Tropical Rainforest Plants

The tropical rainforests are a breathtaking example of diversity of life forms. With its hot and humid climate, rainforest provides such favorable conditions that tropical rainforest plants and animals comprise almost 80% of biodiversity of the planet. The diversity of these plants can also be explained on the basis of specialization that different plant and animal species have undergone in the struggle for existence.

Geography and Climate
Tropical rainforests are spread around the equator in the countries of Asia, Africa, South and Central America and some Pacific Islands. The temperature in these rainforests vary between 35°C to 20°C with no specific hot or cold seasons. However, the average humidity is as high as 77% to 80%. The Amazon rainforests are the most famous of the different tropical rainforests of the world.

Rainforest Layers
The struggle for existence in the rainforests has resulted in vegetation that can be divided into distinct layers. They are:

The Emergent Layer: This forms the topmost layer with trees that reach 100 to 240 feet high. These have umbrella shaped canopies that get maximum amount of sunlight as they reach highest levels in the rainforests. Trees of this layer are home to a large number of animals like eagles, monkeys, bats and butterflies.

The Canopy Layer (Upper Canopy): The canopy layer of rainforests forms a dense ceiling of evergreen trees with broad leaves that grow close to each other. It is because of this layer that sunlight cannot penetrate levels below the canopy and reach the ground. The trees in this region grow 60 to 130 feet tall. This layer is so abundant with food that it forms the main life sustaining layer of the rainforest. The canopy layer is home to most of the animals like leopard, jaguars and the exotic birds of the tropical rainforests.

The Understory (Lower Canopy): Lying just below the canopy layer is the understory that consists of tropical rainforest vegetation that grows up to 60 feet tall. There is little air movement in this layer and humidity is constantly high. Due to the lack of sunlight, this layer is abundant in shade tolerant shrubs, ferns, herbs, small trees and woody vines.

The Forest Floor: The forest floor hardly gets any sunlight. Hardly any plant life is found in this layer but it is rich in microorganisms. Hence, whatever organic matter falls on the forest floor, decomposes very quickly. This layer is rich in animal and insects. Giant anteaters, beetles, frogs, snakes, lizards and a host of insects inhabit the forest floor.

Plant Adaptations
Like the animals of other biomes, the tropical rainforest animals and plants have developed adaptations that help them survive the warm and humid climate that is typical of these forests. Some of the adaptations are:

• The trees of these rainforests do not need to have thick bark to prevent loss of moisture. Hence, they have thin, smooth bark.
• As the rainforests are characterized by high rainfall, the leaves of trees have developed 'drip-tips' to let rainwater drain off quickly. In some trees, this is aided by a central groove and waxy coating over the leaves.
• Leaves of trees at lower canopy levels are broad so that they are able to make the most of the sunlight reaching this layer. Those at higher levels have narrower leaves.
• Tall trees like those forming the emergent layer are large and need extra support to stand. This is provided by the broad, woody flanges at the base of the trunk known as buttresses.
• There are vines that grow up the tree trunks and reach the upper layers of the canopy layer in search of light.
• There are plants like epiphytes that grow on trees of the tropical rainforests.
• Plants in the lower layers of tropical rainforests have large showy flowers to attract insects for pollination as there isn't much wind at these levels.

Tropical Rainforest Plants
A rainforest plants list includes thousands of species. Besides the tall evergreen trees (forming the emergent layer) and other smaller trees and herbs (belonging to the remaining layers), there are other plants too which are quite remarkable from the point of view of adaptation. They are:

The Epiphytes: Epiphytes include orchids, bromeliads, lichens, mosses and ferns that grow on high branches of trees forming the canopy layer. These are non parasitic plants that derive moisture and nutrients from the air and use their roots merely for support.

The Lianas: These are woody vines that grow up the trunk of other trees and reach up in between the upper canopy layer where there is some gap so that they can get some sunlight. These woody wines also bear fruits and flowers.

The Stranglers: Also known as the killer trees in Spanish, the stranglers begin their life like epiphytes. The seeds are brought to the host tree by the birds. Then, the stranglers spread their roots on the ground where the host tree stands. As they grow, they suffocate and kill the host tree. The result is that an erect strangler is left with a hollow core. Stranglers are the members of the fig family.

Carnivorous Plants: Many of these plants derive nutrition from other animals. These have a central cavity filled with nectar that attract insects. Once the insects enter the cavity, the downward pointing bristles prevent them from moving out. These plants usually have a lid or flap that close the opening to the cavity. The insect that is trapped inside is then, digested with the help of digestive juices released by the plant. Common carnivorous plants are the rafflesia, pitcher plant and venus fly trap.

Other Commercially Important Plants: Avocado, cashew, cardamom, cinnamon, clove, coffee, chocolate, mango, banana, papaya, peanut, pineapple, nutmeg, sesame, sugarcane, tamarind, turmeric, vanilla are just a few of the many plants that would feature in the tropical rainforests plants list.

These rainforests that are home to almost 2/3rd of the various life forms is threatened due to relentless deforestation. Clearing forests for agriculture and for obtaining wood, various spices and medicines that these forests provide, has led to a large number of flora and fauna to be enlisted as endangered rainforest animals and plants. These plants and animals weave a remarkable story of making the most of whatever growth conditions available to them. Hence we, human beings definitely need to take a lesson from them.