All for One: The Role of Colony Morphology in Bryophyte Desiccation Tolerance

Abstract

In the last decade, several works showed that even bryophytes from aquatic environments, if slowly dehydrated, can cope with desiccation in a response like the one from desert bryophytes. This led to the hypothesis that, if bryophytes from contrasting habitats can have similar responses, desiccation tolerance (DT) is partially inductive and not only constitutive as previously proposed and, therefore, colony morphology might be the key trait responsible for controlling dehydration rate essential for DT induction. Morphology and life form may be determinant traits in the adaptation of bryophytes to habitats with different water availabilities and corresponding predicted levels in the DT inducibility spectrum. Bryophytes from habitats with different water availabilities were dried as individual shoots and as a colony. The bryophyte Fontinalis antipyretica is fully aquatic presenting a streamer life form, while the three terrestrial species present turf life form with different sizes and degrees of space between individuals in the colony. Two species were collected under trees with moist soil presenting short turf (Tortella tortuosa) and long turf (Campylopus pyriformis) life forms. Another species was completely exposed to sun light with no surrounding trees and a tall turf life form (Pleurochaete squarrosa). We used chlorophyll a fluorescence parameter Fv/Fm (maximum potential quantum efficiency of Photosystem II) as a proxy to photosynthetic fitness throughout the contrasting dehydration rates (fast and slow). These bryophytes with different life forms were submitted to an X-ray computed microtomography (µ-XCT) to assess the three-dimensional inner structure and visualize locations for water storage. Shoots dried slow or fast according to the dehydration they were exposed to, as expected, but they presented similar dehydration rates across different species. However, the aquatic moss F. antipyretica, was unable to recover from fast drying, and after 24 h the recovery following slow drying was lower than the other species. The other three species presented full recovery after 24 h, either at the individual or colony level, and either from slow or fast drying. The only exception was the colonies of Campylopus pyriformis following fast drying that presented a slightly lower recovery, probably due to a looser colony structure.

Unexplored dimensions of variability in vegetative desiccation tolerance

“…Many factors can impact the outcome of a desiccation event including the minimum water content of dried tissues (i.e., the intensity of drying) (Gaff, 1989; Watkins et al, 2007; Marks et al, 2016), the rate of drying (Oliver et al, 1998; Farrant et al, 1999; Cruz de Carvalho et al, 2011, 2019; Stark et al, 2013; Greenwood and Stark, 2014; Greenwood et al, 2019; McLetchie and Stark, 2019), the light and temperature conditions during drying and rehydration (Hearnshaw and Proctor, 1982; Seel et al, 1992; Guo and Zhao, 2018), the duration that tissues are maintained in a dry state (Benkő, 2002), and the condition of tissues before drying (Schonbeck and Bewley, 1981; Beckett et al, 2005a, b; Brinda et al, 2016) (Fig. 2).…”

“…Depending on the species and the conditions under which the tissues were dried and stored, resurrection plants can remain viable for months, years, or even decades in a desiccated state (Hosokawa and Kubota, 1957; Gaff, 1989; Alpert, 2000; Farrant and Kruger, 2001; Benkő, 2002; Proctor, 2003). Artificial manipulation of these variables can lead to contrasting recovery outcomes within a single species (Farrant et al, 1999; Cruz de Carvalho et al, 2011, 2019; Stark et al, 2013; Greenwood and Stark, 2014).…”

Strategies of desiccation tolerance vary across life phases in the moss Syntrichia caninervis

“…Several bryophyte studies using a field approach concluded that photosynthesis reactions in Syntrichia and other species are capable of recovering in seconds (essentially constitutive) after the addition of liquid water (e.g., Proctor and Smirnoff, 2000; Oliver et al, 2005). This rapid rate of recovery (due to prior hardening) lent credence to the hypothesis that most clades of bryophytes were CDT (Oliver et al, 2000; Proctor et al, 2007b; Toldi et al, 2009), which has subsequently been questioned through several experiments indicating that inducible processes operating during a slow‐dry or partial‐dry event are probably widespread in bryophytes (e.g., Werner et al, 1991; Pressel and Duckett, 2010; Cruz de Carvalho et al, 2014, 2019; Greenwood and Stark, 2014; Hájek and Vicherová, 2014; Brinda et al, 2016; Bu et al, 2017; Liu et al, 2019).…”

500 million years of charted territory: functional ecological traits in bryophytes

“…Sphagnum L., Hajek & beckett 2008) and even in aquatic mosses that undergo seasonal inundation (e.g. Fontinalis Hedw., Cruz de Carvalho et al 2019). The suite of mechanisms involved in DT are controlled by traits at the anatomical, physiological, and molecular level, all operating in concert during periods of drying, while desiccated, and when rehydrating (Oliver et al 2000, Proctor et al 2007).…”