B. Determination of weight-to-length ratios
Collect a number of rhizome fragments that represent more than one year's growth of
rhizome along with their attached shoots. At the laboratory, separate and count the fully-grown leaves (for many species, the number three leaf), including the sheaths – if present from
each shoot. (If you use this measurement, it assumes that it is representative of the leaf
size
at any time of year). Separate the rhizome fragments (both vertical and horizontal, for
di-meristematic
species), and count the number of segments in each (Figure 8-5). Wash the
leaf
and rhizome materials free of debris and dry them separately to constant weight (about
24
hrs. at 60° C). Weigh them, avoiding rehydration of the material (use a dessicator to store
them
before weighing), and calculate the mean (±SE) weight of a rhizome segment
(representing an annual average) and the mean (±SE) weight of a mature leaf (representing
only the time of collection). Determine the weight-to-length ratio for the average mature leaf
collected. Determine the weight-to-length ratio for an average rhizome segment. As a
reconstructive growth measurement technique, these weight-to-length ratios (g dry wt cm
)
are used to convert length measurements to weight estimates, keeping in mind that the
rhizome estimate incorporates annual change whereas the leaf estimate is specific for the time
of collection.