Mucilaginous Seeds Research Articles

Functional divergence exists in mucilage-mediated seed dispersal, but not in germination of myxospermic Lepidium campestre and Lepidium draba (Brassicaceae)

The aim of this study was to compare the role of mucilage in seed dispersal and germination of the two closely related invasive weed species, Lepidium campestre and Lepidium draba. The study investigated the staining patterns of mucilage and its effects on seed germination, water uptake, dehydration, adherence to sand particles and dispersal by wind, water and animals following standard protocols. The mucilaginous seeds of L. campestre had a higher pectin and cellulose content than L. draba. This difference has a significant effect on water uptake and retention. The mucilage increased water uptake in both species, with L. campestre seeds absorbing significantly more water (836% compared to 75% in L. draba). Remarkably, the mucilage of both species had very little effect on seed germination. Significantly, the seeds of L. draba readily germinated under dry conditions, suggesting that this species may have developed different germination strategies. In addition, the seeds and fruits of L. draba showed a higher potential for dispersal via water and wind, whereas those of L. campestre adhered to animals. Further, L. campestre seeds showed significantly stronger adherence to sand particles (1872%) compared to those of L. draba (445%). This suggests that L. campestre seeds are more likely to disperse locally and possibly adhere to animals or soil particles. Our results suggest that mucilage produce by the two invasive weed species results in different methods of dispersal, which may help explain differences in their distribution patterns.

How Mucilaginous Seeds of Different Plant Species Respond to Nonthermal Atmospheric Plasma Treatment

How Mucilaginous Seeds of Different Plant Species Respond to Nonthermal Atmospheric Plasma Treatment

The dimorphic diaspore model Aethionema arabicum (Brassicaceae): Distinct molecular and morphological control of responses to parental and germination temperatures.

Plants in habitats with unpredictable conditions often have diversified bet-hedging strategies that ensure fitness over a wider range of variable environmental factors. A striking example is the diaspore (seed and fruit) heteromorphism that evolved to maximize species survival in Aethionema arabicum (Brassicaceae) in which external and endogenous triggers allow the production of two distinct diaspores on the same plant. Using this dimorphic diaspore model, we identified contrasting molecular, biophysical, and ecophysiological mechanisms in the germination responses to different temperatures of the mucilaginous seeds (M+ seed morphs), the dispersed indehiscent fruits (IND fruit morphs), and the bare non-mucilaginous M- seeds obtained by pericarp (fruit coat) removal from IND fruits. Large-scale comparative transcriptome and hormone analyses of M+ seeds, IND fruits, and M- seeds provided comprehensive datasets for their distinct thermal responses. Morph-specific differences in co-expressed gene modules in seeds, as well as in seed and pericarp hormone contents, identified a role of the IND pericarp in imposing coat dormancy by generating hypoxia affecting abscisic acid (ABA) sensitivity. This involved expression of morph-specific transcription factors, hypoxia response, and cell wall remodeling genes, as well as altered ABA metabolism, transport, and signaling. Parental temperature affected ABA contents and ABA-related gene expression and altered IND pericarp biomechanical properties. Elucidating the molecular framework underlying the diaspore heteromorphism can provide insight into developmental responses to globally changing temperatures.

Aethionema arabicum dimorphic seed trait resetting during transition to seedlings.

The transition from germinating seeds to emerging seedlings is one of the most vulnerable plant life cycle stages. Heteromorphic diaspores (seed and fruit dispersal units) are an adaptive bet-hedging strategy to cope with spatiotemporally variable environments. While the roles and mechanisms of seedling traits have been studied in monomorphic species, which produce one type of diaspore, very little is known about seedlings in heteromorphic species. Using the dimorphic diaspore model Aethionema arabicum (Brassicaceae), we identified contrasting mechanisms in the germination responses to different temperatures of the mucilaginous seeds (M+ seed morphs), the dispersed indehiscent fruits (IND fruit morphs), and the bare non-mucilaginous M- seeds obtained from IND fruits by pericarp (fruit coat) removal. What follows the completion of germination is the pre-emergence seedling growth phase, which we investigated by comparative growth assays of early seedlings derived from the M+ seeds, bare M- seeds, and IND fruits. The dimorphic seedlings derived from M+ and M- seeds did not differ in their responses to ambient temperature and water potential. The phenotype of seedlings derived from IND fruits differed in that they had bent hypocotyls and their shoot and root growth was slower, but the biomechanical hypocotyl properties of 15-day-old seedlings did not differ between seedlings derived from germinated M+ seeds, M- seeds, or IND fruits. Comparison of the transcriptomes of the natural dimorphic diaspores, M+ seeds and IND fruits, identified 2,682 differentially expressed genes (DEGs) during late germination. During the subsequent 3 days of seedling pre-emergence growth, the number of DEGs was reduced 10-fold to 277 root DEGs and 16-fold to 164 shoot DEGs. Among the DEGs in early seedlings were hormonal regulators, in particular for auxin, ethylene, and gibberellins. Furthermore, DEGs were identified for water and ion transporters, nitrate transporter and assimilation enzymes, and cell wall remodeling protein genes encoding enzymes targeting xyloglucan and pectin. We conclude that the transcriptomes of seedlings derived from the dimorphic diaspores, M+ seeds and IND fruits, undergo transcriptional resetting during the post-germination pre-emergence growth transition phase from germinated diaspores to growing seedlings.

Engineering a Macroscopic Adhesion System Inspired by Mucilaginous Seeds

AbstractWet adhesion is a challenging process that requires successful interactions between the two surfaces of interest. Current adhesives may offer sufficient strength but often contain toxic components. Thus, when the field of adhesion meets bioinspiration, there is lots of potential for finding an innovative solution. Here, inspired by mucilaginous seeds and by using refined fiber structures provided by renewable materials, it is demonstrated how to build a comparably strong wet adhesive system. The process involves the controlled fibrillation of a wood surface followed by the application of a macromolecular coating employing the main component found in mucilaginous seeds. Moreover, the additional introduction of a thermo‐responsive polymer into the system allows for obtaining control over the strength and the compliance of the detachment process. Thus, this study demonstrates how combining renewable materials with a multi‐step coating process offers an environmentally friendly solution that pinpoints a promising path toward bio‐based wet adhesives.

Seed mucilage as a defense against granivory is influenced by substrate characters.

Many seeds are consumed by granivores despite numerous adaptations to prevent detection or exploitation. The environment can influence the efficacy of these defensive traits. Understanding the mechanisms by which environmental factors modify defensive efficacy is important for understanding spatial patterns of granivory and seed recruitment. Seed mucilage is a sticky coating that binds imbibed seeds to substrates; this attachment has been demonstrated to lessen exploitation by granivores. Seed mucilage as a defense has been recognized for decades, though rarely studied. Here, we investigated whether the environment alters this seed defense by addressing two questions: (1) Does substrate particle size affect attachment strength? (2) Does a change in particle size lead to changes in granivore-related mortality? In the field experiment, ants removed more seeds from finer substrates than their coarser counterparts. Across that same grit range, seeds took less force to dislodge when mucilage-bound to fine sandpaper; however, an investigation across a wider range of grits demonstrated nonlinearities occurred for many species, probably due to structural and chemical mucilage properties. Small differences in substrate grit lead to differential mortality in mucilaginous seeds due to alterations in attachment strength, suggesting that the defensive efficacy of this trait differs across the landscape. This work paves the way for a more integrative look at mucilaginous seeds. Seed mucilage is a widespread trait that is easily studied and has important demographic implications. It represents an ideal system to examine dispersal, germination, and granivory to gain a more holistic view of seed ecology.

The seed coat in the evolutionary context of Bromelioideae (Bromeliaceae): morphoanatomical diversity and ontogeny in the core and tankless lineages

Abstract Seed morphology could provide significant characters for understanding the diversification of some clades in Bromeliaceae subfamily Bromelioideae, but little is known about the anatomical diversity and ontogeny of the seed coat in this diverse subfamily. We analysed the morphoanatomy of the seed coat for 48 species from 25 genera of the major lineages of Bromelioideae, from which we selected four species for ontogenetic analysis. Standard techniques for light microscopy were adapted for the anatomical study of seeds. Thirty-three variable characters were described and compared. Flattened or angular usually exappendiculate, tegmic-endotestal seeds, with secondarily thickened endotesta and undulate or costate tegmen, are common characteristics of the tankless lineages. Long oblongoid–obovoid, appendaged or exappendiculate, exclusively tegmic and mucilaginous seeds are common to core Bromelioideae. Anatomical features of the exotegmen and testa and the number of parenchyma layers in the raphe were more variable and especially useful in delimiting genera and some species. The ontogenetic analysis was essential to propose the primary morphological homology hypotheses for the seed coat characters. Seed coat morphoanatomical features offer a promising source of phylogenetically informative characters for integrative and character evolution approaches for Bromelioideae and possibly other subfamilies of Bromeliaceae.

Seed ecophysiology of Elephant Apple (Dillenia indica)—An important tree species of the Indomalayan realm

AbstractDillenia indica produces mucilaginous seeds embedded in hard, fibrous, megafaunal fruits, and little is known about the ecological function of mucilage in its regeneration. Using standard laboratory protocols, we investigated the role of mucilage on seed dispersal (buoyancy), chemical defense (antibiotic, antifungal, antioxidant, and allelopathic activities), and seed germination. Further, we characterized seed germination, dormancy, and storage physiology of D. indica. Results revealed that mucilage associated with seed‐coat assists seeds in floating on water for a longer duration, acts as an antimicrobial agent without hampering the overall seed germination. It was noticed that fresh mature seeds possess an underdeveloped embryo that grows within the seed before radicle emergence (a sign of morphological dormancy; MD), and seeds took ~70 days to achieve 95% germination (a sign of physiological dormancy; PD). However, the rate of germination increased when seeds were treated with gibberellin or subjected to 1‐month dry‐storage (confirmation of PD). Seeds disperse with ~12% moisture and retain high viability even after ultra‐drying over silica gel, indicating an orthodox seed storage physiology. Study concludes that mucilage plays a crucial ecophysiological function in dispersal‐defense mechanism of D. indica seeds, by enhancing seed buoyancy, helping seeds to disperse long‐distance, and protecting the seeds from soil pathogens through antimicrobial activity. Our study confirmed that seeds of D. indica possess morphophysiological dormancy (MPD), unlike the MD reported in an earlier study from North India. Possible ecophysiological function of mucilage on seed dispersal‐defense mechanism and production of morphophysiological dormant and orthodox seeds in D. indica are discussed.

Anchorage by seed mucilage prevents seed dislodgement in high surface flow: a mechanistic investigation.

Seed mucilage is a common and highly diverse trait shared among thousands of angiosperm species. While it has long been recognized that mucilage allows seeds to anchor to substrates (antitelechory), resisting abiotic and biotic dislodgement, we still lack a mechanistic understanding of this process. We propose a mechanistic model of how mucilage affects substrate anchorage and fluid resistance, ultimately contributing to dislodgement resistance. To test this model, we subjected mucilaginous seeds of 52 species, varying in eight measured seed traits, to 7 d of continuous water flow at a range of dislodgement potentials. Supporting our model, mucilage mass increased the force necessary to dislodge both dry and wet seeds; our measurement of the dislodgement force of dry mucilage explained time to dislodgement well. The effect size was remarkably large; increasing the standardized mucilage mass by 1 s.d. resulted in a 280-fold increase in the time to dislodgement. Fluid resistance was largely dependent on the speed of water flow and the seed's modified drag coefficient, but not seed traits. Neither mucilage expansion speed nor mucilage decay rate explained dislodgement potential well. Our results suggest that the degree of anchorage to a substrate, measured with a simple dislodgement force assay, is highly predictive of mucilaginous seed retention in highly erosive environments. In contrast, we found that other seed and mucilage traits are of lesser importance to anchorage.

Mucilage binding to ground protects seeds of many plants from harvester ants: A functional investigation

Abstract The seeds of many plant species produce mucilage on their surfaces that when wetted and dried, firmly adheres seeds to surfaces and substrates. Previous studies have demonstrated that seed anchorage to the ground can reduce seed predation, although only a few species have thus far been tested. Here we investigated whether binding to the ground reduces seed removal by harvester ants Pogonomyrmex subdentatus, an important granivore, for 53 species with mucilaginous seeds. We also explored functional traits that associate with seed removal risk to understand the ecological and evolutionary context of this granivory resistance trait. Using a field cafeteria choice experiment, we compared harvester ant seed removal of wetted ground‐bound seeds to dry unbound control seeds for these 53 species. We developed a simple assay to score dislodgement force. We examined whether this force, seed mass and seed mucilage production explained the interspecific variation in protection that we observed in field seed removal. We integrated these experiments with a broad scale test of correlates of seed attachment using a previously published dataset of attachment potential of mucilaginous seeds for 432 species, examining correlations of attachment potential with 13 plant traits and the climate characteristics of the species' range. Binding to the ground reduced seed removal in 42 of 53 species tested. The benefit increased with seed dislodgement force, which itself increased with mucilage production, but not with seed mass. In the larger dataset, shorter plant life span, higher temperature, more solar radiation, higher humidity, fewer wet days per year and higher seed density correlated positively with the odds of seed attachment. We also found that attachment potential showed a concave down quadratic relationship with latitude, peaking at roughly 30°. No strong evidence that any of the other six predictors correlated with attachment potential was found. We demonstrate that protection from granivores is a widespread convergent function of seed mucilage and is associated with mucilage production. We highlight the need for increased mechanistic investigations into this common but poorly studied trait, particularly in relation to functional drivers of the broad patterns we found. A free Plain Language Summary can be found within the Supporting Information of this article.

Application of mucilaginous seeds (Alyssum homolocarpum and Salvia macrosiphon Boiss) and wheat bran in improving technological and nutritional properties of pasta.

In recent years, dietary fibers have attracted a lot of attention as they reduce calories and witness the glycemic index. In this study, wheat bran (WB) and mucilaginous seeds flour (Qodume Shirazi seeds [QSS], wild sage seeds [WSS]) as sources of insoluble and soluble dietary fiber were used for pasta enrichment (50% WB, 45% WB-5% seed flour, and 40% WB-10% seed flour). The cooking properties, microstructural, textural, glycemic index, and sensory properties of pasta samples were evaluated. Fiber ingredients increased moisture content, cooking loss, and ash of pasta samples. In contrast, swelling indexing, optimum cooking time, and water absorption decreased. The samples containing high fiber had a darker appearance with a stiffer structure. Microstructure confirmed the presence of a developed protein matrix in the witness sample. But by substitution of the WB, a heterogeneous and dense network with small and large cells formed. The mucilaginous seed flours (WB-QSS and WB-WSS samples) improved the uniformity of pasta microstructure in comparison with WB sample. WB pasta samples reduced all sensory scores, but adding seed flours had a more noticeable influence on increasing the sensory properties. The presence of QSS and WSS resulted in more starchy and elastic texture. By using mucilaginous seeds flour in the production of high-fiber pasta, the glycemic index decreased more noticeably. This investigation indicates the positive impact of mucilaginous seeds, especially WSS, on pasta sensorial properties, in line with a strong influence on technological characteristics and decreasing the glycemic index. PRACTICAL APPLICATION: This study determined a practical approach to produce high-fiber pasta by applying mucilaginous seeds with the improvement of technological and sensory properties.

Plant Seed Mucilage as a Glue: Adhesive Properties of Hydrated and Dried-in-Contact Seed Mucilage of Five Plant Species.

Seed and fruit mucilage is composed of three types of polysaccharides—pectins, cellulose, and hemicelluloses—and demonstrates adhesive properties after hydration. One of the important functions of the mucilage is to enable seeds to attach to diverse natural surfaces. Due to its adhesive properties, which increase during dehydration, the diaspore can be anchored to the substrate (soil) or attached to an animal’s body and dispersed over varied distances. After complete desiccation, the mucilage envelope forms a thin transparent layer around the diaspore creating a strong bond to the substrate. In the present study, we examined the mucilaginous seeds of six different plant taxa (from genera Linum, Lepidium, Ocimum, Salvia and Plantago) and addressed two main questions: (1) How strong is the adhesive bond of the dried mucilage envelope? and (2) What are the differences in adhesion between different mucilage types? Generally, the dried mucilage envelope revealed strong adhesive properties. Some differences between mucilage types were observed, particularly in relation to adhesive force (Fad) whose maximal values varied from 0.58 to 6.22 N. The highest adhesion force was revealed in the cellulose mucilage of Ocimum basilicum. However, mucilage lacking cellulose fibrils, such as that of Plantago ovata, also demonstrated high values of adhesion force with a maximum close to 5.74 N. The adhesion strength, calculated as force per unit contact area (Fad/A0), was comparable between studied taxa. Obtained results demonstrated (1) that the strength of mucilage adhesive bonds strongly surpasses the requirements necessary for epizoochory and (2) that seed mucilage has a high potential as a nontoxic, natural substance that can be used in water-based glues.

The role of mucilage envelope in the endozoochory of selected plant taxa

Myxodiaspory (formation of mucilage envelope around seeds and fruits) is a common adaptation to dry habitats known in many families of Angiosperms. The mucilage envelope of some seeds seems to be also a unique morphological adaptation which protects myxospermatic diaspores while passing through the bird’s digestive system. To evaluate the protective potential of mucilage, we fed the diaspores of seven plant species (representing three different mucilage types and three species of non-mucilaginous plants) to pigeons, Columba livia domestica. Twenty-four hours later, we collected the droppings of pigeons and examined a total of 18,900 non-destroyed diaspores to check for mucilage presence and germination ability. Out of all the examined diaspores, 4.5% were mucilaginous seeds. Among them, the highest number (12.2–13.5%) of viable diaspores belonged to the hemicellulosic type of mucilage (from Plantago species). Only 3.7% of germinating diaspores with pectic mucilage (Linum usitatissimum) were collected, and no seeds representing cellulosic mucilage (e.g., Ocimum basilicum). For non-mucilaginous plants, we collected only a few individual seeds (0.1% out of 8100 seeds used). We noted that the mucilaginous seeds found in the droppings were able to germinate; however, the germination ability was generally smaller in comparison to the control (i.e., not digested) seeds. Our results revealed that the presence of mucilage envelope has an impact on diaspore dispersal and survivability. With our experiments, we demonstrated for the first time that the mucilage envelope, especially of the non-cellulosic type, supports endozoochory. We also showed that non-mucilaginous seeds can be occasionally dispersed via endozoochory and are able to germinate. The results of our studies can explain the ways of plants distribution at a small, local scale as well as in long-distance dispersal, e.g., between islands or even continents.

Adsorption of Basic Violet 16 dye from aqueous solution onto mucilaginous seeds of Salvia sclarea: kinetics and isotherms studies

Adsorption of Basic Violet 16 dye from aqueous solution onto mucilaginous seeds of Salvia sclarea: kinetics and isotherms studies

Chromium biosorption from aqueous environments by mucilaginous seeds of Cydonia oblonga: Thermodynamic, equilibrium and kinetic studies

Hexavalent chromium Cr(VI) is one of the most toxic heavy metals in aqueous solutions, hence it is highly imperative to treat the wastewater containing Cr(VI) before its discharge. At present work, the rate of biosorption was studied under a variety of conditions, including initial Cr(VI) concentration (5-50 mg/L), amount of biosorbent (0.5-3 g/100 mL), pH (1-8), temperature (298-318 K) and contact time (30-120 min). Biosorption of Cr(VI) is in all cases pH-dependent showing a maximum at equilibrium pH values between 2 and 3. The biosorption data fitted well with Langmuir and Freundlich isotherms. The biosorption capacity calculated from the Langmuir isotherm was q = 33.58 mg Cr(VI)/g of dry seeds (at 303 K). Biosorption kinetics data well fitted using pseudo-second-order. Thermodynamic studies confirmed that biosorption of Cr(VI) ions by mucilaginous seeds of Cydonia oblonga was spontaneous and endothermic nature.

SEED MORPHOMETRY AND GERMINATION OF Aechmea costantinii (Mez) L. B. Sm. (BROMELIACEAE)

ABSTRACT: The potential economic and environmental benefits brought by bromeliads production are significant. It is noteworthy that the high degree of degradation of some ecosystems as the Atlantic forest involve reduction of these species. This factor has been worsened by the elevated degree of endemism of these plants, e.g. Aechmea costantinii (Mez) L. B. Sm., which is a high ornamental potential bromeliad but understudied. Thus, the present research aimed to characterize physical and morphological features of A. costantinii fruit and seeds, describing the different stages of post-seminal development, as well as evaluating seed germination behavior with respect to temperature and light. For this purpose, we used fruit and seeds freshly harvested from an Atlantic Forest fragment, located in the city of Maceió, Alagoas State, Brazil. Tests were carried out under a completely randomized design, in a 6x4 factorial scheme (temperature x light) with four replications of 25 seeds. The polyspermic fruit are of tricarpellate/triloculate type and originated from inferior ovary, containing an average of 73 elliptical and mucilaginous seeds with basal embryo. The germination is epigeal-type and occurs in a great intensity and high speed at 35 °C, regardless light presence or quality.

Post-release fates of seeds in dehiscent and indehiscent siliques of the diaspore heteromorphic species Diptychocarpus strictus (Brassicaceae)

Abstract Fruit/seed heteromorphic plants have been studied most extensively for differences in dispersal and germination of the morphs. However, fates of the heteromorphic diaspores beginning with seed release and ending with germination/seed death have been documented for relatively few species. Our primary aim was to follow the fates of the two dispersal unit morphs of Diptychocarpus strictus over a several-year period or until they germinated or died. Our hypothesis was that the winged, mucilaginous seeds (dispersal unit) from the dehiscent upper siliques form a short-lived seed bank and the nearly-wingless, nonmucilaginous seeds inside the indehiscent lower siliques (dispersal unit) a long-lived seed bank. Thus, for the two morphs we monitored phenology of seed release in 2010, germination phenology from 2010 to 2014 and germination and survival during burial in soil from 2010 to 2012. All lower siliques had been released from mother plants by late July, whereas seed release of the winged seeds of upper siliques was not completed until late October, after the main stem had become detached (near the base). Most seeds (18%) from upper siliques that did so (c. 20%) germinated in spring 2011, whereas no seeds in lower siliques germinated until autumn 2011 (0.2%). All seeds from upper siliques had germinated or lost viability by the end of the autumn 2012 germination season, whereas 11% of seeds inside lower siliques germinated in autumn 2014 and a high proportion of the nongerminated seeds was still viable, thus supporting our hypothesis. Buried seeds of both morphs exhibited a 6-mo dormancy cycle in which the nondormant phase coincided with the two germination seasons. Dehiscence of the upper siliques and indehiscence of the lower siliques are required for D. strictus to have a high risk-low risk strategy (H/H-L/L) for diaspore dispersal and dormancy.

Mucilaginous seeds and algal diets attract soil Collembola in preference tests

Collembola are abundant in soils and with primary producers interact directly (by grazing algae, seeds, seedlings or roots) or indirectly (by altering the composition of soil microbial communities). Direct collembolan herbivory influences the establishment of seedlings and the dynamics of plant populations whereas grazing on algae affects their biomass, community composition and dispersal. Studies on feeding behaviour of Collembola have mainly focused on fungi, whereas primary producers as resources have seldom been studied. We assessed the feeding preference of two Collembola species (Folsomia candida and Folsomia fimetaria) for food sources from different functional groups using dual choice olfactometers. A preferred fungal species (Alternaria alternata) was compared with two terrestrial microalgae (Chloroidium angusto-ellipsoideum and Pabia signiensis) as well as mucilaginous seeds (Plantago major). A second experiment investigated the choice behaviour of F. candida between different species of common green algae in soils (Chlorella vulgaris, Stichococcus mirabilis, Stichococcus bacillaris and Coccomyxa sp.). Generally, feeding preferences stabilised over 48 h. F. candida avoided P. signiensis compared to the other three food sources whereas F. fimetaria preferred the seeds of P. major to the alternative diets. When only soil algae were offered, F. candida was able to distinguish between different species: S. mirabilis was clearly preferred to S. bacillaris and C. vulgaris. Our results reflect that both Collembola may use a wide range of resources if available and differ in their preference behaviour. Selective feeding on algae or mucilaginous seeds has the potential to modify soil microorganism communities, soil properties and the establishment of seedlings.

<I>Zuloagocardamum</I> (Brassicaceae: Thelypodieae) a New Genus from the Andes Highlands of Northern Argentina

Abstract Zuloagocardamum jujuyensis , a new genus and species of Brassicaceae from fujuy Province in Argentina, is described and illustrated, and its phylogenetic relationships to nearest relatives are demonstrated. It resembles some genera of the tribe Thelypodieae, such as Chilocardamum and Weberbauera, but differs mainly by having a well-developed woody caudex with reduced leafless stems, rosulate, awl-shaped or linear, sessile, parallel-veined basal leaves conspicuously ciliate with simple trichomes, racemes much shorter than the basal leaves, torulose fruits, and mucilaginous seeds. Phylogenetic analyses, based on DNA sequences of nuclear ITS and plastid ndhF and trnL-F regions, place Z. jujuyensis in the tribe Thelypodieae, where it is related to species of Weberbauera, Englerocharis, and Parodiodoxa. However, it is morphologically different from species of all four genera by the character combinations above.

Germination of mucilaginous seeds of Plantago albicans (Plantaginaceae): effects of temperature, light, pre-sowing treatments, osmotic stress and salinity

Plantago albicans L. (Plantaginaceae) is a perennial herbaceous plant widely distributed throughout the Mediterranean region. The germination requirements (under different controlled conditions of light and temperature, and after two pre-sowing treatments) and tolerance to osmotic stress (polyethylene glycol, PEG 6000) and salinity (NaCl) of P. albicans seeds were studied. Seeds were germinated under constant temperatures (5°C, 10°C, 15°C, 20°C, 25°C and 30°C) and alternating temperature regimes of 20/10°C and 25/15°C with a 16 h/8 h light/dark photoperiod. The outer layer of seeds become mucilaginous when wetted and the presence of mucilage on seeds significantly increased germination percentages at all temperatures tested. P. albicans seeds were non-dormant and temperature significantly affected germination percentages and germination rate (germination velocity expressed as mean germination time, MGT). The final germination percentages ranged from 34% to 89% for intact seeds (seeds with mucilage) and from 9% to 62% for demucilaged seeds, depending on the temperature. Temperatures of 25°C and 25/15°C gave the highest germination percentages. Light did not affect seed germination at both temperature regimes assayed (25°C and 25/15°C). Germination percentages of seeds soaked for 24 h in distilled water or in a gibberellic acid (GA3) solution were not significantly higher than that of untreated seeds. In general, both the final germination percentage and germination rate were reduced by increasing salinity and PEG concentration. Seeds germinated in up to 35% PEG and 300 mmol·L–1 NaCl. Recovery of germination for seeds when transferred to distilled water after being in PEG or salinity treatments for 15 days was quite high, suggesting that P. albicans seeds are tolerant to osmotic and salt stresses.