Structural features of species of Asteraceae that arouse discussions about adaptation to seasonally dry environments of the Neotropics

Abstract

Seasonally-dry environments of the Neotropics, such as the South American Chaco, exert selective pressures on vegetation through a pronounced water defi cit. We describe the underground system and leaf anatomy of three species of Asteraceae from the Brazilian portion of the Chaco (Pterocaulon purpurascens Malme, Wedelia trichostephia DC., and Pectis gardneri Baker), aiming to describe their structural and adaptive features using standard plant anatomy techniques. Pterocaulon purpurascens and W. trichostephia exhibited slightly thickened xylopodia, with gemmiferous character and self-grafted stem shoots; Pectis gardneri displayed a slightly-thickened tuberous root with storage substances. Longitudinal sequences of cells with highly thickened walls forming globular protrusions were found throughout the extension of the periderm of Pectis gardneri, while senescent trichomes were found in the periderm of W. trichostephia. Schyzogenous aerenchyma was found in P. purpurascens. Aquifer cells, composing vascular rays of secondary phloem and xylem, are reported for this species. Leaves of the three species are perennial and amphistomatic, with aquifer cells in a variety of tissues. Pectis gardneri exhibits a "Kranz-type" anatomy with lignifi ed bristles with stomata. Th e features described for the species play important role in water uptake and/or storage, which prevent excessive water loss during environmental or physiological stress periods.

Leaf architecture and anatomy of Asteraceae species in a xerophytic scrub in Mexico City, Mexico

“…This combination of characters has been related to efficiency in leaf hydraulic conductance (Sack and Scoffoni, 2013;Sack et al, 2015), light absorption (Nikolopoulos et al, 2002) and biomechanical support (Read and Stokes, 2006). Rivera et al (2017) tried to explain leaf variation in this xerophytic scrub associating it with different drought-resistance strategies (Ferraro and Scremin-Dias, 2018). However, their results showed that leaf variation could not be solely explained by dry conditions promoted by the volcanic outcrop rocks.…”

“…For example, anatomical characters, especially of leaves, have been extensively used in the systematics of several plant families, including Bromeliaceae (De Faria et al, 2012), Myrtaceae (Al-Edany and Al-Saadi, 2012), Amaryllidaceae (Lin and Tan, 2015), Malpighiaceae (Araújo et al, 2010) and Asteraceae (Castro et al, 1997;Milan et al, 2006;Adedeji and Jewoola, 2008;Bombo et al, 2012;Akinnubi et al, 2014;Rojas-Leal et al, 2017;Lusa et al, 2018). Particularly in Asteraceae, leaf architecture and anatomical characters are extremely diverse (Bombo et al, 2012;Rojas-Leal et al, 2014, 2018 and have been studied from an ecological (Bercu et al, 2012;Moroney et al, 2013;Rivera et al, 2017;Ferraro and Scremin-Dias, 2018), physiological (Bondarev et al, 2003;McKown and Dengler, 2007;Santiago and Kim, 2009), and medical perspective (Cambi et al, 2006;Hulley et al, 2010;García-Sánchez et al, 2012).…”

“…Evidence suggests that North America, particularly Mexico, has been important for diversification in some of the most diverse lineages of the family (Noyes and Rieseberg, 1999;Suárez-Mota and Villaseñor, 2011;Villaseñor, 2018). Leaf diversity in the family has been associated to variable environmental conditions such as drought (Ferraro and Scremin-Dias, 2018), saline soils (Grigore and Toma, 2006;Bercu et al, 2012) and light conditions (Rossatto and Kolb, 2010). However, the environment alone does not explain the variation in leaf anatomical characters, because some of these as well as most leaf architectural characters can be constrained by the phylogenetic history, the growth form or the ploidy level of the species (Rivera et al, 2017).…”

Anatomía foliar de nueve especies de Tagetes L. (Tageteae: Asteraceae)

“…T. lucida fue la única especie que presentó una vaina de esclerénquima en el haz de la vena media. Como lo mencionan García-Sánchez et al (2012) y Martínez et al (2013), la vaina lignificada es interpretada como una característica adaptativa al proporcionar una protección eficaz contra la alta radiación solar y la sequía fisiológica (Ferraro & Scremin-Dias 2018). Las vainas vasculares participan en diversas funciones metabólicas, de protección contra daños por condiciones de sequía y fuertes vientos (Lapp et al 2013).…”

Chemical profile, antimicrobial activity, and leaf anatomy of Adenophyllum porophyllum var. cancellatum

“…The anatomical characters are more homogeneous within the Tageteae tribe than at the level of the Asteraceae family ( Rivera et al, 2017 ). Nevertheless, trichomes can contribute to the delimitation of species or genera belonging to the Tageteae tribe ( Milan et al, 2006 ; Azevedo, 2007 ; García-Sánchez et al, 2012 ; Ferraro and Scremin-Dias, 2018 ; Rivera et al, 2019 ; Younis et al, 2020 ). In addition, a single central vascular bundle in the midvein and the size and shape of the glands could differentiate A. porphyllum var.…”