Natural and Synthetic Hydrophilic Polymers Enhance Salt and Drought Tolerance of Metasequoia glyptostroboides Hu and W.C.Cheng Seedlings

Jing Li,Gang Sa,Cunfu Lu,Dazhai Zhou,Xujun Ma,Xiaojiang Zheng,Rui Zhao,Shaoliang Chen,Xiaoyang Zhou,Shanzhi Lin

doi:10.3390/f9100643

Abstract

We compared the effects of hydrophilic polymer amendments on drought and salt tolerance of Metasequoia glyptostroboides Hu and W.C.Cheng seedlings using commercially available Stockosorb and Luquasorb synthetic hydrogels and a biopolymer, Konjac glucomannan (KGM). Drought, salinity, or the combined stress of both drought and salinity caused growth retardation and leaf injury in M. glyptostroboides. Under a range of simulated stress conditions, biopolymers and synthetic hydrogels alleviated growth inhibition and leaf injury, improved photosynthesis, and enhanced whole-plant and unit transpiration. For plants subjected to drought conditions, Stockosorb hydrogel amendment specifically caused a remarkable increase in water supply to roots due to the water retention capacity of the granular polymer. Under saline stress, hydrophilic polymers restricted Na+ and Cl− concentrations in roots and leaves. Moreover, root K+ uptake resulted from K+ enrichment in Stockosorb and Luquasorb granules. Synthetic polymers and biopolymers increased the ability of M. glyptostroboides to tolerate combined impacts of drought and salt stress due to their water- and salt-bearing capacities. Similar to the synthetic polymers, the biopolymer also enhanced M. glyptostroboides drought and salt stress tolerance.

Highlights

Soil salinity and drought pose major problems in agriculture and forestry [1,2,3,4]
Plants amended with the biopolymer exhibited a pronounced delay of leaf injury relative to that of plants treated with synthetic polymer (Table 1)
Konjac glucomannan (KGM)-treated plants was 56%–60% higher than that of plants treated with synthetic polymers under of KGM-treated plants was 56–60% higher than that of plants treated with synthetic polymers under combined drought and salt stress (Figure 5A)

Summary

Introduction

Soil salinity and drought pose major problems in agriculture and forestry [1,2,3,4]. Soil salinization often accompanies drought due to evaporative salt accumulation in upper soil layers. Molecular physiology indicates that multiple stress signaling networks are involved in the plant response to dehydration and saline conditions These networks include the abscisic acid-activated signaling pathway, mitogen-activated protein kinase (MAPK) cascades, extracellular adenosine triphosphate (ATP) signaling, and hydrogen peroxide catabolic process [3,5,6,7,8]. Mycorrhization, and polymer amendments to soil can enhance drought and salt tolerance at the tissue and cellular level [1,2,3,9]. These interventions can Forests 2018, 9, 643; doi:10.3390/f9100643 www.mdpi.com/journal/forests

Methods

Results

Discussion

Conclusion