Q.In majority of the plants, pollen is liberated at :

The male gametophyte begins with the microspore, the first haploid cell produced by microsporogenesis, while it is still inside the microsporangium. Its nucleus divides mitotically into an unequal pair - a large, food-rich vegetative (tube) cell and a small generative cell enclosed in its own wall - and pollen is normally shed from the anther at this two-celled stage (true for about 60% of angiosperms); in other species the generative cell divides once more, before shedding, into two male gametes, so the pollen is shed already at a three-celled stage. If shed two-celled, the generative cell instead divides into the two male gametes (sperms) only after the pollen lands on a receptive stigma, or while its pollen tube is growing towards the embryo sac. Further growth of the male gametophyte resumes only on a compatible stigma: the …