How the contents of pollen sac (pollen grains) would come out?

The contents of pollen sac will come out with the dehiscence of the anther. There is a line of dehiscence in the anther which separates the theca once the pollens are formed. Hope this helps. read more

Each pollen grain is typically a single cell. They have a tough coat for protection as they travel on the wind or are carried to the plant ovary. They are the male gametes or sperm cells of plants. read more

Pollen is a fine to coarse powdery substance comprising pollen grains which are male microgametophytes of seed plants, which produce male gametes (sperm cells). Pollen grains have a hard coat made of sporopollenin that protects the gametophytes during the process of their movement from the stamens to the pistil of flowering plants, or from the male cone to the female cone of coniferous plants. read more