Combining conventional and advanced microscopy methods to elucidate structural and functional relationships of the floral nectar system of Zeyheria Mart., a genus of Bignoniaceae with vestigial disc.

• Grant number: 25/08437-6
• Support Opportunities: Scholarships in Brazil - Master
• Start date: September 01, 2025
• End date: January 31, 2027
• Field of knowledge: Biological Sciences - Botany - Plant Morphology
• Principal Investigator: Silvia Rodrigues Machado
• Grantee: Aline Rodrigues de Almeida
• Host Institution: Instituto de Biociências (IBB). Universidade Estadual Paulista (UNESP). Campus de Botucatu. Botucatu , SP, Brazil

Abstract

Floral nectar production in most Bignoniaceae is attributed to a conspicuous nectariferous disc that surrounds the base of the ovary. However, in some genera, including Zeyheria Mart, the disc is vestigial, and nectar production has been attributed to a substitutive nectary formed by glandular trichomes lining the nectariferous chamber. Previous studies have shown that in Zeyheria, the disc, although reduced, has a cellular apparatus characteristic of nectariferous cells. In these species, floral nectar production involves more than one secretion site, thus constituting a complex secretory system. The primary goal of this study is to conduct a more in-depth analysis of the floral nectar secretory system in two species of Zeyheria, which share a reduced floral disc but differ in their environment, type of pollinator, and attributes of floral nectar. We intend to clarify whether variations in floral nectar attributes are associated with subcellular specializations in specific domains of the nectar secretory system (nectar chamber, disc, and secretory trichomes), in addition to verifying whether there is in fact a relationship between nectary size and nectar volume and vascularization with nectar concentration, as well as investigating the ultrastructure of the nectary phloem. The collected material will be examined using common methods in light microscopy, scanning electron microscopy, and transmission electron microscopy, along with techniques for studying cell structures and micro-CT scans. We will compare the results between the two species of Zeyheria and those featuring a conspicuous nectariferous disc. The important results are expected to clarify how the floral nectar secretory system works in Bignoniaceae species that have small or reduced discs. The information gathered may help us understand how the disc lost its ability to produce nectar and was replaced by nectar-producing hairs.