With the advent of the industrial revolution, heavy metal contamination has become an ever increasing concern. Thus, it is of major importance to understand the extent of the toxicity in plants and animals and the consequences from the ingestion of contaminated food. Hg is easily modified into several oxidation states, and it can be spread in many ecosystems. Due to the recurrence of Hg pollution and due to the lack of knowledge about the effects of this heavy metal in plants, the aim of the present text is to provide a comprehensive review of the literature regarding Hg phytotoxicity. 1. Heavy Metal Pollution: Environmental Issue Agriculture had a major impact in humans, being the major force behind the passage from a hunter-gatherer/forager society to a sedentary one, becoming a crucial tool for human sustainability and the development of economics worldwide. However, the passage to a sedentary and ever developing society was accompanied by a drastic transformation of the environment and the inherent exposure to new risks caused directly or indirectly by those transformations [1]. One of the many new risks that might have affected those early societies was the continuous exposure to pollutants, namely, heavy metals. The first cases of human exposure to heavy metals, beside the naturally occurring phenomena from Earth processes (e.g., volcanoes and rock constituents), were soon reinforced by the inadvertently discharge of these elements to the environment by human activities (e.g., from ore mining and smelting) [2, 3]. Since then, and with the advent of the industrial revolution, heavy metal contamination has become an ever increasing concern [4, 5]. Moreover, due to their stability and as they cannot be degraded, heavy metals tend to accumulate easily spread in a wide variety of ecosystems [6]. For most of the heavy metals, contamination arises from industrial applications, mining, smelters, combustion of fuel, and byproducts. From these sources, contaminants can be present in the ecosystem as airborne particles, wastewaters, and sludge [7], polluting not only sites near the source but also locations thousands of kilometers apart. Within the many occurrences of ecosystems’ pollution provoked by heavy metals, it easily comes to mind the magnitude and reach of the Minamata disaster (1950), which caught the world unaware of the damage that long exposure to heavy metals can induce in organisms. Mercury (Hg) was the main pollutant, and the subsequent associated diseases caused 2,265 casualties just from direct exposure to Hg [8]. The uncontrolled release
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