Whether pistil show diversity in bisymmetric and zygomorphic flowers in Fumarioideae (Papaveraceae): especially focus on stigma development, structure and secondary pollen presentation.

Abstract

Pistils of Fumarioideae (Papaveraceae) show diversity in morphology, whether it is involved in the formation of flower symmetry is unclear for pistil morphogenesis and ovule development characteristic are poorly known. In this study, seven species of Fumarioideae were studied under SEM, LM and TEM, six developmental stages can be recognized: pistil initiation, circular bulge fusion, ascidiate structure formation, stigma and ovary differentiation (including ovule initiation), pistil development (including stigma specialization and ovule development) and pistil maturation. All syncarpous pistils were fused by two carpels, and stigmas in different shape were all derived from the two horns which formed by dorsal suture extension, e.g. two-lobed deeply, two-lobed deeply with four papillae, boat-shaped with four papillae; and style bend to the spurred-petal at later developmental stages in Corydalis edulis and Fumaria officinalis. During flowering, stigmas were wrapped by "pollen container" formed by two inner petals (expect Hypecoum erectum); the pollen-receptive surfaces of stigma is concentrated or compartmentalized, and is covered with papillae cells which have a large vacuole, abundant mitochondria and plastids, and cell wall was covered by a lot number of secretions. In addition, ovule number in ovary of Fumarioideae varied from few (only one ovule developed normally in F. officinalis) to 200, and the square, banded and near-triangular funicle appendage structures are found in Lamprocapnos spectabilis, Dactylicapnos torulosa and C. edulis. The correlation between pistil development and flower symmetry and the function of secondary pollen presentation on stigma were discussed in this study.