Nitrate facilitates cadmium uptake, transport and accumulation in the hyperaccumulator Sedum plumbizincicola |
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Authors: | Pengjie Hu Yong-Gen Yin Satoru Ishikawa Nobuo Suzui Naoki Kawachi Shu Fujimaki Masato Igura Cheng Yuan Jiexue Huang Zhu Li Tomoyuki Makino Yongming Luo Peter Christie Longhua Wu |
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Affiliation: | 1. Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, 210008, China 2. Japan Atomic Energy Agency, Gunma, 370-1292, Japan 3. National Institute for Agro-Environmental Sciences, Ibaraki, 305-8604, Japan 4. Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences, Yantai, 264003, China 5. Agri-Environment Branch, Agri-Food and Biosciences Institute, Newforge Lane, Belfast, BT9 5PX, UK
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Abstract: | The aims of this study are to investigate whether and how the nitrogen form (nitrate (NO3 –) versus ammonium (NH4 +)) influences cadmium (Cd) uptake and translocation and subsequent Cd phytoextraction by the hyperaccumulator species Sedum plumbizincicola. Plants were grown hydroponically with N supplied as either NO3 – or NH4 +. Short-term (36 h) Cd uptake and translocation were determined innovatively and quantitatively using a positron-emitting 107Cd tracer and positron-emitting tracer imaging system. The results show that the rates of Cd uptake by roots and transport to the shoots in the NO3 – treatment were more rapid than in the NH4 + treatment. After uptake for 36 h, 5.6 (0.056 μM) and 29.0 % (0.290 μM) of total Cd in the solution was non-absorbable in the NO3 – and NH4 + treatments, respectively. The local velocity of Cd transport was approximately 1.5-fold higher in roots (3.30 cm h?1) and 3.7-fold higher in shoots (10.10 cm h?1) of NO3 –- than NH4 +-fed plants. Autoradiographic analysis of 109Cd reveals that NO3 – nutrition enhanced Cd transportation from the main stem to branches and young leaves. Moreover, NO3 – treatment increased Cd, Ca and K concentrations but inhibited Fe and P in the xylem sap. In a 21-day hydroponic culture, shoot biomass and Cd concentration were 1.51 and 2.63 times higher in NO3 –- than in NH4 +-fed plants. We conclude that compared with NH4 +, NO3 – promoted the major steps in the transport route followed by Cd from solution to shoots in S. plumbizincicola, namely its uptake by roots, xylem loading, root-to-shoot translocation in the xylem and uploading to the leaves. S. plumbizincicola prefers NO3 – nutrition to NH4 + for Cd phytoextraction. |
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