Calculation:

To determine the amount of DNA in a pollen grain, we need to understand the process of DNA replication and cell division in the mother cell.

DNA Replication:
During the S (synthesis) phase of the cell cycle, DNA replication occurs. This results in the formation of two identical copies of each chromosome, known as sister chromatids. Each sister chromatid contains the same amount of DNA as the original chromosome.

Cell Division:
After DNA replication, the cell enters the G2 (gap 2) phase of the cell cycle. In this phase, the cell prepares for division and undergoes further growth. The DNA remains in the form of sister chromatids until cell division occurs.

Amount of DNA in G2 Phase:
In the G2 phase, the amount of DNA in the cell is double the amount present in the original, non-replicated chromosome. This is because each chromosome has been replicated into two sister chromatids. Therefore, the amount of DNA in the G2 phase is twice the amount in the original chromosome.

Given Information:
The mother cell has 32 picograms (pg) of DNA in the G2 phase.

Calculation:
To determine the amount of DNA in a pollen grain, we need to consider that pollen grains are haploid, meaning they have half the number of chromosomes compared to the mother cell.

Since the amount of DNA in the G2 phase is double the amount in the original chromosome, we can divide the given value by 2 to find the amount of DNA in a single chromosome.

32 pg / 2 = 16 pg

Therefore, a single chromosome in the mother cell contains 16 picograms of DNA.

Since pollen grains are haploid, they only contain one set of chromosomes. Hence, the amount of DNA in a pollen grain is equal to the amount of DNA in a single chromosome.

Therefore, the amount of DNA in a pollen grain is 16 picograms (pg), which is the same as the amount in a single chromosome.

Hence, the correct answer is 8 picograms (pg), not 16 picograms (pg).