Humic substances alter the uptake and toxicity of nanodiamonds in wheat seedlings
- 204 Downloads
Detonation synthesis nanodiamonds (ND) are among the most widely applied nanoparticles due to their low cost of production and broad scope of applications. However, the fate and behavior of NDs in the environment are largely unknown. The behavior of NDs is greatly affected by humic substances (HSs), which comprise 50 to 80 % of natural organic matter in water and soil ecosystems. The uptake of detonation NDs by wheat seedlings and its toxicity were evaluated in the presence of seven HSs of different origins, including humic acids (HA, HS fraction soluble in alkali and insoluble in acid) and fulvic acids (FA, soluble in both alkali and acid).
Materials and methods
To monitor the uptake of NDs by plants, tritium-labeled NDs were produced. Liquid scintillation spectrometry and autoradiography were used to determine the amount of NDs absorbed by plants. The photosynthetic activity of the plants was measured using light response curves.
Results and discussion
After a 24-h exposure period, the ND content in the plant roots was 1720 μg g−1. The introduction of HSs decreased the ND contents in the plant roots to 680–1570 μg g−1 (except for peat FA, for which the ND content did not differ from the blank value). The observed phenomenon was probably related mainly to the influence of HSs on the zeta potential of the NDs, which shifted from positive to negative. Based on chlorophyll fluorescence evaluation, the toxicity of NDs did not inhibit photosynthesis during illumination in the physiological range. However, NDs were slightly toxic to wheat plants under excessive light, likely due to the inhibition of electron transport between Q A and Q B and the disruption of the formation of a thylakoid transmembrane potential.
The introduction of HA in a suspension of NDs obviously reduced the inhibiting effect of the NDs; however, the mitigating activities of FA were not so apparent. Our results demonstrate the urgent need for further studies of the influences of NDs on plant growth and development.
KeywordsChlorophyll fluorescence Detonation nanodiamonds Tritium labeling Zeta potential
The authors express their deepest appreciation of Prof. Irina Perminova (Department of Chemistry, Lomonosov Moscow State University) and her group for providing standard HS samples and their physicochemical characterization. In addition, the authors thank Associate Professor A.A. Alekseev (Ammosov North Eastern Federal University, Yakutsk) for providing us with the opportunity to conduct experiments using the MPEA—2 device.
We acknowledge financial support from the Russian Foundation of Basic Research (14-03-00280).
- Barber SA (1984) Soil nutrient bioavailability: Mechanstic approach. John Wiley and Sons. Inc., New YorkGoogle Scholar
- Jośko I, Oleszczuk P, Skwarek E (2016) The bioavailability and toxicity of ZnO and Ni nanoparticles and their bulk counterparts in different sediments. J Soils Sediments 16:1798–1808. doi: 10.1007/s11368-016-1365-x
- Kovalevskii DV, Permin AB, Perminova IV, Petrosyan VS (2000) Recovery of conditions for quantitative measuring the 13C NMR spectra of humic acids. Vestnik Moskovskogo universiteta Seriya 2 Khimiya 41:39–42 (in Russian)Google Scholar
- Kulikova NA, Perminova IV, Badun GA, Chernysheva MG, Koroleva OV, Tsvetkova EA (2010) Estimation of uptake of humic substances from different sources by Escherichia coli cells under optimum and salt stress conditions by use of tritium-labeled humic materials. Appl Environ Microbiol 76:6223–6230CrossRefGoogle Scholar
- Perminova IV, Frimmel FH, Kudryavtsev AV, Kulikova NA, Abbt-Braun G, Hesse S, Petrosyan VS (2003) Molecular weight characteristics of aquatic, soil, and peat humic substances as determined by size exclusion chromatography and their statistical evaluation. Environ Sci Technol 37:2477–2485CrossRefGoogle Scholar
- Strasser RJ, Srivastava A, Tsimilli-Michael M (2000) The fluorescence transient as a tool to characterize and screen photosynthetic samples. In: Yunus M, Pathre U, Mohanty UP (eds) Probing photosynthesis: mechanisms. Regulation and Adaptation. Taylor and Francis, London, pp. 445–483Google Scholar
- Tyystjärvi E, Vass I (2004) Light emission as a probe of charge separation and recombination in the photosynthetic apparatus: relation of prompt fluorescence to delayed light emission and thermoluminescence. In: Papageorgiou GC, Govindjee (eds) Chlorophyll fluorescence: a signature of photosynthesis. Springer, Berlin, pp. 363–388CrossRefGoogle Scholar