Preservation of Leaf Material
- Use fresh young leaf material, free from any fungus, other infection or dirt.
- If you want to be extra careful not to contaminate your sample with your own DNA, wear new rubber gloves.
- Wash all instruments with alchohol or Bleach between samples.
- Place torn leaf pieces (less than 2 cm2) into a small (12 x 8 cm) ziplock plastic bag,
or plastic centrifuge tubes with screw caps (e.g. 50 ml tubes).
- Be certain there is no excess water on the leaves prior to drying.
- You can also cut leaf pieces with scissors, there is some debate on whether it is better to cut or tear.
- Add 50-60 grams of 20-200 mesh size, grade 12(e.g. Fisher) silica gel.
- If the gel is to be reused add the smaller mesh size silica gel about 5% indicating gel, 6-16 mesh grade 42.
- Use a generous volume of silica gel, a minimum ratio of 10:1 is required for effective preservation of leaf samples.
- Increase silica gel if the leaves are succulent.
- It is always advisable to use indicator gel if possible.
- Silica beads work well too and are easier to reuse.
- Never reuse gel without first making sure that no contamination from previous specimens is present.
- UV light, baking (be sure to follow directions for your specific gel) etc. can serve to sterilize.
- Both indicator and non-indiocator gel are widely available from florist supply houses in in most major cites in the world.
- Shake bag to distribute the gel between the layers of leaves.
- Leaf tissue should be dry after 12 – 24 hours.
- Check for dryness by bending one of the leaf pieces; if it snaps and brakes cleanly then the leaf is dry.
- Store and ship samples in their bags or tubes in plastic boxes with tightly sealing lids. Refrigerate if possible.
Reference:
Chase, M. and H. Hill 1991.
Silica gel: an ideal material for field preservation of leaf samples.
Taxon 40:215-220.