Genotype-Dependent Differences between Cereals in Response to Manganese Excess in the Environment

Magdalena Skórka,Katarzyna Gawrońska,Andrzej Kornaś,Apolonia Sieprawska,Elżbieta Bednarska-Kozakiewicz,Anna Telk

doi:10.3390/agronomy10040510

Abstract

Industrial and agronomic activities lead to oversupply and accumulation of elements in the environment. Relatively little is known about mechanisms of manganese (Mn) triggered stress. In this study, different cultivars of popular cereals wheat, oat, and barley were investigated for their response to excessive Mn. Manganese ions (MnCl2) at 5 and 10 mM were applied to the grains and then to the media on which the plants grew until they developed their first leaf. It was performed ICP MS aiming to understand the mechanism of manganese stress in susceptible and resistant cultivar. Under Mn-stress a decrease in fresh weight of plants was observed, also differences in water content in first leaves, an increase in superoxide dismutases (SOD) and peroxidases (POX) activity, and a significant rise in catalase (CAT) was only characteristic for barley. Increasing Mn concentration resulted in enhancing of manganese superoxide dismutase (Mn-SOD) and copper, zinc superoxide dismutase (Cu/Zn-SOD) bands intensity. The increase in proline content, depending on a balance between pyrroline-5-carboxylate synthase (P5CS), ornithine-d-aminotransferase (OAT), and proline dehydrogenases (PHD) activities, indicated osmotic disorders in all plants and differentiated the studied cereals. Microscopic observations of changes in the structure of plastids and starch accumulation in Mn presence were particularly visible in sensitive cultivars. The study ranked the tested cereals in terms of their tolerance to Mn from the most tolerant wheat through barley and the least tolerant oats.

Highlights

An increasing demand for cereals, as one of the basic foods in the world, calls for genotypes that are resistant to various stress factors, leading for instance to disturbances in nutrient diffusion and mass flow in the soil
Values are mean of five replications (±SE)
Mn-stress resulted in a disorder of cellular metabolism revealed in microscopic observation as changes in the plastid structure and accumulation of significant amounts of starch, especially visible in the sensitive cultivars

Summary

Introduction

An increasing demand for cereals, as one of the basic foods in the world, calls for genotypes that are resistant to various stress factors, leading for instance to disturbances in nutrient diffusion and mass flow in the soil. Cereals need to adapt to changing climatic conditions such as a progressive global warming, with a limited amount of rainfall [1]. Another problem is an accumulation of significant amounts of elements in agricultural lands due to excessive fertilization. Enhanced levels of various elements, exceeding the plants’ demand, generate oxidative stress resulting in reduced yield [2]. This applies to the elements necessary for proper plant functioning such as Fe, Cu, Zn, and Mn, common components of enzymes involved in photosynthesis and antioxidative reactions. Subba et al [3], Küpper et al [4], Schützendübel, and Polle [5] showed that the excess of Fe, Cu, Agronomy 2020, 10, 510; doi:10.3390/agronomy10040510 www.mdpi.com/journal/agronomy

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