Q.Size of pollen grain in Myosotis

In the majority (about 70%) of angiosperm species, pollen grains are shed from the anther while still at the 2-celled stage.

Working

A pollen grain develops from a haploid microspore. The microspore nucleus first undergoes an asymmetric mitotic division to produce two unequal cells: a large vegetative (tube) cell and a small generative cell. At this point the pollen grain is said to be at the 2-celled stage. In about 70% of flowering plant species, the pollen is shed from the anther and dispersed while still at this 2-celled stage; the generative cell only divides mitotically into two non-motile male gametes (sperm cells) later, typically after the pollen tube has begun to grow, bringing the grain to a 3-celled stage. In the remaining roughly 30% of species, thi …

The microspore is the first cell of the developing male gametophyte in angiosperms.

Inside the anther, diploid microspore mother cells (pollen mother cells) within the microsporangium undergo meiosis to produce a tetrad of four haploid microspores. Each microspore is the first cell of what will become the male gametophyte: it enlarges, develops a characteristic two-layered wall (exine and intine), and its nucleus divides mitotically (microgametogenesis) to form a vegetative cell and a generative cell, with the generative cell later dividing again to produce two male gametes -- together constituting the mature, three-celled (or, at shedding, often two-celled) pollen grain, the fully formed male gametophyte. This is distinct from the megaspore, the haploid product of meiosis in the ovule that is the first cell of the female gametophyte …