• majority of tropical rainforest plants are evergreen - they do not shed all their leaves at particular times of the year
• plants continuously grow new leaves to replace the older ones

• contains a very large variety of plant species due to the favourable climatic conditions
• e.g. tembusu tree, tempinis tree

• characterised by a high annual rainfall (2000ml on average)
• there is rainfall throughout the year, no month in which rainfall is very low or absent

• tropical rainforests and mangroves are found in this climate
• mangroves cover about 70% of the coastlines in the tropics

• climate of a given location determines the type of natural vegetation found there

• temperate grassland
• temperate deciduous forest
• mediterranean forest
• tropical rainforest
• tundra
• temperate coniferous forest
• desert
• tropical grassland

Emergent

• the tallest trees in the tropical rainforest are able to grow to 30m or more
• the crowns of these trees form the emergent layer

Canopy

• most trees grow to about 20-30m in height → grow very close to one another, their crowns interlock to form a thick and near-continuous mass of branches and leave → canopy layer
• prevents 97-98 % of the sunlight from passing through to reach the forest floor

Undergrowth

• found beneath the canopy layer
• very little sunlight is able to reach → not many plants are able to grow here, except smaller ones and the seedlings of taller trees
• amount of vegetation growing near the ground surface is very sparse
  
  

Broad Leaves

• leaves of most plants are broad, which means that they have a large surface area → enables the plant to absorb as much sunlight as possible in order to make food for its own survival and growth

Waxy Leaves

• leaves are also waxy, which gives their surfaces a glossy appearance → helps the plant to reduce the amount of water vapour that it loses to the atmosphere (transpiration) as a result of high temperatures in the tropical rainforest

Drip Tips

• some plants have leaves with small, narrow tips that point downwards → drip tips
• together with the leaves' waxy texture, allow rainwater that falls onto them to flow off easily → helps the leaves to dry quickly and thus prevents the growth of fungi/bacteria on them

Buttress Roots

• trees that grow to great heights usually have buttress roots to keep them upright and prevent them from toppling over
• can grow up to 5m above the ground surface
• trees require the support provided by the buttress roots because the rest of the roots do not extend very deep beneath the ground surface
• nutrients are concentrated in the topmost layer of the soils (released when dead leaves and branches decompose) → trees tend to have shallow underground roots so that they can absorb nutrients quickly

• made up of plant species known as mangroves, which are able to grow in water that has a higher salinity compared to fresh water
• lack of competition from other types of plants which are unable to grow in such conditions

• mangrove plants are unable to withstand freezing conditions
• grow best where the average air and water temperature do not fall below 20°C
• unable to survive in places very far north or south of the tropics

• mangrove plants also require calm water conditions so that their seedlings are able to take root and grow without getting washed away by strong waves
• calm water conditions encourage the accumulation of fine sediments containing nutrients, which mangrove plants require to sustain their growth
• hence, mangrove forests are usually found only in sheltered environments such as shallow river mouths or behind islands

• lower diversity of plant species compared to tropical rainforests
• only a total of 60-70 mangrove tree species worldwide
• not many plant species have evolved to survive in waters of high salinity

• less dense than a tropical rainforest → less competition for sunlight
• coastal environment is difficult for plants to survive in, mangrove plants need to obtain as much energy from the Sun as possible → cannot tolerate shaded conditions
• mangrove plants are relatively uniform in terms of height

Low tide level

• low-lying parts of the coast are flooded for longer periods of time compared to areas which are further inland
• species that are found here include Sonneratia and Avicennia

High tide level

• species which are not as tolerant of these conditions are found closer to the high tide level where the duration of flooding by the tide is shorter
• e.g. Rhizophora and Bruguiera

Salt-secreting leaves

Avicennia

• enable plants to remove salt from the saline water that their roots have absorbed
• concentrated salt solution secreted by the leaves evaporates → salt crystals are left behind on the leaf surfaces → removed by rain or wind
  
  

Sonneratia

• deposit excess salt in older leaves which they eventually shed
• prevent salt from building up within the plant

Rizophora

• curved prop roots
• help the plant breathe and provide support
  
  

Bruguiera

• knee-bend roots, bend upwards to emerge above soil surface before bending downwards into the soil at regular intervals