8-5) plus the number of standing leaves. The age of the shoot in units of number of
plastochrone intervals, can be converted into chronological age by multiplying it by the
average plastochrone interval, in days, which can be derived either from leaf marking
techniques or using reconstructive techniques (see below). This estimate has an inherent
error for plants under one year of age. For mono-meristematic leaf replacing species, shoot
age cannot be determined.
2. Estimation of horizontal rhizome elongation and rhizome plastochrone interval for dimeristematic
species:
Carefully excavate 10 to 20 rhizome fragments as long as possible taking care to avoid
rupture of the rhizomes and attached shoots. If this is impossible due to the presence of a
dense rhizome network, collect 3 – 6 cores (>15 cm diameter), depending on shoot density
and sort out, after washing off the sediment, the rhizome fragments with 2 or more
connected shoots. For each rhizome fragment, calculate the age of the different shoots
present along the rhizome, as outlined above, and the length and number of horizontal
rhizome segments in between them. Use linear regression analysis to fit the equations: