Wettability, water absorption and water storage in rosette leaves of the dragon tree ( Dracaena draco L.)
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ORIGINAL ARTICLE
Wettability, water absorption and water storage in rosette leaves of the dragon tree (Dracaena draco L.) Joanna Jura‑Morawiec1 · Jan Marcinkiewicz1 Received: 22 February 2020 / Accepted: 22 July 2020 © The Author(s) 2020
Abstract Main conclusion Leaf surfaces of Dracaena draco are wettable and can absorb water. The thick, basal leaf part could act as a water reservoir that changes in volume with plant hydration. Abstract Rosettes of leaves of Dracaena draco play an important role in directing fog water through leaf axils into the stem tissues, where it can be stored for further use. However, how water is intercepted and collected by the leaves remains unclear, especially since leaf blade surfaces are considered hydrophobic. Based on the observations of D. draco individuals growing in Spain and in glasshouse conditions in Poland, we hypothesised that their long leaves (~ 70 cm) are able to absorb water along the whole leaf blade, but leaf age affects this process. We used water droplet contact angle measurements, anatomical analyses of leaf cross sections along the age gradient and dye tracer experiments to test this hypothesis. The data showed that the leaf surfaces of D. draco are wettable. In general, the mature leaves of the rosette are more wettable than the young ones. Water can be absorbed both through the adaxial and abaxial surfaces. The hydrenchyma is not uniformly distributed along the leaf, it is especially abundant towards the leaf base where it forms a massive water reservoir, which changes in volume depending on plant water status. The results of these studies shed light on the role of rosettes in water absorption by D. draco, and broaden our understanding of the functioning of this vulnerable species. Keywords Anatomy · Arborescent monocots · Contact angle · Hydrenchyma · Leaf water uptake
Introduction The dragon tree, Dracaena draco L., is a giant, tree-like monocotyledon which may grow to as much as 20 m in height. Its trunk branches sympodially and forms an umbrella-like canopy (Beyhl 1995), with apical rosettes of long (40–90 cm) and flexible leaves (Marrero et al. 1998; Fig. 1). D. draco is a vulnerable species, with distribution restricted to the Canary Islands, Cape Verde Islands, Communicated by Dorothea Bartels. Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00425-020-03433-y) contains supplementary material, which is available to authorized users. * Joanna Jura‑Morawiec [email protected] 1
Polish Academy of Sciences Botanical Garden-Centre for Biological Diversity Conservation in Powsin, Prawdziwka 2, 02‑973 Warsaw, Poland
Madeira and Morocco (Marrero et al. 1998). It grows in areas that are affected by northeast trade winds, with rains in winter and relatively dry summers. Fog is a common occurrence and annual rainfall totals about 400 mm (Marrero et al. 1998; Marzol et al. 2011). On the Canary Islands, fog is possible throughout the year, but especially between June and August, i.e., during the rainless, dry
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