Mention the type of host cells suitable for the gene guns to introduce an alien DNA.

To introduce an alien DNA, undifferentiated plant cells are the most suitable host cells for the gene guns. This is so because the undifferentiated plant cells have a cell wall which can be easily broken down by bombarding them with high-velocity micro-particles of gold or tungsten coated with DNA in a gene gun. The development of the tertiary cell wall in the mature plant cell is a hindrance to the introduction of foreign DNA.