Many of the epiphytes found in this zone have developed sophisticated physiological adaptations
to survive long periods of aridity. These include the following:-
- Leaves have become very thick and fleshy
- Leaf surfaces may be protected by a heavy wax coating. Under bright conditions, leaves
may develop a deep red colouration to protect sensitive photosynthetic tissues.
- Some leaves have become folded into a ‘V’ shape, decreasing the leaf surface exposed
to the dry atmosphere, in extreme cases the leaves becoming rolled into a round profile, only the lower surface
of the leaf exposed to the exterior.
- Stomata, through which the plant breathes, may be confined to the lower leaf surface,
or in pits or depressions, with large guard cells limiting water loss.
Some plants have developed a metabolic adaptation to limit water loss, as portrayed in
the chart which follows