Potassium Improves Drought Stress Tolerance in Plants by Affecting Root Morphology, Root Exudates and Microbial Diversity.

Qiwen Xu,Xiaoqing Tian,Xiaoyu Xie,Meichun Duan,Hao Fu,Bo Zhu,Kangping Zhang,Hafiz Athar Hussain,Longchang Wang

doi:10.3390/metabo11030131

Abstract

Potassium (K) reduces the deleterious effects of drought stress on plants. However, this mitigation has been studied mainly in the aboveground plant pathways, while the effect of K on root-soil interactions in the underground part is still underexplored. Here, we conducted the experiments to investigate how K enhances plant resistance and tolerance to drought by controlling rhizosphere processes. Three culture methods (sand, water, and soil) evaluated two rapeseed cultivars’ root morphology, root exudates, soil nutrients, and microbial community structure under different K supply levels and water conditions to construct a defensive network of the underground part. We found that K supply increased the root length and density and the organic acids secretion. The organic acids were significantly associated with the available potassium decomposition, in order of formic acid > malonic acid > lactic acid > oxalic acid > citric acid. However, the mitigation had the hormesis effect, as the appropriate range of K facilitated the morphological characteristic and physiological function of the root system with increases of supply levels, while the excessive input of K could hinder the plant growth. The positive effect of K-fertilizer on soil pH, available phosphorus and available potassium content, and microbial diversity index was more significant under the water stress. The rhizosphere nutrients and pH further promoted the microbial community development by the structural equation modeling, while the non-rhizosphere nutrients had an indirect negative effect on microbes. In short, K application could alleviate drought stress on the growth and development of plants by regulating the morphology and secretion of roots and soil ecosystems.

Highlights

Climate change induces abiotic stressors which are the major threat to plant growth and productivity under the natural environment
This mitigation varies with the increase of K supply level, closely matching the concept of hormesis effect that mainly described ions of unknown physiological function [26], which assumes that the effect of an element on plant depends on its concentration [27]
The results of partial least squares discriminant analysis (PLS-DA) further verified that KII and KIII supply level could help the CY36 stressed root system develop comparable to its control, and CY36 even restored to YY57 control state under KIV level, while the alleviating state was similar between KII, KIII, and KIV in YY57

Summary

Introduction

Climate change induces abiotic stressors which are the major threat to plant growth and productivity under the natural environment. The United Nations pointed out in the World Water Resources Integrated Assessment Report that water resources will become a significant limiting factor for global economic and social development, with the potential to trigger conflicts and contradictions among countries [3]. It is estimated that losses caused by drought stress account for 40–60% of the total crop yield loss globally [4], indicating that water deficit is the main factor of crop failure among all abiotic stresses. Agriculture accounts for 70% of total freshwater consumption, most of which is used for crop production [5], prompting the urgent need to improve water use efficiency and drought resistance of agricultural production crops

Methods

Findings

Discussion

Conclusion