Abstract
Main conclusionLeaf 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.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.
Highlights
The dragon tree, Dracaena draco L., is a giant, tree-like monocotyledon which may grow to as much as 20 m in height
D. draco is a vulnerable species, with distribution restricted to the Canary Islands, Cape Verde Islands, Communicated by Dorothea Bartels
The anatomy of only the mid-sections of D. draco leaves has been studied, we know that the leaves are slightly succulent and contain hydrenchyma, an achlorophyllous water-storage tissue (Klimko et al 2018)
Summary
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). 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 season (Marzol et al 2011). The leaves of D. draco may store water. The anatomy of only the mid-sections of D. draco leaves has been studied, we know that the leaves are slightly succulent and contain hydrenchyma, an achlorophyllous water-storage tissue (Klimko et al 2018)
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