Question

Describe the development of the angiosperm male gametophyte. Begin with the diploid microspore mother cell (also called the microsporocyte). End with the mature (3-celled) pollen grain, and double fertilization. Include mitosis and meiosis in your description. Include where events are occurring within the flower.

Answer 1

We begin with a microspore mother cell, this cell still belongs to the sporophyte of the plant, is still diploid and is located in the flower, specifically in the anthers of the stamens. This mother cell undergoes meiosis and produces 4 haploid cells, this is called the tetrad. Every cell will survive and develop into a pollen grain through a process known as microgametogenesis. The pollen cell will undergo mitosis and create to different cells, one of those cells will engulf the other, the internal cell is called the generative cell and the external cell is the vegetative cell, and it undergoes mitosis again to form 2 sperm cells. Then the pollen cells will get correctly covered by specific layers that will protect the structure from dehydration and ligh radiation, because this structure is going to be liberated into the environment with the goal of reaching a female ovule.

The pollen is taken into the stigma by any mean, there the external layer and the stigma recognize each other, the pollen then starts to grow the pollinic tube, which is a projection from the vegetative cell. The tube will reach an ovule in the pistil and the 2 sperm cells will travel through the tube and be liberated into the ovule. One sperm cells fertilizes the egg cell and the other one will fuse to the central cell to form a triploid cell that will produce the endosperm.