Introduction of an alien DNA into a plant cell host is done by:

Biolistics method

The correct answer is Option (3) -Biolistics method

There are several methods to introduce alien DNA into host cells. One such method is micro-injection, where recombinant DNA is directly injected into the nucleus of an animal cell.

Biolistics: Biolistics is a method of introducing foreign DNA into host cells, particularly plant cells, using high-velocity micro particles. In this technique, small particles, such as gold or tungsten, are coated with the desired DNA and then shot into the target cells using a device known as a gene gun. The high velocity of the particles allows them to penetrate the cell wall and deliver the DNA into the host cell's nucleus.

Treating the plant cell with chitinase is related to the breakdown of fungal cell walls and is not used for DNA transfer.

Treating plant cells with divalent cations is used in bacterial cells to make them more competent for transformation, not typically in plant cells.