Hydraulic Redistribution in Slender Wheatgrass (Elymus trachycaulus Link Malte) and Yellow Sweet Clover (Melilotus officinalis L.): Potential Benefits for Land Reclamation

Wen-Qing Zhang,Janusz Zwiazek

doi:10.3390/agronomy8120308

Abstract

Hydraulic redistribution (HR) by plant roots can increase moisture content in the dry, mostly upper, parts of the soil. HR helps maintain the viability of fine roots, root hydraulic conductivity, microbial activity and facilitate nutrient uptake. Plants can supply water to other surrounding plants by HR under drought conditions. In oil sands reclamation areas in Northeastern Alberta, Canada, reconstructed soils commonly suffer from the problems of drought, high pH, salinity, and compaction, which often impact revegetation success. In this study, we investigated the HR potential of two herbaceous plants that are frequently present in oil sands reclamation sites: slender wheatgrass (Elymus trachycaulus Link Malte) and yellow sweet clover (Melilotus officinalis L.), using a vertically split-root growth setup and treatments with deuterium-enriched water. Our objective was to test the potential benefits of HR on drought responses of seedlings of the commonly used plant species for oil sand reclamation, balsam poplar (Populus balsamifera L.), when these plants were grown together under controlled environment conditions. We found that both wheatgrass and yellow sweet clover could redistribute water in the upward and downward directions. However, the amount of water released by the roots was not sufficient to alleviate the effects of drought stress on the associated balsam poplar seedlings. Longer-term field studies should be carried out in order to examine, under different environmental conditions, the potential benefits of HR in these herbaceous plants to the establishment and growth of other plant species that are used for land reclamation.

Highlights

Hydraulic redistribution (HR) is the water movement driven by water potential gradients from wet soils to dry soils via plant roots [1]
The much higher δD values of water extracted from poplar leaves than that of tap water evidenced that deuterium-enriched water absorbed from the lower compartment by poplar roots was released to the upper compartment in both clover and wheatgrass
In this study, the amount of water released by the roots of these plants was probably too small and did not appear to alleviate drought stress in associated balsam poplar seedlings

Summary

Introduction

Hydraulic redistribution (HR) is the water movement driven by water potential gradients from wet soils to dry soils via plant roots [1]. HR mostly occurs at night when stomatal conductance and transpiration are low, the root xylem water potential increases and the roots may release water to the soil [1,2]. HR includes upward [2], downward [3], and lateral [4] fluxes of water along the water potential gradients in soil profiles. Increased moisture content in drier soils by HR is supposed to help maintain the viability of fine roots [5], root hydraulic conductivity [6], microbial activity [7], and facilitate in nutrient uptake [8].

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Conclusion