Theory:

3. Used as Bio-fuels:
 
Some of the plants are grown for it to serve as a bio-fuel. Plant fuels are less toxic as there is no emission of harmful gases. Plant fuels are also cheaper compared to the normal diesel or petrol.
Example:
Jatropha is a flowering plant in the spurge family, Euphorbiaceae. The seed oil extracted is used as a bio-diesel directly without filtration.
 
BeFunky-collage.jpg
Jatropha seed oil used as bio-diesel
Plant wastes are also used to generate electricity
Example:
The bagasse (dry, pulp residue after extracting juice from sugar cane) of sugar mills are used to generate steam and electricity.
 
512px-Sugarcane_bagasse.jpg
Bagasse
4. Used to obtain rubber and natural plastic:
 
Rubber for tyres, wiring, seats is obtained from plants. Natural plastics are made from plants. Natural plastics are biodegradable. Thus they serve to be environment friendly and does not pose any harm to the environment. Rubber is harvested from the trees in the form of latex. Latex hardens after the extraction to form rubber.
 
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Latex extraction from the rubber tree
 
5. Neem-coated urea:
 
Indian farmers use urea as a fertiliser to increase yield and productivity. Scientists made neem-coated urea that releases nitrogen gradually, which helps the plant to absorb maximum nitrogen. The gradual release of nitrogen makes it available to the plant for a longer time.
 
Coating of urea with neem reduces the solubility of urea. This helps in the decrease in contamination of the groundwater. Thus there is a reduction in the effect of urea on the environment.
 
6. Perfume from plants:
 
The flowers of plants like jasmine, rose, and lavender are used to make perfumes.
 
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Perfume from rose petals
Reference:
https://upload.wikimedia.org/wikipedia/commons/thumb/d/d6/Jatropha_Crude_Oil_-_DRDO_-_Pride_of_India_-_Exhibition_-_100th_Indian_Science_Congress_-_Kolkata_2013-01-03_2580.JPG/512px-Jatropha_Crude_Oil_-_DRDO_-_Pride_of_India_-_Exhibition_-_100th_Indian_Science_Congress_-_Kolkata_2013-01-03_2580.JPG
https://www.flickr.com/photos/47108884@N07/4324521371
https://upload.wikimedia.org/wikipedia/commons/thumb/f/f6/Sugarcane_bagasse.jpg/512px-Sugarcane_bagasse.jpg
https://upload.wikimedia.org/wikipedia/commons/thumb/b/b2/Rubber_tree_up_%282657925156%29.jpg/512px-Rubber_tree_up_%282657925156%29.jpg