Growth forms: Various growth forms
represent strategies to reach sunlight:
- the so-called air
plants grow on branches high in the trees, using the limbs merely for support
and extracting moisture from the air and trapping the constant leaf-fall and
- Bromeliads (pineapple family) are especially abundant; the
orchid family is widely distributed in all three formations of
the tropical rainforest.
- As demonstration of the relative aridity of exposed
branches in the high canopy, epiphytic cacti also occur in the Americas.
- Lianas: woody vines grow
rapidly up the tree trunks when there is a temporary gap in the canopy and
flower and fruit in the tree tops of the A and B layers. Many are deciduous.
strangler fig liana:
The seed of the strangler fig starts life as an epiphyte
high in the trees, borne by birds and monkeys which eat the fig fruit. The
seedling fig sends down long roots to the ground from where it begins to
surround the host tree. It grows quickly and eventually suffocates the host:
when the host tree dies it leaves an enormous upright strangler with a hollow
core. By using an adult tree as its host, the
strangler fig avoids competition for light and nutrients at ground level.
American Samoa lianas
many lianas around tree trunk
- Climbers: green-stemmed plants
such as philodendron that remain in the understory. Many climbers, including
the ancestors of the domesticated yams (Africa) and sweet potatoes (South
America), store nutrients in roots and tubers.
- Stranglers: these plants begin
life as epiphytes in the canopy and send their roots downward to the forest
floor. The fig family is well represented among stranglers.
non-photosynthetic plants can live on the forest floor.
- Parasites derive their
nutrients by tapping into the roots or stems of photosynthetic species.
Rafflesia arnoldi, a root parasite of a liana, has the world's
largest flower, more than three feet in diameter. It produces an odor
similar to rotting flesh to attract pollinating insects.
- Saprophytes derive their
nutrients from decaying organic matter. Some orchids employ this strategy
common to fungi and bacteria.