Embryoids formed in tissue culture from pollen grain are due to

Embryoids formed in tissue culture from pollen grains are due to Cellular totipotency.
Cellular totipotency is the inherent potentiality of a plant cell to give rise to a whole plant, a capacity that is retained even after a cell has undergone final differentiation in the plant body.
A cell can differentiate into other cell types. The more cell types a cell can differentiate into, the greater its potency.