Leaf anatomy is associated with the type of growth form in Neotropical savanna plants

Abstract

Scleromorphic leaf structures are associated with plants growing under drought-prone conditions, high irradiances and nutrient-poor soils. Sclerophylly can also be a valuable deterrent against herbivores. However, comprehensive studies of leaf anatomical traits encompassing different growth forms are lacking. The savannas of central Brazil (Cerrado) are characterized by high species diversity and a variety of growth forms. We performed a field study to characterize leaf anatomical traits and leaf mass per area (LMA) in 57 cooccurring Cerrado species of distinct plant families (located at different positions in the angiosperm phylogeny) and categorized according to the following growth forms: trees, palms, shrubs, subshrubs, vines, grasses and herbs. Plant growth form and leaf structure were interrelated. Four groups with distinct leaf anatomical syndromes were identified: grasses, palms, herbaceous (herbs, vines and most subshrubs) and woody (trees and shrubs) plants.Trees and shrubs had scleromorphic dorsiventral leaves, with high tissue thickness and LMA.Herbaceous plants had thin, mesomorphic leaves. While most herbaceous plants had dorsiventral type of mesophyll, grasses and palms had homogenous mesophyll with sclerenchymatous bundle sheath extensions. Palms differed from grasses by having thicker leaves and sclerenchymatous hypodermis. In conclusion, Neotropical savannas cannot be exclusively described as scleromorphic vegetation.

Leaf anatomical traits of non-arboreal savanna species along a gradient of tree encroachment

“…Similar qualitative patterns were described in previous studies dealing with trees in Southeastern Brazil (Bieras & Sajo 2009), and for nonarboreal plants of a savanna site in Central Brazil (Rossatto et al 2015). These aspects may suggest a conservative pattern in the qualitative aspects of leaf structure in angiosperms, as previously reported by Brodribb et al (2010).…”

“…irradiance conditions (Rossatto & Franco 2017). Despite the fact that this pattern was clearly observed in the set of typical savanna species studied here, their values of SLA were higher and their tissue thicknesses were lower than those reported for typical non-arboreal savanna species in Central Brazil (see the study by Rossatto et al 2015). This difference may have arisen because the savannas in Southeast Brazil have a lower degree of seasonality and more nutrients in their soils, a condition that can select less scleromorphic leaves (Souza et al 2015).…”

“…It is well established in the literature that woody savanna plants have leaves with xero-and scleromorphic aspects, possessing normally thick cuticles and epidermis, and large amounts of palisade parenchyma (Bieras & Sajo 2009;Rossatto et al 2015); traits that are mainly found when light irradiances are high (Givnish 1988;Rossatto & Kolb 2010). The same pattern occurs in some non-arboreal species; however, there is a wide variation in leaf anatomical traits of these plants, ranging from thinner mesomorphic leaves to leaves with some xeromorphic traits (Rossatto et al 2015).…”

“…The same pattern occurs in some non-arboreal species; however, there is a wide variation in leaf anatomical traits of these plants, ranging from thinner mesomorphic leaves to leaves with some xeromorphic traits (Rossatto et al 2015). The study of Rossatto et al (2015) evaluated such leaf anatomical traits in a typical savanna area without encroachment.…”

“…The same pattern occurs in some non-arboreal species; however, there is a wide variation in leaf anatomical traits of these plants, ranging from thinner mesomorphic leaves to leaves with some xeromorphic traits (Rossatto et al 2015). The study of Rossatto et al (2015) evaluated such leaf anatomical traits in a typical savanna area without encroachment. However, a more detailed description of leaf structural strategies in sites with and without encroachment may shed light on the causes of the disappearance of these non-arboreal typical savanna plants given the widespread tree encroachment in savanna areas under fire absence (Stevens et al 2017).…”