Seed traits and germination behaviour of four Sardinian populations of Helichrysum microphyllum subsp. tyrrhenicum (Asteraceae) along an altitudinal gradient

• Helichrysum microphyllum subsp. tyrrhenicum (Asteraceae) is an endemic taxon of Sardinia and Corsica, where it grows at different altitudes. The objective of this study was to investigate the seed traits and germination behaviour of four Sardinian populations of this taxon located at different altitudes.
• Seed traits were evaluated, and germination tests were carried out by incubating seeds at a range of constant (5–30 °C) and alternating (25/10 °C) temperatures. The dry after‐ripening (DAR) pre‐treatment was also applied by storing seed in dry conditions for 3 months at 25 °C. Seed traits and germination behaviour data were statistically analysed to identify if there was a correlation with altitude.
• Differences in seed size, area and mass among populations were recorded, however, no relationship was found with altitude. High germination percentages were obtained in all populations, both in untreated and DAR seeds, and were positively affected by alternating temperatures. The final germination percentage and time required to reach 50% final germination (T₅₀) showed no relationship with altitude.
• The differences in seed traits and germination detected among the studied populations of H. microphyllum subsp. tyrrhenicum were not correlated with altitude. This study provides new and important knowledge for this taxon. H. microphyllum subsp. tyrrhenicum is characterised by high germination percentages and low T₅₀ values and does not seem to require any dormancy‐breaking treatment. This species represents a high‐potential native plant species that should be considered within environmental management plans.

     

The germination of somePotamogeton species from South-Bohemian fishponds

A study is presented of germination inPotamogeton angustifolius, P. acutifolius, P. obtusifolius, P. crispus, P. lucens, P. natans, P. pectinatus, P. pusillus andP. trichoides, and the possibility of overcoming dormancy in these species under laboratory conditions. Three of the species, viz.Potamogeton pectinatus, P. pusillus andP. trichoides have been examined in greater detail. Impermeability of the fruit coat appears to be the main reason for the dormancy of these species. The lowest percentage of the impermeable achenes has been recorded inPotamogeton crispus.     

Recognition of root exudates by seeds of broomrape (Orobanche and Phelipanche) species

Background and Aims

The long co-existence of broomrapes and their hosts within the same environment has culminated in a strong adaptation and effective parasitism. As a first step of specialization in the parasitic process, seed receptors of parasitic plant species vary in their ability to recognize compounds released by their hosts. This work aims to investigate potential patterns for the reception requirements needed to activate germination within Orobanche and Phelipanche species.

Methods

Induction of the germination of seeds of nine Orobanche and Pheliphanche species by root exudates of 41 plant species was studied and subjected to biplot multivariate analysis.

Key Results

A high level of specialization in root exudate recognition was found in Orobanche densiflora, O. gracilis and O. hederae, which germinated almost exclusively in contact with root exudates from the plants they infect in nature. At the opposite extreme, Phelipanche aegyptiaca, P. ramosa and O. minor were highly generalist, germinating when in contact with the root exudates of most plant species. Orobanche crenata, O. cumana and O. foetida showed intermediate behaviour.

Conclusions

A universal germination stimulant for all broomrape species has not being identified to date. The synthetic stimulant GR24 is active against most of the weedy broomrape species, but fails with the non-weedy species tested in this study and with the very recent weedy species O. foetida. In addition, germination behaviour of broomrape species depends on the crop plant tested. Weedy broomrapes with a broad host spectrum respond better to the different exudates released by a wide range of crops and wild species than do non-weedy broomrapes, which have a narrow host spectrum and are more restricted to their host range. Root exudates of many plant species were active in stimulating germination of seeds of Orobanche and Phelipanche species for which they are not described as hosts, representing interesting examples of potential trap crops.Key words: Xenognosis, broomrape, root exudate, germination, Orobanche, Phelipanche     

Comparative germination ecology of two altitudinal vicariant Saxifraga species endemic to the north of Spain

Seeds of high‐mountain species are thought to germinate rapidly, synchronously and at high percentages after a cold period, with limited dependence on the external environment; yet, empirical evidence only partially supports this behaviour. We performed a comparative study of the germination response of two closely related taxa along an altitude gradient in northern Spain. Seeds from several maternal families of six populations of Saxifraga trifurcata (lowland species) and S. canaliculata (highland species) were subjected to temperature and stratification treatments. Germination percentages and germination rates were analysed using generalised linear mixed modelling and accelerated failure‐time modelling. We found that germination percentages and germination rates were high and dependent on incubation temperature in both species. Within species, seeds from higher altitudes had higher germination percentages under all conditions. Cold–wet stratification negatively affected germination success, particularly in the lowland species. Overall, the highland species was less responsive to the experimental treatments and showed more synchronous germination patterns. We conclude that seeds from these two Saxifraga species germinate as efficiently as species from other habitats, but have a narrower germination response, probably due to the stronger selective pressures in their harsh environments. Finally, a cold, wet stratification period is not a prerequisite for the germination of high‐mountain S. canaliculata, and its strong negative effect on the germination of its lowland relative S. trifurcata may contribute to the altitudinal segregation of these two species.     

Germination ofRubus palmatus var.coptophyllus andR. microphyllus seeds buried in soil for 7.5 years

Seeds of twoRubus species,R. palmatus var.coptophyllus andR. microphyllus, buried for 7.5 years in soil were subjected to germination tests to investigate their germinability and germination traits. Most of the retrieved seeds were viable, and germinated at the alternating temperatures of 20/30°C in both light and dark. The twoRubus species showed similar responses of germination to temperature and light, although the final percentages of germination were slightly higher inR. palmatus var.coptophyllus. These characteristics of seed dormancy and germination would be involved in the species' utilization of ephemeral habitats created by unpredictable and infrequent disturbances.     

Effect of sunscreens,irradiance and resting periods on the germination ofMetarhizium flavoviride conidia

Chemical sunscreens were incorporated into oil formulations of conidia of two isolates of the entomopathogenic fungusMetarhizium spp. and the formulations exposed to simulated solar radiation. After 2 h exposure several sunscreens gave protection as demonstrated by conidial germination after 24 h incubation on gelatin plates at 26°C but only the formulations with Eusolex 8021 showed higher germination than the unprotected control after 48 h incubation. During 5h of exposure, Eusolex 8021 failed to offer significant protection as demonstrated by conidial germination after 48 h incubation. Conidial damage was proportional to the duration of radiation received. Allowing periods of darkness between exposures did not result in decreased loss of viability. Storing conidia, after exposure to simulated radiation, for 24 h prior to germination reduced their viability.     

Germination response to various temperature regimes of four Mediterranean seeder shrubs across a range of altitudes

In dry-summer seasonal climates, the beginning of the rainy season can prompt germination under different temperatures, depending on altitude. Understanding germination responses to temperature with altitude is important in fire-prone environments for species regenerating after fire from seeds (seeders), particularly under changing climate. Here we investigated the role of temperature in four Mediterranean seeder shrubs from Central Spain. Seeds from 17 sites (285–1,253 m altitude), of two hard-seeded nanophanerophytes (Cistus ladanifer and C. salviifolius) and two soft-seeded chamaephytes (Lavandula pedunculata and Thymus mastichina) were investigated. Intact and heat shock treated seeds were set to germinate under four temperature regimes, including a treatment simulating future warming. GLM with binomial or gamma functions were used to test treatment effects using altitude as a covariate. Altitude was a significant covariate only in L. pedunculata. Temperature did not affect final germination in either Cistus, but it significantly affected T. mastichina, and interacted with altitude in L. pedunculata, whereby the higher the altitude the less it germinated with decreasing temperature. Germination speed (T₅₀) was lower at colder temperatures in all but C. salviifolius that was insensitive to our treatments. Heat shock significantly increased final germination in both Cistus and T. mastichina, but did not interact with temperature or altitude. We conclude that germination response to temperature, including varying sensitivity with altitude, differed among these species; thus, changes in the timing of the onset of the rainy season will diversely affect populations at various altitudes. We discuss our results in a context of changing climate and fire.     

Effect of air traffic pollution on seed quality characteristics of Pinus brutia

This study was undertaken to examine to what degree traffic air pollution affect the reproductive material (the seeds) of Pinus brutia. The study focused on the investigation of the seeds morphological characteristics and physiological attitudes as well as heavy metal concentrations of P. brutia trees grown close the ring-road of Thessaloniki (Greece's second biggest city), polluted by heavy traffic conditions, and how these characteristics are changed with the distance from the pollution source. A sampling procedure was established for seed collection from various distances from the pollution source. Seeds were properly prepared, measured for their morphological characteristics and heavy metal concentrations, as well as for their physiological behaviour (germination and viability). Analysis of the results showed that even though there were no significant differences in seed heavy metal concentrations, and only few in seed morphological characteristics, related to the distance from the traffic pollution source, there was a significant alteration of physiological behaviour for the seeds originated closed to the traffic. All the seed collected close to the ring-road (sample distances 0 and 30 m from the road) were unable to germinate, even those subjected to pre-treatments and repeated germination trials over longer duration, while those collected from distances over 100 m from the ring-road showed a common germination behaviour.     

Vascular plant diversity and climate change in the alpine zone of the Lefka Ori,Crete

The aim of this study is to analyse the vascular flora and the local climate along an altitudinal gradient in the Lefka Ori massif Crete and to evaluate the potential effects of climate change on the plant diversity of the sub-alpine and alpine zones. It provides a quantitative/qualitative analysis of vegetation-environment relationships for four summits along an altitude gradient on the Lefka Ori massif Crete (1664–2339 m). The GLORIA multi-summit approach was used to provide vegetation and floristic data together with temperature records for every summit. Species richness and species turnover was calculated together with floristic similarity between the summits. 70 species were recorded, 20 of which were endemic, belonging to 23 different families. Cretan endemics dominate at these high altitudes. Species richness and turnover decreased with altitude. The two highest summits showed greater floristic similarity. Only 20% of the total flora recorded reaches the highest summit while 10% is common among summits. Overall there was a 4.96°C decrease in temperature along the 675 m gradient. Given a scenario of temperature increase the ecotone between the sub-alpine and alpine zone would be likely to have the greatest species turnover. Southern exposures are likely to be invaded first by thermophilous species while northern exposures are likely to be more resistant to changes. Species distribution shifts will also depend on habitat availability. Many, already threatened, local endemic species will be affected first.     

Effect of copper on germination and seedling growth ofMinuartia,Silene, Alyssum andThlaspi

The influence of increasing copper concentrations on seed germination, seedling survival and radicle length ofMinuartia hirsuta, Silene compacta, Alyssum montanum andThlaspi ochroleucum was studied. Seed germination was highly affected by the higher Cu²⁺ concentrations (80 and 160 μM), while lower Cu²⁺ concentrations seemed to be necessary for seed germination, even for the plants originated from non-Cu²⁺-rich soils (i.e. A. montanum). Nevertheless, plants originated from Cu²⁺-rich soils (M. hirsuta, S. compacta) showed a higher demand of Cu²⁺ for rapid seed germination. Cu²⁺ at higher concentrations severely reduced growth rate of radicle, especially inA. montanum andT. ochroleucum. These data clearly indicate the reduced suitability of the above mentioned plant species for reclamation on Cu²⁺ soils. Lower Cu²⁺-concentrations had no influence on seedling survival inM. hirsuta andS. compacta, but a progressive reduction of a number of survived seedlings with increasing Cu²⁺ concentration was found, that was more pronounced inA. montanum andT. ochroleucum.     

The role of seed germination in the invasion process of Honey locust (Gleditsia triacanthos L., Fabaceae): comparison with a native confamilial

Identifying plant traits that promote invasiveness has been a major goal in invasion ecology. Germination plays a central role in the life cycle of plants and therefore could be a key trait in determining species invasiveness. In this study, seed germination of two confamilial, co‐occurring species that share ecological characteristics, the exotic invasive Gleditsia triacanthos L and the native Acacia aroma Gillies ex. Hook. & Arn., was compared. Seeds were obtained from individuals of three localities in the Chaco Serrano region of Córdoba, Argentina. Percent of seed germination and mean germination time were recorded in chemically and mechanically scarified seeds, and the former variable was also recorded in seeds subjected to: passage through the digestive tract of dispersers, fire simulations, fire simulation plus mechanical scarification, seed longevity, and dormancy break over time. In general, both species showed similar germination percentage. However, non‐scarified seeds of the exotic species lost physical dormancy when subjected to experiments of dormancy break over time, whereas, the native species had shorter mean germination time. The greater percentage of seed germination over time of the exotic species than of the native one might be triggering the spread of the former, whereas the shorter mean germination time might be hindering its expansion to more arid regions. The study of different mechanisms for achieving seed germination, particularly in hard seed species, could provide important information on the expansion of invasive species as well as useful knowledge for their management.     

Study on reproduction ecology of endangered species Abies chensiensis

Qinling fir, Abies chensiensis, is endemic to China and has been listed in the China Plant Red Data Book as one of the second class conservation plants. It is found scattered only in the forested pockets of the Qinling, Bashan, and Shennongjia Mountains with altitude from 1 300 m to 2200 m in Shaanxi, Gansu, Henan, Sichuan, and Hubei Provinces. To conserve and effectively restore this species and explore its processes of reproduction, the production characteristics of cone and seed yields, seed bank dynamics, and seed germination rates of five Abies chensiensis populations (A, B, C, D, and E, respectively, in the Abies chensiensis-Pinus tabulaeformis-Sinarundinaria nitida-Carex lanceolata association, Abies chensiensis-Quercus aliena var. acutserrata-Litsea pungens-Carex lanceolata association, Abies chensiensis-Betula albo-sinensis-Sinarundinaria nitida-Duchesnea indica association, Abies chensiensis-Indigofera amblyantha-Carex lanceolata association and Abies chensiensis-Pinus tabulaeformis-Smilax stans-Carex lanceolata association) were studied in their natural habitats across 18 plots in the Qinling Mountain area. Experiments were carried out in laboratory and field conditions. The results showed that all the five populations had the potential to produce seeds, and higher yields occurred in the lower and middle altitude areas every three to five years. The majority of cones appeared on the upper and middle crown and the west, south, and east faces of the crown, and the majority of full seed appeared on the middle portion of the cone. The weight per 1000 seeds was 43.2 g, in which 44.8% had growing potential. The germination rate of seeds in the natural forest was 6.1% and the proportion of seeds lost or destroyed in different populations in the natural forest was 93.9%. The germination rate of seeds planted in the nursery was higher than that in the natural forest, and the germination rate in the lower or middle altitude populations was higher than that in the upper altitude populations. The course from seed to seedling was the critical period in the life cycle of A. chensiensis populations under natural conditions. Reproduction courses were influenced positively by an abundant coverage of tree layer, organic material in the soil, thick soil, and a dense population of parent trees, whereas they were influenced negatively by human disturbance and light. In situ conservation of A. chensiensis should be carried out in the future so as to promote expansion of the population. Thinning the shrub layer and grass layer will also help seeds to penetrate the soil, promoting seed germination. The artificial population should be expanded by collecting seeds in the harvest years. Fast-growing and high-yield plantations should be developed on cloudy slopes at lower or middle altitudes.     

Strategies of seed dispersal and germination in plants inhabiting deserts

Massive seed consumption is typical in many deserts. The “escape” or “protection” strategies of seed dispersal are important, as they prevent massive seed consumption. The more extreme the desert, the more unpredictable the low amounts and distribution of the rains as well as the beginning and length of the season or seasons with rains. Seeds, which have the highest resistance to extreme environmental conditions, develop during germination into seedlings, which are the most sensitive. Therefore, germination of parts of the seed population at their respective proper times spreads the risk over time and is thus very important for plant survival, especially in those plants inhabiting the more extreme deserts. Each of the plant species studied was found to have its own survival strategies of seed dispersal and germination. At least two extreme seed-dispersal and germination strategies have been observed: 1) the “escape” seed dispersal and “opportunistic” portioned seed-germination strategies, such as inSchismus arabicas andSpergularia diandra, and 2) the “cautious” portioned dispersal by rain of the protected seeds, such as inAsteriscus hierochunticus and portioned dispersal and rapid germination strategies such as inBlepharis spp. The fate of future generations, as far as the germinability of seeds of some species is concerned, depends on the influences of maternal and environmental factors when the seeds are still on the mother plant, mostly during the final stage of seed maturation, as inTrigonella arabica. It may even depend on the position of the caryopsis from which the mother plant originated, as inAegilops geniculata. The dry post-maturation conditions and the environmental factors during seed wetting and germination may also affect the percentage of seed germination, as inSchismus arabicus.     

Dormancy and germination of sixRhinanthus species in relation to climate

The genusRhinanthus (Orobanchaceae) consists of annual hemiparasites that occur in a wide range of climates. Patterns of dormancy and germination were studied for six species sampled in areas ranging from the Pyrenees to Northern Scandinavia, and from sea level up to about 2500 m altitude in the Alpine region. Dormancy was broken by a 2 to 6 months period of cold stratification. Optimal temperature and length of the stratification period appeared to vary between and within species. Two patterns of dormancy and germination were distinguished. Seeds of the first group, including the widely distributedR. minor andR. angustifolius, further referred to as the LW group, require a relatively long period of cold stratification. Moreover, their germination is accelerated if they are subjected to a widening range of higher temperatures in the last weeks of the stratification period. In the other species (R. alectorolophus, R. glacialis, R. mediterraneus and perhapsR. antiquus) the release of dormancy is completed in a rather short period. Higher temperatures in the last weeks of the stratification period hardly affect the germination process of this SN-group, with short dormancy and no accelerated germination at higher temperatures. In both groups, temperatures above the low values during stratification reduce germination percentages and induce secondary dormancy in non-germinated seeds. The effects strongly vary with timing and temperature. The patterns have a genetic basis and seem to be species-specific. They do not vary with climate conditions, since samplesR. minor, whether collected in sub-arctic or sub-alpine areas or at sea level, generally react according to the LW pattern, and samples ofR. alectorolophus from areas at sea level up to montane regions according to the SN one. The ecological significance of the various stratification requirements and effects of higher temperatures on germination is discussed in relation to the local climate of the species and the evolutionary history of the genus.     

Pioneer trees in Amazonian floodplains: Three key species form monospecific stands in different habitats

Three pioneer tree species —Salix humboldtiana, Cecropia latiloba, Senna reticulata — form monospecific stands in the Central Amazonian white-water flood plain. In contrast toterra firma forests where species composition is unpredictable even for pioneer species, in Central Amazonianvárzea the occurrence of the main colonizing species seems to be predictable. This predictability is linked to characteristic habitat conditions and the low number of pioneer species. This preference for different habitats is reflected by different germination and early growth, by the structural and physiological characteristics, as well as by the reproductive and morphological adaptations of the three main species. The germination rate was above 90% in all species, and the duration until germination ranged between one day inSalix and 14 days inCecropia. Stem elongation was more than 10 cm per month inSalix andCecropia, and about 50 cm per month inSenna. Wood specific gravity ranged from 0.33 g cm⁻³ inCecropia to 0.45 g cm⁻³ inSenna. The annual wood increment increased by 1.20 (Cecropia), 1.23 (Salix) to 2.14 cm per year (Senna). All species produced adventitious roots, lenticels and/or stem hypertrophy. Leaf photosynthesis was between 17 and 20 μmol m⁻²s⁻¹, and reached a maximum of 30 μmol m⁻²s⁻¹ inSenna. Flowering and fruiting inSalix occurred throughout the year, whereas inCecropia andSenna they were concentrated in the flooded period.Salix humboldtiana occurs mainly at low sites subjected to long periods of inundation and high sedimentation rates. OnceSalix has formed dense forest stands, sedimentation and water currents are reduced at these sites andCecropia latiloba may take over. This species grows on low to middle elevations in the flooding gradient at sites with lower current and sedimentation rates.Senna reticulata does not tolerate submergence and colonizes habitats that may have strong currents and high sedimentation on higher levels in the flooding gradient.     

濒危植物金花猕猴桃繁殖生物学初步研究

繁殖生物学是目前濒危植物保护生物学研究的重点领域之一,金花猕猴桃(Actinidia chrysantha)是猕猴桃属濒危物种之一,目前未见其繁殖生物学相关报道。因此,该文以分布于花坪国家级自然保护区的野生金花猕猴桃为研究对象,用游标卡尺测量了花器官及果实形态,通过野外观察记录了其物候、访花昆虫及开花结果习性,用人工授粉和套袋法确定其传粉媒介,开展田间播种试验确定种子繁殖力,对其繁殖生物学开展了较为系统的研究。结果表明：金花猕猴桃物候因海拔高度不同而不同,较低海拔地区5月中下旬开花,高海拔地区5月下旬至6月上旬开花,花期持续7~10 d,果实每年9月下旬至10月上旬成熟;雄株花枝率76.5％,雌株果枝率61.9％,果实长圆柱形、短圆柱形或椭圆形,平均单果重7.34~27.53 g,最大果重35.0 g;金花猕猴桃为虫媒和风媒共同授粉,主要访花昆虫有蜜蜂科、细蜂科、鼻蝇亚科、食蚜蝇科、蜡蝉科、大蚊科长脚蚊属昆虫等;金花猕猴桃种子发芽率低,参试的3个居群的种子发芽率存在差异,分别为花坪17.5％,资源车田15.36％,贺州姑婆山0;4种不同种子处理方式中,低温＋GA3处理的种子发芽率(22.67％)最高。综上所述,金花猕猴桃不存在传粉障碍,种子萌发率低可能是致其濒危的重要原因。该研究结果为保护金花猕猴桃种质资源提供了科学依据。     

Dormancy,viability and germination of Magnolia lanuginosa (Wall.) Figlar & Noot. seeds: A threatened tree species of Northeast India

The population of Magnolia lanuginosa a rare tree species of northeastern India has declined drastically owing to habitat destruction, low natural regeneration and over harvesting for its multipurpose uses. The present study was carried out to understand the type of dormancy and analyse the effect of storage on viability and germination behaviour of M. lanuginosa under various physical and chemical treatments. Seeds subjected to physical treatments such as water (cold, hot, and boiling), acid (H₂SO₄) and manual scarification failed in breaking dormancy. Seeds treated with growth regulators (GA₃) had a significant effect on germination. It reduced the germination time and the shortest T₅₀ was observed in seeds treated with 2000 mg/l of GA₃ (non-scarified seeds) and 1000 mg/l of GA₃ (scarified seeds). The use of KNO₃ did not have any significant effect in breaking dormancy. However, the use of KNO₃ along with GA₃, increased the germination percentage. Seeds cold stratified (CS) for 60 days at 5 °C was effective in breaking dormancy and resulted in 84.26% germination. This indicates the prevalence of Type-1 Non deep physiological dormancy in M. lanuginosa seeds that requires a crucial CS period for proper embryo growth and development. The seeds stored in moist sand at 5 °C remained viable even after 120 days with 48.88% viability. The study would be helpful in devising seed germination protocols for mass production and reintroduction of the species into the wild.     

Effects of smoke water and karrikin on seed germination of 13 species growing in China

Plant-derived smoke water (SW), derived from combusted plant material, has been shown to stimulate seed germination and improve seedling vigor of a number of plant species from fire-dependent Mediterranean-type climate areas. The effects of SW on seed germination of 13 plant species from southern tropical and subtropical monsoon climate regions of South China are reported for the first time in this study using laboratory and pot trials. Among the 13 species tested, only Aristolochia debilis showed a significant positive response to commercial SW when diluted 1:10. Seed germination of A. debilis was also stimulated by 1–100 nM 3-methyl-2H-furo [2, 3-c] pyran-2-one (karrikin 1 or KAR₁) and by 10–1000 µM gibberellic acid (GA₃). GA₃ stimulated seed germination of Santalum album and significantly elongated the radicles of A. debilis while SW could not. The functions and/or metabolic pathways of Kar₁ and GA₃ are likely to be separate and/or distinct.     

Comparative seed dormancy and germination of eight annual species of ephemeral wetland vegetation in a Mediterranean climate

Ephemeral wetland vegetation (EWV) in the Mediterranean Basin appears in temporary wetlands where favourable hydrological conditions exist only for a short time and year-to-year variability is high. Here, we report results of the seed germination, dormancy and desiccation tolerance of eight annual species living in this vulnerable habitat. Experiments were performed in laboratory conditions under constant and alternating temperatures and using a 12-h daily photoperiod or continuous darkness. Whilst germination and dormancy differed between the species, seeds demonstrated an absolute light requirement and prefer cool temperatures to germinate (mean ≤15 °C). Logistic regression analysis showed significant effects of alternating temperature in all the species except in Tillaea vaillantii whose germination was stimulated by constant temperature. Mean temperature was a significant term in the logistic models for the dormant species Cicendia filiformis, Linum radiola and T. vaillantii for which after-ripening was an effective dormancy-breaking treatment. From these results we infer three strategies of regeneration by seeds: (1) species germinating during the whole vegetative season (2) species germinating in a narrow temperature niche and (3) species requiring flooding (T. vaillantii). Seeds possessed orthodox storage behaviour (tolerating drying to 15 % relative humidity) and may be amenable to seed banking as a means of ex-situ conservation. We conclude that EWV species are adapted to the irregular presence of water with characteristics that are typical of neither truly aquatic nor wetland plants. These EWV species showed a more plastic germination response based on alternating and constant temperature sensitivity and a low proportion of dormant seeds.     

Effects of various salts on the germination of three perennial salt marsh species

We studied the germination responses of Arthrocnemum macrostachyum, Juncus acutus and Schoenus nigricans to saline stress caused by different salt types. The germination percentage and mean time to germination data were obtained by incubating seeds for 30 d in 1, 2, 3, 4 or 5% saline solutions of NaCl, MgCl₂, MgSO₄ and Na₂SO₄ at 30/20 °C and with a 12 h photoperiod. A. macrostachyum was the most tolerant species to salinity during the germination (65% in 2% NaCl). S. nigricans showed the lowest germination (none germinated in salt and only 26% in distilled water). J. acutus showed intermediate behaviour between the two above species, its germination being inhibited by high salt concentrations. The sulphates had less inhibitory effect than the equivalent chloride concentrations.