Leaf ontogenesis of Trembleya phlogiformis DC. (Microlicieae, Melastomataceae): functional aspects and indumentum characterization

Abstract

Leaf ontogenesis is determinant for the establishment and regulation of its structural and functional properties, in addition to being an excellent tool for assignment to different groups of angiosperms. Even though the importance of leaf morphology and anatomy for taxonomic use is well known, few studies have addressed the processes of leaf ontogeny in Melastomataceae. Herein, we sought to define the ontogenetic steps of leaf of Trembleya phlogiformis, highlighting the indumentum, to understand the main functional traits. Shoot apex, young and fully expanded leaves were processed by usual light microscopy procedures. At the first node, leaf primordia are densely covered with trichomes and emergences. The adaxial layer of ground meristem gives rise to the palisade parenchyma, the procambium originates from median layers of ground meristem and the spongy parenchyma develops from abaxial layers of ground meristem. The differentiation of isobilateral mesophyll on leaves of T. phlogiformis, a common feature in Microlicieae, comes from ground meristem stratification. However, T. phlogiformis stands out by showing in the leaf mature spongy parenchyma cells with irregular shapes. The leaf ontogeny reveals distinct mechanisms of cell differentiation and may be important for the establishment of functional adaptive traits.

Three New Species of the Megadiverse Genus Microlicia (Melastomataceae) with Notes on Leaf Anatomy

“…Since amphistomy and hypostomy have been reported in Lavoisiereae (see Silva et al 2018;Carmo et al 2019Carmo et al , 2020Romero et al 2021a), which has species distributed in different microhabitats (Fritsch et al 2004), the tribe can be an excellent model to test the relationship between anatomical leaf traits and vegetation/habitat type. The short-stalked glandular trichomes found in M. arenaria, M. dentisepala, and M. membranacea, referred to as spherical glands here, are typically observed in species of the tribe (Silva et al 2018;Carmo et al 2019Carmo et al , 2020Romero et al 2021aRomero et al , 2021bLima et al 2022). It is important to mention that these spherical glands have been named with different terms such as "glandular punctations" (Wurdack 1981;Koschnitzke and Martins 2007;Pacifico and Almeda 2018), "unfurrowed sessile glands" (Wurdack 1986) glands" (Romero et al 2017), and "gland-tipped trichomes" (Pacifico et al 2020a).…”

“…Anatomical studies have revealed that these glands correspond to short-stalked glandular trichomes and should not be described as sessile (Cassiano et al 2010;Romero and Castro 2014;Romero et al 2015Romero et al , 2017Romero et al , 20192021a;Silva et al 2018;Carmo et al 2019). Additionally, long-stalked glandular trichomes, similar to those found in M. membranacea are described in some taxa (Silva et al 2018;Carmo et al 2019;Lima et al 2022). The leaf indumentum in Lavoisiereae exhibits considerable variation, even within the same species, encompassing different types of glandular and non-glandular trichomes and emergences (see Silva et al 2018;Carmo et al 2019;Lima et al 2022).…”

“…Additionally, long-stalked glandular trichomes, similar to those found in M. membranacea are described in some taxa (Silva et al 2018;Carmo et al 2019;Lima et al 2022). The leaf indumentum in Lavoisiereae exhibits considerable variation, even within the same species, encompassing different types of glandular and non-glandular trichomes and emergences (see Silva et al 2018;Carmo et al 2019;Lima et al 2022). Despite efforts and progress in classifying epidermal appendages within the group (Wurdack 1986;Carmo et al 2019), a comprehensive and systematic review is needed to standardize the indumentum terminology.…”

“…The short-stalked glandular trichomes found in M. arenaria , M. dentisepala, and M. membranacea , referred to as spherical glands here, are typically observed in species of the tribe (Silva et al 2018; Carmo et al 2019, 2020; Romero et al 2021a, 2021b; Lima et al 2022). It is important to mention that these spherical glands have been named with different terms such as “glandular punctations” (Wurdack 1981; Koschnitzke and Martins 2007; Pacifico et al 2017; Pacifico and Almeda 2018), “unfurrowed sessile glands” (Wurdack 1986), “sessile glands” (Romero et al 2014; Pacifico et al 2019b), “short-stalked glands” (Romero et al 2017), and “gland-tipped trichomes” (Pacifico et al 2020a).…”

“…Additionally, they are compared morphologically with similar species, and information is provided about geographic distribution and conservation status, with morphological illustrations included. We also include a discussion on the anatomical features of the leaf lamina, as these data provide a solid basis for understanding the diversity of leaf indumentum in Lavoisiereae (see Romero and Castro 2014;Romero et al 2015Romero et al , 2017Romero et al , 2019Romero et al , 2021aSilva et al 2018;Carmo et al 2019) and for identifying adaptive characteristics related to the environment occupied by species of this tribe (Carmo et al 2020;Lima et al 2022), which are predominantly found in the campo rupestre and cerrado of Brazil (Versiane et al 2021). In addition, leaf anatomy data has been used to delimit clades in Lavoisiereae (see Silva et al 2018;Carmo et al 2019Carmo et al , 2020Pacifico et al 2019a).…”