Floral development in Scutellaria pinnatifida (Lamiaceae): the ontogenetic basis for sepal reduction

• Published in: Plant biology (Stuttgart, Germany) Vol. 17; no. 1; pp. 238 - 244
• Main Authors: Naghiloo, S., Gohari, G.R., Nikzat Siahkolaee, S., Dadpour, M.R.
• Format: Journal Article
• Language: English
• Published: England Blackwell Publishing Ltd 01.01.2015
• Subjects: Biological Evolution; Disc nectary; epi-illumination light microscopy; floral ontogeny; Flowers - anatomy & histology; Flowers - genetics; Flowers - growth & development; organ reduction; Scutellaria - anatomy & histology; Scutellaria - genetics; Scutellaria - growth & development; Scutellaria pinnatifida; Disc nectary; Scutellaria pinnatifida; organ reduction; epi-illumination light microscopy; floral ontogeny
• ISSN: 1435-8603; 1438-8677
• DOI: 10.1111/plb.12193

The Scutellaria is a Labiatae genus (subfamily Scutellarioideae) with a highly specialised floral structure. The genus is characterised by a peculiar two-lobed calyx with a projecting appendage, named the scutellum. Here, we present a detailed analysis of floral development, using epi-illumination light microscopy, to clarify open questions about its floral organisation. Floral whorls appeared in an acropetal sequence, with a marked temporal overlap of petal and stamen appearance. Organ appearance in each whorl proceeded unidirectionally from the abaxial to the adaxial side. Significant developmental features included the formation of the scutellum, reduction of sepal lobes and formation of a three-lobed nectary disc. Our study revealed that both loss of organ initiation and fusion of primordia are responsible for the reduction in sepal members in Scutellaria. The nectary structure was markedly different from most other studied Lamiaceae.