Question

what possible functions could be petals & sepals serve

Answer 1

petals help to attract the insects so that the pollen grains can attach to them and fly with them to another flower and the pollination takes place. which helps the plant for continuation of species.
similarlly, sepals r the base to hold the thalamus of the flower and after formation of fruit they help the fruit to stay attached to the plant body...
i hope it helps u...

Answer 2

Petals are modified leaves that surround the reproductive parts of flowers. They are often brightly colored or unusually shaped to attract pollinators.

The sepals are the lower, or outermost, part of the flower. They fold over the tender, closed bud and protect it from cold and other injuries while it is developing. Usually sepals are green. In many flowers, however, they are as colorful as the petals and increase the flower's attractiveness to insects.