Comparative leaf anatomy of Baccharis (Asteraceae) from high-altitude grasslands in Brazil: taxonomic and ecological implications

Abstract

Baccharis L. is an important genus in the high-altitude environments of South America. In the State of Rio de Janeiro, southeastern Brazil, the greatest richness is found at montane and high-montane ecological refuges, known as high-altitude grasslands. The high altitude provides several environmental factors that turn the high-altitude grasslands into singular tropical habitats. In this article we describe the leaf anatomy of six shrubby species of Baccharis, pointing out ecological aspects of the structures, and testing the use of statistical analyses to compare the species. Using light and scanning electron microscopy, we compared the anatomical features of the leaves and performed a cluster and principal component analyses. The results show novel features in the leaf anatomy for the genus, such as an undulated cuticle, three secretory ducts in the midrib, secretory ducts associated with the xylem, and biseriate glandular trichomes with an irregular organization of the cells. Our statistical analyses indicate that the anatomical features of the leaves, especially trichomes, are useful for distinguishing the different species, whereas others, such as isobilateral mesophyll, amphistomatic leaves, and an epidermis with thick cell walls correlate with their high-elevation habitat.

Phyllocnistis furcata sp. nov.: a new species of leaf-miner associated with Baccharis (Asteraceae) from Southern Peru (Lepidoptera, Gracillariidae)

“…Despite histological descriptions of leaves of B. anomala mined by P. ourea not being available, it appears that the remarkable difference between the distribution pattern of the mines of the two species in the leaves of their hosts could be due, at least in part, to differences in leaf anatomy of the two hosts and the ability of the larvae to feed on palisade parenchyma. The organization of the mesophyll in B. alnifolia is isobilateral, with two or three layers of palisade parenchyma in each side and one or two layers of spongy parenchyma in the middle, a pattern reported for several species of Baccharis (Budel et al 2018;Ornellas et al 2019), while the organization of the mesophyll of B. anomala is dorsoventral, with two or three layers of palisade parenchyma and approximately three layers of spongy parenchyma (Budel and Duarte 2008). Given this diversity in leaf tissue structure, additional studies are needed to better understand the ecology and evolution of herbivory in Phyllocnistis.…”

Microscopy and Histochemistry of Leaves and Stems of Baccharis Subgenus Coridifoliae (Asteraceae) Through LM and SEM-EDS

“…However, species such as B. calvescens DC., B. itatiaiae Wawra, B. parvidentata Malag., B. phylicifolia DC. (Ornellas et al, 2019), and B. microdonta DC. (Budel et al, 2018 a ) had smooth cuticle on the adaxial side, and B. uncinella DC.…”

“…Most species of Baccharis have similar morphology, which makes it difficult to identify the species of this complex genus (Budel et al, 2018 a ). Microscopical studies have been performed in order to investigate anatomical markers that support for the quality control of herbal products, since these materials are commonly used and traded in fragmented or pulverized forms (Freire et al, 2007; Budel & Duarte, 2010; Pereira et al, 2014; Barreto et al, 2015; Bobek et al, 2015; Budel et al, 2018 a ; Ornellas et al, 2019).…”

Morphological features of the leaves in clematises as a reflection of their ecological peculiarities

“…The common feature of high-altitudinal plants is relatively thick leaf blades (Kogami et al, 2001;Zarinkamar et al, 2011;Ahmad et al, 2016;Arimy et al, 2017). It was also found that such plants, if compare with the plants from lower altitudes, have lower stomata density (Zarinkamar et al, 2011;Arimy et al, 2017), intensive sclerification around the vascular bundles (Ahmad et al, 2016), thick walls of epidermal cells, and, usually, amphistomatic leaves (Ornellas et al, 2019). From the other hand, in case of sufficient insolation, neutral and filtered shades cause the decrease of leaf thickness and area, leaf weight, stomatal density, palisade cell length, mesophyll thickness, and increase in chlorophyll content, degree of air spaces, adaxial width of palisade cell, and perimeter to area ratio (Buisson & Lee, 1993;Hanba et al, 2002).…”

“…Adaptation to environmental conditions is reflected in the size, orientation, and density of structural elements of the leaf (Pashkevych, 2014;Arimy et al, 2017;Zanão Júnior et al, 2017;Araujo et al, 2019;Ornellas et al, 2019).…”