how is mutations done in plants??

You may refer to the answer provided by your friend, I would like to add more points

The mutation is induced in plants by using mutagens, the substances that cause mutation. These may be chemical mutagens or radiation.

Chemical mutagens:

Some chemical mutagens, such as nitrous acid cause chemical modifications of purine and pyrimidine bases that alter their hydrogen-bonding properties. For example, nitrous acid converts cytosine to uracil which then forms hydrogen bonds with adenine rather than guanine. 

Other chemical mutagens function as base analogs. They are compounds that chemically resemble a nucleotide base and are  incorporated into the DNA in place of the natural base during DNA replication. Examples include 2-amino purine, a compound that resembles adenine.

The other chemical mutagens function as intercalating agents. Intercalating agents molecules that are about the same size as a nucleotide base pair. During DNA replication, these compounds can insert or intercalate between adjacent base pairs.

Radaitions:

Ultraviolet Radiation.  The ultraviolet portion of the light spectrum includes all radiations with wavelengths from 100 nm to 400 nm.  UV light is absorbed by DNA and causes adjacent thymine bases on the same DNA strand to covalently bond together, forming what are called thymine-thymine dimers

 Ionizing Radiation. Ionizing radiation, such as X-rays and gamma rays, has much more energy and penetrating power than ultraviolet radiation. It can break DNA strands and alter purine and pyrimidine bases. 

@  akanksha......Good work...Keep posting!