Toxic effects of Pb2+ on growth of cowpea (Vigna unguiculata)

Abstract

A concentration as low as 1 μM lead (Pb) is highly toxic to plants, but previous studies have typically related plant growth to the total amount of Pb added to a solution. In the present experiment, the relative fresh mass of cowpea (Vigna unguiculata) was reduced by 10 % at a Pb 2+ activity of 0.2 μM for the shoots and at a Pb 2+ activity of 0.06 μM for the roots. The primary site of Pb 2+ toxicity was the root, causing severe reductions in root growth, loss of apical dominance (shown by an increase in branching per unit root length), the formation of localized swelling behind the root tips (due to the initiation of lateral roots), and the bending of some root tips. In the root, Pb was found to accumulate primarily within the cell walls and intercellular spaces.Abbreviations: CDTA -cyclohexane-1,2-diaminetetra-acetic acid; DAP -days after planting; DIdeionised; EC -electrical conductivity; I -ionic strength; ICPOES -inductively coupled plasma optical emission spectrometry; ICPMS -inductively coupled plasma mass spectrometry; TEMtransmission electron microscopy Kopittke PM, Asher CJ, Kopittke RA, Menzies NW, 2007. Environmental Pollution 150, 280-287.

Accumulation and distribution of lead (Pb) in plant tissues of guar (Cyamopsis tetragonolobaL.) and sesame (Sesamum indicumL.): profitable phytoremediation with biofuel crops

“…It has been well documented in the literature that germination is an essential process to determine the effects of Pb toxicity on different plant species. Germination is strongly inhibited at very low concentrations of Pb, even at micromolar levels (Kopittke, Asher, Kopittke, & Menzies, 2007). In this study, C. tetragonoloba and S. indicum seeds were able to germinate in the presence of low to moderate level of Pb concentrations in soil.…”

“…of lead exposure. Decrease in plant biomass may be associated with disturbed metabolic activities due to reduced uptake of essential nutrients when grown under Pb stress (Gopal & Rizvi, 2008;Kopittke et al, 2007). Lead, if present at high levels, can interfere with normal enzyme functions in plants and especially photosynthesis which is one of the plant processes most drastically affected by Pb toxicity.…”

Nitric Oxide Increases Pb Tolerance by Lowering Pb Uptake and Translocation as well as Phytohormonal Changes in Cowpea (Vigna unguiculata (L.) Walp.)

“…There are several reasons why the transport of lead from roots to aerial plant parts is limited. These reasons include immobilization by negatively charged pectins within the cell wall, precipitation of insoluble lead salts in intercellular spaces (Islam et al 2007;Kopittke et al 2007), accumulation in plasma membranes (Islam et al 2007;Jiang & Liu 2010;Seregin et al 2004), or sequestration in the vacuoles of rhizodermal and cortical cells (Kopittke et al 2007;Seregin et al 2004). However, these reasons are not sufficient to explain the low rate of lead translocation from root to shoot.…”

Effects of nickel and nitrogen soil fertilization on lettuce growth and urease activity

“…However, research with Ni has mainly addressed its toxic effects on plants and on how Ni-hyperaccumulator plants respond to high Ni concentrations. Apparently, Ni 2+ reaches toxicity levels in the shoots first, but higher Ni 2+ activities can also be toxic to the roots, decreasing growth and inhibiting lateral root formation (Kopittke et al, 2007). Although Ni is an important environmental contaminant, its action mechanism in plants is not yet clear (Sengar et al, 2008) It is known that Ni is directly related to the nitrogen (N) metabolism of plants because Ni deficiency impairs the urease activity, resulting in accumulation of urea in the plant.…”