Taxonomical significance of the floral ontogeny in the genus Salvia (Lamiaceae): a case study in S. santolinifolia

The genus Salvia L. is the largest genus of Lamiaceae family. Species of this genus are determined by two anterior fertile stamens, each consisting of a lever-like structure with two unequal arms held by a filament. Based on these characteristics, this genus has traditionally been classified as a monophyletic group. The recent new classification using molecular data, however, has rejected this opinion. According to one of these findings, S. santolinifolia has been re-established as Pleudia santolinifolia. To determine its taxonomic status, the floral ontogeny of S. santolinifolia is studied using SEM (scanning electron microscopy). The results showed that the floral organs initiate as centripetal sequence. First, sepals appear, followed by petals, stamens, and then carpels. Sepals initiate in a unidirectional pattern, starting with adaxial sepals and then followed by abaxial ones. Petals appear in a bidirectional pattern, starting with the middle abaxial petal, followed by two adaxial ones, and ending with two lateral ones. The sterile stamens initiate initiating later. Finally, carpels are formed. The results show that the order and sequence of the floral organs in S. santolinifolia differ from those in Salvia, which follow a strict pattern with no overlaps among the organs. The floral ontogeny of this species is similar to that of S. majdae. Based on these findings, transferring this species into the genus Pleudia is reasonable decision.