The coconut odyssey - the bounteous possibilities of the ... - ACIAR

Another popular image among
Europeans was the ‘desert island’
inhabited by a lone marooned person
and a coconut palm, suggesting that
the person was provided for by fruit
falling from the palm.
Figure 1-11. An ancient palm at
Mapoon on the east coast of
the Gulf of Carpentaria, Australia
– 24 m tall and around 100 years old.
It was the last survivor (year 2000)
of hundreds planted by missionaries
in the late 1800s with a view to
securing a source of food for the
local aboriginal tribes.
�ere are now many tens of
thousands of coconut palms,
scattered along 20 000 kilometres of
coastline from Geraldton (latitude
29 degrees south) in Western
Australia, through the towns of the
north-west coast (although much of
that coastline is too hot and arid),
Darwin, Arnhem Land, the islands
and coast of the Gulf of Carpentaria,
and in pockets all the way down the
east coast from the tip of Cape York
to Cape Byron (spanning latitudes
11–29 degrees). �is spread of
distribution, lying outside the
equatorial zone (zone 1 in Figure
1-5) has enabled observation of the
effects on coconut palm growth of
substantial variations in seasonal
cool temperatures (see Figure 1-13
and Chapter 3).
What are the
environmental limits for
the coconut?
Little information has been gathered
about the effect of temperature
on the fruit development of the
coconut, although there have been
descriptions of the effect of severe
drought on fruit growth in Africa.
Altitude and temperature combined
can limit the range of the coconut
palm. In tropical and subtropical
28
latitudes, the temperature is known
to decline, on average, 0.6°C for each
100-metre increase in altitude. If
the mean temperature at sea level
is 27°C, which is not uncommon
on tropical coastlines, on adjacent
highlands at 1000 metres it will be
close to 21°C—the approximate
limit for reproductive growth of the
coconut. At the higher altitude, the
palm may survive and be capable of
growing fronds, but not fruit.
Latitude and seasonal temperature
also play a part. Although the palm
grows attractively on the coast in
latitudes as high as 29 degrees, it
rarely retains fruit beyond the early
developmental stage in latitudes
beyond 24 degrees. �is fact
frequently gives rise to the question,
‘Why are there no fruit when the
palms look quite healthy?’ Fruit
will fail to set if the inflorescence
(the flower stalk) does not develop
properly and, as most kinds of
palm need cross-pollination to
produce fruit, isolated palms are
disadvantaged. �e exception is the
Dwarf palm, which is able to selfpollinate.
Failure can also be induced
by three to four months of mean
temperatures below 21°C, too low
for the palm to achieve the vigour of
growth needed for fruit development.