In sexual reproduction in plants, the first step is pollination, which is the transfer of pollen from a male anther to a female stigma. Option 1, 2 and 4 do not start with this process, so they are incorrect.

The second step is fertilization, which occurs when the sperm nucleus in the pollen tube fuses with the egg nucleus in the ovule. Only options 3 properly follow this order.

After fertilization, the zygote (a single cell resulting from the fusion of the sperm and egg nucleus) begins to divide and grow into a new individual, which is the third step.

The zygote develops into the embryo, which represents the fourth step. Finally, as the embryo matures and the surrounding ovule develops into a seed, a new plant or seedling emerges after germination.

Therefore option 3, `Pollination, fertilization, division of the zygote, the formation of embryo, seedling` is the correct sequence of events for sexual reproduction in plants.