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

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Hyphae invade the neck region of the old oonceptacle after the
ostiole is sealed off and a dense plug of hyphae forms where the
opening had been. These plugs lie at the same level as the dark
bands in the outer cortex (Fig 6.ld). In the female plants
ova are caught up in this mass of hyphae and the plugs become orange
or yellowish.
Conceptacles of one season form a layer above the previous
season's oonceptacles, a feature which Naylor (1953a) pointed out
might be used to age plants. A close relationship was found between
the thickness of D. willana laminae and the number of conceptacle
layers (Table 6.1, Fig. 6.1e).
Table 6.1
lamina thickness.
Relationship between the number of conceptacle layers and
Number of layers
visible
Mean
(mm)
lamina thickness
at 95% confidence
limits
n
1
2
3
4
2.2 ± 0.21
2.8 ± 0.17
3.8 ± 0.17
4.4 ± 0.25
30
30
22
15
There are problems, however, in estimating the age of plants
from the numbers of conceptacle layers. When spent, the conceptacles
slowly fill with hyphae, and after about four years only a faint outline
of the conceptacle can be discerned amongst the tnner cortical
and medullary cells. In very old specimens l the earliest season's
conceptacles are almost entirely obliterated. The number of layers
also varies at different positions on the lamina. so that when estimating
the age of a plant, it is important to section the oldest region.
At best, the number of layers can be used only to estimate the minimum
age of a specimen.
Individuals of both species may live 8 years or more.
7.
See Chapter