These photos by Dave Kimble show Pandanus solms-laubachii specimens
which are growing in post-Cyclone Larry litoral rainforest close to mangroves on Hull River,
in the Wet Tropics of Far North Queensland. ( See Orchid Forest Photo Tour )
Annual rainfall for 2006 was 3,906 mm.

Pandanus solms-laubachii tree in flower

This is the trunk, showing the "prongs" sticking upwards,
and mosses and lichens growing on the bark.
Pandanus solms-laubachii bark

These are prongs taken from the trunk, close up, showing that the young prong is photosynthetic.
Pandanus solms-laubachii prong Pandanus solms-laubachii prong

On the branches, the prongs stick upwards, rather than along the branch.
Pandanus solms-laubachii prong

There are prongs on the prop roots, and the new prop roots develop them quickly.
Pandanus solms-laubachii prop roots and prongs

Prongs even appear out of the soil immediately around the trunk and prop roots.
Pandanus solms-laubachii prop roots with pneumatophores

Then after a heavy wet period, when this locality is water-logged,
about 2 to 3 metres from the nearest P. solms-laubachii,
in a puddle that is starting to recede, are more prongs.
Only these now look a lot like pneumatophores.
Pandanus solms-laubachii pneumatophores in puddle

Pandanus solms-laubachii pneumatophores in puddle

These are the common small prongs close up
Pandanus solms-laubachii pneumatophore Pandanus solms-laubachii pneumatophore showing water level when cut Pandanus solms-laubachii pneumatophore Pandanus solms-laubachii pneumatophore dried Pandanus solms-laubachii pneumatophore in section section

The prongs develop by sloughing off the white outer layer, to reveal a layer which responds to sunlight by developing chlorophyll. The brown flakey material at the tip is like a root cap, and this is mirrored in the cap of the prop-root.


This is one of the largest I have found.
It was about 30 cm from the trunk+proproots,
in a tangle of its old leaves, with only the top part in the sunlight.
Note how the lower rootlets don't seem to be negatively geotropic,
while the upper ones do.
Pandanus solms-laubachii pneumatophore large

What I can't show properly is that some of these prongs are fresh, plump and actively growing,
while most are dried up and eventually get brittle and fall away.

Questions

Is it a coincidence that Pandanus have prop roots and so do mangroves,
and mangroves are the group that we associate with pneumatophores ?

Why do pneumatophores form all over the trunk and branches,
when forming on the roots would seem to be enough ?

Could it be that mosses, lichens and orchids can 'drown' the trunk in the wet season,
so that it needs pneumatophores on its trunk to get air ?
Pandanus solms-laubachii with moss, lichens and Bulbophyllum baileyi