Nectar Secretion of Floral Buds of Tococa guianensis Mediates Interactions With Generalist Ants That Reduce Florivory

Abstract

The specialised mutualism between Tococa guianensis and ants housed in its leaf domatia is a well-known example of myrmecophily. A pollination study on this species revealed that flowers in the bud stage exude a sugary solution that is collected by ants. Given the presence of this unexpected nectar secretion, we investigated how, where, and when floral buds of T. guianensis secret nectar and what function it serves. We studied a population of T. guianensis occurring in a swampy area in the Cerrado of Brazil by analyzing the chemical composition and secretion dynamics of the floral-bud nectar and the distribution and ultrastructure of secretory tissues. We also measured flower damage using ant-exclusion experiments. Floral bud nectar was secreted at the tip of the petals, which lack a typical glandular structure but possess distinctive mesophyll due to the presence of numerous calcium oxalate crystals. The nectar, the production of which ceased after flower opening, was composed mainly of sucrose and low amounts of glucose and fructose. Nectar was consumed by generalist ants and sporadically by stingless bees. Ant exclusion experiments resulted in significantly increased flower damage. The floral nectar of T. guianensis is produced during the bud stage. This bud-nectar has the extranuptial function of attracting generalist ants that reduce florivory. Pollen is the unique floral resource attracting pollinators during anthesis. Tococa guianensis, thus, establishes relationships with two functional groups of ant species: specialist ants acting against herbivory and generalist ants acting against florivory.

Species-Specific Variation in Abscisic Acid Homeostasis and Responses Impacts Important Traits in Crassocephalum Orphan Crops

“…When this stage was reached, the florets had fully developed and drops of liquid began to be exuded from the tips of the closed capitula ( Figure 1B ). This liquid was likely nectar secreted from the florets, a phenomenon also found in other plant species with composite flowers ( Mesquita-Neto et al, 2020 ).…”

Functional Ecology of External Secretory Structures in Rivea ornata (Roxb.) Choisy (Convolvulaceae)

“…Although the petiolar nectaries and calycinal glands of R. ornata are located on different parts of the plant, they appear to have the same function in feeding visitors, especially diverse species of ants. Ants are widely known to be the main nectar consumer of extrafloral nectaries and are generally acknowledged as guards against herbivores [ 9 , 108 , 109 ], but we have not found any reports about ants or other insects visiting secretory organs that function as colleters. Therefore, our study may be the first to report another potential role of calycinal glands, or calycinal colleters, beyond protection from abiotic factors.…”

“…Michelang., Turnera subulata Sm., and Mallotus japonicus (L.f.) Müll.Arg. [ 109 , 112 , 113 , 114 , 115 ], petiolar nectaries and calycinal glands in R. ornata appear to only attract ants on certain parts of the plant. Specifically, in R. ornata , ants gather at the petiolar nectaries and calycinal glands and also traverse stems, branches, petioles, and inflorescence axes, but other parts were left ant-free most of the time (i.e., leaf blades and corolla tubes and lobes), leaving herbivores on these areas (tortoise beetles and katydids) undisturbed by ants.…”

Nectar Secretion, Morphology, Anatomy and Ultrastructure of Floral Nectary in Selected Rubus idaeus L. Varieties

“…The wax present in the cuticle structure increases the permeability and facilitates the release of fat-soluble substances [52,[80][81][82]. The nectary epidermis cuticle in many species of the Prunus perisca has microchannels involved in nectar secretion [72,83,84]. As suggested by Nepi [85], these microstructures support the apoplastic route of nectar secretion onto the nectary surface.…”