Influence of root density on the critical soil water potential

Abstract

Estimation of root water uptake in crops is important for making many other agricultural predictions. This estimation often involves two assumptions: (1) that a critical soil water potential exists which is constant for a given combination of soil and crop and which does not depend on root length density, and (2) that the local root water uptake at given soil water potential is proportional to root length density.Recent results of both mathematical modeling and computer tomography show that these assumptions may not be valid when the soil water potential is averaged over a volume of soil containing roots. We tested these assumptions for plants with distinctly different root systems. Root water uptake rates and the critical soil water potential values were determined in several adjacent soil layers for horse bean (Viciafaba) and oat (Avena sativa) grown in lysimeters, and for field-grown cotton (Gossypium L.), maize (Zea mays) and alfalfa (Medicago sativa L.) crops. Root water uptake was calculated from the water balance of each layer in lysimeters. Water uptake rate was proportional to root length density at high soil water potentials, for both horse bean and oat plants, but root water uptake did not depend on root density for horse bean at potentials lower than -2 5 kPa. We observed a linear dependency of a critical soil water potential on the logarithm of root length density for all plants studied. Soil texture modified the critical water potential values, but not the linearity of the relationship.

Effects of silicon on plant resistance to environmental stresses: review

“…In turn, a plant growing in a wet soil is able to take up soil water corresponding to the transpiration demand as soil dries until the soil water content falls below some threshold value. Then the transpiration rate begins to decrease as the roots have difficulty extracting water (Shein and Pachepsky, 1995). …”

“…In turn, a plant growing in a wet soil is able to take up soil water corresponding to the transpiration demand as soil dries until the soil water content falls below some threshold value. Then the transpiration rate begins to decrease as the roots have difficulty extracting water (Shein and Pachepsky, 1995). Under stress conditions, the reactive oxygen species (ROS) are generated in plants which can exceed the antioxidant potential of the cell and cause an oxidative damage (Ali and Alqurainy, 2006 tation.…”

Soil water potential determines the presence of hydraulic lift of Populus euphratica Olivier across growing seasons in an arid desert region

“…Due to the absence of transpiration, the water potential in the root system was basically a constant, roughly equalling to the water potential of deep soils during the presence of HL at night (Phillips et al 2002;Williams, Araujo 2002). On the contrary, SWP differed among soil layers at night in the arid desert regions due to the influence of the uneven distribution of water resource and roots (Shein, Pachepsky 1995;Tierney et al 2003). In this case, the water potential difference between the plant roots and its adjacent soils may be different among the soil layers.…”

“…In the early stage of plant growing season (i.e. June), due to plant owning higher demand in minerals, P. euphratica develop numerous fine roots in shallow soil layers to absorb minerals (Shein, Pachepsky 1995;Tierney et al 2003;Cheng et al 2009). This might increase the water potential difference between fine roots and their adjust soils, and subsequently, result in the lowest SWP soil layer appearing in shallow layers.…”

“…Due to the water transportation from plant roots to stem and leaves, previous studies indicated that RWP decreases from deep roots to shallow roots in the plant (Zimmermann 1984;Kramer, Boyer 1995). Oppositely, because SWP could be influenced by the variations in fine roots distribution, and the relationship between roots and soils (Shein, Pachepsky 1995;Tierney et al 2003), it has no monotonically decreasing trends with soil depth and RWP (Eissenstat, Yanai 1997;Jiang et al 2006;Hao et al 2013). Thus, it is possible that the relative relationship between RWP and SWP, as a consequent influence SWP threshold may vary among soil layers within the process of HL.…”