Silicon alleviates Cd stress of wheat seedlings (Triticum turgidum L. cv. Claudio) grown in hydroponics
We investigated the potential role of silicon in improving tolerance and decreasing cadmium (Cd) toxicity in durum wheat (Triticum turgidum L. durum) either through a reduced Cd uptake or exclusion/sequestration in non-metabolic tissues. For this, plants were grown in hydroponic conditions for 10 days either in presence or absence of 1 mM Si and for 11 additional days in various Cd concentrations (0, 0.5, 5.0 and 50 μM). After harvesting, morphological and physiological parameters as well as elemental concentrations were recorded. Cadmium caused reduction in growth parameters, photosynthetic pigments and mineral nutrient concentrations both in shoots and roots. Shoot and root contents of malate, citrate and aconitate increased, while contents of phosphate, nitrate and sulphate decreased with increasing Cd concentrations in plants. Addition of Si to the nutrient solution mitigated these adverse effects: Cd concentration in shoots decreased while concentration of Cd adsorbed at the root cell apoplasmic level increased together with Zn uptake by roots. Overall, total Cd uptake decreased in presence of Si. There was no co-localisation of Cd and Si either at the shoot or at the root levels. No Cd was detected in leaf phytoliths. In roots, Cd was mainly detected in the cortical parenchyma and Si at the endodermis level, while analysis of the outer thin root surface of the plants grown in the 50 μM Cd + 1 mM Si treatment highlighted non-homogeneous Cd and Si enrichments. These data strongly suggest the existence of a root localised protection mechanism consisting in armoring the root surface by Si- and Cd-bearing compounds and in limiting root–shoot translocation.
KeywordsAnions Cd Durum wheat Triticum turgidum Mineral nutrients Photosynthetic pigments μXRF Si SEM-EDX XPS
This work was financed by the French Institut National des Sciences de l’Univers (INSU, CNRS) programme Ecosphère continentale et côtière (EC2CO). Muhammad Rizwan was financed by the Higher Education Commission (HEC) of Pakistan. We thank Stéphane Jézequel (Arvalis-Institut du Végétal, France) for his help in the selection of the durum wheat cultivar and for providing the seeds, Perrine Chaurand (Aix-Marseille University, France) for the XRF analysis and Wim Voogt (Wageningen University, NL) for providing Si(KOH)2 and expertise concerning Si in nutrient solution. Partial support from BIO-GEO-CLIM project (14.B25.31.0001) of the MinObrNauki is also acknowledged (OP).
- Bavi K, Kholdebarin B, Moradshahi A (2011) Effect of cadmium on growth, protein content and peroxidase activity in pea plants. Pak J Bot 43:1467–1470Google Scholar
- Britton (1995) Structure and properties of carotenoids in relation to function. FASEB J 9:1551–1558Google Scholar
- Chaney RL, Ryan JA, Li YM, Welch RM, Reeves PG, Brown SL, Green CE (1996) Phyto-availability and bio-availability in risk assessment of cadmium in agricultural environments. In: Proceedings of sources of cadmium in the environment. Organization for Economic Co-Operation and Development, Paris, pp 49-78Google Scholar
- Chaney R, Brown S, Angle J (1998) Soil-root interface: ecosystem health and human food-chain protection. Soil chemistry and ecosystem health. P. Huang. Madison, Wisconsin, Soil Sci Soc Am, pp 279-311Google Scholar
- Haouari CC, Nasraoui AH, Bouthour D, Houda MD, Daieb CB, Mnai J, Gouia H (2012) Response of tomato (Solanum lycopersicon) to cadmium toxicity: growth, element uptake, chlorophyll content and photosynthesis rate. Afr J Plant Sci 6:1–7Google Scholar
- Hasan SA, Fariduddin Q, Ali B, Hayat S, Ahmad A (2009) Cadmium: toxicity and tolerance in plants. J Environ Biol 30:165–174Google Scholar
- Lichtenthaler HK (1987) Chlorophylls and carotenoids—pigments of photosynthetic biomembranes In: Colowick SP, Kaplan NO (ed.) Methods in enzymology. Academic Press, San Diego-New York-Berkeley-Boston-London-Sydney-Tokyo-Toronto, 148:350-382Google Scholar
- Meyer MW, Fricke FL, Holmgren GGS, Kubota J, Chaney RL (1982) Cadmium and lead in wheat grain and associated surface soils of major wheat production areas of the United States. pp 34. In: Agronomy abstracts, the Am Soc Agron, MadisonGoogle Scholar
- Naeem A, Saifullah, Ghafoor A, Farooq M (2015) Suppression of cadmium concentration in wheat grains by silicon is related to its application rate and cadmium accumulating abilities of cultivars. J Sci Food Agric 95:2467–2472Google Scholar
- Sandalio LM, Dalurzo HC, Gomez M, Romero-Puertas MC, Del Rio LA (2001) Cadmium-induced changes in the growth and oxidative metabolism of pea plants. J Exp Bot 52:2115–2126Google Scholar
- Voogt W, Sonneveld C, Datnoff LE, Korndrfer GHS (2001) Silicon in horticultural crops grown in soilless culture, chapter 6. In: Studies in plant science, Elsevier, pp 115–131Google Scholar