Morphoanatomy of the inflorescence and flowers of Solidago chilensis (Asteraceae)

Abstract

The genus Solidago is one of the most complex taxa in the Asteraceae, with a large number of species mostly from North America. Solidago chilensis Meyen is a South American species with a wide distribution, known mainly for its medicinal properties. Due to the scarce information on the reproductive structures, we studied the morphoanatomy of the inflorescence and flowers with conventional histological techniques of light and scanning electron microscopy. The floral axes show abundant fascicular and interfascicular fibres. The leaves exhibit an isobilateral mesophyll, and in the phyllaries and the bracts of the peduncle, the mesophyll contains numerous fibres. There are schizogenous secretory spaces associated with the vascular bundles of leaves, stems, receptacle, bracts, phyllaries, ovaries and corolla of the disc florets. The latter present an annular nectary at the base of the style. The indumentum of the florets is represented by biseriate glandular trichomes in the corollas and ovaries, and twin hairs on the ovaries; in the rest of the organs, the trichomes are biseriate glandular and eglandular conical, whip-like, and biseriate only on the phyllaries and bracts. The predominant crystals in the floral parts are druses, and raphides and styloids in the rest of the inflorescence. The general morphological features agree with those reported for Astereae, while several other anatomical features are described for the first time for the species and may have taxonomic value for the genus and the tribe. Likewise, these characteristics also contribute to the quality control of the species as a crude drug.