Wood anatomy of the neotropical liana lineage Paullinia L. (Sapindaceae)

Abstract

<jats:title>Abstract</jats:title> <jats:p>The liana genus <jats:italic>Paullinia</jats:italic> L. is one of the most speciose in the neotropics and is unusual in its diversity of stem macromorphologies and cambial conformations. These so-called “vascular cambial variants” are morphologically disparate, evolutionarily labile, and are implicated in injury repair and flexibility. In this study, we explore at the finer scale how wood anatomy translates into functions related to the climbing habit. We present the wood anatomy of <jats:italic>Paullinia</jats:italic> and discuss the functional implications of key anatomical features. Wood anatomy characters were surveyed for 21 <jats:italic>Paullinia</jats:italic> species through detailed anatomical study. <jats:italic>Paullinia</jats:italic> woods have dimorphic vessels, rays of two size classes, and both septate and non-septate fibers. Fibriform vessels, fusiform axial parenchyma, and elements morphologically intermediate between fibers and axial parenchyma were observed. Prismatic crystals are common in the axial and/or ray parenchyma, and laticifers are present in the cortex and/or the early-formed secondary phloem. Some features appear as unique to <jats:italic>Paullinia</jats:italic> or the Sapindaceae, such as the paucity of axial parenchyma and the abundance of starch storing fibers. Although many features are conserved across the genus, the <jats:italic>Paullinia</jats:italic> wood anatomy converges on several features of the liana-specific functional anatomy expressed across distantly related lianas, demonstrating an example of convergent evolution. Hence, the conservation of wood anatomy in <jats:italic>Paullinia</jats:italic> suggests a combination of phylogenetic constraint as a member of Sapindaceae and functional constraint from the liana habit.</jats:p>

Climbing since the early Miocene: The fossil record of Paullinieae (Sapindaceae)

“…The combination of peripheral vascular strands (Figs 2A–2C and 4A & 4B ), vessel dimorphism (Figs 2F & 2I and 4B–4D ), wide vessels solitary or in tangential multiples of 2–3 ( Fig 2F and 4C ), narrow vessels in long radial multiples of 2–21 (Figs 2F and 4C & 4D ), alternate intervessel pits with slit-like coalescent apertures (Figs 2G and 2H and 4E ), heterocellular rays, prismatic crystals in axial parenchyma (Figs 3D and 4F ), and dark content (possibly phenolic compounds) in primary vascular parenchyma and ray parenchyma ( Fig 2D and 2E ) support the inclusion of Ampelorhiza in Paullinieae [ 13 , 16 , 18 , 64 , 66 , 92 , 93 , 94 ]. Two wood anatomical characters typical of extant Paullinieae were not observed in the fossils: 1) alternating bands of thin and thick-walled regions in the wood which may either be axial parenchyma alternating with ordinary fibers (e.g., Serjania spp.)…”

“…Terminology and measurement protocols for the wood anatomy generally follow the IAWA Hardwood List [ 56 ] but we adapted our approach for characters particular to Paullinieae [ 64 ]. Summary statistics for anatomical characters were calculated from 25 measurements.…”

“…We then obtained wood anatomy data for 11 terminals from [ 13 ] and 33 terminals from [ 64 ], and one terminal from [ 20 ], now available on morphobank ( morphobank.org/permalink/?P3910 ), and scored the fossil for 22 out of the 27 anatomy characters. Finally, we added the character “habit” (0 = self-supporter, 1 = climber) and scored it for all extant species.…”

Polishing entire stems and roots using sandpaper under water: An alternative method for macroscopic analyses

“…Note the increase in vessel width from the center to the periphery. Finally, the stem of Serjania lethalis exhibits the typical compound structure of many Sapindaceae lianas (Tamaio and Angyalossy, 2009; Pellissari et al, 2018; Chery et al, 2020a, b), in this particular case with a central cylinder surrounded by three peripheral cylinders (Fig. 1G).…”

The role of ontogeny in wood diversity and evolution

“…ap, axial parenchyma; ie, intermediary element; lv, libiriform vessel. A: Modified from Chery et al (2020a) with permission. B: Courtesy of Marina Victorio…”