Corona development and floral nectaries of Asclepiadeae (Asclepiadoideae, Apocynaceae)

Abstract

Flowers of Asclepiadoideae are notable for possessing numerous nectaries and elaborate coronas, where nectar can accumulate but is not necessarily produced. Given the complexity and importance of these structures for reproduction, this study aimed to analyze the ontogeny of the corona, the structure and position of nectaries and the histochemistry of the nectar of species of Asclepiadeae. Two types of coronas were observed: androecial [C(is)] and corolline (Ca). Th e development of the C(is)-type of corona initiates opposite the stamens in all species examined with the exception of Matelea in which it begins to develop as a ring around the fi lament tube. Despite their morphological variation, coronas typically originate from the androecium. A notable diff erence among the studied species was the location of the nectaries. Primarily, they are located in the stigmatic chamber, where nectar composed of carbohydrates and lipids is produced. A secondary location of nectaries found in species of Peplonia and Matelea is within the corona, where nectar is produced and stored, composed of carbohydrates and lipids in Peplonia and only carbohydrates in Matelea. Th e functional role of nectar is related to the location of its production since it is a resource for pollinators and inducers of pollen germination.

How different is similar – exploring development of Ceropegia sandersonii pitfall flowers to elucidate convergent evolution of floral synorganization

“…Absence of vascular bundles in the corona of Ceropegia sandersonii supports that this organ is an emergence of the stamens. It further suggests that the corona does not produce nectar via coronal nectaries as described for other species of Apocynaceae-Asclepiadoideae (35). The presence of nectar in C. sandersonii was never empirically veri ed.…”

“…The development of the gynostegial corona only starts its development in phase P7 out of ten phases, which is relatively late. Late appearance of corona tissue has been described in other Ceropegia species (5) as well as in other Asclepiadoideae (see 35). The evolution of the gynostegial corona, as determined by previous morphological studies, was described to be of staminoid (androecial) origin for Asclepiadoideae (see 6).…”

“…Though several morphological studies on ower development are published for Apocynaceae (e.g. 8,35,36), development of Ceropegia owers was never visualized from primordia to fully developed owers (but see 2, 10). We used scanning electron microscopy to circumscribe ower development of Ceropegia sandersonii from initiation of oral primordia to a mature ower.…”

Taxonomic implications of floral morphology in the subfamily Asclepiadoideae (Apocynaceae s.l.) in Korea

“…The function and homology of the coronas in Asclepiadoideae are little known. The role of the corona may be to lead pollinators into the guide rail (Ollerton and Liede, 2003) and/or to store nectar on the interstaminal part of the corona (Monteiro and Demarco, 2017). According to Ollerton and Liede (2003), if the corona is reduced or missing, its role can be filled by the trichomes inside the corolla.…”

Ontogenia y aspectos histoquímicos de los esporangios y escamas receptáculares del helecho epífito Pleopeltis macrocarpa (Polypodiaceae)

“…Se obtuvieron secciones transversales con micrótomo rotatorio LEICA RM 2125, entre 5-7 μm de grosor. Finalmente, se procedió a la tinción de las secciones con los protocolos para descripción de tejidos en general y las pruebas histoquímicas específicas que se indican en la tabla 1 (Ruzin, 1999;Demarco 2014Demarco , 2017Soukup, 2014;Yeung, Stasolla, Sumner, & Huang, 2015;Monteiro & Demarco, 2017).…”