Rhytidiadelphus Loreus Research Articles

The genome sequence of the little shaggy moss, Rhytidiadelphus loreus (Hedw.) Warnst. (Hylocomiaceae)

We present a genome assembly from an individual Rhytidiadelphus loreus gametophyte (the little shaggy moss; Bryophyta; Bryopsida; Hypnales; Hylocomiaceae). The genome sequence is 407.2 megabases in span. Most of the assembly is scaffolded into 5 chromosomal pseudomolecules. The organelle genomes have also been assembled, and the mitochondrial genome is 104.81 kilobases and the plastid genome 124.83 kilobases in length.

Diverse Ecological Pathways of Salmon Nutrients Through an Intact Marine-terrestrial Interface

Based on five years of field studies (1992, 1993, 1994, 1998, 2000), I quantified bi-directional movement of salmon nutrients through an estuary, stream, and old growth forest in a large protected reserve on Haida Gwaii, British Columbia. In 1993, when most data were collected, about 6000 Chum Salmon (Oncorhynchus keta) entered the river of which 22% of the total biomass of senescent carcasses were swept downstream into the estuary and were scavenged by gulls (n = 350) and subtidal invertebrates. Of the 3700 salmon (10 000 kg) transferred by American Black Bear (Ursus americanus) to the riparian zone and partially consumed along the 800 m of stream channel, 5070 kg of salmon tissues abandoned by the bears were scavenged by Northwestern Crows (Corvus caurinus; n = 200) but mostly (4100 kg) by calliphorid blowfly larvae resulting in larval densities averaging 240/m2 throughout the riparian zone. Total nitrogen input to the soils from the combined effects of bear and scavenger activity as well as carcass input was 18 g/m2 within 10 m of the stream channel. δ15N of foliar tissues of Lanky Moss (Rhytidiadelphus loreus), Red Huckleberry (Vaccinium parvifolium), Salal (Gaultheria shallon), and Western Hemlock (Tsuga heterophylla) ranged about 15‰ to 20‰ among adjacent microsites in each species, with higher values occurring in salmon carcass zones. Total nitrogen in foliar tissues ranged from 1% to 2.4% among microsites and was best predicted by positive correlations with foliar 15N values and secondarily by presence/absence of salmon carcasses. This is the first study to integrate estuarine to riparian ecological processes in the cycling of salmonid nutrients and identifies a range of ecological baselines that can inform the multiple restoration programs underway in degraded watersheds in the North Pacific.

Central European medicinal bryophytes in the 16th-century work by Caspar Schwenckfeld, and their ethnopharmacological origin

Ethnopharmacological relevanceUbiquitous bryophyte species are reported from European, American and Asian ethnopharmacies. Some of their traditional medicinal uses are similar in distant and isolated cultures, and moreover, medicinal properties of some bryophytes are currently confirmed as justified by their chemical constituents. Aims of the work: we identify bryophytes listed in a medicinal and botanical work from 1600, and compare their medicinal applications (known in Europe between 1530–1600) with other ethnopharmacological data about these species and with modern pharmacological knowledge. This way we attempt to display origins of medicinal usage of bryophytes in Central Europe. Materials and methodsBryophyte species in bibliographical sources printed in Central Europe (starting from O. Brunfels’ Herbarum vivae Eicones… Argentorati, 1530) were identified according to old and recent taxonomical references. Caspar Schwenckfeld’s scientific output from 1600 was treated here as a summary of 16th-century knowledge about medicinal bryophytes. ResultsCentral European pharmacy about the year 1600 was familiar with the following bryophytes: Marchantia polymorpha L., Polytrichum commune Hedw., P. formosum Hedw. and Funaria hygrometrica Hedw. ConclusionsBetween 1530–1600 in Central Europe the number of medicinal bryophytes increased from 2 (Lichen sive Hepatica and Polytrichon) to 4. Pharmaceutical usage of them was similar as in other, distant ethnopharmacies. Further 2–4 mosses (Rhytidiadelphus loreus and Rh. squarrosus; Thuidium tamariscinum and Th. delicatulum) were recognised as non-medicinal.

Nitrogen and carbon contents and δ15N and δ13C signatures in six bryophyte species: assessment of long‐term deposition changes (1980–2010) in Spanish beech forests

In this study we used recent (2010) and herbarium material (1980) of six bryophyte species to assess long-term atmospheric deposition in natural forested areas in northern Spain. For this purpose, tissue nitrogen and carbon content, as well as δ(13) C and δ(15) N signatures of samples of Hypnum cupressiforme, Polytrichastrum formosum, Leucobryum juniperoideum, Rhytidiadelphus loreus, Homalothecium lutescens and Diplophyllum albicans were analysed and comparisons made between years and species. In addition, the usefulness of each of the six species was evaluated. The range of values observed was similar to that in other studies carried out in rural areas. Significantly lower values were found in 2010 for N (H. cupressiforme), δ(15) N (R. loreus and D. albicans), C (R. loreus) and δ(13) C (all except L. juniperoideum). Our natural areas are thus now less influenced by atmospheric pollutants than they were, most probably due to changes in some traditional local activities. Differences were observed between species for all the four parameters studied, so different species must not be analysed together. Finally, R. loreus and H. lutescens seem to be good bioindicators, sensitive even with a few samples, although further studies are needed to corroborate their usefulness.

Athyrium distentifolium Tausch ex Opiz (A. alpestre (Hoppe) Rylands ex T. Moore‐non‐Clairv.) including A. distentifolium var. flexile (Newman) Jermy

Woodsiaceae. Athyrium distentifolium, Alpine lady-fern. Fronds bi-pinnate, ovate-lanceolate, yellow-green 20 cm to over 100 cm, arising in a 'shuttlecock' from a central crown. Stipe straight, one fifth to one quarter the length of the blade with pale brown scales, usually broad, but occasionally narrow. Pinnae widely spaced near base of the frond, and sometimes deflexed, crowded near the tip, meeting the rachis at an angle of 900 at the midpoint of the blade, or slightly ascending. Pinnules broadest at the base, tapering to a point. Sori circular, with irregular filaments making up a rudimentary indusium when young, soon obscured as the sori grow. Sori concentrated in the upper part of the frond, becoming sparse towards the base. Number of sori varies with size of frond. Plants frequently infertile (McHaffie et al. 2002). Athyrium distentifolium var.flexile Newman's lady-fern. Fronds bi-pinnate, narrow, blue-green, 10-40 cm, arising from a central crown, erect or sharply angled near the base of the rachis to lie nearly flat against the substrate. Stipe short, one sixth to one eighth the length of the blade, often densely covered with broad, pale scales that may continue beyond the midpoint of the blade. Blade broadest near the base, or nearer the mid-point. Pinnae close together near base of frond, often strongly deflexed to at least half way up the frond. Uppermost pinnae widely spaced. Pinnules taper towards the base. Sori circular, sometimes with only a few sporangia; rudimentary indusium visible while the sorus is still immature. Sori concentrated at base of the frond, becoming less frequent towards the tip. Plants usually fertile (McHaffie et al. 2002). Athyrium distentifolium is a chionophilous fern that grows at altitudes or latitudes which ensure long-lying winter snow cover. Deep snow provides insulation from severe winters, and prevents early growth in a mild spring. Only a limited number of species can tolerate these conditions and this reduces competition. Although previously known as a Scandinavian and continental European species, A. distentifolium was not recognized in Britain until 1844 (Newman 1851). Within Britain it is found only in Scotland where it is confined to the remote Highlands. Soon after it was identified, another similar taxon of uncertain taxonomic status was described (Backhouse 1852). Subsequent research has determined that this is a recessive variety which is now known as A. distentifolium var.flexile. Both taxa are covered in this account.

Uptake of salmon‐derived nitrogen by mosses and liverworts in coastal British Columbia

Throughout forested watersheds bordering the North Pacific, anadromous salmon (Oncorhynchus spp.) are transferred into coastal forests by numerous predators and scavengers with remnants providing an important nutrient subsidy to riparian zones. The contribution of these nutrients to mosses and liverworts, which are the dominant ground cover of coastal forests, has not been investigated. We examine here δ15N isotope signatures and foliar percent N of eight moss and liverwort species, as well as moss and liverwort community structure, in multiple habitat blocks that vary in access to salmon nutrients from two watersheds on the central coast of British Columbia. For the most common moss Rhytidiadelphus loreus, we also examine δ15N values and foliar percent N among salmon carcass micro‐sites and along wildlife trails. Overall, δ15N signatures ranged from 2‰ to 7‰ higher below the falls near the salmon stream than above the small falls that are impassable to salmon, or at the adjacent control watershed that had no salmon. Among micro‐sites, δ15N and %N values were highest near bony carcass remnants from transfer during previous years and high adjacent to wildlife trails indicating spatial heterogeneity in the salmon nutrient pools of these forests. Species richness and prevalence of nitrogen‐rich soil indicators were also highest in forests adjacent to the salmon stream. These data suggest an important contribution of salmon‐derived nutrients to the non‐vascular plants of the riparian zone of old‐growth forests throughout the Pacific Rim.

Bole Epiphytes on Three Conifer Species from Queen Charlotte Islands, Canada

To compare effects of aspect, height on tree, and host species on species richness and cover of epiphytic lichens and bryophytes on conifers, we sampled Chamaecyparis nootkatensis, Picea sitchensis, and Tsuga heterophylla on the north and south sides in the first, second, and third meters of tree trunks in Vladimir J. Krajina Ecological Reserve. A total of 11 taxa of mosses, 26 of liverworts, and 4 of lichens were recognized. Bryophytes, especially liverworts, dominated in both cover and number of occurrences, with the most common being Dicranum scoparium, Isothecium myosuroides, Bazzania flaccida, and Scapania bolanderi. Rhytidiadelphus loreus was abundant at the tree bases but not at other heights. There was no host specificity. The rough mat growth form comprised both the highest cover and greatest number of species of bryophytes on each of the three tree species. This study demonstrates that under the right bark conditions liverworts can be more abundant than mosses and both more abundant than lichens on conifer bark.

Rehabilitation of degraded Calluna vulgaris (L.) Hull-dominated wet heath by controlled sheep grazing

Many upland areas of the British Isles have seen declines in the area and condition of heather ( Calluna vulgaris)-dominated heathland vegetation. To reverse this decline, management regimes must be designed to rehabilitate areas that have seen this decline. As most of this heathland vegetation is primarily managed by grazing, such management has to determine what stocking levels can maintain the vegetation in a desired state. This paper describes how to reverse this decline through suitable grazing management. A degraded ‘wet-heath’ system, previously grazed at 2.1 sheep ha −1, was subject to a range of grazing treatments over a 5-year period. Treatments varied in intensity (0–1.4 sheep ha −1) and timing (summer only, winter only, or year round) of grazing. Grazing levels were maintained at 2.1 sheep ha −1 outside the fenced areas. Vegetation composition remained stable outside the fenced treatments. All the fenced treatments showed an increase in the relative frequency of the evergreen Calluna vulgaris, with the greatest increase being in the ungrazed treatment, and the least in the year round 1.4 sheep ha −1 treatment. This increase was in line with a reduction in heather utilisation to relatively low and sustainable levels. Other species that benefited from reduced grazing included Carex nigra, Deschampsia flexuosa and to a lesser extent Galium saxatile and Erica tetralix, whereas a range of moss species including Hypnum jutlandicum and Rhytidiadelphus loreus were more frequent at higher grazing levels. Though the recovery of heather was similar in the two seasonally grazed treatments, the vegetation showed different overall trajectories. Winter only grazed allowed a substantial increase in the cover of the deciduous Molinia caerulea, whereas this species was kept in check by summer only grazing. A stocking level of between 0.7 and 1.4 sheep ha −1 appears to be appropriate to maintain and even enhance the cover of heather on degraded wet heath. Complete removal is not necessary. Grazing restricted to the winter period is inappropriate in areas where M. caerulea occurs. Setting appropriate stocking levels to maintain the condition of the vegetation must take into account site conditions, especially the presence of species that can affect the utilisation of heather.

The impact of watering regime and ambient relative humidity on the effect of density on growth in two boreal forest mosses, Dicranum majus and Rhytidiadelphus loreus

The impact of watering regime, ambient relative humidity and shoot density on production of offshoots, biomass increase and elongation growth in two boreal forest mosses, Dicranum majus and Rhytidiadelphus loreus, was studied under controlled conditions. Experimental colonies of the mosses at three shoot densities were subjected to humidity conditions differing with respect to desiccation rate, desiccation severity and length of the moist period, by varying the ambient relative humidity (RH), and the frequency and continuity of days when the shoots were watered. Overall, increased density had a negative effect on relative growth rate (RGR) and green biomass in both species. However, under several watering regimes, optima for both RGR and green biomass were found at intermediate densities, especially at low RH. Production of offshoots decreased with density in D. majus. Length growth rate (LGR) increased with RH in both species, and LGR also increased with density in D. majus. The differences in response to watering regimes were large, but few consistent patterns emerged with respect to the impact of the length of wet and dry periods, watering frequency, and the desiccation rate and intensity. Nevertheless, RGR increased with the length of the wet-dry cycle when the total number of wet and dry days remained equal.

TESTING FOR POSITIVE DENSITY-DEPENDENT PERFORMANCE IN FOUR BRYOPHYTE SPECIES

The impact of environmental conditions on the relative importance of competitive and facilitative interactions and their responses to shoot density was studied in four boreal forest bryophytes. Increased density is believed to have both a positive effect, by increasing water retention, and a negative effect, by reducing light availability. Mortality of shoot apices, offshoot production, and rates of biomass increase of both individual shoots and whole colonies were recorded in experimental monospecific, known-density colonies of Dicranum majus, Plagiochila asplenioides, Ptilium crista-castrensis, and Rhytidiadelphus loreus under controlled relative humidity (four levels) and irradiance (two levels). A phenomenological model was developed, and predictions were made about the responses to increased density under different humidity and resource (light) levels. Mortality was low, but offshoot production generally decreased with density. The effects of density on growth rates varied among species and environmental conditions. As predicted, in dry environments under the high light level, growth rates of D. majus and R. loreus peaked at an intermediate density at which the positive effects of a close packing of shoots balanced the increased competition for light. In humid or dark environments, the relationships between growth rates and density were mostly monotonic and negative. Growth rates of P. crista-castrensis decreased with density under most environmental conditions, whereas density was not shown to have an effect on growth rates of P. asplenioides. The results show that relatively high light levels, compared to those found in their natural spruce forest habitat, are necessary for aggregation to facilitate growth of these bryophytes. Thus, our results indicate that competition for light, rather than a low water availability, limits the performance of individual shoots in colonies of these bryophytes under a wide range of densities and humidity conditions.

Rapid recovery of photosystems on rewetting desiccation-tolerant mosses: chlorophyll fluorescence and inhibitor experiments.

In the mosses Racomitrium lanuginosum, Anomodon viticulosus and Rhytidiadelphus loreus, after a few days air dry, F:(v)/F:(m) reached, within the first minute of remoistening in the dark, two-thirds or more of the value attained after 40 min. A fast initial phase of recovery was completed within 10-20 min after which further change was slow. Initial recovery of Phi(PSII) in the light was somewhat slower, but was generally substantially complete within a similar time. Remoistening with 0.3 mM cycloheximide (CHX) or 3 mM dithiothreitol (DTT) made little difference to this short-term (40 min) recovery of either F:(v)/F:(m) or Phi(PSII); 3 mM chloramphenicol (CMP) had little effect on recovery of F:(v)/F:(m), but resulted in substantial (though not total) depression of Phi(PSII) and (14)CO(2) uptake. Effects of the protein-synthesis inhibitors and DTT were much more clearly apparent in longer-term experiments (>20 h) but only in the light. In the dark, the three inhibitors had at most only slight effects over periods of 60-100 h. In the light, CMP-treated samples of all three species showed a progressive decline of dark-adapted F:(v)/F:(m), falling to zero within 1-5 d (possibly due to blocking of the turnover of the D1 protein of PSII) and accelerated by DTT. CHX-treated samples showed a similar but slower decline. In the shade-adapted and relatively desiccation-sensitive Rhytidiadelphus loreus, slow recovery of F:(v)/F:(m) continued in the dark even in the presence of CMP and CHX for much of the 142 h of the experiment. The results indicate that in desiccation-tolerant bryophytes recovery of photosynthesis after periods of a few days air dry requires only limited chloroplast protein synthesis and is substantially independent of protein synthesis in the cytoplasm.

THE MOSSES OF KENT ISLAND,NEW BRUNSWICK

Thirty-nine moss species occur on Kent Island, New Brunswick. Two-thirds of the moss species found on the island have mainly boreal ranges, which reflects the cool growing season and generally boreal character of the Bay of Fundy's vegetation. One species, Rhytidiadelphus loreus, has been recorded only once previously in the province. Most moss species showed distinctive habitat distributions. Percent cover of the 12 commonest species was highest in spruce-fir forest and lowest in mountain ash stands. Sporophyte production was relatively low in all species and varied between habitats. Sporophytes were observed in fewer than 1% of 25 x 25 cm quadrats during the months of June and July. The low species richness of mosses on Kent Island relative to mainland habitats is presumably due to the island's small size, isolation from the mainland, low elevation, relatively simple plant community, and harsh physical environment.

Chlorophyll Fluorescence during Drying and Rehydration in the Mosses Rhytidiadelphus loreus (Hedw.) Warnst.,Anomodon viticulosus (Hedw.) Hook. & Tayl. and Grimmia pulvinata (Hedw.) Sm.

Chlorophyll-fluorescence parameters of three mosses, Rhytidiadelphus loreus (Hedw.) Warnst.,Anomodon viticulosus (Hedw.) Hook & Tayl. and Grimmia pulvinata (Hedw.) Sm. were measured during drying, and following remoistening after a period of desiccation. Most changed little with drying until the full-turgor point was approached, when rapid changes accompanied loss of cell water. In R. loreus all parameters decreased together down to a water content of about 30% d.wt (RWC approx. 0.15). At low water contents (5–16% d.wt; RWC approx. 0.02–0.08) saturating pulses tended to suppress rather than stimulate fluorescence. In A. viticulosus Fv/Fm, qPand ΦPSII declined with loss of cell water, but NPQ peaked at approx. 70% d.wt (RWC approx. 0.3). On remoistening after a few days air dry, Fv/Fmrecovered very rapidly (<1 min) in all three species to initial values of 0.6–0.7 in R. loreus, and approx. 0.7 in A. viticulosus and G. pulvinata. ΦPSII (ΔF/FAm) recovered to near-normal levels within 10–15 min (perhaps close to the attainable minimum time) in G. pulvinata and A. viticulosus. Recovery of Φ:PSII was very variable but generally slower and less complete in R. loreus. NPQ peaked sharply in the first minutes of re-wetting in A. viticulosus, G. pulvinata, and the faster-recovering shoots of R. loreus, but rose only slowly in the shoots of R. loreus that showed slowest and least complete recovery, or in the other species after prolonged desiccation. The initial peak in NPQ was suppressed by dithiothreitol (DTT), suggesting that it is zeaxanthin dependent. After short or moderate periods of drying, A. viticulosus and G. pulvinata showed enhanced levels of NPQ for several hours, but returned to the predesiccation state within 24 h. Recovery from longer drying (or of more sensitive species, such as R. loreus) was slower, and effects of desiccation (including high NPQ) were still evident more than 24 h after remoistening. Slow-fluorescence parameters such as Rfd, and the widely used parameter Fv/Fm, are valuable in ecophysiology and stress physiology if their limitations are recognized, but even simple quenching analysis can yield valuable additional information.

Seasonal dynamics of biomass increase and shoot elongation in five co-occurring boreal forest bryophytes

The seasonal patterns of length and biomass increase in five co-occurring bryophytes (Dicranum majus, Hylocomium splendens, Plagiochila asplenioides, Ptilium crista-castrensis and Rhytidiadelphus loreus), were studied throughout one growing season in a boreal spruce forest by growing shoots in experimental assemblages at two densities at consecutive four-week intervals. Seasonal trends in the mean relative growth rate (RGR) were found, with highest RGR in spring and early summer (0.0025-0.005 gg-1 day-1) and a low or negative RGR in autumn. This temporal variation could best be explained by the variation in precipitation, but interactions with other environmental factors were important, especially in spring and autumn. The five species responded differently to the environmental conditions, with the result that their relative rank in RGR changed from period to period. However, the effect of density on RGR varied between periods, indicating that the impact of macroenvironmental conditions depends on shoot density. Mean rate of length increase (LGR) peaked in early summer (0.12-0.20 mm day-1) with low length increases in spring and late in the season. LGR varied among species, showing differences in both maximum length growth rate and temporal patterns of growth. Length increase did not follow the temporal patterns of biomass increase, and an evident uncoupling of biomass and length increase was found in all species. The cumulative seasonal increase in length and biomass varied among species with a twofold and ninefold variation among species in cumulative length and biomass increase respectively. Further, an effect of shoot density on cumulative biomass increase was found, with the higher biomass increase at the lower shoot density.

Nematodes and Other Aquatic Invertebrates in Eurhynchium oreganum from Mary's Peak, Oregon Coast Range

Nematodes and Other Aquatic Invertebrates in Eurhynchium oreganum from Mary's Peak, Oregon Coast Range

Redifferentiation of moss protonemata: an experimental and immunofluorescence study of brood cell formation

The formation of ovoid or spherical brood cells from chloronemal filaments by swelling and symmetrical subapical divisions preceded by phragmosomes, but not preprophase bands, is described in the mosses Physcomitrella patens, Dicranoweisia cirrata, Bryum tenuisetum, Bryum bicolor, and Rhytidiadelphus loreus. This is a widespread phenomenon that occurs in protonemal colonies cultured for long periods of time or allowed to dry out. It involves the redifferentiation of highly polarized chloronemal cells with a net axial array of microtubules into nonpolar cells containing microtubules with no preferred orientation. Brood cells in some species become thick walled and retain their viability for long periods even in a desiccated state. When transferred to new medium they immediately regenerate protonemata from new filaments of no fixed position. Experiments using activated charcoal, which prevents brood cell formation, and transferring protonemata or spores onto old medium in which brood cells had been produced previously, indicate that the redifferentiation process is triggered by substances released into the medium by protonemata. Addition of abscisic acid, an endogenous growth regulator in mosses, causes precocious brood cell formation in young cultures and is very likely the natural compound triggering their development and inducing their tolerance to desiccation. Key words: abscisic acid, activated charcoal, redifferentiation, desiccation tolerance, microtubules, polarity, protonema, regeneration.

Human Uses of Bryophytes. I. Use of Mosses for Chinking Log Structures in Alaska

Human Uses of Bryophytes. I. Use of Mosses for Chinking Log Structures in Alaska

The Ecological Role of Bryophytes in a North Wales Woodland

(1) The mineral relations of bryophytes in a moist sessile oakwood (Quercetum petraeae) in north-west Wales were investigated, to examine possible long-term effects on the ecosystem of prolonged commercial moss-gathering. (2) The principal species of the ground vegetation in terms of standing crop, productivity and nutrient content were the mosses Dicranum majus, Rhytidiadelphus loreus, Plagiothecium undulatum, Polytrichumformosum and Thuidium tamariscinum. In 1968 the only herb of significance was Deschampsia flexuosa. Bryophytes formed c. 90% of the standing crop of the ground vegetation in the study area, and contained a correspondingly high proportion of the mineral-element resources. Epiphytic bryophytes formed c. 4%. of the total bryophyte standing crop. (3) No consistent seasonal growth patterns were found, but there were indications that Dicranum majus and Rhytidiadelphus loreus grew more rapidly in late summer than at other times. Plagiothecium undulatum had a higher concentration, and Polytrichumformosum a lower concentration of the four elements Ca, Mg, K and Na than the other species. (4) Changes in concentration of these elements in rainfall, throughfall and leachate from the bryophyte mat were monitored for periods of up to 5 months. It was evident that the moss layer altered the chemical composition of the precipitation percolating through it. Potassium was removed from the tree crowns by the rainfall, and was then taken up by the moss layer. Calcium and nitrogen were also removed by the bryophytes. There was a net loss of magnesium from the moss layer. (5) The role of bryophytes in the nutrient economy of a woodland ecosystem in a region of high rainfall is discussed.

Effects of intermittent desiccation on bryophytes

(1) Gas exchange measurements on Rhytidiadelphus loreus and Anomodon viticulosus following re-moistening after a period of desiccation showed an initial stimulation of respiration, followed immediately by progressive recovery of photosynthesis within the first 1–6 h. A. viticulosus after 48 h dry reached the compensation point within a few minutes of re-moistening; R. lore us after 7 days dry reached the compensation point after about 4 hours.(2) Hylocomium splendens, R. loreus and Tortula ruraliformis were subjected to the following patterns of alternating wet and dry periods over a period of 18 weeks: continuous dry, 1 day wet/6 days dry, 6 days wetll day dry, 1 day wet/1 day dry, 7 days wet/7 days dry, continuous wet.(3) Only T. ruraliformis still attained a positive net assimilation rate after the continuous dry treatment for the duration of the experiment. All three species retained a positive net assimilation rate throughout after all the remaining treatments.(4) A moist period of 24 h allowed substantially complete recovery from the after-effects of preceding desiccation.(5) Experiments in which two dry periods were separated by moist periods of 6 h, 24 hand 7 days showed that recovery in H. splendens and R. loreus was incomplete in 6 h but confirmed that it was complete in 24 h.(6) H. splendens showed constant or slightly increased desiccation-tolerance in successive dry periods. R. loreus showed a well marked increase in tolerance (hardening) following a previous dry/wet cycle.(7) The effect of intermittent desiccation can be predicted approximately from the successive effect of the individual dry periods.(8) It is doubtful whether there is any specific deleterious effect of drying and re-moistening; any such effect that does exist can only be small.

The pattern of recovery of bryophytes after desiccation

Abstract(1) Net assimilation and respiration rates were measured at intervals after re-moistening, following various periods of desiccation, in Hookeria lucens, Hylocomium splendens, Neckera crispa, Plagiochila spinulosa, Plagiothecium undulatum, Rhacomitrium lanuginosum, Rhytidiadelphus loreus, Saccogyna viticulosa, Scorpiurium circinatum and Tortula ruraliformis.(2) Rhacomitrium lanuginosum was extremely resistant, recovering apparently normally after 239 days' desiccation at 32% R.H.; Plagiochila spinulosa and Hookeria lucens were the most sensitive.(3) Rhacomitrium lanuginosum and Tortula ruraliformis were most quickly damaged at the highest humidity (76%) and Plagiothecium undulatum at the lowest humidity tested (32%).(4) Saccogyna viticulosa and Scorpiurium circinatum combined relatively rapid impairment and slow recovery of assimilation with the capacity to survive long dry periods.(5) Dark respiration was relatively slow (commonly c. 5–20% of net assimilation). It usually showed a slight initial s...