Sepal Sepal A sepal ( or ) is a part of the flower of angiosperms (flowering plants). Usually green, sepals typically function as protection for the flower in bud, and often as support for the petals when in bloom. The term "sepalum" was coined by Noël Martin Joseph de Necker in 1790, and derived from the Greek σκεπη ("skepi"), a covering. Collectively the sepals are called the calyx (plural calyces), the outermost whorl of parts that form a flower. The word "calyx" was adopted from the Latin "calyx", not to be confused with "calix", a cup or goblet. "Calyx" derived from
Calyx of Held embryonic calyx formation. One characteristic that distinguishes Eph proteins and their receptors from other signaling systems is their ability to transmit information bidirectionally. Forward and reverse signaling in VCN and MNTB cells is essential for the proper number and formation of VCN and ipsilateral MNTB projections in the calyx. Eph proteins also ensure that while axons pass through the ipsilateral MNTB, branching and final termination of these projections only occur in the contralateral MNTB, possibly because the proteins are only targeted towards specific regions on the axons. Overall, there are two ultrastructural changes that occur in the calyx of Held.