Palm snorkelling: leaf bases as aeration structures in the mangrove palm (Nypa fruticans)

Abstract

We thank Paula Rudall and Jeremy Aroles for critical reading of the manuscript. The first author expresses his gratitude to P. B. Tomlinson, who not only proposed the hypothesis investigated in this study, but also provided the opportunity to investigate it. Patrick Griffith is acknowledged for permission and technical help to collect Nypa material at the Montgomery Botanical Center (MBC), Miami, FL, USA, and Larry Noblick for providing phenological data on N.fruticans growing at MBC. The National Botanical Tropical Gardens (NTBG) is thanked for a scholarship to G.C. in 2009. Two anonymous reviewers are thanked for comments on the manuscript. We wish to dedicate this paper to P. B. Tomlinson and his remarkable career in the structure of plants and, in particular, palms. Wiley-blackwell HobokenMangrove species have evolved specialized structures, such as pneumatophores, to supply oxygen to the roots, but, in Nypa fruticans, the only mangrove palm, no such structure has been reported. This study aimed to determine the adaptations of N.fruticans to the mangal habitat with special reference to the air-supplying structure. Following senescence, the rachis is abscised at the zone of junction with the leaf base. Simultaneously, lenticels develop so that, when abscission is completed, a network of mature lenticels covers the leaf base. Expansigenous aerenchyma with increasing porosity towards the stem junction occurs in the leaf base. The first two root branching orders present a subero-lignified rhizodermis and exodermis, and the cortex consists of schizo-lysigenous aerenchyma with wide lacuna, limiting radial oxygen loss and facilitating longitudinal oxygen transport to living tissues. Lifespan estimation suggests that leaf bases can live for up to 4years following abscission, ensuring the persistence of aeration structures. This study provides structural evidence indicating that N.fruticans has evolved a unique type of air-supplying structure in the mangal habitat.(c) 2013 The Linnean Society of London, Botanical Journal of the Linnean Society, 2014, 174, 257-270

Mangrove root: adaptations and ecological importance

“…N. fruticans Wurmb. is the only extant mangrove palm which has no specialized root structures to provide oxygen supply to the submerged roots (Chomicki et al 2014). Since Nypa does not produce any breathing roots, it is believed that the leaves play the role of a 'giant pneumatophore', as they are the only emergent parts of the plant (Tomlinson 1994).…”

“…Soon after, these leaf bases will develop aerenchyma with increasing porosity towards the stem junction. Subsequently, a network of mature lenticels covers the leaf base and connects with aerenchyma network which helps in gases exchange up to 4 years following abscission (Chomicki et al 2014).…”

Ventilation Systems in Wetland Plant Species

“…or "snorkeling palm" adapted to life in mangrove forests; usually only the leaves appear above the water surface. These leaves eventually abscise when aging, but the leaf bases remain, and function as air inlets by developing a network of lenticels covering the leaf base [96]. These lenticels are connected with expansigenous aerenchyma [96].…”

“…These leaves eventually abscise when aging, but the leaf bases remain, and function as air inlets by developing a network of lenticels covering the leaf base [96]. These lenticels are connected with expansigenous aerenchyma [96]. The lenticels allow gases through, but prevent the entry of fluid water.…”

“…The mature crown may contain 6 to 8 living leaves, and 12 to 15 bulbous leaf bases at a time [97]. These leaf bases can function for up to 4 years after leaf abscission [96].…”