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

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longe:r.: than D. anta:.r'ctica stipes. At this stage, D. antarctica
stipes usually form 10-20 9 6 of the total plant length y whereas Do
U),LUana stipes are rarely less than one third of the frond length,
At low tide, small D. antaY'ctica plants usually sticJc to the
film on the rock surface, whereas D. wilZana laminC'.e are usually
held up off the surface by their more rigid stipes. Lmninae of
both species are broadly oval, ovate'or oblanceolate, and perforated
by sma.ll holes (Figo 5.4a 1 e) " but they differ in thickness and
especially in texture. D. antarc"t;ic:a laminae are "thinner, more
tl:anslucent and more slippery and elastic than D. wiUana laminae"
D. gntarctica:
At Tautuku and Ohau Point r D. antar-ctica stipes grew proportionately
faster than laminae until plants were 30-50 em long, at
which stage (Fig. 5.4b) they formed about half of total plant length
and weight. Subsequent decrease in the rate of stipe elongation,
and an increase in the rate of elongation of the lalnina, caused this
"stipe fraction" to decline. Once plants were 0.75-1.0 \l1 long-,
stipe growth was almost solely caused by increments in thickness.
l~e
simple lamina shape of very small D. antapctica specimens
'llTaS never re'cained at ei ther of these two exposed localities once
plants were about 10-15 em 10n9" At Oaro and similar places however,
some plants 1-2 m long still possessed laminae with the same simple
shape as juvenile specimens.
Once D. antaFCtica plants are about 1 m long, signs of honeycombing
begin to appear, and conceptacles soon form in the honeycombed
regions. Perforations in the lamina have usually vanished by this
time, and rapid elongation of the thongs callses the lamina to become
deeply cleft. Honeycomb tissue usually first app" subterminally,
about three-quarters the distance along the lamina from the stipe.
It subsequently spreads, somewhat irregularly, down the lamina, and
may ultima.tely extend into '(.he palmate region.
The fraction that the stipe contributes to plo.nt weight
declines steadily "lith growth. S~cipes of three,"y~ar plants usually
form less than 5% of the total weight (holdfasts elwluded), while
the stipes of specimens longer than 5 m rarely exceed 1-3% of
total weight.