Root clumping may affect the root water potential and the resistance to soil-root water transport

Abstract

We have appraised for clumped root systems the widely-accepted view that the resistance to water flux from soil to roots ('soil resistance') is low under most field conditions, so that root water potential would closely follow the mean soil water potential. Three root spatial arrangements were studied, simulating either the regular pattern generally assumed in models, or two degrees of root clumping frequently observed in the field. We used a numerical 2-dimensional model of water transfer which assumes a control of evapotranspiration by root signalling. Calculations were carried out at two evaporative demands and for two contrasting soil hydraulic properties. The rate of soil depletion, the timing of the reduction in evapotranspiration and the difference between root water potential and mean soil water potential were all affected by the root spatial arrangement, with a greater effect at high evaporative demand and low soil hydraulic conductivity. Almost all the soil water reserve was available to plants without reduction in evapotranspiration in the regular case, while only a part of it was available in clumped cases. In the regular case, calculated 'soil resistances' were similar to those calculated using Newman's (1969) method. Conversely they were higher by up to two orders of magnitude in clumped root spatial arrangements. These results place doubt on the generality of the view that 'soil resistance' is low under common field conditions. They are consistent with the results of field experiments, especially with recent data dealing with root-to-shoot communication. 2040

Effect of drought and heat stresses on plant growth and yield: a review

“…The first level of interaction originates from root system architecture and soil transfers: at a local scale, an increase in root clumping will decrease the efficiency of water uptake (Beudez et al, 2013;Tardieu et al, 1992); at the root system scale, vertical heterogeneity of soil water availability induced by water uptake combined with water transfer in the soil and in the plant leads to a water extraction front propagating downwards (Garrigues and Doussan, 2006). The extension and speed of this front can be modulated by the variation in Lp (aquaporines, suberization) of roots and helps in compensating the lower uptake in drier zones by an increase in the wetter zones.…”

A mathematical model of plant nutrient uptake

“…For example Lafolie, Tardieu et al [71], [72], [120] calculate the water uptake by an array of parallel cylindrical roots. They conclude that the spatial arrangement can make a huge difference on how much water the plant takes up.…”

Constitutive Expression of a miR319 Gene Alters Plant Development and Enhances Salt and Drought Tolerance in Transgenic Creeping Bentgrass

“…It also has been argued that plant root capacity in water uptake, one of the key factors contributing to the plant response to water stress, is determined by root spatial distribution rather than root biomass or length, even when plants are grown in better field conditions with deep soil layers (Tardieu et al, 1992;Manschadi et al, 2006Manschadi et al, , 2008Tardieu, 2012). Thus, it is not surprising to observe that with a less robust root system than wild-type controls, Osa-miR319a transgenic creeping bentgrass plants still perform better under drought stress.…”

“…A strong correlation between salt exclusion and salt tolerance has been reported in many plant species, including rice, durum wheat (Triticum durum), bread wheat (Triticum aestivum), barley (Hordeum vulgare), pearl millet (Pennisetum americanum), Hordeum spp., tall wheatgrass, and Triticum tauschii (Yeo and Flowers, 1983;Läuchli, 1984;Tardieu et al, 1992;Bolaños and Edmeades, 1993;Bruce et al, 2002;Tester and Davenport, 2003;Campos et al, 2004;Manschadi et al, 2006Manschadi et al, , 2008Tardieu, 2012). Salt-sensitive cultivars tend to have higher accumulations of Na + .…”