In plants, Asexual reproduction involves a variety of methods for producing new plants identical to the parent plant. There is no involvement of the two parents and therefore no union of nuclei of the cell, therefore no variation is seen.
Plant may be bisexual or unisexual depending upon both the gametes are produced on the same plant or in different plants of same species. This involves sexual reproduction as there is involvement of both the male and female gametes. Hence variation is seen in sexual reproduction.