The upside-down water collection system of Syntrichia caninervis

Abstract

Desert plants possess highly evolved water conservation and transport systems, from the root structures that maximize absorption of scarce ground water15, to the minimization of leaf surface area6 to enhance water retention. Recent attention has focused on leaf structures that are adapted to collect water and promote nucleation from humid air79. Syntrichia caninervis Mitt. (Pottiaceae) is one of the most abundant desert mosses in the world and thrives in an extreme environment with multiple but limited water resources (such as dew, fog, snow and rain), yet the mechanisms for water collection and transport have never been completely revealed. S. caninervis has a unique adaptation: it uses a tiny hair (awn) on the end of each leaf to collect water, in addition to that collected by the leaves themselves. Here we show that the unique multiscale structures of the hair are equipped to collect and transport water in four modes: nucleation of water droplets and films on the leaf hair from humid atmospheres; collection of fog droplets on leaf hairs; collection of splash water from raindrops; and transportation of the acquired water to the leaf itself. Fluid nucleation is accomplished in nanostructures, whereas fog droplets are gathered in areas where a high density of small barbs are present and then quickly transported to the leaf at the base of the hair. Our observations reveal nature's optimization of water collection by coupling relevant multiscale physical plant structures with multiscale sources of water.

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Figure 1: Morphology of S. caninervis and the associated awns.
Figure 2: Nucleation of dew on a moss awn surface.
Figure 3: Fog collection on an awn of S. caninervis.
Figure 4: Multifunctional hierarchical water harvest mechanisms of the moss awn.

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Acknowledgements

We want to thank M. Standing for providing SEM/ESEM support, L. Allphin-Rapier for providing ideas and discussions, Z. Aanderud and his students for providing samples, A. Downing for proof reading and BYU internal support for Z.P. and the SEM/ESEM experiments. The work of Y.Z., N.W. and Y.T. were funded by the National Basic Research Program of China (2014CB954202).

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Contributions

N.W. and Y.Z. originated the research on S. caninervis and provided anatomical studies, both macro and microscopic. Z.P., T.T.T. and W.G.P. designed the experiments, and Z.P. and T.T.T. performed the experiments and analysed the data. Z.P and W.G.P. proposed the mechanisms of nucleation on the moss awn. W.G.P., Z.P. and T.T.T. wrote the text.

Corresponding author

Correspondence to Tadd T. Truscott.

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The authors declare that they have no competing financial interests.

Supplementary information

Supplementary Information

Supplementary Section ‘Dew nucleation and fog droplet collection in a groove’, Supplementary References, Supplementary Figs 1–3 and captions for Supplementary Videos 1–5. (PDF 1448 kb)

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Supplementary Video 1 (MP4 383 kb)

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Supplementary Video 2 (MP4 480 kb)

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Supplementary Video 3 (MP4 22053 kb)

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Supplementary Video 4 (MP4 2722 kb)

Supplementary Video

Supplementary Video 5 (MP4 1309 kb)

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Pan, Z., Pitt, W., Zhang, Y. et al. The upside-down water collection system of Syntrichia caninervis. Nature Plants 2, 16076 (2016). https://doi.org/10.1038/nplants.2016.76

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