The assertion is correct, and the reasoning provided is also accurate.

Flowers are indeed the structures of sexual reproduction in plants. They are the reproductive organs that facilitate the fusion of male and female gametes, leading to the formation of seeds and fruits. Flowers contain the reproductive structures necessary for sexual reproduction, including the male parts called stamens and the female part called the pistil.

The reasoning is also correct. Various embryological processes of plants occur within a flower. These processes include the development of male gametes (pollen grains) within the anthers of the stamens and the development of female gametes (ovules) within the ovary of the pistil. Pollination, which is the transfer of pollen from the male reproductive organs to the female reproductive organs, takes place within the flower. Fertilization occurs when the pollen reaches the stigma and the sperm cells within the pollen grain fuse with the egg cells in the ovules. This leads to the development of seeds and fruits.

Therefore, both the assertion and the reasoning are accurate. Flowers are indeed the structures of sexual reproduction in plants, and various embryological processes necessary for reproduction occur within them.