A biological study of Durvillaea antarctica (Chamisso) Hariot and D ...

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Holes punched longitudinally along the middle of' laminae
o~ lobes of laminae:
Each lamina, or lamina lobe, contained fewer holes at the end
of the experiment, than had been originally punched. Distanc(')s
bebtleen holes \'lere quite variable, but generally there was an increase
distally (Table 7.2).
Table 7.2 Mean distance (mm) between the most proximal pair of
holes, the mid pair of holes and the most. dist.al pair of holes.
Locality n Bottom Mid 'fop Days after
punching
Iron Gate 24 118 IB7 249 315
Oaro 10 75 143 248 244
The distanc€Sbeb~een
holes were graphed for each marked plant
(Figs. 7.2 and 7.3). Greatest growth occurred in the distal third of
the lamina or lamina lobe, but there toJas not always a smooth exponential
increase along the lamina. Six of the ten surviving Oaro specimens,
and several of the Iron Gate specimens possessed curves very similar
to that of specimen No. 205, IIa (Fig 0 7.2): i.e. \"i th a growth peak
in the lower third of the lamina. In each case, this growth peak
region near 'the base of the lamina was several centimetres wide.
Sectioning revealed no narrow zone of meristematic cells. The region
cannot I therefore, be regarded as comparable with the na.:rrCJW meristematic
zone fOlli1d in the stipe-lamina transition region of certain
laminarian algae.
After one year's growth, most holes were still positioned
o.long the midline of the lamina or lamina lobe. A fev), however J moved
ilt an angle to the midline. a.nd became incorpora.ted into the formation
of a new lobe" If this lobe grew at a rate fas·tel' than the original,
then it was possible for some holes to "overtake" others which ha,d
originally been punched at higher levels on the frond. In general,
the pattern of growth fm' an individual lobe Nas very similar to that
observed for a.n undivided cape form lamina.
As we 11 as the distance between holes f hole si ZG ,inct:eased
distally. Mean length and width of the lowest, middle and most dist~l