Lead toxicity in plants

Abstract

Contamination of soils by heavy metals is of widespread occurrence as a result of human, agricultural and industrial activities. Among heavy metals, lead is a potential pollutant that readily accumulates in soils and sediments. Although lead is not an essential element for plants, it gets easily absorbed and accumulated in different plant parts. Uptake of Pb in plants is regulated by pH, particle size and cation exchange capacity of the soils as well as by root exudation and other physico-chemical parameters. Excess Pb causes a number of toxicity symptoms in plants e.g. stunted growth, chlorosis and blackening of root system. Pb inhibits photosynthesis, upsets mineral nutrition and water balance, changes hormonal status and affects membrane structure and permeability. This review addresses various morphological, physiological and biochemical effects of Pb toxicity and also strategies adopted by plants for Pb-detoxification and developing tolerance to Pb. Mechanisms of Pb-detoxification include sequestration of Pb in the vacuole, phytochelatin synthesis and binding to glutathione and aminoacids etc. Pb tolerance is associated with the capacity of plants to restrict Pb to the cell walls, synthesis of osmolytes and activation of antioxidant defense system. Remediation of soils contaminated with Pb using phytoremediation and rhizofiltration technologies appear to have great potential for cleaning of Pb-contaminated soils.

Mineral nutrient imbalance, total antioxidants level and DNA damage in common bean (Phaseolus vulgaris L.) exposed to heavy metals

“…In other study is proposed that inhibition of shoot growth in corn seedlings is not a consequence of Pb accumulation but due to unknown signal induced in roots as a response to Pb exposure (Malkowski et al 2002). Plant biochemical tolerance to Pb is related to capacity to restrict Pb to the cell walls, synthesis of osmolytes and activation of the antioxidant defense system (Sharma and Dubey 2005). This is in correlation with results for high GTS for the samples treated with Pb and the lowest FRAP value obtained in this study.…”

Assessment of Heavy Metals in Sediments of Iloilo Batiano River, Philippines

“…Lead is considered as one of the industrial hazards and is considered as one of the dangerous environmental pollutants [4]. Cadmium, on the other hand, is a non-essential heavy metal resulting from agricultural, mining, industrial and even from the exhaust smoke emitted by vehicles [5].…”

Lichen Rehydration in Heavy Metal-Polluted Environments: Pb Modulates the Oxidative Response of Both Ramalina farinacea Thalli and Its Isolated Microalgae

“…The close contact with mycobiont hyphae would facilitate the migration of diffusible ROS (such as H 2 O 2 or other ROS-metastable derivatives) which could induce and propagate new ROS formation within fungal cells. Related to this, it is known that lead damages the photosynthetic membranes due to its affinity for N-and S-ligands: chlorophyll b and thus photosystem II being especially sensitive to Pb toxicity [39]. This toxic effect might be related with the observed diminishing of chlorophyll autofluorescence in both thallus and isolated algae rehydrated in the presence of lead.…”

“…One of the physiological processes which is highly sensitive to Pb is photosynthesis, probably due to the strong detrimental effects of ROS on some critical components of the photosynthetic machinery. According to Sharma and Dubey [39] Pb inhibits photosynthesis by causing multiple disorders at both structural and biochemical levels, compromising the thylakoid ultrastructure, the pigment and lipid composition and photochemical activities in plants. In addition, Pb inhibits the carboxylase activity of RuBisCO and probably other enzymes of the Calvin cycle due to its direct interaction with -SH groups, or indirectly via Pb-induced ROS which oxidize protein -SH groups [33].…”