Growth strategies of four salt marsh plants on Mankyung River estuary in Korea

The emergence of seedlings, the length of roots and shoots, and the biomass of four dominant plant species and shore height were measured to investigate the growth strategy of these plants on the salt marsh of Mankyung River estuary. Four salt marsh plants showed a distinctive zonation, for example, Suaeda japonica was predominantly spread around the low salt marsh, Atriplex gmelini and Aster tripolium were in the middle, and S. asparagoides was in the upper part of the marsh. In terms of emergence of seedlings, S. japonica appeared first followed by A. gmelini, S. asparagoides, and A. tripolium. The growth strategies of halophytes were as follows: S. japonica germinated earlier than the other halophytes so that its root grew rapidly and extensively at the beginning of growth. This species adopted a continuous germination strategy, allowing growth whenever favorable conditions were provided. A. gmelini germinated later than S. japonica, as a quasi-simultaneous germination type, it showed the highest germination rate within the shortest time. Aster tripolium germinated later than any other halophyte. Since this species exhibited characteristics between the continuous germination type and the quasi-simultaneous germination type, it did not show a very high germination rate. Instead, it showed continuous germination and consistent growth of both above-ground and underground parts. Suaeda asparagoides showed an especially high emergence rate at the beginning of its growth. However, the high density retarded its growth until the middle stage. Its roots extended longer than the other halophytes, allowing it to grow well in the dry conditions of the upper marsh.     

Impact of different sheep grazing intensities on salt marsh vegetation in northern Germany

Abstract. Mainland salt marshes in Schleswig-Holstein (northern Germany) have been grazed intensively by sheep for several decades. In 1988 experimental sites were established in the lower and middle salt marsh of Sönke-Nissen-Koog and subjected to different grazing intensities. From 1989 to 1993 the impact of sheep grazing on the composition and structure of the salt marsh vegetation was studied through the yearly analysis of permanent plots, vegetation mapping and measurements of the vegetation height. The intensively grazed site (10 sheep/ha) is covered by a short monotonous Puccinellia maritima sward with Salicornia europaea and Suaeda maritima. Halimione portulacoides and Aster tripolium, especially flowering plants, are rare. On the sites with 1.5 and 3 sheep/ha Puccinellia maritima remained dominant. The population density of Salicornia europaea decreases after reduction of the grazing intensity, whereas Suaeda maritima finds optimal growing conditions. Stands of Halimione portulacoides and flowering Aster tripolium plants are rare near the sea dike but their cover and size increases further away from the dike. In the plot with 1.5 sheep/ha the height of the vegetation increases along the gradient from the dike towards the tidal flats, due to local differences in actual grazing intensity. When grazing is stopped, Puccinellia maritima is successively replaced by Festuca rubra, Halimione portulacoides and Aster tripolium. High variability of vegetation height indicates structural diversity. Patches of higher and lower vegetation correspond with the distribution pattern of different plant species. In terms of nature conservation cessation of grazing is recommended.     

The performance of the leaf mining microlepidopteran Bucculatrix maritima (Stt.) on the salt marsh halophyte,Aster tripolium (L.), exposed to different salinity conditions

Summary The performance of phytophagous insects is influenced by the nutritional quality of the food plant, which may vary with environmental conditions. Hardly any information exists on food-plant mediated effects of variable soil salinity on the performance of phytophagous insects. Conspicuous differences in salinity levels, however, are found in soils of intertidal wetlands such as salt marshes and mangroves. The growth of larvae of Bucculatrix maritima, a leaf miner of the salt marsh halophyte Aster tripolium, was studied on the host plant along the salinity gradient of the Westerschelde estuary (S.W. Netherlands). In addition, its performance on A. tripolium grown on low or high salinity culture medium was investigated experimentally. Although salinity conditions significantly influenced the chemistry of the host plants, insect performance seemed almost unaffected, although near the mouth of the estuary high environmental salinities may have caused some inhibition of larval growth. The results contrast with our previous studies on the stem-borer Agapanthia villosoviridescens, which showed that growth and development was conspicuously influenced by the changing characteristics of Aster tripolium along the estuarine salinity gradient. The location-dependent qualities of halophytes in an estuary thus appear to have species-specific effects on insect performance. We hypothesize that this phenomenon contributes to the existence of non-identical distribution patterns of phytophagous insects associated with the same halophyte in an estuary.     

Drought, but not salinity, determines the apparent effectiveness of halophytes colonized by arbuscular mycorrhizal fungi

The halophytes Plantago maritima, Aster tripolium, Artemisia santonicum, Puccinellia limosa, Festuca pseudovina and Lepidium crassifolium from two different saline soils of the Hungarian steppe were examined for colonization by arbuscular mycorrhizal fungi (AMF). The salt aster (A. tripolium) and the sea plantain (P. maritima) were examined more thoroughly by recording root colonization parameters, the salt content in the soil and monthly precipitations in 2001 and 2002. Mycorrhizal colonization was maximal in late spring to early summer and had a second peak later in the autumn. Arbuscule formation and overall mycorrhizal colonization appeared to be inversely correlated with the intensity of rainfall at the investigated sites. The results suggest that, in addition to seasonality, drought may play an important role in governing mycorrhizal activity in saline habitats. In greenhouse experiments, conditions in which AMF could overcome the inhibitory effects of sodium chloride on establishing plant–mycorrhizal symbiosis were not met.     

Do Conditions During Dormancy Influence Germination of Suaeda maritima?

Background and Aims

Seeds of annual halophytes such as Suaeda maritima experience fluctuating salinity, hydration, hypoxia and temperature during dormancy. Germination then occurs in one flush of 2–3 weeks after about 5 months of winter dormancy during which time the seeds can remain in saline, often waterlogged soil. The aim of this study was to investigate the effect of simulated natural conditions during dormancy on germination and to compare this with germination following the usual conditions of storing seeds dry. The effects of hydration, salinity, hypoxia and temperature regimes imposed during dormancy on germination were investigated. Also looked at were the effects of seed size on germination and the interaction between salinity during dormancy and salinity at the time of germination.

Methods

Various pre-treatments were imposed on samples of seeds that had been stored dry or wet for different periods of time during the 5 months of natural dormancy. Subsequent germination tests were carried out in conditions that simulated those found in the spring when germination occurs naturally. Various salinities were imposed at germination for a test of interaction between storage salinity and salinity at germination.

Key Results

A temperature of about 15 °C was needed for germination and large seeds germinated earlier and better than small seeds. Cold seawater pre-treatment was necessary for good germination; the longer the saline pre-treatment during the natural dormancy period the better the germination. There appeared to be no effect of any specific ion of the seawater pre-treatment on germination and severe hypoxia did not prevent good germination. A short period of freezing stimulated early germination in dry-stored seed. Storage in cold saline or equivalent osmotic medium appeared to inhibit germination during the natural dormancy period and predispose the seed to germinate when the temperature rose and the salinity fell. Seeds that were stored in cold wet conditions germinated better in saline conditions than those stored dry.

Conclusions

The conditions under which seeds of S. maritima are stored affect their subsequent germination. Under natural conditions seeds remain dormant in highly saline, anoxic mud and then germinate when the temperature rises above about 15 °C and the salinity is reduced.Key words: Suaeda maritima, germination, pre-treatment, salinity, temperature     

Germination and early establishment of lower salt-marsh species in grazed and mown salt marsh

Abstract. Lower salt-marsh species occur more in the grazed than in the mown sites of a salt marsh in Schiermonnikoog in the Netherlands. This was demonstrated by a sowing experiment which determined which characteristic of the stand structure, height of the canopy or percentage of bare soil, is responsible for this difference. The total number of seedlings which emerged was negatively related to the height of the canopy and positively to the percentage of bare soil. The survival of seedlings of Suaeda maritima and Plantago maritima could be explained by the height of the canopy and for the latter species also by the percentage of bare soil. The survival of Aster tripolium and Plantago maritima was higher in grazed than in mown sites. Since the amount of bare soil was higher than seemed necessary for germination and survival, it was concluded that the taller canopy was responsible for the absence of lower salt-marsh species in the mown sites.     

Factors affecting the population dynamics of Suaeda maritima at initial stages of development

This study describes life history and population dynamics of the annual halophyte Suaeda maritima, at initial stages of seedling development, in salt-marshes of the Mont-Saint-Michel Bay. Effects of salinity on seed germination and seedling development were studied both in the laboratory and in the field. Salinity was measured as sediment electrical conductivity. Experiments in the laboratory showed that Suaeda maritima was relatively tolerant to salinity during the germination stage. In the field, germination occurred when soil salinity was minimal. Almost all seeds germinated in the field; this may explain the absence of a persistent seed bank. Salinity did not seem to affect the growth of seedlings either. Mortality in the field was attributed to physical factors such as anoxia during temporary immersion, burial by sediment and tidal uprooting. The intensity of these effects varied according to the location of Suaeda maritima seedlings: in hollows, along the edge of tidal creeks, in gaps among dense vegetation cover, or in pattern with Puccinellia maritima. Perennial vegetation did not restrict Suaeda maritima germination. In contrast, perennials such as Puccinellia maritima and Halimione portulacoides limited the development of Suaeda maritima seedlings since only a small number of this annual emerged beneath their canopies. The fate of seedlings depended to a great extent on the permeability of the perennial canopy to light. Thus, disturbance resulting in bare patches inside the perennial vegetation seemed essential for the development of this annual species. Suaeda maritima can grow in the presence of Puccinellia maritima so long as the latter present as an open matrix. Suaeda maritima may also benefit from protection against desiccation and tidal action where this occurs.     

Protocols for Use of Potamogeton perfoliatus and Ruppia maritima Seeds in Large‐Scale Restoration

Restoration of submerged aquatic vegetation from seed has been hampered by a lack of information on the appropriate conditions for collecting, processing, and storing seeds prior to dispersal. Seeds must be processed and stored under conditions that maintain seed viability, meet dormancy requirements, and prevent premature germination. This study examined the effects of collection date, processing technique, aeration, storage and induction temperature and salinity, and storage period on seed germination of two mesohaline aquatic species, Potamogeton perfoliatus and Ruppia maritima. Collection date and processing technique were significant factors affecting seed yield from donor populations. Seeds of both species remained viable and germinated best when stored at 4°C, and then exposed to freshwater induction conditions. However, their responses to other factors differed. Aeration during storage was necessary in order to maintain viability of P. perfoliatus seeds, whereas it was unnecessary for R. maritima seeds. Storage in freshwater at 4°C prevented germination of P. perfoliatus seeds, while high salinity during cold storage was necessary to minimize premature germination of R. maritima. Mean germination time of P. perfoliatus was dependent on storage salinity; in contrast, mean germination time of R. maritima seeds was dependent on induction salinity. These differences indicate that the methods required to produce large quantities of underwater plant seed amenable to large‐scale restoration efforts must be tailored to the specific requirements of individual species and must consider the range of processes from initial harvest through seed testing prior to field establishment.     

Temporal and spatial variation of arbuscular mycorrhizas in salt marsh plants of the Tagus estuary (Portugal)

The factors which may influence temporal and spatial variation in plant arbuscular mycorrhizal (AM) colonization and propagule occurrence were evaluated in a Portuguese salt marsh poor in plant diversity. Two distinct sites were studied: a more-flooded (low marsh) and a less-flooded zone (high marsh). AM root colonization, AM fungal spore number and inoculum potential, soil edaphic parameters and tidal flooding time periods were analysed. Levels of AM colonization were considerable in Aster tripolium and Inula crithmoides but very low in Puccinellia maritima and non-existent in Spartina maritima, Halimione portulacoides, Arthrocnemum fruticosum and Arthrocnemum perenne. Fungal diversity was very low, with Glomus geosporum dominant at both marsh zones. Colonization showed no spatial variation within marsh zones but temporal variation was observed in the high marsh, dependent on plant phenological phases. In the low marsh, no significantly seasonal variation was observed. Apparently, plant phenological events were diluted by stressful conditions (e.g. flooding, salinity). Spore density was significantly different between marsh zones and showed temporal variation in both zones. This study showed that distribution of mycorrhizas in salt marsh is more dependent on host plant species than on environmental stresses.     

Salt regulation in halophytes

Summary Ion concentration and saturation water content were measured in various aged leaves of halophytes growing in saline soils east of lake Neusiedlersee (Austria).All species investigated showed a substantial sodium accumulation within the maturing organs accompanied by a considerable potassium decline. In most species chloride concentration rises distinctly with increasing leaf age, too, whereas concentration shifts of alkaline earth ions and of sulfate (except in Plantago maritima, Lepidium crassifolium and Crypsis aculeata) are of comparably less importance.Saturation water increases markedly in succulent species (Suaeda maritima, Chenopodium glaucum, Spergularia media, Lepidium crassifolium) and to a less degree in xerophytic monocotyledons (Puccinellia distans, Crypsis aculeata, Bolboschoenus maritimus). However, this surplus of water in older leaves is not sufficient to dilute the salt to such an extent that a rise in concentration can be prevented (except chloride in Suaeda maritima and Chenopodium glaucum).Rosette plants (Triglochin maritimum, Plantago maritima, Scorzonera parviflora, Aster tripolium) with the ability to renew their leaves continuously throughout the growth period are characterized by only insignificant changes of saturation water content with increasing leaf age. In these plants, shedding of old salt-saturated leaves is thought to be the main strategy for salt regulation.A modification of Steiner's classical concept of different salt regulation types is proposed, based on original findings about salt regulation in Austrian halophytes and on new bibliographical data upon additionally revealed regulatory principles in halophytes and saltaffected nonhalophytes.Respectfully and thankfully dedicated to Prof. Dr. H. Kinzel on the occasion of his 50th birthday.     

High salinity impacts germination of the halophyte Cakile maritima but primes seeds for rapid germination upon stress release

Seed germination recovery aptitude is an adaptive trait of overriding significance for the successful establishment and dispersal of extremophile plants in their native ecosystems. Cakile maritima is an annual halophyte frequent on Mediterranean coasts, which produces transiently dormant seeds under high salinity, that germinate fast when soil salinity is lowered by rainfall. Here, we report ecophysiological and proteomic data about (1) the effect of high salt (200 mM NaCl) on the early developmental stages (germination and seedling) and (2) the seed germination recovery capacity of this species. Upon salt exposure, seed germination was severely inhibited and delayed and seedling length was restricted. Interestingly, non‐germinated seeds remained viable, showing high germination percentage and faster germination than the control seeds after their transfer onto distilled water. The plant phenotypic plasticity during germination was better highlighted by the proteomic data. Salt exposure triggered (1) a marked slower degradation of seed storage reserves and (2) a significant lower abundance of proteins involved in several biological processes (primary metabolism, energy, stress‐response, folding and stability). Yet, these proteins showed strong increased abundance early after stress release, thereby sustaining the faster seed storage proteins mobilization under recovery conditions compared to the control. Overall, as part of the plant survival strategy, C. maritima seems to avoid germination and establishment under high salinity. However, this harsh condition may have a priming‐like effect, boosting seed germination and vigor under post‐stress conditions, sustained by active metabolic machinery.     

Sulphide tolerance in coastal halophytes

The effect of sulphide on the growth of several species of salt-marsh plants was investigated. Relative growth rates were significantly reduced in two upper-marsh species, Festuca rubra and Atriplex patula, and in the lower-marsh species Puccinellia maritima. However the growth of Salicornia europaea, a species frequently associated with sulphide-containing sediments, was unaffected. In a separate experiment the wide ranging halophyte Aster tripolium, also appeared to be tolerant of sulphide at a concentration frequently encountered in salt marshes. Sulphide pretreatment inhibited the activity of two metallo-enzymes, polyphenol oxidase and external phosphatase, in plants from the upper marsh, but had no effect on enzymes from P. maritima or S. europaea. The rate of respiration by root tissue was significantly reduced in all of the species investigated but whereas the uptake of ⁸⁶rubidium was markedly inhibited in the other three species, uptake by S. europaea showed a significant stimulation. Similarly, whereas sulphide-grown plants of F. rubra, A. patula and P. maritima had a considerably reduced tissue iron content, the total iron concentration in S. europaea tissues was comparable to that of the controls. When the sulphide-tolerant species A. tripolium was grown in sulphide-containing media there was no significant effect on the tissue concentration of any of the elements investigated. These results are discussed in relation to possible mechanisms of sulphide toxicity and resistance.     

High occurrence of rare inland halophytes on post‐mining sites in western Ukraine

Rare inland halophytic vegetation including the associations Salicornietum prostratae, Spergulario marginatae‐Suaedetum prostratae, Puccinellietum limosae, com. Puccinellietum limosae – a variant of Aster tripolium subsp. pannonicus and Astero pannonici‐Bolboschoenetum compacti have been found on 3 localities in the Drohobych region of western Ukraine. These are isolated (‘island’) localities, almost unknown until today. Halophytes grew there on salted sites in the vicinity of the old salt industry. Species of halophytes previously not known from this region were discovered: Aster tripolium subsp. pannonicus, Bolboschoenus maritimus, Gypsophila paniculata, Limonium gmelinii, Lotus tenuis, Puccinellia distans, Sonchus palustris, Suaeda prostrata, Trifolium fragiferum var. bonannii, Triglochin maritima, Typha laxmannii and Zannichellia palustris subsp. pedicellata. The occurence of these plants strictly depends on the presence of salt in the soil and they are endangered by shrinkage of salted sites following the termination of the salt industry in Drohobych region.     

Aggregative responses of brent geese on salt marsh and their impact on plant community dynamics

The aggregative responses and habitat preferences of a generalist herbivore, the dark-bellied brent goose Branta bernicla bernicla, feeding on salt marshes are examined in relation to vegetation community characteristics and the abundances of individual plant species. In the autumn, feeding was strongly concentrated on the low marsh, which had the highest biomass of the preferred food plant, Salicornia europaea. There was a strong aggregative response of the geese to the abundance of S. europaea. A decline in the availability of S. europaea led to an increase in the pattern of aggregation in relation to the two other major food plants on the low marsh, Aster tripolium and Puccinellia maritima. The availability of these food plants, however, reached critically low levels in mid-winter and the geese abandoned the low marsh for the high marsh. Within the high marsh, the plant communities selected tended to be dominated by the inedible species Limonium vulgare. The food plants selected were P. maritima in the winter and P. maritima and Triglochinmaritimum in the spring. On the high marsh, aggregative responses were shown to both P. maritima and T. maritimum, but in both cases, aggregation increased up to a critical level of biomass, and then declined. The prevention of grazing with exclosures for 3 years led to an increase in the abundance of P. maritima on both high and low marshes. This change was slight on high marsh but pronounced on low marsh, where S. europaea showed a decrease in abundance in the exclosures over this time. The implications of the aggregative responses for the population dynamics of P. maritima and S. europaea are discussed. Received: 11 September 1997 / Accepted: 12 December 1997     

The effect of extended exposure to hypersaline conditions on the germination of five inland halophyte species

In order to determine how salinity and exposure time affect seed viability and germination, seeds of five halophytes, Atriplex prostrata, Hordeum jubatum, Salicornia europaea, Spergularia marina, and Suaeda calceoliformis were exposed to 3.0, 5.0, and 10.0% NaCl solutions for 30, 60, 90, 365, and 730 d. Recovery experiments in distilled water indicated significantly different species responses to salinity over time. Percentage germination and rate of germination in H. jubatum were dramatically reduced following extended exposure and all seeds exposed to 10% NaCl for > 1 yr failed to germinate. Spergularia marina seeds were stimulated following short-term exposure to 3% NaCl; however, germination was delayed and overall germination was significantly reduced with exposure time in the two higher salinity levels. Percentage germination in A. prostrata decreased over time, but salinity level was not related to this reduction. Germination of S. europaea and S. calceoliformis, the most salt-tolerant species being tested, was stimulated by exposure to high salinity. Both species had a significant increase in percentage germination and in the germination rate when compared to seeds germinated in distilled water. Baseline germination data from seeds placed in 0, 1, 2, and 3% NaCl solutions indicated that S. europaea and S. calceoliformis were the only species to germinate in the 3% NaCl solution. Spergularia marina failed to germinate in the 2% NaCl treatment, and germination of A. prostrata and H. jubatum was significantly reduced at this salinity level. It is concluded that prolonged exposure to saline solutions can inhibit or stimulate germination in certain species, and the resulting germination and recovery responses are related to the duration and intensity of their exposure to salt in their natural habitats.     

The effect of sodium chloride on enzyme activities from four halophyte species of chenopodiaceae

The in vitro effect of sodium chloride on the enzyme activity of four halophytes, Beta vulgaris ssp. maritima (L.) Thell., Halimione portulacoides (L.) Aell., Salicornia ramosissima Woods and Suaeda maritima (L.) Dum. was investigated. The activity was, in general, affected by sodium chloride in a similar manner to that reported for salt sensitive species. The most notable exceptions were the sodium chloride stimulated ATPases of Beta and Salicornia.     

Dormancy and germination responses of halophyte seeds to the application of ethylene

Ethylene is invariably produced during seed germination but its role in regulating seed dormancy and germination is poorly understood. Seeds of 22 halophytic species having different life forms – salt secreting dicots, salt secreting monocots, stem succulents and leaf succulents were germinated in Petri dishes kept in a growth chamber set at 20/30 °C (night/day) temperature and a 12 hr light period. Sodium chloride and ethephon were added to the medium from the beginning of the experiment. Seed germination was recorded every other day for twenty days. Application of ethylene did not have any significant effect on releasing seeds from innate dormancy. However, it appeared to have a role in alleviation of salinity effects which varied from negative in certain species to almost complete alleviation of high salinity effects in others.Our data indicates that ethylene appears to have little role in breaking innate seed dormancy however, in most halophyte seeds studied, application of ethylene alleviate the salinity effect to various degrees. Halophyte seeds which could germinate under saline conditions approaching twice the salinity of seawater may offer clues to understand management of seed germination under highly saline conditions. To cite this article: M.A. Khan et al., C. R. Biologies 332 (2009).     

Seasonal changes in the germination responses of Hordeum maritimum and H. murinum seeds in relation to salinity,temperature and after‐ripening time

Abstract

The effects of temperature and salinity (NaCl) on germination of Hordeum maritimum With, (halophyte) and H. murinum L. (glycophyte) seeds were investigated. Dehulled caryopses were used for monthly germination trials, starting from November (120 days of after‐ripening in darkness at 20±1°C). Trials were continued for one year. Differences in germination response between the two species were observed, confirming that H. Maritimum is better adapted to high salinity levels and to variations in external temperature than H. murinum. H. maritimum showed a germination control mechanism related to after‐ripening time and based on seed dormancy break/resumption. At higher temperature (30°C), thermodormancy was also recorded. No germination strategies were observed in H. murinum that is relatively insensitive to the combined effects of temperature and salinity. Thus, in virtually all treatments, H. murinum exhibited a higher germination rate compared with H. maritimum, as early as 72 h after imbibition, suggesting that dormancy, both in the presence or absence of salt, is totally abolished by early fall or at the latest in winter.     

The distribution and ecology of coastal species on roadsides

The invasion of roadsides by coastal species is a response to the use of de-icing salt. The most widespread species on Britain's roadsides, Puccinellia distans, occurs in the north and east of England and Wales. This distribution is due to the varying use and effects of de-icing salt which are related in turn to regional differences in climate and traffic density. On roadsides, seed dispersal is greater in the direction of traffic flow and the smaller seeds of Puccinellia distans are carried further than the larger seeds of Plantago maritima. Species on roadsides occur in distinct zones with the coastal species confined to the saline road margin. The causes of this zonation were investigated by examining seedling establishment in experimental plots. Seedlings were only able to establish in grass plots when the salinity was sufficiently high to kill the competing glycophytic grasses. On bare soil, the halophytes established and grew satisfactorily when salt was added but grew very poorly in the absence of salt. After two years Plantago maritima overcame this apparent requirement for salt on bare soil but Puccinellia distans and Spergularia marina did not.Acknowledgements: N. E. Scott was in receipt of a N.E.R.C. Studentship. The authors wish to thank the members of the B.S.B.I. and the Biological Records Office for information on species distribution.     

Stomatal responses to sodium ions in Aster tripolium: a new hypothesis to explain salinity regulation in above-ground tissues

A study has been made of the ionic relations of stomata of Aster tripolium L., a maritime halophyte which colonizes coastal saltmarshes. The results obtained allow us to add this species to the growing list for which an involvement of K⁺ transport in stomatal movements has been demonstrated. However, an additional and ecologically important characteristic was found: there was a suppression of stomatal opening by increasing NaCl concentrations. A new hypothesis is offered of the mechanism for controlling salt and water relations in A. tripolium, a species which does not possess glands or other means of excreting salt. It is suggested that when the capacity of the tissues to accumulate salt in cell vacuoles is exceeded, the concentration of Na⁺ ions in the apoplast around the guard cells begins to rise. This causes partial stomatal closure, reduces transpiration and increases water-use-efficiency. Therefore, the flow of salt into the leaves is reduced but growth (and the manufacture of the new photosynthates required to support it) can continue. Aster tripolium can be added to the small list of known species which readily yield isolated epidermis suitable for detailed stomatal studies. Throughout this study, we have compared its stomatal physiology with C. communis, which has been thoroughly investigated in the past.