Can fruit ontogenetic features prove to be an important tool in the circumscription of Psychotrieae alliance?

Abstract

The Rubiaceae tribe Psychotrieae sensu lato and its two largest genera, Psychotria L. and Palicourea Aubl., have been considered taxonomically controversial for a long time. We aimed to identify structural features of the ontogeny of the fruits and seeds with taxonomic potential for the tribe by using species of these two genera, and Rudgea jasminoides (Cham.) Müll.Arg. The samples were obtained from a herbarium and from Brazilian state parks, and sectioned by using a rotation microtome. The fruits were found to be derived from an inferior ovary, and were characterised by a fleshy mesocarp and sclerenchymatic sinuate pyrene. The seeds were pachychalazal and arillate. The fruit was classified as a pomaceous drupoid nuculanium. The investigation showed the utility of some fruit features to discriminate species. Our study also showed that ontogenetic features of fruits and seeds are very homogeneous in Palicourea and Psychotria, which supports the inclusion of both genera in the tribe Psychotrieae.

An Approach to Spermacoceae Cham. & Schltdl. sensu lato from the view-point of certain floral characters

“…This precursor tissue of the fruit pyrene must originate from the inner epidermis of the ovary and from periclinal cell divisions that occur in the subepidermal layer of the mesophyll, characterizing in the latter case a ventral or adaxial meristem that is installed in a younger phase of the ovary. Hitherto the similar origin of the pyrene was reported by Santos et al (2021) for some types of fruits of Psychotrieae s.l., which is a tribe closely related to Spermacoceae.…”

“…The comparative investigation of the ovary structure of Spermacoceae and species of Palicourea Aubl. and Psychotria L. (Psychotrieae)(Santos et al, 2021) reveals common characters between both tribes or alliances, such as ring-shaped nectary that surrounds the style base; inferior ovary, probably appendicular in nature; presence of precursor tissue of the pyrene/sclerenchyma of the fruit, which originates from the adaxial meristem; the compitum represented by a split in the ovarian septum and a single strand of transmitting tissue (eu-syncarpy); and the unitegmic and tenuinucellate ovule, devoid of endothelium. Both groups differ, however, as they present ovules with pachychalaza and basal or sub-basal placentation in Psychotrieae species, and strophiole (aryl) and axile placentation in Spermacoceae.…”

Sobre a Estrutura Floral E Coléteres E Sua Influência Na Sistemática E Evolução Em Algumas Espécies De Rubiaceae

“…Rubiaceae 3 has great uniformity in its colleters, the standard type being the most taxonomically important (JUDD et al, 1999), but the morphological variation, distribution and quantity also have taxonomic utility in the group (LERSTEN, 1975). Santos et al (2021) and Ramos (2022) found colleters in the flowers of some Psychotrieae and Spermacoceae species but did not describe them.…”