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I've been a Canberran since moving here from Adelaide on the first day of 1980. I now live in suburban Duffy with my partner Louise Maher, ABC 666 radio and on-line journalist. Among my early memories is following Sleepy Lizards (Shinglebacks) around the paddocks north of Adelaide, guarded by the faithful bull terrier. I have always been passionate about the natural world, trying to understand how it works, how the nature of Australia came to be, and sharing those understandings. My especial passions are birds, orchids and mammals. For much of my life I have been a full-time naturalist, running bush tours, writing books etc, doing consultancies, presenting a regular radio slot on local ABC, chairing a government environment advisory committee and running adult education classes. Recently I have eased back somewhat, but am still writing, teaching, doing some radio work and running overseas tours - as part of my fascination with our Gondwanan origins I've been running tours to South America for the past decade. I was awarded the Australian Plants Society Award in 2001 and the Australian Natural History Medallion in 2006, both for services to education and conservation.

Friday, 8 February 2013

Taken as Red; more on plants

Any flower pollinated by animals needs to be seen; red is a good way to achieve that. Having been pollinated, the next function of the flower is to form a fruit, which both protects the developing embryo (which we call a seed) and in many cases provides the mechanism for its distribution. Animals are important in this too - and again red is an important signal that the fruit is ripe, meaning that it is now full of appealing sugars. Obviously enough this coincides with the time that the seed is mature and ready to start life as an independent plant. Interestingly, blues, purples and black are also used to promote the same message.

Most of the animal vectors are birds (hence the prevalence of red as an "I'm ready!" signal), but in lower latitudes fruit bats are very important; however, as night foragers, colour isn't an important cue to them. Many examples are available; here are a few.
Ruby Saltbush Enchylaena tomentosa Chenopodiaceae
inland northern New South Wales.
Many saltbushes have luscious berries (these particular ones are very pleasant to eat),
though others have dry papery fruit.
False Rosewood Synoum glandulosum Melicaceae, Nowra, New South Wales.
Many rainforest fruits are distributed by bowerbirds and fruit pigeons.
Yellow Pittosporum Pittosporum revolutum Pittosporaceae, Bawley Point, New South Wales.
Another rainforest plant; however long ago as Australia dried out,
one member of the genus adapted to the new arid regime.
Berrigan P. angustifolium (Whyalla, South Australia) below, has apparently recruited dry county birds (possibly inland honeyeaters or bowerbirds) to do the job.
 
Native Raspberry Rubus parvifolius Rosaceae, Namadgi National Park near Canberra.
We probably wouldn't argue with the birds over the previous couple of fruits,
but I certainly share their tastes with regard to this one!
Quandong Santalum acuminatum Santalaceae, Pinnacles NP, Western Australia.
Quandong jam is a traditional staple among inland European-Australians, recently 'rediscovered' and marketed.
Other genera in the family however have taken a different approach.
Dwarf Ballart, Exocarpos strictus Santalaceae, Pilliga NP, New South Wales.
Here the true fruit is the hard seed at the tip of the red 'fruit' which is actually just a section of stem,
swollen, filled with sugar, red; different origin, same job.

Oddly, at least one Australian conifer - non-flowering by definition, so no true fruit is possible - has adopted the same strategy.
Mountain Plum Pine Podocarpos lawrencei Podocarpaceae, Namadgi National Park near Canberra.
Here the seed is the large green structure on top of the red bird-attractor.
Other structures can turn red to act as bird-attractors too.
New South Wales Christmas Bush, Ceratopetalum gummiferum Cunoniaceae, Nowra, New South Wales.
Here the sepals, hitherto inconspicuous, have expanded and turned red to draw attention to the seeds.
Nor are birds the only vector; many Australian plants - and presumably elsewhere too - use ants to do the job. They don't want the ants to eat the seeds, which are usually protected by being too big and hard, so offer a fleshy structure to attract them. Presumably the ants can see red.
Blackwood Acacia melanoxylon, Namadgi National Park.
The red elaiosome is full of desirable protein and fat; the ants haul the whole structure away and strip the
undesirable seed off before taking the elaiosome into the nest.
It is widely recognised - though not common among Australian plants - that leaves often turn red before they drop, as the plant withdraws the valuable chlorophyll, leaving less valuable chemicals, notably anthocyanins which protect the photosynthetic systems from light overload.

Bleeding Heart Tree Omolanthus populifolius, Euphorbiaceae, Nowra, New South Wales.
In many eucalypts - and other trees - bark turns red before it dies and drops off. Probably a similar story explains this too, though I'm not sure what it is in this case. It can be very aesthetic though!
Red Bloodwood (though several species are called that) Eucalyptus erythrophloia, Cooktown, north Queensland.
And with that I'm about redded out, though I still want to feature the common and striking juxtaposition of red and black, especially in many birds. However we'll leave that for a little while, and look elsewhere next time.

I just realised that this is my 100th posting; thanks for making it possible!

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1 comment:

Susan said...

And new growth on plants is often red, to protect it from sunburn, I believe.