Bead Beating: A Primer (continued)

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Plant Stem Homogenization

Stems are characterized by a high concentration of vascular tissues that can be resistant to shearing and grinding. Small young stems are soft and can be processed much like leaves. Plant stem masses less than 50 mg can be homogenized in polypropylene deep well plates with one 5/32” stainless steel grinding ball per well; they can also be processed in disruption tubes with 1.7- 3.0 mm zirconium beads or 2.8 mm stainless steel balls.

Unlike the softer stems of young plants, tougher, larger stem samples are best homogenized in 4 ml or 15 ml grinding vials. Processing up to 200 mg of stem tissue is best done in 4 ml polycarbonate or polypropylene vials with one 5/16” or 3/8” stainless steel grinding ball. Up to one gram of stem tissue can be homogenized in a 15 ml polycarbonate vial with two 7/16” stainless steel grinding balls. Zirconium oxide grinding satellites are resistant to corrosive chemicals such, as phenol, and can be used as a substitute for stainless steel in order to prevent reactions that may interfere with sample processes.


  1. Stem can be homogenized with buffer, dry ground following lyophilization or bead beaten cryogenically. Dry grinding and cryogenic grinding are done without buffer, which can be added after bead beating. Cryogenic grinding should be done in 4 or 15 ml polycarbonate vials, as polypropylene tubes and plates may crack during cryogenic grinding.
  2. Prepare samples according to the following table:
    Disruption Tubes (2 ml) Deep Well Plates (square wells) 4 ml Vials 15 ml Vials
    Sample Size 50 mg 50 mg 200 mg Up to 1 gm
    Homogenization Buffer Volume 600 µl 600 µl 2 ml 6 ml
    Grinding Balls 8 x 2.8 mm 1 x 5/32” 1 x 3/8” 2 x 7/16”
    Processing Time 2 minutes 2 minutes 2 minutes 2-5 minutes
    Bead Beater Speed high speed high speed high speed high speed
  3. Process the samples as stated in the table. Processing can be divided into short bursts followed by a cooling period for heat sensitive samples.
  4. Samples should be processed until a homogenate is generated, i.e., fine powder for dry and cryogenic grinding, or a fine puree for wet grinding.
  5. Sample can be stored or processed as needed.

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