Effects of Heavy metals on plants and resistance mechanisms

Abstract

Goal, Scope and Background. As one of the consequences of heavy metal pollution in soil, water and air, plants are contaminated by heavy metals in some parts of China. To understand the effects of heavy metals upon plants and the resistance mechanisms, would make it possible to use plants for cleaning and remediating heavy metal-polluted sites.Methods. The research results on the effects of heavy metals on plants and resistant mechanisms are compiled from Chinese publications from scientific journals and university journals, mostly published during the last decade.Results and Discussion. Effects of heavy metals on plants result in growth inhibition, structure damage, a decline of physiological and biochemical activities as well as of the function of plants. The effects and bioavailability of heavy metals depend on many factors, such as environmental conditions, pH, species of element, organic substances of the media and fertilization, plant species. But, there are also studies on plant resistance mechanisms to protect plants against the toxic effects of heavy metals such as combining heavy metals by proteins and expressing of detoxifying enzyme and nucleic acid, these mechanisms are integrated to protect the plants against injury by heavy metals.Conclusions. There are two aspects on the interaction of plants and heavy metals. On one hand, heavy metals show negative effects on plants. On the other hand, plants have their own resistance mechanisms against toxic effects and for detoxifying heavy metal pollution.Recommendations and Outlook. To study the effects of heavy metals on plants and mechanisms of resistance, one must select crop cuhivars and/or plants for removing heavy metals from soil and water. More highly resistant plants can be selected especially for a remediation of the pollution site. The molecular mechanisms of resistance of plants to heavy metals should be studied further to develop the actual resistance of these plants to heavy metals. Understanding the bioavailability of heavy metals is advantageous for plant cultivation and phytoremediation. Decrease in the bioavailability to farmlands would reduce the accumulation of heavy metals in food. Alternatively, one could increase the bioavailability of plants to extract more heavy metals.

Evaluation of Leachate Contamination Index Obtained from Dumpsite in Onitsha, Nigeria

“…The ratio of the heavy metal concentrations in the leachate sample clearly indicates the high rate of anthropogenic influence that has adversely affected the environment. The adverse effect on the experimental bioassays (Beans and Maize) indicated how it inhibited their growth and the effect of heavy metal assessment expressing their line of action in inhibiting the growth by altering their physiological activities as well as morphologically decreases the functionality of plant structures [4] ( Table 2). …”

“…Thus, random disposal of such unexamined wastes indicates imminent harm to livelihood [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. The rate of metal contamination in our soil environment result from the constant disposal of waste generated from industrial and municipal activities ranging from batteries, leads foils, glass, metallurgical process, inks, effluent of fertilizer companies and are highly recalcitrant in nature with their presence in the soil not easily be eliminate or degraded by soil organisms through metabolic processes [4,21,22]. The negative effect of heavy metals cannot be easily underestimated as it reduces the quality of soil.…”

“…Moreover, haphazard discharge of industrial and municipal effluent can result in environmental pollution with diverse heavy metal such as (Zn, Cr, Cd, Pb) [1][2][3][4][5][6][7][8][9][10][11]. Consequently, these heavy metals are been absorbed by plant through their root and eventually into the food chain of mammals feeding on plant for daily survival.…”

Role of Plant Growth Promoting Rhizobacteria in Accumulation of Heavy Metal in Metal Contaminated Soil

“…The effect and bioavailability of heavy metals depend on many factors, such as environmental conditions, pH, and types of element, organic substances and plant species [20]. However, there are integrated mechanisms to protect the plants against heavy metals injury such as combining heavy metals with proteins and expression of detoxifying enzyme.…”

“…There are two aspects on the interaction of plants and heavy metals. On one hand, heavy metals show negative effects on plants, and other hand, plants have their own resistance mechanisms against toxic effects of heavy metal and for detoxifying the heavy metal pollution [20]. PGPR provide additional support in the survival of plant in presence of heavy metals.…”