Water relations responses of the pea (Pisum sativum L.) mutant SGECdt to mercury

Andrey A Belimov,Ian C Dodd,Vera I Safronova

doi:10.1051/bioconf/20202301003

Andrey A Belimov, Ian C Dodd + Show 1 more

Open Access

https://doi.org/10.1051/bioconf/20202301003

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Abstract

Mercury (Hg) is one of the most toxic heavy metals and has multiple impacts on plant growth and physiology, including disturbances of plant water status. The impact of Hg on water relations was assessed by exposing the unique Hg-sensitive pea (Pisum sativum L.) mutant SGECdt and its wild-type (WT) line SGE in hydroponic culture. When the plants were grown in the presence of 1 or 2 µM HgCl2 for 11 days, the SGECdt mutant had lower whole plant transpiration rate and increased leaf temperature, indicating stomatal closure. Shoot removal of Hg-untreated plants resulted in greater root-pressure induced xylem sap flow in the SGECdt mutant than WT plants. Treating these plants with 50 µM HgCl2 (an inhibitor of aquaporins) for 1 h decreased xylem sap flow of both genotypes by about 5 times and eliminated differences between WT and mutant. Adding 1 mM dithiothreitol (the reducing thiol reagent used for opening aquaporins) to the nutrient solution of Hg-treated plants partially restored xylem sap flow in SGECdt roots only, suggesting genotypic differences in aquaporin function. Thus root water uptake is important in mediating sensitivity of SGECdt to toxic Hg.

Highlights

Heavy metals, such as cadmium (Cd) and mercury (Hg), are widespread soil pollutants inhibiting plant growth and nutrition [1]
Root and shoot growth inhibition was associated with decreased root sap flow rate, root xylem and phloem areas and stomatal conductance, suggesting that Hg negatively affected plant water relations [20]
We propose that leaf temperature could be useful in toxicological studies to determine genotypic differences in tolerance to toxic metals, as a rapid alternative and adjunct to traditional biomass-based measurements [27,28]

Summary

Introduction

Heavy metals, such as cadmium (Cd) and mercury (Hg), are widespread soil pollutants inhibiting plant growth and nutrition [1]. These toxicants decrease xylem vessel size [2], root hydraulic conductivity [3,4,5], stomatal conductance [6] and inhibited activity of the molecular water channels aquaporins (AQPs) [7,8]. Plant mutants with altered tolerance to heavy metals can enhance our understanding of the mechanisms by which heavy metals affect plant water status

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