Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Advanced vascular function discovered in a widespread moss


The evolution of terrestrial plants capable of growing upwards into the dry atmosphere profoundly transformed the Earth. A transition from small, ‘non-vascular’ bryophytes to arborescent vascular plants during the Devonian period is partially attributed to the evolutionary innovation of an internal vascular system capable of functioning under the substantial water tension associated with vascular water transport. Here, we show that vascular function in one of the most widespread living bryophytes (Polytrichum commune) exhibits strong functional parallels with the vascular systems of higher plants. These parallels include vascular conduits in Polytrichum that resist buckling while transporting water under tension, and leaves capable of regulating transpiration, permitting photosynthetic gas exchange without cavitation inside the vascular system. The advanced vascular function discovered in this tallest bryophyte family contrasts with the highly inefficient water use found in their leaves, emphasizing the importance of stomatal evolution enabling photosynthesis far above the soil surface.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Fig. 1: P. commune vascular tissue is capable of sustaining large hydraulic tension without collapsing.
Fig. 2: The water transport system in P. commune shows a pattern of vulnerability to cavitation-induced failure similar to that seen in vascular plants.
Fig. 3: Similar to vascular plants, the leaves of P. commune regulate water loss during water stress to delay the onset of damaging cavitation in the water transport system.
Fig. 4: Compared to vascular plants, photosynthesis in P. commune is highly sensitive to humidity as a result of its intrinsically inefficient exchange of water vapour for CO2.

Data availability

All processed data are contained in the manuscript or Extended Data. Raw images and image sequences can be supplied upon request from the corresponding author.


  1. 1.

    Kenrick, P. & Crane, P. R. The origin and early evolution of plants on land. Nature 389, 33–39 (1997).

    CAS  Google Scholar 

  2. 2.

    Edwards, D., Davies, K. L. & Axe, L. A vascular conducting strand in the early land plant Cooksonia. Nature 357, 683–685 (1992).

    Google Scholar 

  3. 3.

    Lang, W. H. IV—On the plant-remains from the Downtonian of England and Wales. Philos. Trans. R. Soc. Lond. B 227, 245–291 (1937).

    Google Scholar 

  4. 4.

    Renzaglia, K., McFarland, K. & Smith, D. Anatomy and ultrastructure of the sporophyte of Takakia ceratophylla (Bryophyta). Am. J. Bot. 84, 1337–1350 (1997).

    Google Scholar 

  5. 5.

    Stein, W. E., Mannolini, F., Hernick, L. V., Landing, E. & Berry, C. M. Giant cladoxylopsid trees resolve the enigma of the Earth’s earliest forest stumps at Gilboa. Nature 446, 904–907 (2007).

    CAS  PubMed  Google Scholar 

  6. 6.

    Harrison, C. J. & Morris, J. L. The origin and early evolution of vascular plant shoots and leaves. Phil. Trans. R. Soc. Lond. B 373, 20160496 (2017).

    Google Scholar 

  7. 7.

    Carlquist, S. J. Ecological Strategies of Xylem Evolution (Univ. of California Press, 1975).

  8. 8.

    Raven, J. A. Evolution of vascular land plants in relation to supracellular transport processes. Adv. Bot. Res. 5, 153–219 (1977).

    CAS  Google Scholar 

  9. 9.

    Duckett, J. G. & Pressel, S. The evolution of the stomatal apparatus: intercellular spaces and sporophyte water relations in bryophytes—two ignored dimensions. Phil. Trans. R. Soc. B 373, 20160498 (2017).

    Google Scholar 

  10. 10.

    Bowman, J. L. et al. Insights into land plant evolution garnered from the Marchantia polymorpha genome. Cell 171, 287–304 (2017).

    CAS  PubMed  Google Scholar 

  11. 11.

    Xu, B. et al. Contribution of NAC transcription factors to plant adaptation to land. Science 343, 1505–1508 (2014).

    CAS  PubMed  Google Scholar 

  12. 12.

    Honkanen, S., Thamm, A., Arteaga-Vazquez, M. A. & Dolan, L. Negative regulation of conserved RSL class I bHLH transcription factors evolved independently among land plants. eLife 7, e38529 (2018).

    PubMed  PubMed Central  Google Scholar 

  13. 13.

    Ohtani, M., Akiyoshi, N., Takenaka, Y., Sano, R. & Demura, T. Evolution of plant conducting cells: perspectives from key regulators of vascular cell differentiation. J. Exp. Bot. 68, 17–26 (2017).

    CAS  PubMed  Google Scholar 

  14. 14.

    Hébant, C. The Conducting Tissues of Bryophytes (J. Cramer, 1977).

  15. 15.

    Edwards, D., Axe, L. & Duckett, J. Diversity in conducting cells in early land plants and comparisons with extant bryophytes. Bot. J. Linn. Soc. 141, 297–347 (2003).

    Google Scholar 

  16. 16.

    Haberlandt, G. Beiträge zur Anatomie und Physiologie der Laubmoose. Jahrb. Wiss. Bot. 17, 359–498 (1886).

    Google Scholar 

  17. 17.

    Tansley, A. G. & Chick, E. Notes on the conducting tissue-system in Bryophyta. Ann. Bot. 15, 1–38 (1901).

    Google Scholar 

  18. 18.

    Atala, C. Water transport and gas exchange in the non-vascular plant Dendroligotrichum dendroides (Brid. ex Hedw.) Broth. (Polytrichaceae, Bryophyta). Gayana Bot. 68, 89–92 (2011).

    Google Scholar 

  19. 19.

    Blaikley, N. M. Absorption and conduction of water and transpiration in Polytrichum commune. Ann. Bot. 46, 289–300 (1932).

    Google Scholar 

  20. 20.

    Ligrone, R., Duckett, J. & Renzaglia, K. Conducting tissues and phyletic relationships of bryophytes. Phil. Trans. R. Soc. Lond. B 355, 795–813 (2000).

    CAS  Google Scholar 

  21. 21.

    Vanderpoorten, A. & Goffinet, B. Introduction to Bryophytes (Cambridge Univ. Press, 2009).

  22. 22.

    Tyree, M. T. & Zimmermann, M. H. Xylem Structure and the Ascent of Sap (Springer Science & Business Media, 2013).

  23. 23.

    Weng, J. K. & Chapple, C. The origin and evolution of lignin biosynthesis. New Phytol. 187, 273–285 (2010).

    CAS  PubMed  Google Scholar 

  24. 24.

    Espiñeira, J. et al. Distribution of lignin monomers and the evolution of lignification among lower plants. Plant Biol. 13, 59–68 (2011).

    PubMed  Google Scholar 

  25. 25.

    Martin StPaul, N., Delzon, S. & Cochard, H. Plant resistance to drought depends on timely stomatal closure. Ecol. Lett. 20, 1437–1447 (2017).

    PubMed  Google Scholar 

  26. 26.

    Ligrone, R., Carafa, A., Duckett, J., Renzaglia, K. & Ruel, K. Immunocytochemical detection of lignin-related epitopes in cell walls in bryophytes and the charalean alga Nitella. Plant Syst. Evol. 270, 257–272 (2008).

    CAS  Google Scholar 

  27. 27.

    Brodribb, T. J., Feild, T. S. & Jordan, G. J. Leaf maximum photosynthetic rate and venation are linked by hydraulics. Plant Physiol. 144, 1890–1898 (2007).

    CAS  PubMed  PubMed Central  Google Scholar 

  28. 28.

    Becker, P., Tyree, M. T. & Tsuda, M. Hydraulic conductances of angiosperms versus conifers: similar transport sufficiency at the whole-plant level. Tree Physiol. 19, 445–452 (1999).

    PubMed  Google Scholar 

  29. 29.

    Sperry, J. S. & Tyree, M. T. Mechanism of water stress-induced xylem embolism. Plant Physiol. 88, 581–587 (1988).

    CAS  PubMed  PubMed Central  Google Scholar 

  30. 30.

    Choat, B. et al. Global convergence in the vulnerability of forests to drought. Nature 491, 752 (2012).

    CAS  PubMed  Google Scholar 

  31. 31.

    Lenne, T., Bryant, G., Hocart, C. H., Huang, C. X. & Ball, M. C. Freeze avoidance: a dehydrating moss gathers no ice. Plant Cell Environ. 33, 1731–1741 (2010).

    CAS  PubMed  Google Scholar 

  32. 32.

    Cardoso, A. A., Brodribb, T. J., Lucani, C. J., DaMatta, F. M. & McAdam, S. A. Coordinated plasticity maintains hydraulic safety in sunflower leaves. Plant Cell Environ. 41, 2567–2576 (2018).

    CAS  PubMed  Google Scholar 

  33. 33.

    Cochard, H., Casella, E. & Mencuccini, M. Xylem vulnerability to cavitation varies among poplar and willow clones and correlates with yield. Tree Physiol. 27, 1761–1767 (2007).

    PubMed  Google Scholar 

  34. 34.

    Rolland, V. et al. Easy come, easy go: capillary forces enable rapid refilling of embolized primary xylem vessels. Plant Physiol. 168, 1636–1647 (2015).

    CAS  PubMed  PubMed Central  Google Scholar 

  35. 35.

    Cochard, H., Coll, L., Le Roux, X. & Améglio, T. Unraveling the effects of plant hydraulics on stomatal closure during water stress in walnut. Plant Physiol. 128, 282–290 (2002).

    CAS  PubMed  PubMed Central  Google Scholar 

  36. 36.

    Brodribb, T. J. & McAdam, S. A. Evolution of the stomatal regulation of plant water content. Plant Physiol. 174, 639–649 (2017).

    CAS  PubMed  PubMed Central  Google Scholar 

  37. 37.

    Bayfield, N. G. Notes on water relations of Polytrichum commune Hedw. J. Bryol. 7, 607–617 (1973).

    Google Scholar 

  38. 38.

    Clayton-Greene, K., Collins, N., Green, T. & Proctor, M. Surface wax, structure and function in leaves of Polytrichaceae. J. Bryol. 13, 549–562 (1985).

    Google Scholar 

  39. 39.

    Carriquí, M. et al. Anatomical constraints to non-stomatal diffusion conductance and photosynthesis in lycophytes and bryophytes. New Phytol. (2019).

    PubMed  Google Scholar 

  40. 40.

    Pressel, S. & Duckett, J. G. Do motile spermatozoids limit the effectiveness of sexual reproduction in bryophytes? Not in the liverwort Marchantia polymorpha. J. Syst. Evol. 57, 371–381 (2019).

    Google Scholar 

  41. 41.

    Essig, F. B. Plant Life: A Brief History (Oxford Univ. Press, 2015).

  42. 42.

    Brodribb, T. J. & Cochard, H. Hydraulic failure defines the recovery and point of death in water-stressed conifers. Plant Physiol. 149, 575–584 (2009).

    CAS  PubMed  PubMed Central  Google Scholar 

  43. 43.

    Brodribb, T. J., Carriqui, M., Delzon, S. & Lucani, C. Optical measurement of stem xylem vulnerability. Plant Physiol. 174, 2054–2061 (2017).

    CAS  PubMed  PubMed Central  Google Scholar 

  44. 44.

    Sarafis, V. A biological account of Polytrichum commune. N. Z. J. Bot. 9, 711–724 (1971).

    Google Scholar 

  45. 45.

    Pammenter, Nv & Van der Willigen, C. A mathematical and statistical analysis of the curves illustrating vulnerability of xylem to cavitation. Tree Physiol. 18, 589–593 (1998).

    PubMed  Google Scholar 

  46. 46.

    King, A. et al. Tomography and imaging at the PSICHE beam line of the SOLEIL synchrotron. Rev. Sci. Instrum. 87, 093704 (2016).

    CAS  PubMed  Google Scholar 

  47. 47.

    Paganin, D., Mayo, S., Gureyev, T. E., Miller, P. R. & Wilkins, S. W. Simultaneous phase and amplitude extraction from a single defocused image of a homogeneous object. J. Microsc. 206, 33–40 (2002).

    CAS  PubMed  Google Scholar 

  48. 48.

    Mirone, A., Brun, E., Gouillart, E., Tafforeau, P. & Kieffer, J. The PyHST2 hybrid distributed code for high speed tomographic reconstruction with iterative reconstruction and a priori knowledge capabilities. Nucl. Instrum. Methods Phys. Res. B 324, 41–48 (2014).

    CAS  Google Scholar 

  49. 49.

    Van den Honert, T. Water transport in plants as a catenary process. Discuss. Faraday Soc. 3, 146–153 (1948).

    Google Scholar 

  50. 50.

    McAdam, S. A. M. & Brodribb, T. J. Ancestral stomatal control results in a canalization of fern and lycophyte adaptation to drought. New Phytol. 198, 429–441 (2013).

    CAS  PubMed  Google Scholar 

  51. 51.

    McAdam, S. A. M. & Brodribb, T. J. Linking turgor with ABA biosynthesis: implications for stomatal responses to vapour pressure deficit across land plants. Plant Physiol. 171, 2008–2016 (2016).

    CAS  PubMed  PubMed Central  Google Scholar 

  52. 52.

    Brodribb, T. J. & McAdam, S. A. M. Passive origins of stomatal control in vascular plants. Science 331, 582–585 (2011).

    CAS  PubMed  Google Scholar 

  53. 53.

    McAdam, S. A. M. & Brodribb, T. J. Separating active and passive influences on stomatal control of transpiration. Plant Physiol. 164, 1578–1586 (2014).

    CAS  PubMed  PubMed Central  Google Scholar 

  54. 54.

    McAdam, S. A. M. & Brodribb, T. J. The evolution of mechanisms driving the stomatal response to vapour pressure deficit. Plant Physiol. 167, 833–843 (2015).

    CAS  PubMed  PubMed Central  Google Scholar 

  55. 55.

    Campany, C. E., Martin, L. & Watkins, J. J. E. Convergence of ecophysiological traits drives floristic composition of early lineage vascular plants in a tropical forest floor. Ann. Bot. 123, 793–803 (2019).

    CAS  PubMed  Google Scholar 

  56. 56.

    Soni, D. K. et al. Photosynthetic characteristics and the response of stomata to environmental determinants and ABA in Selaginella bryopteris, a resurrection spike moss species. Plant Sci. 191–192, 43–52 (2012).

    PubMed  Google Scholar 

  57. 57.

    Doi, M., Kitagawa, Y. & Shimazaki, K.-i Stomatal blue light response is present in early vascular plants. Plant Physiol. 169, 1205–1213 (2015).

    PubMed  PubMed Central  Google Scholar 

  58. 58.

    Zier, J., Belanger, B., Trahan, G. & Watkins, J. E. Ecophysiology of four co-occurring lycophyte species: an investigation of functional convergence. AoB Plants 7, plv137 (2015).

    PubMed  PubMed Central  Google Scholar 

  59. 59.

    Tosens, T. et al. The photosynthetic capacity in 35 ferns and fern allies: mesophyll CO2 diffusion as a key trait. New Phytol. 209, 1576–1590 (2016).

    CAS  PubMed  Google Scholar 

Download references


We thank A. Graham at the Harvard Center for Nanoscale Studies for his expert technical assistance with Cryo-SEM. We acknowledge the SOLEIL synchrotron, Saclay, France for provision of synchrotron radiation beamtime at the PSICHE beamline, and thank A. King for assistance. This research was funded by an Australian Research Council Discovery Grant (no. DP 170100761 awarded to T.J.B.). M.C. received a travel grant from La Caixa Banking Foundation and from the Conselleria d’Educació i Universitats (Govern de les Illes Balears) and European Social Fund (predoctoral fellowship no. FPI/1700/2014). N.M.H. was supported by a Visiting Scholar award from the University of Tasmania, and NSF grants nos. IOS-1659918 and DMR-1420570 studies. This work was supported by the programme Investments for the Future (nos. ANR-10-EQPX-16, XYLOFOREST and Labex COTE) from the French National Agency for Research.

Author information




T.J.B., M.C. and N.M.H. designed the study. T.J.B., N.M.H., M.C. and S.D. carried out the experiments. T.J.B. wrote the manuscript with input from N.M.H., M.C., S.D. and S.A.M.M. S.A.M.M. provided additional data.

Corresponding authors

Correspondence to T. J. Brodribb or N. M. Holbrook.

Ethics declarations

Competing interests

The authors declare they have no competing interests.

Additional information

Peer review information Nature Plants thanks Jeffrey Duckett, Karen Renzaglia and the other, anonymous, reviewer for their contribution to the peer review of this work.

Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Extended data

Extended Data Fig 1 Coordinated hydraulic conductance and assimilation.

The mean shoot hydraulic conductance and mean photosynthetic capacity of Polytrichum commune ( + /- SD, n = 7 individuals) measured here (triangle) falls close to the relationship found in leaves from the major groups of vascular plants; lycophytes and ferns (green), seed plants (blue) (published data from (27)).

Extended Data Fig 2 Above and below ground hydraulic resistance.

The distribution of hydraulic resistances as a percentage of total resistance (grey bars + SD, n = 7) between belowground (rhizoid) and aboveground (shoot) tissues in Polytrichum commune plants. Absolute values of hydraulic conductance (means shown as green bars, + SD, n = 7) show considerable variation, but the split between tissues is similar.

Extended Data Fig 3 Shoot hydraulic vulnerability.

The hydraulic conductance of Polytrichum commune shoots (Kshoot) was observed to decline sharply upon exposure to water stress. Each point represents a separate plant (n = 18 individuals) subjected to different degrees of dehydration stress. A rapid decline of Kshoot between -1 and −2MPa matched the observed pattern of cavitation using visual methods (Fig. 2). The form of the sigmoidal function fitted here was used in the hydraulic model used in Fig. 3.

Extended Data Fig 4 Refilling kinetics in Polytrichum.

Hydroids of the central strand of a single Polytrichum commune caulidium are shown to refill after a droughted plant that had fully cavitated was rehydrated after several hours ( > 12) after the last cavitation event was observed. Data from a single individual stem from an intact plant shows that 90 min after rewatering from both phyllidia and rhizome the hydroids begin to effectively refill with water, compressing the air into nanobubbles (which should dissolve over time) at around 125 min after rewatering of the plant. Average relative hydroid refilling state (proportion of water present in hydroids) over time is shown as black dots, while individual hydroid refilling states for each hydroid are shown as grey dots.

Extended Data Fig 5 Dynamic response to humidity in Polytrichum gas exchange.

Dynamic changes in photosynthetic assimilation rate and leaf diffusive conductance to water vapor during a transition from a vapor pressure deficit of 1.5 kPa (approximately 50% RH) to 3 kPa (approximately 5% RH). The pink box shows measurements made at 3 kPa, after which vapor pressure deficit was decreased to 1.0 kPa and recovery recorded. A rapid reduction in diffusive conductance and photosynthesis is evident upon exposure to drier air, while a complete recovery occurs upon return to more humid conditions. Changes in photosynthetic assimilation (A) measured by gas analysis correspond with changes in photosynthetic electron transport rate (ETR) measured by chlorophyll fluorescence (graph insert).

Extended Data Fig 6 Leaf movement in response to dehydration in Polytrichum.

As shoots of Polytrichum commune desiccate, leaves move from a position that is perpendicular to the stem (image top right) to being arranged parallel to the stem (image lower right). The relationship between leaf angle and ψshoot for five individuals subjected to slow desiccation (each color represents a different replicate plant) shows a rapid decline in leaf angle as ψshoot fell from 0 to −1.5 MPa. This pattern of decline matched closely the pattern of declining diffusive conductance seen in Fig. 3.

Extended Data Fig 7 Humidity sensitivity of assimilation.

Sensitivity of absolute assimilation rate to VPD in P. commune (open circles) and vascular plants (black points).

Extended Data Fig 8 Table of humidity sensitivity in diverse species.

Steady state leaf gas exchange across variable vapor pressure differences for vascular plant species taken from the literature.

Extended Data Fig 9 Table of maximum photosynthetic gas exchange in diverse species.

Maximum rates of gas exchange collected under standard conditions for species of lycophyte and ferns taken from the literature or measured in this study.

Supplementary information

Reporting Summary

Supplementary Video 1

Rehydration and refilling of hydroids as described in Extended Data Fig. 4. Similar results were found for all samples (n = 3).

Source data

Source Data Fig. 1

Anatomy data.

Source Data Fig. 2

Optical vulnerability data.

Source Data Fig. 3

Gas exchange in Polytrichum.

Source Data Fig. 4

Gas exchange in all species.

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Brodribb, T.J., Carriquí, M., Delzon, S. et al. Advanced vascular function discovered in a widespread moss. Nat. Plants 6, 273–279 (2020).

Download citation

Further reading


Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing