How to count Roots and Tubers

If tubers or roots are preserved whole they are recorded as a single unit. Small tubers, such as those produced by Ranunculus ficaria or Arrhenatherum elatius, or grass roots are more likely to be found whole and can be counted individually. Most commonly however, roots and tubers are preserved as fragments. A fragment count, where whole organs and fragments are recorded separately, or volume measure for each identifiable root/tuber type is useful. Volume measures can be determined easily by using a measuring cylinder. Semi-quantitative abundance scales can be used to give a rough estimate of parenchyma quantities in a sample. A 4 or a 5 point scale can be adapted to suit each study, however, when comparing material recorded as abundance scales it is important to maintain the same abundance scales within each study. At the most basic level tubers and roots could be recorded as either present or absent in each sample.

Sometimes it is possible to count the number of individual roots or tubers from fragments. If trying to quantify fragments it is important to minimise the possibility of recounting the same tuber/root that may have been broken into smaller pieces. By selecting a feature for each type of tuber/root that is unique, durable and recognisable, a minimum number of individual organs can be recorded. Such features will vary between organ type and species. Tubers, like Conopodium majus or Bolboschoenus maritimus, have a single proximal attachment scar or node where the tuber connects to the parent plant. In C. majus, even in fragmented form, this is often preserved as a projecting stub of root tissue with a hollow depression around the root stub and can be distinguished from the small fibrous roots scars on the tuber surface. The proximal attachment scar/node preserves well, occurs once on each tuber and is identifiable making it an ideal characteristic for quantifying individual tubers when present. In small samples it is sometimes possible to match the pieces of an organ that has fragmented and thereby calculate how many individual tubers are present in the sample.

Below is an example of quantification of parenchymatous fragments for a ficticious site.