1
|
Jiang P, Zheng Y, Liu J, Yu G, Lin F. Pathways of cadmium fluxes in the root of the hyperaccumulator Celosia argentea Linn. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2022; 29:44413-44421. [PMID: 35137315 DOI: 10.1007/s11356-021-17352-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2021] [Accepted: 10/30/2021] [Indexed: 06/14/2023]
Abstract
In order to study the mechanism of cadmium (Cd) uptake by the roots of Celosia argentea Linn. (Amaranthaceae), the effects of various inhibitors, ion channel blockers, and hydroponic conditions on Cd2+ fluxes in the roots were characterized using non-invasive micro-test technology (NMT). The net Cd2+ flux (72.5 pmol∙cm-2∙s-1) in roots that had been pretreated with Mn was significantly higher than that in non-pretreated roots (58.1 pmol∙cm-2∙s-1), indicating that Mn pretreatment enhanced Cd uptake by the roots. This finding may be explained by the fact that the addition of Mn significantly increased the expression of the transporter gene and thus promoted Cd uptake and transport. In addition, Mn pretreatment resulted in an increase in root growth, which may in turn promote root vigor. The uncoupler 2,4-dinitrophenol (DNP) caused a significant reduction in net Cd2+ fluxes in the roots, by 70.5% and 41.4% when exposed to Mn and Cd stress, respectively. In contrast, a P-type ATPase inhibitor (Na3VO4) had only a small effect on net Cd2+ fluxes to the plant roots, indicating that ATP has a relatively minor role in Cd uptake by roots. La3+ (a Ca channel inhibitor) had a more significant inhibitory effect on net Cd2+ fluxes than did TEA (a K channel inhibitor). Therefore, Cd uptake by plant roots may occur mainly through Ca channels rather than K channels. In summary, uptake of Cd by the roots of C. argentea appears to occur via several types of ion channels, and Mn can promote Cd uptake.
Collapse
Affiliation(s)
- Pingping Jiang
- Guangxi Key Laboratory of Environmental Pollution Control Theory and Technology, Guilin University of Technology, Guilin, 541004, China
- Technical Innovation Center of Mine Geological Environmental Restoration Engineering in Southern Karst Area, MNR, Guilin, 541004, China
| | - Yingyi Zheng
- Guangxi Key Laboratory of Environmental Pollution Control Theory and Technology, Guilin University of Technology, Guilin, 541004, China
| | - Jie Liu
- Guangxi Key Laboratory of Environmental Pollution Control Theory and Technology, Guilin University of Technology, Guilin, 541004, China.
- Technical Innovation Center of Mine Geological Environmental Restoration Engineering in Southern Karst Area, MNR, Guilin, 541004, China.
| | - Guo Yu
- Guangxi Key Laboratory of Environmental Pollution Control Theory and Technology, Guilin University of Technology, Guilin, 541004, China
| | - Fanyu Lin
- Third Institute of Oceanography, Ministry of Natural Resources, Xiamen, China
| |
Collapse
|
2
|
Zhang L, Zhang C, Du B, Lu B, Zhou D, Zhou J, Zhou J. Effects of node restriction on cadmium accumulation in eight Chinese wheat (Triticum turgidum) cultivars. THE SCIENCE OF THE TOTAL ENVIRONMENT 2020; 725:138358. [PMID: 32464746 DOI: 10.1016/j.scitotenv.2020.138358] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/20/2020] [Revised: 03/28/2020] [Accepted: 03/30/2020] [Indexed: 06/11/2023]
Abstract
Minimization of cadmium (Cd) accumulation in wheat is an effective method to prevent Cd-related health risks to humans. To understand the underlying mechanisms of restricting Cd transport, the role of nodes in Cd restriction was studied in eight Chinese wheat cultivars. The Cd accumulation differed significantly among the cultivars. The grain Cd concentrations were mainly dependent on the Cd concentrations in the roots and shoots. The Cd transport in the shoots controlled the wheat grain Cd accumulations. Nodes in the wheat stem have distinct functions in the transfer, distribution, and restriction of Cd. The node connected to the panicle showed the lowest translocation factors. The area of the vascular bundles, especially the diffuse vascular bundles, in the junctional node with the flag leaf was the key factor in restricting Cd transfer to the wheat grain. There was a significant relation between these areas and the grain Cd concentrations. The conclusion of this study is that screening or breeding cultivars with low Cd concentrations in the roots or with smaller areas of diffuse vascular bundles in the junctional nodes with the flag leaf is an effective strategy to decrease Cd concentration in wheat grains.
Collapse
Affiliation(s)
- Ligan Zhang
- Anhui Province Key Laboratory of Farmland Ecological Conservation and Pollution Prevention, School of Resources and Environment, Anhui Agricultural University, Hefei 230036, China.
| | - Chen Zhang
- Anhui Province Key Laboratory of Farmland Ecological Conservation and Pollution Prevention, School of Resources and Environment, Anhui Agricultural University, Hefei 230036, China; Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China
| | - Buyun Du
- Nanjing Institute of Environmental Sciences, Ministry of Ecological Environment, Nanjing 210042, China
| | - Bingxin Lu
- Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China
| | - Dongmei Zhou
- Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China
| | - Jing Zhou
- Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China
| | - Jun Zhou
- Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China.
| |
Collapse
|
3
|
Gray CW, Yi Z, Munir K, Lehto NJ, Robinson BH, Cavanagh JAE. Cadmium Concentrations in New Zealand Wheat: Effect of Cultivar Type, Soil Properties, and Crop Management. JOURNAL OF ENVIRONMENTAL QUALITY 2019; 48:701-708. [PMID: 31180444 DOI: 10.2134/jeq2018.12.0430] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Wheat ( L.) grain is a contributing source of dietary Cd in New Zealand, but despite this, there is a dearth of information on Cd concentrations in wheat and the factors that affect uptake. We measured Cd concentrations in 12 wheat cultivars grown in field sites across New Zealand and also assessed the soil, plant, and crop factors that have been reported to affect Cd uptake. We found there was a wide range in grain Cd concentrations (0.004 to 0.205 mg kg fresh weight [FW]). The overall mean concentration (0.066 mg kg FW) was below the maximum limit (ML) of 0.1 mg kg FW. Only 7% of grain samples across seven sites exceeded the ML. There were significant ( < 0.05) differences (2.5-fold) in Cd concentrations in wheat grain between cultivars. No strong significant relationships were found between soil properties and Cd concentrations in grain. Further, management factors affecting grain Cd concentrations were inconsistent. Given the lack of relationships between soils and management practices, the most effective way of limiting Cd uptake in wheat grain at sites where Cd exceeds MLs may be the use of low-Cd-accumulating cultivars. Further studies are required to explore specifically the influence of irrigation and effects of type and rate of fertilizer on Cd uptake in wheat, as well as to better understand the mechanisms of Cd uptake in wheat.
Collapse
|
4
|
Zhu B, Liao Q, Zhao X, Gu X, Gu C. A multi-surface model to predict Cd phytoavailability to wheat (Triticum aestivum L.). THE SCIENCE OF THE TOTAL ENVIRONMENT 2018; 630:1374-1380. [PMID: 29554757 DOI: 10.1016/j.scitotenv.2018.03.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/28/2017] [Revised: 02/26/2018] [Accepted: 03/01/2018] [Indexed: 06/08/2023]
Abstract
The prediction of metal bioavailability in soils is critical to metal risk assessments and the amount of dissolved metal in soils is a key factor determining bioavailability. Because the recently developed geochemical multi-surface models (MSMs) offer a promising tool for the determination of metal partitioning in soils, in this study, a MSM based on generic parameters was used to assess the bioavailability of Cd in wheat (Triticum aestivum L.) growing in 12 soils with a wide range of properties. The amount of MSM-calculated dissolved Cd correlated strongly with the amount of Cd uptake by wheat (R2=0.873 for roots and R2=0.837 for shoots), and the model's performance was better than that of chemical extraction methods (0.01M CaCl2, 0.43M HNO3 and soil total Cd). The reactive fraction of soil organic matter, the soil/solution ratio, and the inclusion/exclusion of background cations influenced the calculation results. The best calculation condition was optimized. The application of the MSM was also examined in 84 wheat-soil samples from the field. The amount of Cd in wheat seeds had a stronger correlation with the amount of MSM-predicted Cd than with the amount of Cd obtained using chemical extraction methods. Our results suggested that MSM-calculated Cd is an effective indicator of the bioavailability of Cd in soils and demonstrated the utility of the method as a tool to assess the risk of Cd contamination in soils.
Collapse
Affiliation(s)
- Bojing Zhu
- State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Xianlin Ave. 163, Nanjing 210023, PR China
| | - Qilin Liao
- Geological Survey of Jiangsu Province, Zhujiang Rd. 700, 210002, PR China
| | - Xiaopeng Zhao
- State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Xianlin Ave. 163, Nanjing 210023, PR China
| | - Xueyuan Gu
- State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Xianlin Ave. 163, Nanjing 210023, PR China.
| | - Cheng Gu
- State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Xianlin Ave. 163, Nanjing 210023, PR China
| |
Collapse
|
5
|
Evaluation of Cadmium Concentration in Wheat Crop Affected by Cropping System. ACTA ACUST UNITED AC 2018. [DOI: 10.5812/jjhs.14400] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/07/2022]
|
6
|
Li LZ, Tu C, Peijnenburg WJGM, Luo YM. Characteristics of cadmium uptake and membrane transport in roots of intact wheat (Triticum aestivum L.) seedlings. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2017; 221:351-358. [PMID: 28012673 DOI: 10.1016/j.envpol.2016.11.085] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/12/2016] [Revised: 11/16/2016] [Accepted: 11/30/2016] [Indexed: 06/06/2023]
Abstract
Wheat is one of several cereals that is capable of accumulating higher amounts of Cd in plant tissues. It is important to understand the Cd2+ transport processes in roots that result in excess Cd accumulation. Traditional destructive technologies have limited capabilities in analyzing root samples due to methodological limitations, and sometimes may result in false conclusions. The mechanisms of Cd2+ uptake into the roots of wheat seedlings (Triticum aestivum L.) were investigated by assessing the impact of various inhibitors and channel blockers on Cd accumulation as well as the real-time net Cd2+ flux at roots with the non-destructive scanning ion-selective electrode technique. The P-type ATPase inhibitor Na3VO4 (500 μM) had little effect on Cd uptake (p < 0.05) and the kinetics of transport in the root of wheat, suggesting that Cd2+ uptake into wheat root cells is not directly dependent on H+ gradients. While, the uncoupler 2,4-dinitrophenol significantly limited Cd2+ uptake (p < 0.05) and transport kinetics in the root of wheat, suggesting the existence of metabolic mediation in the Cd2+ uptake process by wheat. The Cd content at the whole-plant level in wheat was significantly (p < 0.05) decreased upon pretreatment with the Ca2+ channel blockers La3+ or Gd3+ and Verapamil, but not in case of pretreatment with the K+ channel blocker tetraethylammonium (TEA). In addition, the inhibitors of the Ca2+ channel, as well as high concentrations of Ca2+, reduced the real-time net Cd2+ fluxes at the root surface in SIET experiments. These results indicate that Cd2+ moves across the plasma lemma of the wheat root via Ca2+ channels. In addition, our results suggested a role for protein synthesis in mediating Cd2+ uptake and transport by wheat.
Collapse
Affiliation(s)
- Lian-Zhen Li
- Key Laboratory of Coastal Zone Environmental Processes and Ecological Remediation, Yantai Institute of Coastal Zone Research (YIC), Chinese Academy of Sciences (CAS), Shandong Provincial Key Laboratory of Coastal Zone Environmental Processes, YICCAS, Yantai, PR China.
| | - Chen Tu
- Key Laboratory of Coastal Zone Environmental Processes and Ecological Remediation, Yantai Institute of Coastal Zone Research (YIC), Chinese Academy of Sciences (CAS), Shandong Provincial Key Laboratory of Coastal Zone Environmental Processes, YICCAS, Yantai, PR China.
| | - Willie J G M Peijnenburg
- National Institute of Public Health and the Environment, Center for Safety of Substances and Products, P.O. Box 1, 3720 BA Bilthoven, The Netherlands; Institute of Environmental Sciences (CML), Leiden University, Leiden, The Netherlands.
| | - Yong-Ming Luo
- Key Laboratory of Coastal Zone Environmental Processes and Ecological Remediation, Yantai Institute of Coastal Zone Research (YIC), Chinese Academy of Sciences (CAS), Shandong Provincial Key Laboratory of Coastal Zone Environmental Processes, YICCAS, Yantai, PR China.
| |
Collapse
|
7
|
Macfie SM, Bahrami S, McGarvey BD. Differential accumulation of cadmium in near-isogenic lines of durum wheat: no role for phytochelatins. PHYSIOLOGY AND MOLECULAR BIOLOGY OF PLANTS : AN INTERNATIONAL JOURNAL OF FUNCTIONAL PLANT BIOLOGY 2016; 22:461-472. [PMID: 27924119 PMCID: PMC5120040 DOI: 10.1007/s12298-016-0383-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/29/2016] [Revised: 09/19/2016] [Accepted: 09/26/2016] [Indexed: 05/20/2023]
Abstract
Certain cultivars of some crops, including durum wheat (Triticum durum Desf.), have a propensity to accumulate cadmium in the grain. In the 1980s, a Canadian wheat breeding program generated five pairs of near-isogenic lines of durum wheat that vary in cadmium-accumulation. Within each pair, one member accumulates twofold to threefold higher concentrations of cadmium in the shoot and grain. However, the physiological explanation for the high-low phenotype is unknown. We studied correlations between concentrations of cadmium and non-protein thiols, including phytochelatins, in these five pairs of near-isogenic lines to test the hypothesis that differential retention of cadmium-binding complexes in the root would explain the phenotype. The expected high-low pattern of cadmium accumulation was found in three of the pairs. In one pair, cadmium was positively correlated with cysteine and glutathione in the roots and with phytochelatins 2 and 4 in the shoots but in another pair cadmium was strongly negatively correlated with phytochelatins 2 and 4 in the shoots and unrelated to cysteine or glutathione. No correlations between concentrations of cadmium and the non-protein thiols were found in the third pair or in the remaining two pairs. The production of phytochelatins is a well-described response to cadmium but the lack of consistent correlation between cadmium and non-protein thiols in these five near-isogenic lines indicates that complexation with non-protein thiols does not explain differential translocation of cadmium in durum wheat.
Collapse
Affiliation(s)
- Sheila M. Macfie
- Department of Biology, The University of Western Ontario, London, ON N6A 5B7 Canada
| | - Shirin Bahrami
- Department of Biology, The University of Western Ontario, London, ON N6A 5B7 Canada
| | - Brian D. McGarvey
- Southern Crop Protection and Food Research, Agriculture and Agri-Food Canada, 1391 Sandford St., London, ON N5V 4T3 Canada
- Southwest University for Nationalities, No. 16, South 4th Section First Ring Road, Chengdu, 610041 Sichuan People’s Republic of China
| |
Collapse
|
8
|
Rizwan M, Ali S, Abbas T, Zia-Ur-Rehman M, Hannan F, Keller C, Al-Wabel MI, Ok YS. Cadmium minimization in wheat: A critical review. ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2016; 130:43-53. [PMID: 27062345 DOI: 10.1016/j.ecoenv.2016.04.001] [Citation(s) in RCA: 306] [Impact Index Per Article: 38.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/11/2015] [Revised: 04/01/2016] [Accepted: 04/01/2016] [Indexed: 05/03/2023]
Abstract
Cadmium (Cd) accumulation in wheat (Triticum aestivum L.) and its subsequent transfer to food chain is a major environmental issue worldwide. Understanding wheat response to Cd stress and its management for aiming to reduce Cd uptake and accumulation in wheat may help to improve wheat growth and grain quality. This paper reviewed the toxic effects, tolerance mechanisms, and management of Cd stress in wheat. It was concluded that Cd decreased germination, growth, mineral nutrients, photosynthesis and grain yield of wheat and plant response to Cd toxicity varies with cultivars, growth conditions and duration of stress applied. Cadmium caused oxidative stress and genotoxicity in wheat plants. Stimulation of antioxidant defense system, osmoregulation, ion homeostasis and over production of signalling molecules are important adaptive strategies of wheat under Cd stress. Exogenous application of plant growth regulators, inorganic amendments, proper fertilization, silicon, and organic, manures and biochar, amendments are commonly used for the reduction of Cd uptake in wheat. Selection of low Cd-accumulating wheat cultivars, crop rotation, soil type, and exogenous application of microbes are among the other agronomic practices successfully employed in reducing Cd uptake by wheat. These management practices could enhance wheat tolerance to Cd stress and reduce the transfer of Cd to the food chain. However, their long-term sustainability in reducing Cd uptake by wheat needs further assessment.
Collapse
Affiliation(s)
- Muhammad Rizwan
- Department of Environmental Sciences and Engineering, Government College University, Allama Iqbal Road, 38000 Faisalabad, Pakistan.
| | - Shafaqat Ali
- Department of Environmental Sciences and Engineering, Government College University, Allama Iqbal Road, 38000 Faisalabad, Pakistan
| | - Tahir Abbas
- Department of Environmental Sciences and Engineering, Government College University, Allama Iqbal Road, 38000 Faisalabad, Pakistan
| | - Muhammad Zia-Ur-Rehman
- Institute of Soil and Environmental Sciences, University of Agriculture, Faisalabad 38040, Pakistan
| | - Fakhir Hannan
- Department of Environmental Sciences and Engineering, Government College University, Allama Iqbal Road, 38000 Faisalabad, Pakistan
| | - Catherine Keller
- Aix-Marseille Université, CNRS, IRD, CEREGE UM34, 13545 Aix en Provence, France
| | - Mohammad I Al-Wabel
- Soil Sciences Department, College of Food and Agricultural Sciences, King Saud University, P.O. Box 2460, Riyadh 11451, Saudi Arabia
| | - Yong Sik Ok
- Korea Biochar Research Center and Department of Biological Environment, Kangwon National University, Chuncheon 200-701, South Korea
| |
Collapse
|
9
|
Liu H, Wang H, Ma Y, Wang H, Shi Y. Role of transpiration and metabolism in translocation and accumulation of cadmium in tobacco plants (Nicotiana tabacum L.). CHEMOSPHERE 2016; 144:1960-5. [PMID: 26547876 DOI: 10.1016/j.chemosphere.2015.10.093] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/14/2015] [Revised: 10/07/2015] [Accepted: 10/22/2015] [Indexed: 06/05/2023]
Abstract
Tobacco plants grown in pots and in hydroponic culture accumulated cadmium (Cd) particularly: the Cd content of tobacco leaves exceeded 100 mg/kg and the enrichment factor (the ratio of Cd in leaves to that in soil) was more than 4. These high levels of accumulation identify tobacco as a hyperaccumulator of Cd. Two transpiration inhibitors (paraffin or CaCl2) and shade decreased the Cd content of tobacco leaves, and the decrease showed a linear relationship with the leaf transpiration rate. A metabolism inhibitor, namely 2,4-dinitrophenol (DNP), and low temperature (4 °C) also lowered the Cd content of tobacco leaves, but the inhibitory effect of low temperature was greater. In the half number of leaves that were shaded, the Cd content decreased to 26.5% of that in leaves that were not shaded in the same tobacco plants. These results suggests that translocation of Cd from the medium to the leaves is driven by the symplastic and the apoplastic pathways. Probably, of the two crucial steps in the translocation of Cd in tobacco plants, one, namely uptake from the medium to the xylem, is energy-dependent whereas the other, namely the transfer from the xylem to the leaves, is driven mainly by transpiration.
Collapse
Affiliation(s)
- Haiwei Liu
- Key Laboratory of Tobacco Biology and Processing, Ministry of Agriculture, Tobacco Research Institute, Chinese Academy of Agricultural Sciences, Qingdao 266101, China
| | - Haiyun Wang
- Key Laboratory of Tobacco Biology and Processing, Ministry of Agriculture, Tobacco Research Institute, Chinese Academy of Agricultural Sciences, Qingdao 266101, China
| | - Yibing Ma
- National Soil Fertility and Fertilizer Effects Long-term Monitoring Network, Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences, Beijing 100081, China
| | - Haohao Wang
- Key Laboratory of Tobacco Biology and Processing, Ministry of Agriculture, Tobacco Research Institute, Chinese Academy of Agricultural Sciences, Qingdao 266101, China
| | - Yi Shi
- Key Laboratory of Tobacco Biology and Processing, Ministry of Agriculture, Tobacco Research Institute, Chinese Academy of Agricultural Sciences, Qingdao 266101, China.
| |
Collapse
|
10
|
Harris NS, Taylor GJ. Cadmium uptake and partitioning in durum wheat during grain filling. BMC PLANT BIOLOGY 2013; 13:103. [PMID: 23856013 PMCID: PMC3726410 DOI: 10.1186/1471-2229-13-103] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/01/2013] [Accepted: 07/05/2013] [Indexed: 05/18/2023]
Abstract
BACKGROUND Concentrations of cadmium (Cd) in the grain of many durum wheats (Triticum turgidum subsp. durum) grown in North American prairie soils often exceed international trade standards. Genotypic differences in root-to-shoot translocation of Cd are a major determinant of intraspecific variation in the accumulation of Cd in grain. We tested the extent to which changes in whole-plant Cd accumulation and the distribution of Cd between tissues influences Cd accumulation in grain by measuring Cd accumulation throughout the grain filling period in two near-isogenic lines (NILs) of durum wheat that differ in grain Cd accumulation. RESULTS Roots absorbed Cd and transported it to the shoots throughout the grain filling period, but the low- and high-Cd NILs did not differ in whole-plant Cd uptake. Although the majority of Cd accumulation was retained in the roots, the low- and high-Cd NILs differed substantively in root-to-shoot translocation of Cd. At grain maturity, accumulation of Cd in the shoots was 13% (low-Cd NIL) or 37% (high-Cd NIL) of whole-plant Cd accumulation. Accumulation of Cd in all shoot tissue, including grain, was at least 2-fold greater in the high-Cd NIL at all harvests. There was no net remobilization of shoot Cd pools during grain filling. The timing of Cd accumulation in grain was positively correlated with grain biomass accumulation, and the rate of grain filling peaked between 14 and 28 days post-anthesis, when both NILs accumulated 60% of total grain biomass and 61-66% of total grain Cd content. CONCLUSIONS These results show that genotypic variation in root-to-shoot translocation of Cd controls accumulation of Cd in durum wheat grain. Continued uptake of Cd by roots and the absence of net remobilization of Cd from leaves during grain filling support a direct pathway of Cd transport from roots to grain via xylem-to-phloem transfer in the stem.
Collapse
Affiliation(s)
- Neil S Harris
- Department of Biological Sciences, University of Alberta, Edmonton AB T6G 2E9, Canada
| | - Gregory J Taylor
- Department of Biological Sciences, University of Alberta, Edmonton AB T6G 2E9, Canada
| |
Collapse
|