What are tropical plants?
Growing along the equator, the hot and humid tropical rainforest ecosystems are home to the most biodiversity in the world. Tropical rainforests are typically characterized by heavy rainfall, which can reach up to 100 inches per year. These biomes are found in Southeast Asia, parts of South and Central America, Australia, and West and Central Africa. An especially diverse selection of angiosperms, or flowering plants, can be found in these tropical ecosystems. Their role as carbon sinks makes rainforests extremely important, as their absorption of carbon dioxide helps to reduce the effects of global warming.
What makes tropical plants special?
Rainforests are vertically split up into different layers, each containing a unique variety of flora and fauna. Different plant species have unique adaptations to survive in the forest floor, understory, canopy, or emergent layers of the rainforest.
The forest floor is the lowest level of the rainforest and receives the least amount of sunlight. One plant family adapted to these low light conditions are aroids. Also known as Araceae, these plants are characterized by their inflorescence structures, which are soft stems covered with tiny, compact flowers. The Mexico-native Monstera plant is an example of an aroid species growing right here in the Conservatory. Their leaves, covered in Swiss cheese-like holes, are thought to be adaptations for withstanding stormy winds, allowing rain to reach their roots, or catching dappled sunlight. These special adaptations help species living on the forest floor to thrive in their shady conditions.
Above the forest floor sits the lush understory layer where plants have adapted broader leaves to absorb sunlight that passes through the canopy. In the understory, you can find tree-climbing vines, aromatic and colorful flowers, and shorter trees, like the cacao tree, which also grows here in the Conservatory. Originally hailing from the Amazon rainforest, this plant is beloved for its seeds that are used to make chocolate. Cacao trees have adapted to the shady understory with their wide, waxy leaves that can repel water and rotate up and down to catch sunlight.
The dense canopy layer above acts as a roof, preventing much rain and sunlight from reaching the understory and forest floor. The canopy is composed mainly of tall evergreen trees with broad, waxy leaves. Growing on these trees are a diverse variety of epiphytes—or plants that grow on the surface of others—such as orchids, bromeliads, and ferns. While most plants get their nutrients from the air, soil, and water, epiphytes also rely on debris from their hosts for their nutrients.
Towering over the rainforest is the emergent layer, which consists of extremely tall trees. Not many trees grow tall enough to break through the canopy, making the emergent layer relatively sparse. Conditions at this layer of the rainforest can be especially harsh, with trees having to face the full force of the hot tropical sun, strong winds, and torrential rainfall. To withstand these stressors, emergent trees have adapted waxy leaves to prevent evaporation and seeds or pollen that can disperse in the wind.
Fun facts
One of the more dazzling adaptations to low light conditions in the understory is the development of iridescent leaves. Native to Malaysia, the Begonia pavonina is a plant with this very adaptation growing here in the Conservatory. The blue iridescence in their leaves helps to reflect blue light and absorb red-green light, thus maximizing the energy they get from what little sunlight that reaches the understory. Similarly, the Selaginella willdenowii, or peacock plants, have blue iridescence in their leaves which may help to prevent bright tropical sunlight from damaging the plant.