Increasing Cd Supply Research Articles

Comparing soil-to-plant cadmium (Cd) transfer and potential human intake among rice cultivars with different Cd tolerance levels grown in a tropical contaminated soil.

With its accumulation in upland rice, cadmium (Cd) can easily enter the human food chain, which poses a global health threat considering nearly half of the human population depends on rice as a staple food source. A study was conducted to (1) evaluate Cd accumulation by rice cultivars, grown in Cd-polluted Tropical Oxisols, with different levels of Cd tolerance; (2) quantify Cd transfer from soil to rice shoots and grain; and (3) estimate daily Cd intake by humans. Three rice cultivars, characterized by low (Cateto Seda-CS), medium (BRSMG Talento-BT), and high (BRSMG Caravera-BC) Cd uptake capacity, were investigated. Rice cultivars were exposed to increasing soil Cd concentrations (0.0, 0.7, 1.3, 3.9, 7.8, and 11.7mgkg-1). Analysis was performed on soil, shoots, and grain. Shoot biomass and grain yield decreased with increasing Cd supply, suggesting the following Cd tolerance: CS > BT > BC. Cadmium concentrations in shoots and grain increased when exposed to Cd. Only CS did not exceed the maximum Cd limit permitted in food (0.40mgkg-1), when rates up to 1.3mgkg-1 of Cd were applied to soil. Considering daily rice consumption levels in Brazil, Cd intake often exceeds maximum tolerable levels. Continuous monitoring of soil Cd concentrations is a pivotal step in avoiding hazards to humans. Such monitoring is important on a global scale since outside of Asia, Brazil is the leading rice-producing and rice-consuming country.

The Absorption and Metabolism of Heavy Metals and Mineral Matters in the Halophyte Plant Artemisia aucheri

To our knowledge there has been no research on Artemisia aucheri as a halophyte plant, when grown in cadmium (Cd) contaminated soils. We tried to quantify the ability of A. aucheri in uptake of Cd and some nutrients in contaminated soil. In a pot culture experiment, five levels of Cd concentration were tested by adding 15, 30, 60, 120 and 240 mg of Cd per kilogram of dried soil. Plants were harvested and analyzed for Cd, N, P, K, Mg, Mn, Cu, Fe and Zn uptake. Depression in biomass production of plants as a result of excess Cd was observed. Cadmium concentration in plant shoots plant increased with increasing Cd supply significantly affecting the content of plant nutrients. Cd excess amounts increased macronutrients and decreased micronutrients concentrations in plant.

Uptake and translocation of cadmium and nutrients by Aeluropus littoralis

To our knowledge there has been no research on Aeluropus littoralis as a halophyte plant, when grown in soil contaminated with cadmium (Cd). Hence, the ability of A. littoralis to take up Cd and some nutrients was investigated in a pot experiment. Five levels of soil Cd concentration were tested (15, 30, 60, 120 and 240 mg Cd kg−1 soil). Plants were harvested at three different times and analyzed for Cd, N, P, K, Mg, Mn, Cu, Fe and Zn concentrations. Plant biomass decreased as a result of excess Cd. Cadmium concentration in plant shoots increased with increasing Cd supply, significantly affecting the plant nutrient content. An excess Cd supply increased macronutrient and decreased micronutrient concentrations in the plant. Although, the research process will become more complicated, this new approach may help to investigate the tolerance of A. littoralis to Cd stress for use in phytoremediation.

Increase of CD Accumulation in Five Poplar (Populus L.) with Different Supply Levels of CD

The present investigation reports the results of the Cd accumulated by five Populus at six Cd supply levels (0, 0.5, 2, 6, 25, 60 mg/kg) in soils. For all tested Populus species, Cd accumulated by the leaves, stems, and roots linearly increased with increasing Cd supply levels, the higher concentration Cd treatments significantly promoted the Cd accumulation. P. hopeiensis, and P. tomentosa always performed the stronger ability of Cd accumulation than other three Populus species under different Cd supply treatments, and P. nira var. thevestina and P. leucoides had the poorer accumulation ability. Cd in soil was more intensively absorbed in the leaves and stems for all 5 Populus species, was not retained in roots and was transferred to aboveground plant tissues.

Induction of phytochelatin and responses of antioxidants under cadmium stress in safflower (Carthamus tinctorius) seedlings

We investigated the role of antioxidant compounds (e.g.,\alpha-tocopherol, phytochelatins, glutathione, and other non-protein thiols) in the cadmium (Cd) tolerance of safflower (Carthamus tinctorius L. cv. Arak2811) seedlings exposed to different concentrations of Cd (0-100 \muM) for a week. A concentration- and tissue- dependent response to Cd was observed. Increasing Cd supply markedly reduced the dry weight of roots. Plants accumulated a substantial amount of Cd, especially in the roots. Levels of \alpha-tocopherol showed a significant increase with an increase in the concentration of Cd in leaves. Upon Cd exposure, \alpha-tocopherol levels followed a similar pattern in the root tissue with no significant change as compared to the control. Cadmium exposure caused a significant increase in non-protein thiols and phytochelatin levels in roots, whereas non-protein thiols and phytochelatin levels were not affected in leaves. The glutathione content in leaves significantly increased with increasing Cd concentrations, whereas in roots glutathione contents increased up to a concentration of 50 µM Cd and then decreased. The results indicate that the non-protein thiol and phytochelatin biosynthesis induction in roots and enhanced level of \alpha-tocopherol and glutathione in leaves may be involved in Cd tolerance and hyperaccumulation in safflower.

GENOTYPIC EFFECTS, OXIDATIVE STRESS AND TOLERANCE MECHANISMS INDUCED BY CADMIUM IN TWO Lactuca sativa CULTIVARS.

A hydroponic experiment was carried out to investigate the effect of cadmium (Cd) on differential expression, oxidative stress and some antioxidant enzyme activities in two Lactuca sativa cultivars (Balady, related Romaine Group and Great leaks, related Crisp Group). Cd phytotoxicity was shown by growth retardation of Balady and Great leaks. Results showed that Great leaks showed more sensitivity to Cd toxicity than Balady cultivar. Increasing Cd supply markedly reduced the total chlorophyll, dry matter of both Lactuca cultivarsand these decreases were more marked in great leaks. Increased Cd accumulation in various plant parts in both the Lactuca cultivars was observed as Cd concentration increased. Cd accumulated in the roots was much higher than in the shoot in the two cultivars, but more observed in the case of Balady cultivar. Balady cultivar had less uptake of Cd by shoot about two times than Great leaks shoot cultivar indicating that there are co-ordination of gene expression, regulation ion transport process operating in different root layer more efficient in Balady cultivar compared with Great leaks. Moreover, the induction of expression and activities of antioxidant enzymes and non protein thiol (NPT) increased in Balady cultivar more than Great leaks leading to H2O2 burst, lipid peroxidation, and growth inhibition. These gene expression and activities of antioxidant enzymes confer Balady cultivar some measure of Cd tolerance and presence of strong Cd-binding proteins in the roots. In conclusion, these results may be regarded as an indication of better tolerance mechanism of Balady cultivarmore than that of Great leaks to Cd contamination.

Antioxidant defense mechanisms in response to cadmium treatments in two safflower cultivars

By using two safflower (Carthamus tinctorius L.) cultivars, Arak2811 and Goldasht, the experiments were conducted in order to study (i) the genotypic variation in cadmium (Cd) tolerance, (ii) Cd concentrations in plants, and (iii) changes in the antioxidant defense systems in leaves, including antioxidant enzymes and nonenzymatic antioxidants. Plants were grown under controlled environmental conditions and subjected to Cd treatments (0, 25, 50, 75, and 100 μM Cd) for different time periods. Cd concentrations and cultivar-dependent response to Cd were assessed. Of the two cultivars, Goldasht showed a greater sensitivity to Cd toxicity as judged from the severity of Cd toxicity symptoms on leaves, much stronger enhancement in the MDA level, and decreases in dry matter production. Increasing Cd supply markedly reduced the shoot and root dry weights in both cultivars, but at the higher Cd concentrations and longer exposure durations, this decrease was more marked in cv. Goldasht. Plants accumulated substantial amount of Cd, especially in the roots, the highest being in the roots of cv. Arak2811 at 100 μM Cd after 4 days. Cd-induced oxidative stress as was indicated by the increase in lipid peroxidation with the increase in metal concentration and exposure duration. Under different Cd stress levels, activities of antioxidant enzymes differed in the two cultivars. The results indicated that Cd tolerance of cv. Arak2811 was related to the retention of Cd in the roots and avoiding the toxic effect by activation of the antioxidant system.

Changes in proline accumulation and antioxidative enzyme activities in Groenlandia densa under cadmium stress

In this study an experiment was carried out to study the process of stress adaptation in Groenlandia densa (opposite-leaved pondweed) grown under cadmium stress (0–20 mg L −1 Cd). The results showed that Cd concentrations in plants increased with increasing Cd supply levels and reached a maximum of 0.43 mg kg −1 DW at 0.5 mg L −1 Cd concentrations. The level of photosynthetic pigments and soluble proteins decreased only upon exposure to high Cd concentrations. At the same time, the level of malondialdehyde (MDA) increased with increasing Cd concentration. These results suggested an alleviation of stress that was presumably the result of by antioxidants such as superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR) and glutathione S-transferase (GST) as well as ascorbate peroxidase (APX), which increased linearly with increasing Cd levels. Cellular antioxidants levels showed a decline suggesting a defensive mechanism to protect against oxidative stress caused by Cd. In addition, the proline content in G. densa increased with increasing cadmium levels. These findings suggest that G. densa is equipped with an efficient antioxidant mechanism against Cd-induced oxidative stress which protects the plant's photosynthetic machinery from damage. Our present work concluded that G. densa has a high level of Cd tolerance and accumulation. We also found that moderate Cd treatment (0.05–5 mg L −1 Cd) alleviated oxidative stress in plants, while the addition of higher amounts of Cd (10–20 mg L −1) could cause an increasing generation of ROS, which was effectively scavenged by the antioxidative system.

Cadmium accumulation in vetiveria zizanioides and its effects on growth, physiological and biochemical characters

Hydroponic experiment was carried out to investigate the effect of cadmium (Cd) on growth, Cd accumulation, lipid peroxidation, antioxidative enzymes, leaf chlorophyll, root activity, protein content and Cd uptake kinetics of vetiver grass. The results showed that 1 mg/L Cd in solution led to increased chlorophyll contents, root activity and enhanced the growth of vetiver grass after 15 days, with 2.2% biomass increased compared to the control. Malondialdehyde (MDA) contents were significantly enhanced by all Cd supply levels. The development of toxic symptoms corresponded to a high accumulation of Cd and to the decrease of water content, chlorophyll, protein content and root activity, but to high increase in catalase and peroxidase activities in plants. Cd concentration in shoots and roots increased with increasing Cd supply levels, and reached a maximum of 93 and 2232 mg/kg Cd dry weight at 30 mg/L treatment, respectively.

Response of ATP sulfurylase and serine acetyltransferase towards cadmium in hyperaccumulator Sedum alfredii Hance.

We studied the responses of the activities of adenosine-triphosphate (ATP) sulfurylase (ATPS) and serine acetyltransferase (SAT) to cadmium (Cd) levels and treatment time in hyperaccumulating ecotype (HE) Sedum alfredii Hance, as compared with its non-hyperaccumulating ecotype (NHE). The results show that plant growth was inhibited in NHE but promoted in HE when exposed to high Cd level. Cd concentrations in leaves and shoots rapidly increased in HE rather than in NHE, and they became much higher in HE than in NHE along with increasing treatment time and Cd supply levels. ATPS activity was higher in HE than in NHE in all Cd treatments, and increased with increasing Cd supply levels in both HE and NHE when exposed to Cd treatment within 8 h. However, a marked difference of ATPS activity between HE and NHE was found with Cd treatment for 168 h, where ATPS activity increased in HE but decreased in NHE. Similarly, SAT activity was higher in HE than in NHE at all Cd treatments, but was more sensitive in NHE than in HE. Both ATPS and SAT activities in NHE leaves tended to decrease with increasing treatment time after 8 h at all Cd levels. The results reveal the different responses in sulfur assimilation enzymes and Cd accumulation between HE and NHE. With increasing Cd stress, the activities of sulfur assimilation enzymes (ATPS and SAT) were induced in HE, which may contribute to Cd accumulation in the hyperaccumulator Sedum alfredii Hance.

Cd AND Zn TOLERANCE AND ACCUMULATION BY SEDUM JINIANUM IN EAST CHINA

Field survey, hydroponic culture, and pot experiments were carried out to examine and characterize cadmium (Cd) and zinc (Zn) uptake and accumulation by Sedum jinianum, a plant species native to China. Shoot Cd and Zn concentrations in S. jinianum growing on a lead/Zn mine area reached 103–478 and 4165–8349 mg kg−1 (DM), respectively. The shoot Cd concentration increased with the increasing Cd supply, peaking at 5083 mg kg−1 (DM) when grown in nutrient at a concentration of 100 μmol L−1 for 32 d, and decreased as the solution concentration increased from 200 to 400 μmol L−1. The shoot-to-root ratio of plant Cd concentrations was > 1 when grown in solution Cd concentrations ≤ 200 μmol L−1. Foliar, stem, and root Zn concentrations increased linearly with the increasing Zn level from 1 to 9600 μmol L−1. The Zn concentrations in various plant parts decreased in the order roots > stem > leaves, with maximum concentrations of 19.3, 33.8, and 46.1 g kg−1 (DM), respectively, when plants were grown at 9600 μmol Zn L−1 for 32 d. Shoot Cd concentrations reached 16.4 and 79.8 mg kg−1 (DM) when plants were grown in the pots of soil with Cd levels of 2.4 mg kg−1 and 9.2 mg kg−1, respectively. At soil Zn levels of 619 and 4082 mg kg−1, shoot Zn concentrations reached 1560 and 15,558 mg kg−1 (DM), respectively. The results indicate that S. jinianum is a Cd hyperaccumulator with a high capacity to accumulate Zn in the shoots.

Antioxidative response to Cd in a newly discovered cadmium hyperaccumulator, Arabis paniculata F.

A hydroponic experiment was carried out to study the effect of cadmium (Cd) on growth, Cd accumulation, lipid peroxidation, reactive oxygen species (ROS) content and antioxidative enzymes in leaves and roots of Arabis paniculata F., a new Cd hyperaccumuator found in China. The results showed that 22–89 μM Cd in solution enhanced the growth of A. paniculata after three weeks, with 21–27% biomass increase compared to the control. Cd concentrations in shoots and roots increased with increasing Cd supply levels, and reached a maximum of 1662 and 8670 mg kg −1 Cd dry weight at 178 μM Cd treatment, respectively. In roots, 22–89 μM Cd reduced the content of malondialdehyde (MDA), superoxide ( O 2 - 1 ) and H 2O 2 as well as the activities of superoxide dismutase (SOD), guaiacol peroxidase (GPX), ascorbate peroxidase (APX) and glutathione reductase (GR). In leaves, the contents of MDA, O 2 - 1 and H 2O 2 remained unaffected by 22–89 μM Cd, while 178 μM Cd treatment significantly increased the MDA content, 69.5% higher than that of the control; generally, the activities of SOD, catalase (CAT), GPX and APX showed an increasing pattern with increasing Cd supply levels. Our present work concluded that A. paniculata has a great capability of Cd tolerance and accumulation. Moderate Cd treatment (22–89 μM Cd) alleviated the oxidative stress in roots, while higher level of Cd addition (178 μM) could cause an increasing generation of ROS, which was effectively scavenged by the antioxidative system.

Antioxidant defense system in leaves of Indian mustard (Brassica juncea) and rape (Brassica napus) under cadmium stress

Plant species capable of hyper-accumulating heavy metals are of considerable interest for phytoremediation, and differ in their ability to accumulate metals from environment. Using two brassica species (Brassica juncea and Brassica napus), nutrient solution experiments were conducted to study variation in tolerance to cadmium (Cd) toxicity based on (1) lipid peroxidation and (2) changes in antioxidative defense system in leaves of both plants (i.e., superoxide dismutase (SOD EC 1.15.1.1), catalase (CAT EC 1.11.1.6), ascorbate peroxidase (APX EC 1.11.1.11), guaiacol peroxidase (GPX EC 1.11.1.7), glutathione reductase (GR EC 1.6.4.2), levels of phytochelatins (PCs), non-protein thiols (NP-SH), and glutathione. Plants were grown in nutrient solution under controlled environmental conditions, and subjected to increasing concentrations of Cd (0, 10, 25 and 50 μM) for 15 days. Results showed marked differences between both species. Brassica napus under Cd stress exhibited increased level of lipid peroxidation, as was evidenced by the increased malondialdehyde (MDA) content in leaves. However, in Brassicajuncea treated plants, MDA content remained unchanged. In Brassica napus, with the exception of GPX, activity levels of some antioxidant enzymes involved in detoxification of reactive oxygen species (ROS), including SOD, CAT, GR, and APX, decreased drastically at high Cd concentrations. By contrast, in leaves of Brassica juncea treated plants, there was either only slight or no change in the activities of the antioxidative enzymes. Analysis of the profile of anionic isoenzymes of GPX revealed qualitative changes occurring during Cd exposure for both species. Moreover, levels of NP-SH and PCs, monitored as metal detoxifying responses, were much increased in leaves of Brassica juncea by increasing Cd supply, but did not change in Brassica napus. These results indicate that Brassica juncea plants possess the greater potential for Cd accumulation and tolerance than Brassica napus.

Role of iron plaque in Cd uptake by and translocation within rice ( Oryza sativa L.) seedlings grown in solution culture

A hydroponics culture experiment was conducted to investigate the effect of iron plaque on Cd uptake by and translocation within rice seedlings grown under controlled growth chamber conditions. Rice seedlings were pre-cultivated for 43 days and then transferred to nutrient solution containing six levels of Fe (0, 10, 30, 50, 80 and 100 mg L −1) for 6 days to induce different amounts of iron plaque on the root surfaces. Seedlings were then exposed to solution containing three levels of Cd (0, 0.1 and 1.0 mg L −1) for 4 days. In order to differentiate the uptake capability of Cd by roots with or without iron plaque, root tips (white root part without iron plaque) and middle root parts (with iron plaque) of pre-cultivated seedlings treated with 0, 30 and 50 mg L −1 Fe were exposed to 109Cd for 24 h. Reddish iron plaque gradually became visible on the surface of rice roots but the visual symptoms of the iron plaque on the roots differed among treatments. In general, the reddish color of the iron plaque became darker with increasing Fe supply, and the iron plaque was more homogeneously distributed all along the roots. The Fe concentrations increased significantly with increasing Fe supply regardless of Cd additions. The Cd concentrations in dithionite–citrate–bicarbonate (DCB)-extracts and in shoots and roots were significantly affected by Cd and Fe supply in the nutrient solution. The Cd concentrations increased significantly with increasing Cd supply in the solution and were undetectable when no Cd was added. The Cd concentrations in DCB-extracts with Fe supplied tended to be higher than that at Fe 0 at Cd 0.1, and at Cd 1.0, DCB-Cd with Fe supplied was significantly lower. Cd concentrations in roots and shoots decreased with increasing Fe supply at both Cd additions. The proportion of Cd in DCB-extracts was significantly lower than in roots or shoots. Compared to the control seedlings without Fe supply, the radioactivity of 109Cd in shoots of seedlings treated with Fe decreased when root tips were exposed to 109Cd and did not change significantly when middle parts of roots were exposed. Our results suggest that root tissue rather than iron plaque on the root surface is a barrier to Cd uptake and translocation within rice plants, and the uptake and translocation of Cd appear to be related to Fe nutritional levels in the plants.

Antioxidant defense system and cadmium uptake in barley genotypes differing in cadmium tolerance

Using two barley ( Hordeum vulgare) cultivars (cvs. Tokak and Hamidiye) nutrient solution experiments were conducted in order to study the genotypic variation in tolerance to Cd toxicity based on (i) development of leaf symptoms, (ii) decreases in dry matter production, (iii) Cd concentration and (iv) changes in antioxidative defense system in leaves (i.e., superoxide dismutase, ascorbate peroxidase, glutathione reductase, catalase, ascorbic acid and non-protein SH-groups). Plants were grown in nutrient solution under controlled environmental conditions, and subjected to increasing concentrations of Cd (0, 15, 30, 60 and 120 μmol/L Cd) for different time periods. Of the barley cultivars Hamidiye was particularly sensitive to Cd as judged by the severity and earlier development of Cd toxicity symptoms on leaves. Within 48 h of Cd application Hamidiye rapidly developed severe leaf Cd toxicity symptoms whereas in Tokak the leaf symptoms appeared only slightly. Hamidiye also tended to show more decrease in growth caused by Cd supply when compared to Tokak. The differences in sensitivity to Cd between Tokak and Hamidiye were not related to Cd concentrations in roots and shoots or Cd accumulation per plant. With the exception of catalase, activities of the enzymes involved in detoxification of reactive oxygen species (ROS) were markedly enhanced in Hamidiye by increasing Cd supply. By contrast, in Tokak there was either only a slight increase or no change in the activities of the antioxidative enzymes. Similarly, levels of ascorbic acid and especially non-protein SH-groups were increased in Hamidiye by Cd supply, but not affected in Tokak. The results indicate the existence of a large genotypic variation between barley cultivars for Cd tolerance. The differential Cd tolerance found in the barley cultivars was not related to uptake or accumulation of Cd in plants, indicating importance of internal mechanisms in expression of differential Cd tolerance in barley. As a response to increasing Cd supply particular increases in antioxidative mechanisms in the Cd-sensitive barley cultivar Hamidiye suggest that the high Cd sensitivity of Hamidiye is related to enhanced production and oxidative damage of ROS.

Cadmium tolerance and hyperaccumulation in a new Zn-hyperaccumulating plant species (Sedum alfredii Hance)

Sedum alfredii Hance has been identified as a new zinc (Zn) hyperaccumulating plant species. In this study, the effects of cadmium (Cd) supply levels (control, 12.5, 25, 50, 100, 200, 400, 800 µmol Cd L −1 ) on the growth and cadmium accumulation and Zn supply on Cd accumulation in S. alfredii Hance were studied. The results showed that no reduction in shoot and root dry matter yields were noted when the plants were grown at Cd supply levels up to 200 µmol L −1 in nutrient solution. Slight stimulation on shoot growth was noted at relatively low Cd levels (25 to 100µmol L −1 ). Cadmium concentrations in leaves and stems increased with increasing Cd supply levels, and reached a maximum of approximately 9000 and 6500 mg kg −1 (DW) at 400 µmol Cd L −1 , respectively. Root Cd concentration increased sharply only at relatively high Cd levels. Cadmium distribution in different parts of the

Phytotoxicity of cadmium and its effect on two genotypes of Brassica juncea L.

By using two Brassica juncea, L. (Indian mustard) genotypes (Varuna and DHR-9504) agreenhouse experiment was carried out to study the effect of cadmium (Cd) on growth, yield and concentration of cadmium (Cd) in different plant parts at the Agricultural Research Station, Bilaspur Chhattisgarh, India during 2002-2003. Plants were grown under controlled climatic conditions and subjected to increasing Cd supply in the form of CdCl2 @ 0, 20, 40, 60, 80 and 100 mg Cd kg-1 soil. Cdphytotoxicity was shown by growth retardation of Varuna and DHR-9504. Varuna showed greater sensitivity to Cd toxicity than DHR-9504. Increasing Cd supply markedly reduced the seed, stem and root dry weight of both genotypes (Varuna and DHR-9504), and these decreases were more marked in Varuna.Due to increased level of Cd application, the Cd concentration increased significantly in various plant parts in both the Brassica genotypes tested. Increase in Cd concentration of about 5 times in seeds, 7 times in stems and 9 times in roots was noted with an application of 20 mg Cd kg-1 soil more than the control. Cd was accumulated in the roots in much higher amounts than in the stem and seeds, especially in the case of DHR-9504, indicating that there is limited transport of Cd from the root system to the above ground plant parts in DHR-9504 genotype due to the presence of strong Cd-binding proteins in the roots. GenotypeDHR-9504 had significantly less uptake of Cd than genotype Varuna. More data are needed to ascertain the findings of this study.