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Application of silica nanoparticles for increased silica availability in maize R. Suriyaprabha, G. Karunakaran, R. Yuvakkumar, P. Prabu, V. Rajendran et al. Citation: AIP Conf. Proc. 1512, 424 (2013); doi: 10.1063/1.4791092 View online: http://dx.doi.org/10.1063/1.4791092 View Table of Contents: http://proceedings.aip.org/dbt/dbt.jsp?KEY=APCPCS&Volume=1512&Issue=1 Published by the American Institute of Physics.

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Application of Silica Nanoparticles for Increased Silica Availability in Maize R. Suriyaprabha, G. Karunakaran, R. Yuvakkumar, P. Prabu, V. Rajendran* and N. Kannan1 Centre for Nanoscience and Technology, K. S. Rangasamy College of Technology, Tiruchengode - 637215, Tamil Nadu 1 Department of Biotechnology, K. S. Rangasamy College of Arts and Science, Tiruchengode - 637215, Tamil Nadu. (*Email:[email protected])

Abstract. Silica nanoparticles were extracted from rice husk and characterised comprehensively. The synthesised silica powders were amorphous in size with 99.7% purity (20-40 nm). Nanosilica was amended with red soil at 15 kg ha-1 along with micron silica. The influence of nanoscale on silica uptake, accumulation and nutritional variations in maize roots were evaluated through the studies such as root sectioning, elemental analysis and physiological parameters (root length and silica content) and compared with micron silica and control. Nanosilica treated soil reveals enhanced silica uptake and elongated roots which make the plant to resist in stress conditions like drought. Keywords: Nanomaterial, synthesis, silica uptake, maize roots. PACS: 81.07Wx, 81.20Hy, 88.20df, 87.17Uv.

with energy dispersive X-ray analysis (SEM-EDAX), particle size distribution (PSD) and transmission electron microscopy (TEM) studies.

INTRODUCTION Nanoparticles show promise in different fields of agricultural biotechnology. Application of nanosilica for plant growth is still considered a novel approach as they are more reactive than their bulk counterparts. Silica nanoparticles (SNPs) would be required in smaller quantity to improve crop protection. Previous studies are made in plants applying nanoparticles such as ZnO, TiO2 etc., in the aspect of environmental toxicity [1]. But silicon-deficient plants are often structurally weaker with abnormal growth and are more susceptible to biotic and abiotic stresses compared with Si-rich plants [2]. Maize ranks third in global cereal production and is used as food, feed, and fodder. Developing sustainable corn cultivation is necessary for enhanced yield potential. Alternative source of Si is required to reduce the Si deficiency in soil.

Amendment of Soil and Maize Root Study

Nanosilica Synthesis and Characterisation

The fine red soil was collected at the agriculture land of Tiruchengode, Tamil Nadu. Soil was mixed with nano and bulk silica separately at a concentration of 15 kg ha-1. 3-4 maize seeds were sown in each silica amended pots to differentiate the changes in silica content from bulk silica. The test was performed in triplicates. Plants were watered with tap water (pH 7.77.9) twice in a week and maintained under a photoperiod of 12 h at room temperature for 20 days. Germination percentage (GP%) of seeds were calculated by considering the average of triplicate samples 4 days after sowing. Root samples after 15 days of maize culture were collected and measured for root length and number of roots. Then, they were allowed to dry in a hot air oven at 343 K for 36 h and roots were burnt at 1073 K for 5 h. The effect of nanosilica uptake and accumulation in roots were respectively studied using X-ray florescence spectroscopy (XRF) and microscopic observation.

Nano silica was extracted from natural source, rice husk ash using acid precipitation followed by alkali extraction method [3]. Synthesised powders were subjected to characterisation studies such as X-ray diffractometer (XRD), fourier transform infrared spectra (FTIR), scanning electron microscopy coupled

Nanosilica was synthesised using inexpensive method and comprehensively characterised. XRD pattern of prepared nanosilica shows amorphous nature as the broad peak at 22q(2T) (Fig. 1a). FTIR spectrum

MATERIALS AND METHODS

RESULTS AND DISCUSSION

SOLID STATE PHYSICS: Proceedings of the 57th DAE Solid State Physics Symposium 2012 AIP Conf. Proc. 1512, 424-425 (2013); doi: 10.1063/1.4791092 © 2013 American Institute of Physics 978-0-7354-1133-3/$30.00

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elemental analysis in roots is necessary. Sectioning of roots reveal the accumulation of more silica bodies in nanoSiO2 treated the epidermis cells than bulk (Fig. 2).

(Fig. 1b) show the presence of characteristic peak in the absorption range of 1096 and 451 cm-1 corresponds to Si-O-Si and Si-O functional groups. SEM-EDXS results (Fig. 1c & d) shows the aggregated silica particles and spherical in shape with 98.2% purity. PSD and TEM analysis conclude that the prepared particles are in the range of 20-40 nm with spherical morphology (Fig. 1e & f) and shows amorphous structure in diffraction pattern. Further, the nature of nano-SiO2 was confirmed from the previous literature [3]. The number of roots and root length is significantly affected with nano-SiO2 (Table 1) than micro-SiO2 treated plants. Increased root length indicates the drought tolerance of plant. The elemental changes in root ashes after treatments show a marked increase in SiO2 content, nano-SiO2 treatment (47.7%) in particular (Table 2), whereas the other elements are significantly altered when compared with control and bulk. These results show that plant physiological changes are also correlated to the nanoparticles as nutrients [4]. It is well known that roots are the first largest tissues to encounter excess concentration of pollutants/ nutrients compared with shoots and so the

FIGURE 1. Characterisation of synthesised nanosilica a) XRD, b) FTIR, c) SEM, d) EDXS, e) PSD and f) TEM.

TABLE 1. Effect of Silica Sources on Maize Seed Germination and Root Length Variations. Seed treatment Control

GP (%) 93.33

Mean germination time

No. of roots*

Root length (mm)

No. of shoots*

2.8

7 ±1

145 ± 2.1

4.2 ± 0.04

ab

Nano-SiO2

95.5a

1.73

8±2

168a

± 3.4

4.8 ± 0.12

Micro-SiO2

80.0

3.6

7±2

151 ± 2.6

4.2 ± 0.15

Thus, the present study explored the effect of nanosilica for enhanced growth response than bulk silica which is due to nanoscale particle leads the direct uptake and accumulation in maize.

TABLE 2. Elemental Composition of Root Ashes. Analyte (%) Si Fe Ca K S P Zn Mn Cu

Control

Nano-SiO2

Micro-SiO2

39.90 18.08 23.56 11.19 3.24 1.19 0.53 0.24 0.12

47.76 0.65 4.18 18.02 13.01 13.07 0.51 0.36 0.13

43.49 13.45 13.19 6.13 1.67 10.83 0.24 0.16 0.05

ACKNOWLEDGMENTS Authors are thankful to Defence Research and Development Organisation (ERIP/ER/0905113/ M/01/1216), New Delhi, India for the financial support to carry out this research project.

REFERENCES 1. D. Lin and B. Xing. Environ Pollut, 150, 243–50 (2007). 2. R. C. Monica and R. Cremonini. Caryologia, 62,161–65 (2009). 3. U. Kalapathy, A. Proctor and J. Shultz. Bioresour. Technol. 73, 257-262 (2000). 4. M. T. Hossain, R. Mori and K. Soga et al. Plant Res. 115, 23–27 (2002).

Figure 2. Microscopic image of cross sectioned maize roots. Scale bar: 400 X.

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