a balayage, si l'anatomie des racines seminales d'une variete definie de riz est influencee par les conditions de culture. Les resultats obtenus semblent montrer que les lacunes aeriferes du cortex des racines constituent un des parametres de l'adaptation au milieu par leur role dans l'aeration du systeme racinaire

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Citations (2)

Ion movements during stomatal opening in darkness after illumination under nitrogen [Bryophyllum laxiflorum, Setcreasea purpurea]

Physiologia Plantarum (Denmark) (1987)

Alain Vavasseur Gérard Lascève P. Couchat

Darkness

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NEUTRON METHOD FOR MEASURING THE WATER CONTENT OF STONY SOILS.

P. Couchat J. Ramodiharilafy

Content (measure theory)

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Étude numérique de l'influence des conditions aux limites sur les solutions de l'équation de la dispersion pour un écoulement unidimensionnel

Journal of Hydrology (1978)

Florent Brissaud Flavien Lambert P. Couchat

10.1016/0022-1694(78)90027-6

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Effect of hypoxia, acidity and nitrate on inorganic nutrition in rice plants

Plant Physiology and Biochemistry (1990)

Baogui Zhang Michel Puard P. Couchat

Hypoxia

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Citations (11)

Intervention de l'oxygène atmosphériqoe sur l'absorption d'eau chez Helianthus annuus

Physiologia Plantarum (1981)

Gérard Lascève P. Couchat

The role of atmospheric oxygen on root water absorption in Helianthus annuus . The effect of atmospheric anoxia on root water absorption was studied. The experiments were carried out on intact young sunflowers in controlled temperature, light and gas environment; roots were kept in aerated nutrient solution at constant temperature. The evolution of root water absorption and transpiration rate was measured continuously. Before the experiment, the plant was preconditioned at a high transpiration rate by illumination or by CO 2 free air in darkness. Then the atmospheric oxygen was suppressed for 1 h, after which the normal conditions were restored. In anoxia and darkness, the root water absorption cannot balance transpiration, so that an important water stress develops in the plant; the light compensates this effect through the photosynthetic oxygen. The supply of oxygen, in darkness or in light, immediately removes inhibition of stomatal closure and of root water absorption. Two mechanisms control water absorption by roots: the fast one occurs in the leaves and the slower one cannot develop without the root system.

Darkness

Helianthus annuus

10.1111/j.1399-3054.1981.tb06033.x

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Citations (2)