SAMPLING and DRYING METHODS

As methods for extraction, purification and amplification of DNA improve, we actually need very little plant material in order to adequately supply molecular labs. In general, we recommend collecting about 3-5 square inches of fresh, young plant material, normally 3-5 leaves or cut parts of larger leaves. If in doubt, err on the side of generosity. It is preferable to remove the midrib from leaf material before putting it into silica gel. Use scissors or secateurs to cut plant material. Tearing the material will bruise the leaves, releasing enzymes that will breakdown DNA. The most important protocol to follow when collecting material for DNA is getting the plant material to dry quickly and this is accomplished by increasing the surface area (cutting the leaves into smaller pieces) and using an excess of silica gel. The material is then placed in a reclosable plastic bag with enough silica gel to ensure drying of the material in a couple of hours. Once the material is dry, most of the silica gel can be removed from the sample and dehydrated for future use. Indicator silica gel should be used to help determine the overall "dryness" of the sample. Check the sample for signs of mold and add fresh silica gel if necessary. Once dry the sample can be stored at room temperature without degradation of DNA, although it is preferable to store samples at -20° Celsius.

  

Three examples of silica collections.
Click the image to view a larger image.
Prepared by Heidi H. Schmidt & Simon Malcomber.
Photos taken by Heidi Schmidt.
heidi.schmidt@mobot.org