Spatio-temporal Variations in Axial Conductance of Primary and First-order Lateral Roots of a Maize Crop as Predicted by a Model of the Hydraulic Architecture of Root Systems |
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Authors: | A Pierret C Doussan L Pagès |
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Institution: | (1) UR Solutions, IRD-IWMI-NAFRI, BP 06 Vientiane, LAO PDR;(2) Sol and Environment, INRA Climate, Domaine St Paul, Site Agroparc, 84914 Avignon cedex 9, FRANCE;(3) INRA Plants and cultural Systems in Horticulture, Site Agroparc, 84914 Avignon cedex 9, FRANCE |
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Abstract: | Rates at which water can be transported along plant roots (axial pathway) vary through time, in part depending on xylem maturation.
Because of experimental constraints, the dynamics of root functional heterogeneity under field conditions remains mostly uncharted
territory. Recent advances in mechanistic modelling offer opportunities to bypass such experimental limitations. This paper
examines the dynamics of local variations in axial conductance of primary and first-order lateral roots of a maize crop using
the architecture-based modelling approach developed by Doussan et al. (Annals of Botany: 81, 213–223, 1998). Specifically, we hypothesised that points of major resistance to long distance water transfers could
arise from discrepancies between the hydraulic maturity (or water carrying capacity) of main axes and branch roots. To test
this assumption, spatial distributions of root axial conductance were tested after 30, 60 and 100 days at soil depths of 10,
50 and 100 cm under a maize (Zea mays L.) crop sown at a density of 8 plants m−2. As the crop developed, the corresponding root populations encompassed ever increasing amounts of hydraulically mature first-order
laterals (branch roots): after a 100-day growth period, the vast majority of laterals had reached their maximum axial conductance
at all soil depths down to 100 cm. In contrast, the axial conductance of a large proportion of main axes (primary roots) remained
low, even at shallow soil depths and after 100 days of growth. The imbalance between the hydraulic maturity of primary and
lateral roots was most conspicuous at soil depths of 100 cm, where ~10% only of the former compared to ~80% of the latter,
had reached their maximum axial conductance after a 100-day growth period. |
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Keywords: | 3D modelling hydraulic conductance root architecture water uptake xylem |
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