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Lecture 5: Roots and its modification (Buttress or tabular roots…
Lecture 5: Roots and its modification
Buttress or tabular roots
Vertically flattened roots that projects out of the ground and lower trunk at the base of large trees
Can be found in many rainforest trees
Supports the tree weight in shallow soils of rainforest
Increases the surface area over which nutrients can be absorbed from the soil
Most rainforest soil is very poor in nutrients due to leaching and run off. All nutrients are largely found at the surface level
Stilt and Prop roots
Branched/ Adventitious roots arise from the lower parts of the trunk or branches
Provides support to the stem are branches
Common characteristics of mangrove trees
Pneumatophores
Aerial breathing roots
Commonly found in magroves
Aerial roots
Found in epiphytes such as orchids
Aides in absorption of water from rain
Enables plant to climb and anchor to any surfaces it is growing on
Orchids produce chlorophyll in aerial root to manufacture food
Some parasitic epiphytes such as the mistletoe have roots that penetrates the host plant tissues and absorb nutrients
Contractile roots
In order to maintain a corm or bulb under the soil, these roots slowly pull the bulbs/ corms inwards
Contractile roots will Shrivel and hence shrink in length
Mycorrhizae (Fungi)
Forms symbiotic relationship with soil fungi (Mycorrhizae) to better absorb essential minerals
Fungus are able to absorb and concentrate phosphorus much better than root hairs
Can also improve water absorption and uptake of certain minerals from the soil
Nodules
Are found in Legume Family (now called Fabaceae)
Association with nitrogen fixing bacteria
Form symbiotic relationships with nitrogen-fixing bacteria (rhizobial bacteria) and fungi that lives in tumor- like root nodules.
Nitrogen fixing bacteria able to convert atmosphere N2 gas to ammonia to amino acids.
A very special way to deliver nutrients to the shoot (Plants like N2)
Rhizophora
Spongy outgrowths from the roots below
Function as breathing roots
In swampy or tidal envt., where the soil is usually flooded or water- logged, roots often grow upwards until they are above high- tide level.
Even though roots live in soil, they still require oxygen for aerobic respiration. flooded soil = depleted of O2
To avoid suffocation, pneumatophores contain as much as 80% aerenchyma (Functions like a snorkel, O2 diffuses to submerged roots
Food/ water storage
Roots are enlarged and store large quantities of starch and other carbohydrates which may be later used for extensive growth