Answer:
Meiosis
Step-by-step explanation:
The process that could occur in maple trees to decrease the chromosome number in pollen cells from 52 to 26 is called meiosis.
Meiosis is a type of cell division that reduces the chromosome number by half, resulting in the formation of haploid cells with half the number of chromosomes of the original cell. In meiosis I, the chromosomes are replicated and then lined up in homologous pairs, and then are separated into different nuclei during meiosis II, resulting in four haploid cells, each with half the number of chromosomes as the original cell.
So in the case of maple trees the process of meiosis would reduce the number of chromosomes from 52 to 26 in the pollen cells.