Leaf teeth in eudicots: what can anatomy elucidate?

Abstract

Leaf teeth are projections on the leaf blade margin. They are structurally variable, with characters that are important for taxonomy and phylogeny, but there is a paucity of information on the anatomy of these structures and little understanding of the features and their functions. Here we describe and compare the leaf tooth anatomy of 47 eudicot species. Toothed margin samples from leaves at different developmental stages were collected, fixed and studied under light and scanning electron microscopy. We identified eight leaf tooth morphotypes, six of which occurred with glands. Hydathodes were the most common glands, being found in 11 species; colleters were found in ten species and extrafloral nectaries were found in two species. Cunonioid teeth either devoid of glands or associated with hydathodes were found in Lamiales, Asterales and Apiales. Dillenioid teeth associated with hydathodes were found in Dilleniales. Spinose teeth associated with colleters were found in Aquifoliales. In rosids, we found begonioid, malvoid, theoid, urticoid and violoid teeth, which may be associated with either colleters or nectaries or lack an associated gland. For each family studied, there was only one type of association between gland and tooth, demonstrating the systematic potential of these glands in eudicots.

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

“…Given that serrate leaves are a remarkable character for Ouratea [30], it seems reasonable to suppose that colleters, which occur at the apex of each marginal tooth, are a characteristic shared by several species of this genus. The report of marginal colleters in Luxemburgia, together with recent data showing a high correlation between leaf teeth and glands in eudicots [17], might corroborate this hypothesis.…”

“…Marginal glands, however, are commonly reported in Sauvagesia [ 15 , 27 , 28 ] and several additional genera of the subfamily Sauvagesioideae [ 14 ]. Recently, Rios et al [ 17 ] also demonstrated marginal colleters in two species of Luxemburgia . Nonetheless, data on the anatomy, ultrastructure, and secretory activity of these structures is lacking, and the present description appears to be unprecedented, to the best of our knowledge.…”

“…Knowledge regarding chemical defenses in shoot buds of Ochnaceae is far from comprehensive, although nectar secretion in scales and stipules of some taxa is well known. Many authors have recently reported the presence of glands in the family [ 14 , 15 , 16 , 17 ], sometimes relating them to bud protection [ 16 ]. Nevertheless, many aspects of secretion in the family are still poorly understood.…”

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 ].…”

Revisiting an ecophysiological oddity: Hydathode‐mediated foliar water uptake in Crassula species from southern Africa

“…Hydathodes (i.e., hydathodes sensu stricto or epithemal hydathodes; for review see Cerutti et al, 2019) are often overlooked foliar structures that are relatively common among vascular plants, being responsible for the process of guttation (i.e., the exudation of apoplastic fluid; Bellenot et al, 2022). Marginal and apical hydathodes are the most prevalent (Cerutti et al, 2019; Jauneau et al, 2020; Rios et al, 2020), while laminar hydathodes, which are found over the entire leaf surface, seem to be restricted to Crassulaceae and three other eudicot families that have very few or no succulent representatives: Moraceae, Urticaceae and Myrothamnaceae (Chen & Chen, 2005; Drennan et al, 2009; Lersten & Curtis, 1991; Lersten & Peterson, 1974). The noteworthy anatomy of hydathodes in Crassula and their contrasting foliar distribution among different species have led to several exquisitely illustrated publications through the years (de Bary, 1884; Rost, 1969; Smirnova, 1973; Sporer, 1915; Voronin et al, 1976).…”