The Role of Heavy Metals in Plant Response to Biotic Stress.

Iwona Morkunas,Renata Rucińska-Sobkowiak,Philippe Jeandet,Van Mai,Agnieszka Woźniak

doi:10.3390/molecules23092320

Abstract

The present review discusses the impact of heavy metals on the growth of plants at different concentrations, paying particular attention to the hormesis effect. Within the past decade, study of the hormesis phenomenon has generated considerable interest because it was considered not only in the framework of plant growth stimulation but also as an adaptive response of plants to a low level of stress which in turn can play an important role in their responses to other stress factors. In this review, we focused on the defence mechanisms of plants as a response to different metal ion doses and during the crosstalk between metal ions and biotic stressors such as insects and pathogenic fungi. Issues relating to metal ion acquisition and ion homeostasis that may be essential for the survival of plants, pathogens and herbivores competing in the same environment were highlighted. Besides, the influence of heavy metals on insects, especially aphids and pathogenic fungi, was shown. Our intention was also to shed light on the relationship between heavy metals deposition in the environment and ecological communities formed under a strong selective pressure.

Highlights

Heavy metals belong to the group of the most dangerous pollutants in ecotoxicology regarding their high toxicity and their significant amounts released into the environment as a result of natural and anthropogenic processes [1,2,3,4]
We focus on the impact of heavy metals at hormetic and toxic doses on plant responses and how their presence in the surrounding environment affects the response of plants to biotic stressors such as insects, especially aphids and pathogenic fungi playing a definite role in the trophic chain (Table S1 and Table 1)
relative growth rate (RGR) was significantly enhanced with treatments by Cu, Cd and Zn. It is clear from the present results that the presence of heavy metals in the environment has an intense impact on insects as far as food consumption

Summary

Introduction

Heavy metals belong to the group of the most dangerous pollutants in ecotoxicology regarding their high toxicity and their significant amounts released into the environment as a result of natural and anthropogenic processes [1,2,3,4]. Toxic effects of metals on plants are generally well documented in the literature [27,28,29,30,31,32,33,34,35,36,37] but research on the responses of organisms, including plants, insects and fungal pathogens to heavy metals at the hormetic doses are less known and at the same time extremely interesting [38,39]. Exposure of Medicago sativa seedlings to excessive concentrations of Cu or Cd activates different MAPKs such as SIMK, MMK2, MMK3 and SAMK, suggesting that plants respond to heavy metal stress through the induction of several distinct MAPK pathways and that excess amounts of Cu and Cd induce different cellular signalling mechanisms [111] Another screen for Cd-responsive genes identified the Arabidopsis MAPKKK MEKK1 to be transcriptionally induced by high concentrations of Cd [121]. It is clear from the present results that the presence of heavy metals in the environment has an intense impact on insects as far as food consumption

Effects of Heavy Metals on Insects Including Aphids

Effects of Heavy Metals on Fungi

Findings

Conclusions