Moss Polytrichum Formosum Research Articles

Effects of the Salt Stress Duration and Intensity on Developmental and Physiological Features of the Moss Polytrichum formosum.

The two accessions of the polytrichaceous moss species Polytrichum formosum, namely German and Serbian genotypes, were subjected to salt stress, aiming to study the species' developmental and physiological features. Various concentrations of sodium chloride were applied to an axenic in vitro culture of the two moss genotypes, and the growth parameters as well as physiological feature changes were followed. As inferred by the morpho-developmental parameters and survival index, the Serbian genotype showed higher resistance to salt stress as compared to the German one. However, both moss genotypes survived the highest applied concentration (500 mM). As expected, short exposures to salt were rather easily overcome. No clear patterns in sugar content and changes were observed during the stress, but they are surely included in salt stress response and tolerance in P. formosum. Longer stress increased total chlorophyll content in both genotypes. In short-term applied salt stress, the Serbian genotype had a higher total chlorophyll concentration to control unstressed plants, while the German genotype decreased the total amount of chlorophyll. Similarly, carotenoids were shown to be significantly higher in the Serbian genotype, both in unstressed and treated plants, compared to the German one. The contents of tocopherols were higher in the Serbian genotype in controlled unstressed and subsequently short- and long-stressed plantlets compared to the German accession. In general, we can assume that P. formosum is unexpectedly tolerant to salt stress and that there are differences within various accessions of overall European populations, as referred by two randomly selected genotypes, which is most probably a consequence of different genetic structure.

An insight into seasonal changes of carbohydrates and phenolic compounds within the moss Polytrichum formosum (Polytrichaceae)

The same population of the polytrichaceous moss Polytrichum formosum was studied over four different periods of the year, analysing its carbohydrate and polyphenolic content and dynamics related to environmental seasonal changes. A total of 18 different types of sugars (including mono-, di-, tri- and tetra-saccharides) and four sugar alcohols were determined. Chlorogenic acid was the most represented among the 10 detected phenolic compounds. As inferred by the sugar content, sucrose, fructose and glucose were the most dominant sugars, but it is worth mentioning the abundance of trehalose and turanose at least during one of the observed seasons. The presence of four trisaccharides and one tetrasaccharide within P. formosum should be highlighted, as well as the first reports of turanose, isomaltotriose, panose and rhamnose within this species. The quantitative changes over the year clearly demonstrate carbohydrate dynamics in relation to seasonal climatic variation. Sugars are shown to be significant constitutive molecules within P. formosum, but also physiologically active compounds, i.e. signalling and energy storage and supplier molecules. We assume that phenolics have moss-supportive effects during oxidative stress and biotic interaction.

Collagenase and Tyrosinase Inhibitory Effect of Isolated Constituents from the Moss Polytrichum formosum.

Mosses from the genus Polytrichum have been shown to contain rare benzonaphthoxanthenones compounds, and many of these have been reported to have important biological activities. In this study, extracts from Polytrichum formosum were analyzed in vitro for their inhibitory properties on collagenase and tyrosinase activity, two important cosmetic target enzymes involved respectively in skin aging and pigmentation. The 70% ethanol extract showed a dose-dependent inhibitory effect against collagenase (IC50 = 4.65 mg/mL). The methanol extract showed a mild inhibitory effect of 44% against tyrosinase at 5.33 mg/mL. Both extracts were investigated to find the constituents having a specific affinity to the enzyme targets collagenase and tyrosinase. The known compounds ohioensin A (1), ohioensin C (3), and communin B (4), together with nor-ohioensin D (2), a new benzonaphthoxanthenone, were isolated from P. formosum. Their structures were determined by mass spectrometry and NMR spectroscopy. Compounds 1 (IC50 = 71.99 µM) and 2 (IC50 = 167.33 µM) showed inhibitory activity against collagenase. Compound 1 also exhibited inhibition of 30% against tyrosinase activity at 200 µM. The binding mode of the active compounds was theoretically generated by an in-silico approach against the 3D structures of collagenase and tyrosinase. These current results present the potential application from the moss P. formosum as a new natural source of collagenase and tyrosinase inhibitors.

Nitrogen deposition is positively correlated to foliar nitrogen content in Vaccinium myrtillus and other understory species in temperate forests on acidic soil

Excessive atmospheric nitrogen deposition is known to alter nutrient cycles and species composition in temperate forest ecosystems. Foliar N concentrations reflect the nutrient status of plants and can be used to assess the impact of atmospheric N deposition on ecosystems. Our objective was to test whether the foliar N content reflects increasing N deposition in the understory vegetation of temperate forests on acidic soil. Therefore, we analyzed the foliar N content of seven plant taxa representing different functional groups of the understory vegetation and correlated them to modeled deposition datasets. Linear mixed models revealed no relationship of N deposition with foliar N concentrations across all species examined but decreasing foliar concentrations with increasing soil C/N ratio. Nevertheless, we found positive correlations of foliar N concentrations with increasing deposition in conifer saplings (Picea abies and Abies alba), the dwarf shrub Vaccinium myrtillus and the graminoid Luzula luzuloides. Such an increase was, however, not found in saplings of broad-leaved trees (Fagus sylvatica and Quercus petraea/robur) and the moss Polytrichum formosum. This suggests marked species-specific differences in nitrogen uptake and allocation. Foliar N concentrations were more strongly correlated to NOy than NHx and to wet than dry deposition. Since foliar N concentrations were correlated to deposition while the species’ cover was not, they may provide a valuable indicator of N deposition.

Tremella bryonectriae sp. nov. – the first hyperbryophilous fungal species

The tiny, microscopic Tremella bryonectriae (Tremellales, Basidiomycota) is a newly discovered heterobasidiomycete with a presumed mycoparasitic lifestyle. The species is characterized by the absence of basidiomata, by having claviform probasidia, two-celled and longitudinally septate basidia with tubiform sterigmata, ellipsoidal basidiospores, and its occurrence on the mycelia and developing ascomata of Bryonectria cuneifera (Hypocreales). The inconspicuous host, B. cuneifera, grows between the leaf lamellae of the moss Polytrichum formosum . Tremella bryonectriae is documented by just a few records in Europe. It is the first hyperparasite recorded on a bryophilous ascomycete. The species expands both the host spectrum of tremelloid fungi and the complexity of the associations between Polytrichaceae and their many obligate fungal parasites.

Desiccation tolerance in the moss Polytrichum formosum: physiological and fine-structural changes during desiccation and recovery.

This study explores basic physiological features and time relations of recovery of photosynthetic activity and CO2 uptake following rehydration of a desiccation-tolerant moss in relation to the full temporal sequence of cytological changes associated with recovery to the normal hydrated state. It seeks reconciliation of the apparently conflicting published physiological and cytological evidence on recovery from desiccation in bryophytes. Observations were made of water-stress responses and recovery using infrared gas analysis and modulated chlorophyll fluorescence, and of structural and ultrastructural changes by light and transmission electron microscopy. Net CO2 uptake fell to zero at approx. 40 % RWC, paralleling the fluorescence parameter PhiPSII at 200 micromol m(-2) s(-1) PPFD. On re-wetting the moss after 9-18 d desiccation, the initially negative net CO2 uptake became positive 10-30 min after re-wetting, restoring a net carbon balance after approx. 0.3-1 h. The parameter Fv/Fm reached approx. 80 % of its pre-desiccation value within approx. 10 min of re-wetting. In the presence of the protein-synthesis inhibitors chloramphenicol and cycloheximide, recovery of Fv/Fm (and CO2 exchange) proceeded normally in the dark, but declined rapidly in the light. Though initial recovery was rapid, both net CO2 uptake and Fv/Fm required approx. 24 h to recover completely to pre-desiccation values. The fixation protocols produced neither swelling of tissues nor plasmolysis. Thylakoids, grana and mitochondrial cristae remained intact throughout the drying-re-wetting cycle, but there were striking changes in the form of the organelles, especially the chloroplasts, which had prominent lobes and lamellar extensions in the normally hydrated state, but rounded off when desiccated, returning slowly to their normal state within approx. 24 h of re-wetting. Sub-cellular events during desiccation and re-wetting were generally similar to those seen in published data from the pteridophyte Selaginella lepidophylla. Initial recovery of respiration and photosynthesis (as of protein synthesis) is very rapid, and independent of protein synthesis, suggesting physical reactivation of systems conserved intact through desiccation and rehydration, but full recovery takes approx. 24 h. This is consistent with the cytological evidence, which shows the thylakoids and cristae remaining intact through the whole course of dehydration and rehydration. Substantial and co-ordinated changes in other cell components, which must affect spatial relationships of organelles and metabolic systems, return to normal on a time span similar to full recovery of photosynthesis. Comparison of the present data with recently published results suggests a significant role for the cytoskeleton in desiccation responses.

Desiccation tolerance in the moss Polytrichum formosum: physiological and fine-structural changes during desiccation and recovery.

This study explores basic physiological features and time relations of recovery of photosynthetic activity and CO2 uptake following rehydration of a desiccation-tolerant moss in relation to the full temporal sequence of cytological changes associated with recovery to the normal hydrated state. It seeks reconciliation of the apparently conflicting published physiological and cytological evidence on recovery from desiccation in bryophytes. Observations were made of water-stress responses and recovery using infrared gas analysis and modulated chlorophyll fluorescence, and of structural and ultrastructural changes by light and transmission electron microscopy. Net CO2 uptake fell to zero at approx. 40 % RWC, paralleling the fluorescence parameter PhiPSII at 200 micromol m(-2) s(-1) PPFD. On re-wetting the moss after 9-18 d desiccation, the initially negative net CO2 uptake became positive 10-30 min after re-wetting, restoring a net carbon balance after approx. 0.3-1 h. The parameter Fv/Fm reached approx. 80 % of its pre-desiccation value within approx. 10 min of re-wetting. In the presence of the protein-synthesis inhibitors chloramphenicol and cycloheximide, recovery of Fv/Fm (and CO2 exchange) proceeded normally in the dark, but declined rapidly in the light. Though initial recovery was rapid, both net CO2 uptake and Fv/Fm required approx. 24 h to recover completely to pre-desiccation values. The fixation protocols produced neither swelling of tissues nor plasmolysis. Thylakoids, grana and mitochondrial cristae remained intact throughout the drying-re-wetting cycle, but there were striking changes in the form of the organelles, especially the chloroplasts, which had prominent lobes and lamellar extensions in the normally hydrated state, but rounded off when desiccated, returning slowly to their normal state within approx. 24 h of re-wetting. Sub-cellular events during desiccation and re-wetting were generally similar to those seen in published data from the pteridophyte Selaginella lepidophylla. Initial recovery of respiration and photosynthesis (as of protein synthesis) is very rapid, and independent of protein synthesis, suggesting physical reactivation of systems conserved intact through desiccation and rehydration, but full recovery takes approx. 24 h. This is consistent with the cytological evidence, which shows the thylakoids and cristae remaining intact through the whole course of dehydration and rehydration. Substantial and co-ordinated changes in other cell components, which must affect spatial relationships of organelles and metabolic systems, return to normal on a time span similar to full recovery of photosynthesis. Comparison of the present data with recently published results suggests a significant role for the cytoskeleton in desiccation responses.

Desiccation tolerance in the moss Polytrichum formosum: physiological and fine-structural changes during desiccation and recovery.

This study explores basic physiological features and time relations of recovery of photosynthetic activity and CO(2) uptake following rehydration of a desiccation-tolerant moss in relation to the full temporal sequence of cytological changes associated with recovery to the normal hydrated state. It seeks reconciliation of the apparently conflicting published physiological and cytological evidence on recovery from desiccation in bryophytes. Observations were made of water-stress responses and recovery using infrared gas analysis and modulated chlorophyll fluorescence, and of structural and ultrastructural changes by light and transmission electron microscopy. Net CO(2) uptake fell to zero at approx. 40 % RWC, paralleling the fluorescence parameter PhiPSII at 200 micromol m(-2) s(-1) PPFD. On re-wetting the moss after 9-18 d desiccation, the initially negative net CO(2) uptake became positive 10-30 min after re-wetting, restoring a net carbon balance after approx. 0.3-1 h. The parameter F(v)/F(m) reached approx. 80 % of its pre-desiccation value within approx. 10 min of re-wetting. In the presence of the protein-synthesis inhibitors chloramphenicol and cycloheximide, recovery of F(v)/F(m) (and CO(2) exchange) proceeded normally in the dark, but declined rapidly in the light. Though initial recovery was rapid, both net CO(2) uptake and F(v)/F(m) required approx. 24 h to recover completely to pre-desiccation values. The fixation protocols produced neither swelling of tissues nor plasmolysis. Thylakoids, grana and mitochondrial cristae remained intact throughout the drying-re-wetting cycle, but there were striking changes in the form of the organelles, especially the chloroplasts, which had prominent lobes and lamellar extensions in the normally hydrated state, but rounded off when desiccated, returning slowly to their normal state within approx. 24 h of re-wetting. Sub-cellular events during desiccation and re-wetting were generally similar to those seen in published data from the pteridophyte Selaginella lepidophylla. Initial recovery of respiration and photosynthesis (as of protein synthesis) is very rapid, and independent of protein synthesis, suggesting physical reactivation of systems conserved intact through desiccation and rehydration, but full recovery takes approx. 24 h. This is consistent with the cytological evidence, which shows the thylakoids and cristae remaining intact through the whole course of dehydration and rehydration. Substantial and co-ordinated changes in other cell components, which must affect spatial relationships of organelles and metabolic systems, return to normal on a time span similar to full recovery of photosynthesis. Comparison of the present data with recently published results suggests a significant role for the cytoskeleton in desiccation responses.

Effects of de- and rehydration on food-conducting cells in the moss Polytrichum formosum: a cytological study.

Moss food-conducting cells (leptoids and specialized parenchyma cells) have a highly distinctive cytology characterized by a polarized cytoplasmic organization and longitudinal alignment of plastids, mitochondria, endoplasmic reticulum and vesicles along endoplasmic microtubules. Previous studies on the desiccation biology of mosses have focused almost exclusively on photosynthetic tissues; the effects of desiccation on food-conducting cells are unknown. Reported here is a cytological study of the effects of de- and rehydration on food-conducting cells in the desiccation-tolerant moss Polytrichum formosum aimed at exploring whether the remarkable subcellular organization of these cells is related to the ability of mosses to survive desiccation. Shoots of Polytrichum formosum were dehydrated under natural conditions and prepared for transmission and scanning electron microscopy using both standard and anhydrous chemical fixation protocols. Replicate samples were then fixed at intervals over a 24-h period following rehydration in either water or in a 10 microM solution of the microtubule-disrupting drug oryzalin. Desiccation causes dramatic changes; the endoplasmic microtubules disappear; the nucleus, mitochondria and plastids become rounded and the longitudinal alignment of the organelles is lost, though cytoplasmic polarity is in part retained. Prominent stacks of endoplasmic reticulum, typical of the hydrated condition, are replaced with membranous tubules arranged at right angles to the main cellular axis. The internal cytoplasm becomes filled with small vacuoles and the plasmalemma forms labyrinthine tubular extensions outlining newly deposited ingrowths of cell wall material. Whereas plasmodesmata in meristematic cells at the shoot apex and in stem parenchyma cells appear to be unaffected by dehydration, those in leptoids become plugged with electron-opaque material. Starch deposits in parenchyma cells adjoining leptoids are depleted in desiccated plants. Rehydration sees complete reestablishment over a 12- to 24-h period of the cytology seen in the control plants. Oryzalin effectively prevents leptoid recovery. The results point to a key role of the microtubular cytoskeleton in the rapid re-establishment of the elaborate cytoplasmic architecture of leptoids during rehydration. The reassembly of the endoplasmic microtubule system appears to dictate the time frame for the recovery process. The failure of leptoids to recover normal cytology in the presence of oryzalin further underlines the key role of the microtubules in the control of leptoid cytological organization.

Thallium in terrestrial environments--occurrence and effects.

In this investigation thallium contents in soil and plants in the EuroRegion Neisse were analysed and the distribution determined. The median top-soil content is 0.5 mg/kg in the area investigated. In this low-contaminated area the moss Pleurozium schreberi contains 0.04-0.13 microg/g and the moss Polytrichumformosum between 0.01 and 0.05 microg/g Tl. The effects of thallium on man and the terrestrial environment were examined. In an epidemiological study a significant positive correlation was found between the thallium content of the two mosses and the incidence of diseases of the circulatory system. The LOEC for thallium in bioassays with terrestrial invertebrates and plants in artificial soil ranged from 1 to 500 mg/kg, which indicates an toxicity of thallium up to 100 times higher than that of Cadmium.

The Response of Different Cladonia Species after Treatment with Fertilizer or Lime in Heathland

The effect of deposition of different fertilizers and of lime on lichens was investigated under field conditions. Three terricolous lichens were tested: Cladonia floerkeana, C. furcata and C. portentosa. The lichens were exposed to three types of powdered fertilizer (NPK-, N-, P-fertilizer) and lime. The applied nutrients were recorded in lichen thalli and soil. The influence on lichen growth rate and vegetation cover was estimated over 2 years. The response was a clear change in vegetation cover with an exceptional stimulating effect of NPK on the moss Polytrichum formosum. A lethal effect was observed on Cladonia floerkeana following exposure to lime. NPK and P had the most significant stimulatory effect on C. furcata. Only NPK promoted the growth of C. portentosa and P, N or Ca had a negative effect.

THE RESPONSE OF DIFFERENTCLADONIASPECIES AFTER TREATMENT WITH FERTILIZER OF LIME IN HEATHLAND

The effect of deposition of different fertilizers and of lime on lichens was investigated under field conditions. Three terricolous lichens were tested:Cladonia floerkeanaC. furcataandC. portentosa. The lichens were exposed to three types of powdered fertilizer (NPK-, N-, P-fertilizer) and lime. The applied nutrients were recorded in lichen thalli and soil. the influence on lichen growth rate and vegetation cover was estimated over 2 years. The response was a clear change in vegetation cover with an exceptional stimulating effect of NPK on the mossPolytrichum formosum. A lethal effect was observed onCladonia floerkeanafollowing exposure to lime. NPK and P had the most significant stimulatory effect onC. furcata. Only NPK promoted the growth ofC. portentosaand P, N or Ca had a negative effect.

Higher lead concentrations in the environment of former West Germany after the fall of the ‘Berlin Wall’

Biomonitoring for lead and chromium in the moss Polytrichum formosum has shown that in the years before the fall of the Berlin wall, the loading of these elements was decreasing. However in 1989/1990, localized increases in the concentration of lead in this moss in the vicinity of east-west motorways were detected. This was most likely due to the greater use of leaded petrol in eastern Germany. This observation is backed up by results from Bavaria at the Czech boarder, where localized increases in lead concentrations in the environment were found during this time period. As a result of the overall generally decreasing heavy metal loading in plants, deficiencies of essential macronutrients (Mg, Ca, K) seem to be lower also. This could be interpreted from data on Polytrichum formosum which showed an increase in these elements.

Use of Polytrichum formosum (moss) as a passive biomonitor for heavy metal pollution (cadmium, copper, lead and zinc)

After sampling over regular intervals from 1985 to 1987 the heavy metals Cd, Cu, Pb and Zn were quantitatively determined by atomic emission spectrometry/inductively coupled plasma in above-ground parts of the moss Polytrichum formosum (Hedw.). All metals present a typical summer-winter oscillation (seasonal variation), which is much greater than the “inter-stand” variation of Polytrichum formosum within the forest ecosystem under investigation. To obtain comparable results on a regional or global scale it is suggested to collect all samples of Polytrichum formosum for biomonitoring purposes in the last week of September.

Fluctuations of element concentrations during the growing season of Polytrichum formosum (Hedw.)

Fourteen elements (Al, Ba, Ca, Cd, Cr, Cu, Fe, K, Mg, Ni, Pb, Sr, Ti, and Zn) were quantitatively determined by AES/ICP in aboveground parts of the endohydric moss Polytrichum formosum (Hedw.) after sampling over regular intervals from 1985 to 1987. With the exception of K, Mg, and Zn all elements showed a large continuous fluctuation (> 30%) during the growing season. Four different patterns of seasonal variation were found: (1) large seasonal variations of element concentrations (∼80%) with maximum concentrations in winter and lowest concentrations in the summer months (Al, Fe, Cr, Mg, Pb, and Ti), (2) smaller seasonal variations (∼50%) with maximum concentrations in winter and lowest concentrations in summer (Ba, Ca, Cd, Cu, Sr), (3) slight seasonal variations (∼30%) with maximum concentrations in the summer (K), and (4) slight seasonal changes (∼30%) with maximum concentrations in the winter (Mg and Zn). The relative biological variance of element concentrations between 9 different stands of Polytrichum formosum decreases in the following sequence: Ti, Al, Pb, Fe, Cr, Ni, Ba, Ca, Cu, Cd, K, Mg, Sr, Zn. The relative biological variance of individual elements is generally lower than the variance in element concentrations caused by seasonal changes. Because of its high biological variance for most elements investigated (seasonal as well as between different stands of Polytrichum formosum) this moss should only be used as a passive bioindicator, if all other environmental parameters are standardized.

Evolution de la structure plastidiale et des reserves polysaccharidiques au cours de la déshydratation des gamétophytes feuillés duPolytrichum formosumHedw. (Polytrichales)

AbstractThe effects of a 24 h dehydration period on plastid ultrastructure and their starch content have been studied on the leafy gametophyte of a poikilohydrous moss Polytrichum formosum Hedw. It has been shown that desiccation induces a swift resorption of the starch grains in the plastids of the meristematic cells of the shoot apex without any major disorganisation of the thylakoids. However starch grains are preserved in the dehydrated tissues of the adult leaves. The starch hydrolysis is continued with a marked increase of the sucrose concentration to this may be attributed an osmoregulatory role in the first stages of the water loss. Upon rehydration the plastid ultrastructure is entirely restored with new starch inclusions appearing in less than 4 h.

Echinenone (ß,ß-Caroten-4-one) from the Gametophyte of Polytrichum formosum (Bryophyta, Musci)

Summary For the first time the keto-carotenoid echinenone has been found in the gametophyte of some samples of the moss Polytrichum formosum , besides the normal chloroplast pigments. This carotenoid was not detected in the sporophyte. Pollution by echinenone containing microorganisms (blue-green algae, bacteria) could be excluded. Protonemata and moss plantlets cultivated from the spores of those echinenone containing mosses have been able to biosynthesize this keto-carotenoid, too.

EFFECT OF DESICCATION ON DNA SYNTHESIS AND THE CELL CYCLE OF THE MOSS POLYTRICHUM FORMOSUM

SUMMARYThe effects of a 24‐h dehydration period on the mitotic and DNA‐synthetic activities have been studied in the meristematic cells of the leafy gametophyte of the moss Polytrichum formosum. During the first 2 h of water stress the mitotic index decreased dramatically, and after 6 h none of the cells was observed in division. It is concluded that the stress provokes not only cessation, but also completion of the mitotic phase, so that all the cells of the desiccated plants become interphasic. On rehydration, a period of 24 h was necessary for the first cell to enter division. After 4 h of recovery from water stress, DNA synthesis resumed in the nuclei of a few cells indicating that replication processes were not injured to any marked extent by the desiccation treatment. However, a clear increase in the number of nuclei entering the S phase was only observed 24 h after the start of rehydration. It is suggested that the effect of the dehydration period is to prevent the cells which are situated in G1 or G2 phases to enter respectively the phases of S and M of the cell cycle immediately upon rehydration. In any case the result is to delay, for about 24 h from the beginning of rehydration, the return of proliferative activity. These data are compared with those previously obtained on the metabolism of water‐stressed mosses.

Beobachtungen zur biologie und ultrastruktur der moosbewohnenden thekamöbe Nebela tincta (Rhizopoda)

Summary The present paper includes observations on the population, the structure and ultrastructure of the shell and of the cyst, and the vertical distribution in the moss as well as observations on the excystment of Nebela tincta. The population of Nebela tincta in the moss Polytrichum formosum is characterized biometrically as a distinct group. The theca of Nebela tincta consists of innumerable siliceous platelets which are embedded into a layer of a homogeneous cement at the outside. The platelets are of different size and shape. They originate from various thecamoebean species, thus representing xenosomes in the theca of Nebela tincta. The platelet-pattern differs from theca to theca, not only with respect to platelet variety, but also in the extent of surface covering by the platelets. There is no indication towards a production of platelets by Nebela tincta itself. The stages of duration (cysts) are characterized by the plasma being motionless and rounded off within a homogeneous cystic membrane. The cystic membrane fastens the plasma to the plug by which the mouth of the theca is closed. This plug is composed of organic waste particles and more or less parallel layers of the same types of siliceous platelets which are used in the construction of the shell. The vertical distribution of Nebela tincta in the moss exhibits a maximum in the zone of decomposition of the green leaflets. Excystment occurs by uptake of water, rupture of the cystic membrane, and disintegration of the plug. Both the cystic membrane and the components of the plug are phagocytized. The possible functions of the lateral pores during encystment, excystment, and active life are discussed.