Types

• Most of the cells found in most plants are diploid like human cells, meaning they have two of each chromosome. Haploid cells only have one of each chromosome. Sperm and eggs are haploid cells.
  
  

Function

• Inside the anthers of a flower, cells called microsporangia divide by meiosis (the type of cell division that produces haploid sex cells) to produce four haploid microspores each. A microspore develops into a pollen grain; each pollen grain contains a generative cell that will give rise to two sperm once the pollen land on the stigma (the stalk at the center of the flower). In the ovary of the flower, meanwhile, a megaspore mother cell divides by meiosis to yield four haploid cells, only one of which will live. The surviving megaspore divides to form an embryo sac containing an egg and two polar nuclei.
  
  

Effects

• When a pollen grain lands on a stigma, it grows a pollen tube that tunnels down through the stigma into the ovary. The sperm travels through the pollen tube to fertilize the egg and form a diploid zygote. The diploid zygote develops into the seed that will someday form a new plant, completing the reproductive cycle.