Physiological consequences of desiccation in the aquatic bryophyte Fontinalis antipyretica

Abstract

The moss Fontinalis antipyretica, an aquatic bryophyte previously described as desiccation-intolerant, is known to survive intermittent desiccation events in Mediterranean rivers. To better understand the mechanisms of desiccation tolerance in this species and to reconcile the apparently conflicting evidence between desiccation tolerance classifications and field observations, gross photosynthesis and chlorophyll a fluorescence were measured in field-desiccated bryophyte tips and in bryophyte tips subjected in the laboratory to slow, fast, and very fast drying followed by either a short (30 min) or prolonged (5 days) recovery. Our results show, for the first time, that the metabolic response of F. antipyretica to desiccation, both under field and laboratory conditions, is consistent with a desiccation-tolerance pattern; however, drying must proceed slowly for the bryophyte to regain its pre-desiccation state following rehydration. In addition, the extent of dehydration was found to influence metabolism whereas the drying rate determined the degree of recovery. Photosystem II (PSII) regulation and structural maintenance may be part of the induced desiccation tolerance mechanism allowing this moss to recover from slow drying. The decrease in the photochemical quenching coefficient (qP) immediately following rehydration may serve to alleviate the effects of excess energy on photosystem I (PSI), while low-level non-photochemical quenching (NPQ) would allow an energy shift enabling recovery subsequent to extended periods of desiccation. The findings were confirmed in field-desiccated samples, whose behavior was similar to that of samples slowly dried in the laboratory.

Erratum: Sex differences and plasticity in dehydration tolerance: insight from a tropical liverwort

“…In other words, it implies that DhT in M. inflexa is a plastic trait. The ability of M. inflexa to acclimate to dry conditions corroborates pervious work on protoplasts showing that slight decreases in water potential can lead to increased DhT and multiple studies demonstrating hardening in vegetative tissue (Schonbeck and Bewley, 1981;Beckett, 1999;Walters et al, 2002;Beckett et al, 2005;Cruz de Carvalho et al, 2011). We conclude that genetic adaptations are not responsible for the habitat difference in DhT, but rather that acclimation to dry conditions can increase DhT in M. inflexa.…”

“…However, such extreme phenotypes are not applicable to many plant forms and may obscure nuanced components of the process. There has been a relative paucity of research on bryophytes that show lower levels of tolerance, although some recent studies address this Cruz de Carvalho et al, 2011Pardow and Lakatos, 2013;Bader et al, 2013;Stark et al, 2013), and numerous studies have investigated moderate levels of dehydration in the drought response of vascular plants (Hsiao, 1973;Osakabe et al, 2014). Bryophytes showing moderate DhT likely occupy a large ecological niche, and understanding their response to abiotic stress is important for predicting species range shifts due to environmental changes.…”

Influence of dehydration rate on cell sucrose and water relations parameters in an inducible desiccation tolerant aquatic bryophyte

“…The initial hypothesis was that sucrose content is essential to DT induction and is related with dehydration rate, leading to differences in water relation parameters, especially in osmotic potential. Thus, a higher sucrose content would be expected in a slow dehydration rate in order to osmoregulate, compensating the water loss and postponing the shutdown of the metabolism, allowing time for acclimation and to attain the high cell survival previously observed (Cruz de Carvalho et al, 2011). For the same reasons, a higher cell wall elasticity was expected in the slow dehydrated samples.…”

“…During this period, conditions where maintained under controlled temperature (circa 20-23 C) and at low PAR (2-5 mmol m À2 s À1 ). In the water relations assay, slow dehydration was attained by air drying bryophytes at lab conditions (circa 80% RH) a value lower than the one used in previous works (Cruz de Carvalho et al, 2011, but still high enough to allow slow dehydration (0.25 AE 0.02 g H 2 O g À1 dry weight h À1 , circa 8 h). Rehydration was made through immersion in culture medium for 72 h under similar growth conditions.…”

“…Drying rate is crucial for DT induction in bryophytes (Stark et al, 2013;Greenwood and Stark, 2014), namely in the aquatic bryophyte Fontinalis antipyretica Hedw., where slow drying was previously shown to be essential (Cruz de Carvalho et al, 2011. The aim of the present work was to investigate how contrasting (fast and slow) dehydration rates change cell water relations in an aquatic bryophyte and how those changes explain the need for slow dehydration to induce DT.…”