Answer:
24 chromosomes.
Step-by-step explanation:
The diploid number for a lily whose pollen contains 12 chromosomes would be 24 chromosomes and is produced when the pollen moves from a stamen to the stigma and fecundates the female gamete. Thus, a diploid cell, with 24 chromosomes (12 pairs, 12 x 2), is formed.
Gametes are haploid, it means, they contains half of the chromosomes.