Significance and limits in the use of predawn leaf water potential for tree irrigation

• Published in: Plant and soil Vol. 207; no. 2; pp. 155 - 167
• Main Authors: Ameglio, T. (Blaise Pascal Univ., Clermont-Ferrand (France). Unite Associee Bioclimatologie), Archer, P, Cohen, M, Valancogne, C, Daudet, F.A, Dayau, S, Cruiziat, P
• Format: Journal Article
• Language: English
• Published: Dordrecht Kluwer Academic Publishers 01.01.1999; Springer; Springer Nature B.V; Springer Verlag
• Subjects: Agronomy. Soil science and plant productions; Biological and medical sciences; CONTENIDO DE AGUA EN EL SUELO; Dehydration; Economic plant physiology; EMBOLIA; EMBOLIE; EMBOLISM; Fundamental and applied biological sciences. Psychology; IRRIGATION; JUGLANS; Life Sciences; Moisture content; NUTRIENT TRANSPORT; Orchard soils; Orchards; Plant physiology and development; Plant roots; Plants; POTENTIEL HYDRIQUE; RACINE; RAICES; RIEGO; ROOTS; Sap flow; Soil conditioners; Soil water; SOIL WATER CONTENT; TENEUR EN EAU DU SOL; TENSION DE ABSORCION; TRANSPIRACION; TRANSPIRATION; TRANSPORT DES SUBSTANCES NUTRITIVES; TRANSPORTE DE NUTRIENTES; Trees; Vegetal Biology; Water and solutes. Absorption, translocation and permeability; WATER POTENTIAL; Water relations, transpiration, stomata; Irrigation; Sap; Container growing; Biological indicator; Plant leaf; Water potential; Field experiment; Juglandaceae; Water regime; Dicotyledones; Angiospermae; Evapotranspiration; Water content; Spermatophyta; Fruit tree; Comparative study; Juglans regia; walnut; TENEUR EN EAU DU SOL; predawn leaf water potential; sap flow; TRANSPORT DES SUBSTANCES NUTRITIVES; relative transpiration; split root; root embolism
• ISSN: 0032-079X; 1573-5036
• DOI: 10.1023/a:1026415302759

Research in estimating the water status of crops is increasingly based on plant responses to water stress. Several indicators can now be used to estimate this response, the most widely available of which is leaf water potential (ΨLWP) as measured with a pressure chamber. For many annual crops, the predawn leaf water potential (ΨPLWP), assumed to represent the mean soil water potential next to the roots, is closely correlated to the relative transpiration rate, RT. A similar correlation also holds for young fruit trees grown in containers. However, exceptions to this rule are common when soil water content is markedly heterogeneous. Two experimental conditions were chosen to assess the validity of this correlation for heterogeneous soil water content: 1) young walnut trees in split-root containers. The heterogeneity was created by two unequal compartments (20% and 80% of total volume), of which only the smaller was irrigated and kept at a moisture content higher than field capacity (permanent drainage). 2) adult walnut trees in an orchard. In this case, soil water heterogeneity was achieved by limiting the amount of localised irrigation (20% of the irrigated control) which was applied every evening. Values of sap flux and of minimum and predawn leaf water potentials with homogeneous and heterogeneous soil water content were compared for trees grown in the orchard and in containers. In spite of intense drought reflected by very low RT or stem water potential, ΨPLWP of trees under heterogeneous moisture conditions remained high (between — 0. 2 and — 0.4 MPa) both in the orchard and in containers. These values were higher than those usually considered critical under homogeneous soil conditions. A semi-quantitative model, based on the application of Ohm's analogy to split-root conditions, is proposed to explain the apparently conflicting results in the literature on the relation between ΨPLWP and soil water potential.