Interactions of Soil-plant Hydraulic Resistances under Drought Stress

Abstract

Plant transpiration is a critical hydrological process that regulates the water, carbon, and energy fluxes in the terrestrial system. However, there is significant uncertainty in the transpiration estimation due to a limited understanding of the hydro-physiological responses of plants to drought stress. In recent years, there has been increasing attention to exploring the primary component of hydraulic resistance that restricts soil-water water transport under drought stress. The impact of specific soil-plant hydraulic resistances on water transport is the preferred focus over their interactive way. We utilized a soil-plant water transport model to illustrate the interactions of stomatal sensitivity, plant hydraulic resistance, and soil planting conditions under drought stress. Results show soil drought almost simultaneously triggers hydraulic resistance variations in multiple components, including stomata, stem xylem, roots, and soil. These variations have distinct influences on water transport and interact with each other. Stomata-sensitive plants can slow down the increase in plant hydraulic resistance and water potential gradient between soil and leaf by promptly closing their stomata. Soil texture and its distribution in the rhizosphere are critical factors affecting transpiration, root water uptake distribution, and plant hydraulic conductance. Stomatal behavior, plant hydraulic resistance, and soil planting conditions all contribute to iso/anisohydric behaviors. Thus, we advocate adopting a systematic view to examine the process of soil-plant water transport.