The purpose of sepals is to protect the flower of a plant and prevent it from drying out, the Education Portal explains. They form a tightly closed area, known as a bud, wherein the flower develops.
Sepals are formed once a plant is ready to produce flowers, according to the Education Portal. They grow from the top of the stem and produce a bud, which encloses the flower. The flower grows along with all the reproductive parts of the plants, including the stamens and pistils. When the flower is fully developed, the sepals open to let the petals spread and expose the flower’s inner area. After the flower formation process, sepals begin to serve other purposes. Some plants have hairy and thorny sepals that protect them against insects that attempt to climb up the stem of the plant and invade the flower. Other sepals fall off the flower once it blooms, as they no longer serve a useful purpose.
Adrienne HK Roeder explains on the Wiley Online Library that sepals are the outermost organs of a flower. Sepals overlap each other to cover and protect the developing bud. They usually have defensive cell types, such as hair cells, and produce harmful chemicals to safeguard the developing reproductive organs from predators.