Plant and soil resistance to water flow in faba bean (Vicia faba L. major Harz.) |
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Authors: | Ruggiero Celestino De Pascale Stefania Fagnano Massimo |
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Institution: | (1) Department of Agricultural Engineering and Agronomy, University of Naples Federico II, 80055 Portici (Naples), Italy |
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Abstract: | An experiment was conducted to determine soil and plant resistance to water flow in faba bean under field conditions during
the growing season. During each sampling period transpiration flux and leaf water potential measured hourly were used with
daily measurements of root and soil water potential to calculate total resistance using Ohm's law analogy. Plant growth, root
density and soil water content distributions with depth were measured. Leaf area and root length per plant reached their maximum
value during flowering and pod setting (0.31 m2 and 2200 m, respectively), then decreasing until the end of the growing period. Root distribution decreased with depth ranging,
on average, between 34.2% (in the 0–0.25 m soil layer) and 18.1% (in the 0.75–1.0 m soil layer). Mean root diameter was 0.6
mm but most of the roots were less than 0.7 mm in diameter. Changes in plant and soil water potentials reflected plant growth
characteristics and climatic patterns. The overall relationship between the difference in water potential between soil and
leaf and transpiration was linear, with the slope equal to average plant resistance (0.0165 MPa/(cm3 m-1 h-1 10-3). Different regression parameters were obtained for the various measurement days. The water potential difference was inversely
related to transpiration at high leaf stomatal resistance and at high values of VPD. Total resistance decreased with transpiration
flux in a linear relationship (r=−0.68). Different slope values were obtained for the different measurement days. Estimated
soil resistance was much lower than the observed total resistance to water flow. The change from vegetative growth to pod
filling was accompanied by an increase in plant resistance. The experimental results support previous findings that resistance
to water flow through plants is not constant but is influenced by plant age, growth stage and environmental conditions. A
more complex model than Ohm's law analogy may be necessary for describing the dynamic flow system under field conditions.
This revised version was published online in June 2006 with corrections to the Cover Date. |
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Keywords: | total resistance transpiration leaf water potential root water potential root density |
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