This will be my last post in the series on my recent travel to Costa Rica. It is focused on Epiphytes, plants that grow on the surface of other plants and deriving their nutrients mostly from the air and rainfall. In the tropics these organisms include many ferns, cacti, orchids, bromeliads and Philodendron vines.
Both bromedliads and orchids have a special kind of photosynthesis termed Crassulacean Acid Metabolism. This photosynthesis mechanism involves the processes of:
capture of CO2 at night in the form of malic acid while plant stomates are open (this restricts water loss from the plant).
closure of stomates during the day time (further restricting water loss from the plant)
conversion of stored malic acid to CO2 during the day time in the often succulent leaf tissue.
reassimilation of the CO2 into sugars and starch during the day time via conventional C3 photosynthesis.
For more details of this pathway, please see: Crassulacean Acid Metabolism. CAM plants have exceptional drought tolerance and water-use efficiency. This enables the species to survive long periods of water deficits during the dry season.
Philodendron is a large genus of flowering plants in the Araceae family. Philodendron vines are found in abundance growing on a wide range of rainforest trees at Manuel Antonio National Park (Parque Nacional Manuel Antonio).
The leaves of seedling philodendrons are usually heart-shaped. Early in the life of the plant, but after it has matured past the seedling stage, the leaves will have acquired the typical juvenile leaf's shape and size. Later in the philodendron's life, it starts producing adult leaves, a process called metamorphosis.
During my visit (January 2019) it was the dry season, and I am determined to return in September during the rainy season when the epiphytes are likely to be at their best!
Previous articles in this series: