Abstract
Desiccation tolerance (DT) in poikilohydric organisms is dependent upon four principal sequential factors, (1) the rate of drying (RoD), (2) the water content (WC) of the organism deriving from the equilibrating relative humidity (RHeq), (3) the duration of the desiccation event, and (4) the rate of rehydration (RoR). The first two factors are often combined in experiments as the "intensity" of desiccation, and thus the effect of one on the other is relatively unknown but likely to be important ecologically. We hypothesized that more protracted rates of drying should mitigate damage at lower equilibrating RHs in a known inducibly DT species. Cultured uniclonal shoots of the moss Funaria hygrometrica were dried at different RoDs (time from full turgor to leaf curling, from 0.067 to 120 h) at five different RHs (12, 33, 54, 75 and 93%), allowed to equilibrate at each RH, rehydrated and assessed using chlorophyll fluorescence at 0.5 and 24 h postrehydration. At 24 h postrehydration, shoots of F. hygrometrica subjected to a rapid-dry event (<10 min) were unable to recover to control levels of fluorescence (Fv/Fm and φPSII <80% of control levels) when equilibrated at RHeqs of ≤54%. Recovery was improved when the rate of drying was extended for more than ∼15 hours from full turgor to the onset of leaf curling at these RHeqs. When shoots were rapidly dried at RHeqs >54%, recovery was complete. At 0.5 h postrehydration, Fv/Fm levels indicated moderate damage at all RHeqs except 93%, with no mitigation of damage when the rate of drying was extended. Intensity of desiccation is normally construed as the ability to tolerate a combination of rate of drying × equilibrating RH. By varying the rate of drying across a range of RHeqs, F. hygrometrica is found to be able to tolerate all water contents tested, providing the rate of drying is extended to at least 15 h from full turgor to leaf curling. By adopting either the "step-down" approach to drying or the "wet substrate" technique used here, future studies on the desiccation tolerance of poikilohydric organisms can more accurately assess responses to desiccation stress.
Original language | English |
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Pages (from-to) | 271-280 |
Number of pages | 10 |
Journal | Bryologist |
Volume | 122 |
Issue number | 2 |
DOIs | |
State | Published - May 1 2019 |
Bibliographical note
Publisher Copyright:© 2019 by The American Bryological and Lichenological Society, Inc.
Funding
The authors thank the National Science Foundation (DEB 1638943) for providing support for this project, Josh Greenwood for laboratory support, Henry Grover for providing the initial material of Funaria, and Robin Riker for assistance with Figure 1. Glime, J. M. 2019. Water Relations. Chapter 7. In: J. M. Glime (ed.), Bryophyte Ecology. Volume 1. Physiological Ecology. Ebook sponsored by Michigan Technological University and the International Association of Bryologists. [Available at www. bryoecol.mtu.edu, accessed 7 January 2019.] Green, T. G. A. & M. C. F. Proctor. 2016. Physiology of photosynthetic organisms within biological soil crusts: their adaptation, flexibility, and plasticity. Pages 347–381. In: B. Weber, B. Büdel & J. Belnap (eds.), Biological soil crusts: an organizing principle in drylands. Ecological Studies 226, Springer, Cham, Switzerland.
Funders | Funder number |
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International Association of Bryologists | |
National Science Foundation (NSF) | DEB 1638943, 1638943 |
Michigan Technological University |
Keywords
- Bryophyta
- Equilibrating relative humidity
- chlorophyll fluorescence
- constitutive
- inducible
- suprasaturation
ASJC Scopus subject areas
- Ecology, Evolution, Behavior and Systematics
- Plant Science