Plant Alkaline Fusion Technique Followed by Colorimetric Procedure for the Detection and Quantification of Total Silicon in Ornamental Plants

Abstract

Silicon (Si)–determination procedures currently available require expensive equipment and must be modified to assess Si concentrations in plant tissues. A Si-determination procedure referred to as the plant alkaline fusion technique, or PAFT, was developed to assess total Si concentrations, specifically in plant tissue. The procedure consists of dry-ashing the plant material, alkaline fusion, solubilization of the fusion cake, dilution, and colorimetric determination to quantify total Si content. The fusion technique for solubilizing plant Si can be performed using sodium hydroxide (NaOH), nickel crucibles, and Bunsen burners. Silicon concentrations of two National Institute of Standards and Technology (NIST) standard reference materials (SRM) [pine needles (SRM 1575) and peach leaves (SRM 1547)], a rice straw standard (LSU#5), an NIST soil standard (SRM 2709), and five ornamental plant species were all assessed using the PAFT procedure, and then these values were compared to two different inductively coupled plasma–optical emission spectroscopy (ICP-OES) procedures conducted by independent laboratories. The PAFT Si determination procedure typically reported the greatest value or was within 15% of the two ICP-OES procedures while costing significantly less than both ICP-OES procedures.

Keywords:

• Emission spectroscopy
• dry-ashing
• horticulture
• nickel crucibles
• solubilization

Acknowledgments

We thank Emily Nixon, Kevin Starks, and Cary Mitchell for technical assistance; Ruth Green, Debbie Black, Heather Lash, Kelly Alsip, and the University of Illinois Plant Health Care staff; Drs. James Locke, Jonathan Frantz, Christopher Ranger, and associated colleagues from the USDA-ARS associated with the greenhouse production research group (University of Toledo; Toledo, Ohio) for technical assistance with Si determination of plant samples; Dr. Brenda Tubana for providing the LSU#5 rice straw samples; Dr. Mark David for providing the NIST plant samples and the use of equipment and laboratory; Jeffery Dillener and Galbraith Laboratories, Inc. (Knoxville, Tenn.) for technical assistance; Drs. Donald Briskin, Art Spomer, and James Stucki for technical advice and assistance; and Dr. Kun Yan Zhu of the Department of Entomology at Kansas State University (Manhattan, Kan.) for his initial review of the manuscript.