Colleters, Extrafloral Nectaries, and Resin Glands Protect Buds and Young Leaves of Ouratea castaneifolia (DC.) Engl. (Ochnaceae)

Abstract

Buds usually possess mechanical or chemical protection and may also have secretory structures. We discovered an intricate secretory system in Ouratea castaneifolia (Ochnaceae) related to the protection of buds and young leaves. We studied this system, focusing on the distribution, morphology, histochemistry, and ultrastructure of glands during sprouting. Samples of buds and leaves were processed following the usual procedures for light and electron microscopy. Overlapping bud scales protect dormant buds, and each young leaf is covered with a pair of stipules. Stipules and scales possess a resin gland, while the former also possess an extrafloral nectary. Despite their distinct secretions, these glands are similar and comprise secreting palisade epidermis. Young leaves also possess marginal colleters. All the studied glands shared some structural traits, including palisade secretory epidermis and the absence of stomata. Secretory activity is carried out by epidermal cells. Functionally, the activity of these glands is synchronous with the young and vulnerable stage of vegetative organs. This is the first report of colleters and resin glands for O. castaneifolia. We found evidence that these glands are correlated with protection against herbivores and/or abiotic agents during a developmental stage that precedes the establishment of mechanical defenses.

An overview of secretion in floral bracts of Tillandsioideae (Bromeliaceae), with emphasis on the secretory scales

“…2015 ). In this sense, the secretory trichomes in the adaxial surface of floral bracts likely act as colleters, producing an exudate that covers the young portions and avoid desiccation, herbivores or pathogens ( Thomas 1991 ; Paiva 2012 ; Mayer et al 2013 ; Tresmondi et al 2015 ; Paiva et al . 2021 ; Gonçalves et al 2022 ; see also Ballego-Campos et al .…”

First Report of Colleters in Araceae: A Case Study in Anthurium andraeanum Reveals Diverse Mucilage Glands Associated with the Developing Shoot

“…Secretory structures in leaf apexes or the tips of marginal teeth are not unusual, with records including extrafloral nectaries, hydathodes, and colleters [ 26 , 27 , 28 , 29 ]. Specifically, the presence of colleters in leaf apexes or marginal teeth is reported for Aquifoliaceae, Caryocaraceae, Celastraceae, Euphorbiaceae, Lechytidaceae, Ochnaceae, and Turneraceae [ 16 , 29 , 30 , 31 ], thus comprising a common position for foliar colleters. In Araceae, there is evidence of hydathodes at the leaf tip of Colocasia esculenta L. [ 4 , 27 ].…”

“…Many of the functions attributed to colleters are controversial and may be restricted to particular cases; lubrication and protection of meristems and young organs, protection against desiccation, the facilitation of symbiotic processes, and protection against herbivores stand out as the most studied (see [ 13 ] and references therein). Among these functions, protection against excessive water loss seems to be the most relevant, as suggested by several authors and in different taxonomic groups [ 14 , 15 , 16 , 17 ]. Colleters present great structural diversity, ranging from simple trichomes to complex structures [ 14 ].…”

Unravelling the Homology between Calycine Glands in Malpighiales: New Data from Basal Malpighiaceae

“…Note that calycine nectaries are not described for clade 2. Superscript numbers after the genera whose flowers are illustrated indicate the data source: 1 Farias et al [30]; 2 Almeida [29]; 3 Narayana and Rao [31]; 4 Knapp and Mallet [32]; 5 Wurdack and Zartman [36]; 6 Prance and White [37]; 7 Niedenzu [42]; 8 Bonifácio et al [39]; 9 Castro et al [24]; 10 This work; 11 Oliveira [40]. Abbreviations: cn, calycine nectary; cn*, calycine nectary not confirmed by histochemical tests; el, elaiophore.…”