Response to cadmium in higher plants

SummaryCadmium (Cd) is a non-essential trace element and its environmental concentrations are approaching toxic levels, especially in some agricultural soils. Understanding how and where Cd is stored in plants is important for ensuring food safety. In this study, we examined two plant species that differ in the distribution of Cd among roots and leaves. Lettuce and barley were grown in nutrient solution under two conditions: chronic (4 week) exposure to a low, environmentally relevant concentration (1.0 µM) of Cd and acute (1 h) exposure to a high concentration (5.0 mM) of Cd. Seedlings grown in solution containing 1.0 µM CdCl 2 did not show symptoms of toxicity and, at this concentration, 77% of the total Cd was translocated to leaves of lettuce, whereas only 24% of the total Cd was translocated to barley leaves. We tested the hypothesis that differential accumulation of Cd in roots and leaves is related to differential concentrations of phytochelatins (PCs), and its precursor peptides. The amounts of PCs and their precursor peptides in the roots and shoots were measured using HPLC. Each of PC 2-4 was synthesized in the barley root upon chronic exposure to Cd and did not increase further upon acute exposure. In the case of lettuce, no PCs were detected in the root given either Cd treatment.The high amounts of PCs produced in barley root could have contributed to preferential retention of Cd in barley roots.

Section: + -Pc N Complex Formationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 98%

Reduced translocation of cadmium from roots is associated with increased production of phytochelatins and their precursors

Akhter

McGarvey

Macfie

2012

“…Reducing the Mn supply to the plants promoted a reduction in Cd uptake, although the opposite has been reported by other authors (Baszynski et al, 1980;Pal'ove-Balang et al, 2006). Plant cells activate different detoxification mechanisms to avoid Cd stress, such as binding the Cd by phytochelatins, accumulating it in cell organelles, immobilising it in cell walls, and the synthesis of stress proteins (Sanità di Toppi and Gabbrielli, 1999). Oxidative stress promoted by Cd exposure, possibly by the generation of free radicals and active oxygen species, might cause lipid peroxidation.…”

Section: Discussionmentioning

confidence: 94%

Interaction and accumulation of manganese and cadmium in the manganese accumulator Lupinus albus

Zornoza

Sánchez-Pardo

Carpena

2010

“…However, a number of 13 authors later reported it to be affected even at relatively low soil concentrations (Chaudri et al, 1993;Giller et al, 1998) 14 In addition to the compartmentalisation of Cd, plant organs possess other mechanisms of detoxifying Cd, e.g., phytochelatin synthesis (Sanitá di Toppi and Gabbrielli, 1999). This may have also been operating in the nodules of the Cd-treated plants.…”

Section: Discussionmentioning

confidence: 99%

“…In particular, N 2 -fixing Rhizobium is highly sensitive to high concentrations of heavy metals (Giller et al, 1998; Broos et al, 2005). Cadmium (Cd), which has no biological function, is very toxic to both plants and animals (Sanità di Toppi and Gabbrielli, 1999); indeed, some authors refer to its toxicity as being 2-20 times greater than that of other heavy metals (Kabata-Pendias and Pendias, 2001). It enters agricultural soils via the application of sewage sludge and the extensive use of pesticides and phosphate fertilisers (Kabata-Pendias and Pendias, 2001), and is easily taken up by plant root systems.…”

mentioning

confidence: 99%

Cadmium in white lupin nodules: Impact on nitrogen and carbon metabolism

Sánchez-Pardo

Carpena

Zornoza

2013

Esta es la versión de autor del artículo publicado en: This is an author produced version of a paper published in: The aims of this work were to investigate the microlocalisation of cadmium (Cd) in Lupinus albus L. cv. Multolupa nodules, and to determine its effects on carbon and nitrogen metabolism. Nodulated white lupin plants were grown in a growth chamber with or without Cd (150 µM). Energy-dispersive X-ray microanalysis showed the walls of the outer nodule cortex cells to be the main area of Cd retention, helping to reduce the harmful effect Cd might have on the amount of N 2 fixed by the bacteroids. Sucrose synthase activity declined by 33% in the nodules of the Cd-treated plants, and smaller reductions were recorded in glutamine synthetase, aspartate aminotransferase, alkaline invertase and NADP-dependent isocitrate dehydrogenase activities. The Cd treatment also sharply reduced nodule concentrations of malate, succinate and citrate, while that of starch doubled, but that of sucrose experienced no significant change. In summary, the present results show that white lupins accumulate significant amounts of Cd in their root nodules. However, the activity of some enzymes involved in ammonium assimilation did decline, promoting a reduction in the plant N content. The downregulation of sucrose synthase limits the availability of carbon to the bacteroids, which might interfere with their respiration. Carbon metabolism therefore plays a primary role in the impaired function of the white lupin root nodule caused by Cd, while N metabolism appears to have a more secondary involvement. Other plants, most notably legumes, can also obtain N from atmospheric N 2 via the entry of the roots into an endosymbiotic association with nitrogen-fixing bacteria (Stougaard, 2000). This interaction gives rise to a new plant organ: the root nodule.These nodules provide optimal living conditions for nitrogen-fixing bacteria, which reduce N 2 to NH 4 + via the action of nitrogenase (Nase) (Temple et al., 1998). Once NH 4 + is formed it binds to glutamic acid (in the presence of ATP and via the action of glutamine synthetase [GS]), to form glutamine. Glutamine can then form two glutamic acid molecules in the presence of oxoglutarate and glutamate synthase (glutamine-2-oxoglutarate-amino-transferase; GOGAT). The glutamine synthetase/glutamate synthase (GS/GOGAT) system is of vital importance since the glutamine and glutamate produced act as N donors for the biosynthesis of major N-containing compounds such as amino acids, nucleotides and chlorophylls (Lea and Ireland, 1999). The symbiotic fixation of N 2 is dependent on the supply of carbohydrates by the host plant to the bacteroids in the root nodules. Photosynthates, predominantly sucrose, are translocated from the shoots to the root nodules, providing the bacteroids the energy and reductants required by Nase, and the carbon skeletons needed for the assimilation of NH 4 + . N 2 fixing bacteria-legume symbiosis is therefore based on the exchange of carbon and nitrogen between the ...