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FACT SHEET The remarkable world of plants
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The remarkable
world of plants
Plants have been developing new characteristics since the first land plants emerged 450 million years
ago. These natural adaptations support the survival of plants in different environmental conditions.
Some of these adaptations include unique relationships between plants and insects or animals.
A walk around the Gold Coast Regional Botanic
Gardens will reveal some distinctive plant features.
When selecting plants for the conditions in your
garden, it is useful to consider the specialist
adaptations that might impact on their success.
Silver / grey leaves
Make observation of plants with grey or silver leaves and
take the time to have a closer look at their leaf surface. The
grey or silver colour is not actually the result of a colour
pigment, but is a covering of fine, usually white, hairs.
These tiny hairs reduce wind velocity across the leaf surface,
thereby insulating the plant against moisture loss. Many
plants with soft grey leaves originate in drier climates, such
as Australia or the Mediterranean, where this leaf surface
modification helps them to survive. Therefore, plants like
lavender and the silver leaf emu bush don’t like to grow in
wet or humid conditions.
Banksia aemula
Banksia
The iconic Australian genus Banksia often grows in regions
that experience a relatively high level of fire activity. Some
Banksia plants will die when fire conditions are severe, but
these plants have a range of adaptations that enable their
survival. In some species, the seed is only released during or
after a fire event. Germination of the seed in the nutrientrich, ash-laden soil guarantees survival of the species.
Other Banksia regenerate by either shoots from a woody
underground swelling, called a lignotuber, or from epicormic
buds – dormant shoots in the trunk.
Banksia aemula, the floral emblem of the Gold Coast,
survives fires by germination from seed, lignotuber and
epicormic growth. The thick, gnarled trunk of mature
specimens acts as a protection against fire damage.
The flowers of Banksia plants are formed from a spike of
thousands of individual flowers grouped in pairs. After
pollination, the spike develops into a woody cone with
follicles present where flower pollination occurred. In times
of fire, the spent flowers, which are retained on the cone,
slow combustion, allowing the seed to be dispersed after
the follicles split open. Insects and birds are the principal
pollinators of Banksia flowers, but some small mammals
attracted to the nectar carry pollen on their fur and so also
pollinate Banksia species.
FACT SHEET The remarkable world of plants
The fig and the wasp
Have you ever seen the flower of a fig tree? The plants do
flower, but are concealed until the fruit is cut in half. The
flowers line the inside of the fruit, called a synconium. The
true fruit develops on the inside walls of the synconium after
fertilisation.
The remarkable
relationship between
the fig and the wasp
The fig wasp is the tiny pollinator of these majestic trees
and has a remarkable life cycle. Female wasps enter the
fruit through a minute hole at its base and once inside they
deposit pollen previously collected. Male wasps live their
entire lives inside the fruit and after mating with a visiting
female their life ends. The female wasp visits multiple fruits,
collecting pollen and searching for the perfect flower on
which to lay her fertilised eggs. The extraordinary association
between the fig and the wasp is an example of a remarkable
symbiotic relationship. There are many examples of these
types of relationships between plant and insect and their
study provides examples of the importance and delicacy of
natural ecosystems. Without fig wasps, there would be no
new fig trees.
fig wasp
Pig face
Plants have tiny holes, principally on the underside of their
leaves, called stomatas. It is through these holes that carbon
is absorbed into plant cells during the daylight hours.
Carbon drives the process of photosynthesis and it is from
the stomates that the by-product oxygen is emitted back
into the atmosphere. The native plant pig face (Carpobrotus
glaucescens) is able to store some carbon in its cells and can
therefore close the opening of the stomata during the heat
of the day. The stomates reopen at night when it is cool and
therefore less moisture is lost. Along with the tough leaf
surface, this adaptation reduces water loss and allows the
plant to survive in a dry and harsh environment.
Inside the leaf there are specially evolved cell structures that
can expand to store water when it is available. These two
incredible modifications make it possible for pig face to
survive the very tough environmental conditions of both the
oceanfront and the Australian desert.
Carpobrotus
glaucescens,
pig face
She oaks
When a plant has evolved next to the ocean or in the
arid inland, protective modifications to its foliage are not
uncommon. Casuarina and Allocasuarina species appear
to have long needle-like leaves, but these are actually the
stem, with the leaf reduced to a small set of scale-like teeth
at the end of each stem section. Close inspection will reveal
between six and nine teeth. These teeth interlock with the
adjoining stem and are known as a cladode. Along the
cladode are raised ridges that protect the stomata from
direct heat, reducing water loss through transpiration.
There are also fine hairs around the stomata which insulate
against heat and moisture loss. The she oak is a strong tree
with soft drooping foliage that belies it’s incredible ability to
survive in Australia’s toughest environments.
leaf teeth
branchlet (cladode)
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For more information, visit
goldcoastcity.com.au/parks
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The cladode of the
Casuarina species