The corpse flower may keep you up at night - Daniel Nickrent
Deep inside the Sumatran rainforest,
a carrion fly descends,
guided by the scent
of its favorite place to lay eggs:
dead and rotting animal carcasses.
But when it lands,
it isn’t on liquefying flesh,
but instead on the world’s biggest,
and perhaps strangest, flower—
Rafflesia arnoldii.
Rafflesia is a genus of over 30 species
found across the tropical forests
of Southeast Asia.
While its smallest representative has
a flower only a few centimeters wide,
its biggest weighs seven kilograms
and spans over a meter wide.
And its putrid aroma isn’t the only thing
that sets these plants apart—
all Rafflesia are parasites.
For most of its life, the Rafflesia plant
exists as an endophyte,
a single thin strand of almost uniform
cells beneath the bark of its host.
It strictly infects Tetrastigma,
a genus of large vines
related to the grape.
Like typical leafy plants, the host
Tetrastigma’s cells contain chloroplasts.
These organelles convert
sunlight into energy
and are each equipped with their own DNA.
Rafflesia’s plastids, on the other hand,
appear to have lost their DNA,
and with it the ability
to photosynthesize.
This sort of loss is incredibly rare.
With no roots and no ability
to produce its own food,
Rafflesia is completely dependent
on its host,
siphoning the Tetrastigma’s water
and nutrients to fuel its own growth.
And Rafflesia’s propensity for theft
doesn’t end there.
Using a process known
as horizontal gene transfer, or HGT,
Rafflesia has stolen quite a bit
of genetic material from its host
and other plants in its habitat.
While HGT is well known in bacteria,
it has only recently been documented
in parasitic plants.
And scientists are still
trying to understand
exactly how this DNA transfer happens.
Rafflesia appears to utilize several
of these stolen sequences
as if they were their own,
transcribing the DNA into RNA
and then translating it into proteins,
which are used in key cellular processes.
After living some time embedded
in the host vine,
Rafflesia emerges as a single bud,
which then takes several months,
or even a year, to reach full size.
When it opens, its fleshy maroon petals
emit several foul-smelling
sulfur-containing compounds.
The evolutionary reason for this odor
is relatively straightforward:
to attract pollinators.
For most species of Rafflesia,
single flowers are either male or female.
So, to produce a seed,
pollen must be transferred
from one flower to the next.
The rotten stench is ideal for attracting
corpse-loving carrion flies,
and the massive size of the flower
may help broadcast it
through the stagnant rainforest air.
A deceived fly will explore
the flower’s interior,
laying thousands of ill-fated eggs.
But during the fly’s visit,
the male Rafflesia’s liquid pollen may
end up on the fly’s back where it dries.
If the fly encounters
an open female Rafflesia flower,
the pollen will rehydrate when rubbed
against the flower’s damp stigma,
completing cross-pollination.
A pollinated Rafflesia flower
gradually withers and turns black,
but this doesn't mean it's dead.
Over several months, a fruit forms
which contains thousands of tiny seeds.
But what disperses these seeds
is still debated,
with hypotheses ranging
from elephants to rodents to ants.
We do know that the seeds have
an oily appendage called an elaiosome,
a structure ants often
feed to their larvae.
And scientists have even observed
ants carrying Rafflesia seeds.
But what happens to the Rafflesia seeds
once inside the ant nest remains unclear.
In any case, nobody has seen
Rafflesia seeds germinate,
or attach to and infect a host root.
Because this crucial step of their
development is still not fully understood,
cultivation of Rafflesia is difficult.
Despite many attempts,
botanists from around the globe
have been largely unsuccessful
at growing Rafflesia
from seeds outside its natural habitat.
As these tropical forests
are under threat,
we’re at risk of losing Rafflesia,
and our ability to unravel
some of its many remaining secrets.
