In the study, micropropagation of three varieties of Lavandula angustifolia was developed, and the appearance of trichomes, antioxidant activity of extracts and antimicrobial activity of essential oils isolated from plants growing in field conditions and in vitro cultures were compared. The study evaluated the number of shoots, and the height and weight of the plants grown on media with additions of BAP, KIN and 2iP. The greatest height was attained by the lavenders growing on MS medium with the addition of 1 mg dm -3 2iP -'Ellagance Purple'. The greatest number of shoots was developed by the 'Ellagance Purple' and 'Munstead' plants growing on the medium with 2 mg dm -3 BAP. The highest weight was attained by the plants growing on the medium with the highest concentration of BAP -3 and 5 mg dm . Moreover, the present study determined the influence of media with the addition of different concentrations of IBA and media with a variable mineral composition (½, ¼, and complete composition of MS medium) and with the addition of IBA or NAA for rooting. The majority of the media used had a positive influence on the development of the root system. The longest root system was observed in 'Ellagance Purple' growing on the medium composed of ¼ MS with 0.2 mg dm -3 NAA. All the examined oils exhibited activity towards S. aureus, S. epidermidis, P. aeruginosa, E. coli and C. albicans. The majority of the essential oils isolated from the plants propagated in vitro exhibited stronger antimicrobial activity than the field-grown plants. The plants propagated under in vitro conditions demonstrated considerably higher antioxidant activity as compared with the field-grown plants, which was determined using the DPPH, FRAP and ABTS assay.

Neither ethylene nor 1-aminocyclopropane-1-carboxylic acid (ACC) was able to prevent the induction of secondary dormancy ofAmaranthus caudatusat 45°C. Both ethylene (4.5 × 10-9–4.5 × 10-7M) and ACC (10-3–10-2M) removed secondary dormancy at 25°C, although ethylene was much more effective. The presence of ethylene for only 10 h was sufficient to remove secondary dormancy in almost all seeds. Incubation of secondary dormant seeds for up to 5 d at 25°C did not change sensitivity to ethylene. The breaking of secondary dormancy by ethylene was prevented by 2,5-norbornadiene (NBD; 1.5 × 10-5–3 × 10-4M), indicating the physiological action of ethylene. Abscisic acid (ABA; 10-4–10-3M) increased the requirement for exogenous ethylene. It is suggested that secondary dormancy inA. caudatusseeds might be related to insufficient ethylene production associated with an insufficient amount of ACC.

Elatine L. contains ca. 25 small, herbaceous, annual species distributed in ephemeral waters in both hemispheres. All species are amphibious and characterized by a high degree of morphological variability. The importance of seed morphology in Elatine taxonomy has been emphasized by many authors. The degree of seed curvature and seed coat reticulation have been traditionally considered very important in recognizing individual species of this genus. Seed morphometric characteristics of 10 Elatine species, including all European native taxa, are provided on the basis of material from two or three populations of each species. A total of 24-50 seeds were studied from each population, altogether 1,260 images were used for the morphometric study. In total, six parameters were measured from SEM pictures: object surface area, profile specific perimeter (object circuit), rectangle of the object (a) length, rectangle of the object (b) width, angle of the seed curvature, and number of pits in the seed coat counted in the middle row. Our study shows that the range of morphological variation of seeds in European species of Elatine is great, both between the species and the populations. Discrimination analysis showed that all six traits significantly differentiate the populations studied (λ = 0.001, p < 0.001), and the greatest contributions were ''number of pits'', ''rectangle_a'', and ''the angle curvature''. Multidimensional scaling based on a correlation matrix of Mahalanobis distance of the six features studied revealed the greatest similarity between the three populations of E. alsinastrum, E. macropoda, and E. hexandra. Regarding interspecific differences, a Kruskal-Wallis tests showed that, in many cases, lack of statistically significant differences between species relative to the studied seed traits. If distinction of species is only based on seeds, especially if only a few seeds are evaluated, the following species pairs can be easily confused: E. alsinastrum and E. orthosperma, E. hexandra and E. macropoda, E. campylosperma and E. hydropiper, as well and E. gussonei and E. hungarica. We found no diversity in seed coat micromorphology within pits that could have potential taxonomic importance. An identification key and descriptions of species are provided on the basis of seeds traits.How to cite this article Popiela et al. (2017), Seed morphometric characteristics of European species of Elatine (Elatinaceae). PeerJ 5:e3399;

Ethephon (Eth), gibberellin A 3 , A 4+7 (GA 3 , GA 4+7 ), and 6-benzyladenine (BA) removed secondary dormancy of Amaranthus caudatus seeds. The GAs and BA potentiated the effect of ethephon or 1-aminocyclopropane-1-carboxylic acid (ACC), an ethylene biosynthesis precursor, in terms of the rate or final percent of germination. Aminoethoxyvinylglycine (AVG), an ACC synthase activity inhibitor, was observed to simultaneously inhibit the release from dormancy effected by GA 3 or BA as well as the ethylene production stimulated by these regulators. Breaking of secondary dormancy by GA 3 , GA 4+7 or BA was prevented by 2,5-norbornadiene (NBD), an inhibitor of ethylene binding. Ethylene completely or markedly reversed the inhibitory effect of NBD. We thus conclude that the removal of secondary dormancy in Amaranthus caudatus seeds by gibberellin or benzyladenine involves ethylene biosynthesis and action.

The aim of this study was determined how an addition of gold nanoparticle (AuNPs) and silver NPs (AgNPs) into culture media affects plant development and formation of oil glands in narrow-leaved lavender (Lavandula angustifolia) cv. 'Munstead'. Plant shoots were propagated on media supplemented with 1, 2, 5, 10, 20 and 50 mg dm −3 AuNPs or AgNPs (diameter of 24.2 ± 2.4 nm and 27.5 ± 4.8 nm). Both of NPs positively influenced the growth and development of lavender propagated in vitro. The culture media with NPs stimulated formation of shoots and increased plant weight. Roots of plants propagated on the media supplemented with NPs were usually longer than those in the control. Only high concentrations of NPs (20 and 50 mg dm −3) in the culture media were toxic to plants, as demonstrated by restricted shoot length and gradual decrease in the value of other morphological features. Increases in AgNPs concentration caused the number of secretory trichomes to decrease. The diameter of the trichomes on both sides of the leaf blade was larger when the plants were propagated on the media supplemented with 1 and 2 mg dm −3 NPs. The diameter of trichomes formed on the adaxial surface of the leaf blade was greatest in the media enriched with 2 mg dm −3 AgNPs and 5 mg dm −3 AuNPs, and smallest in the media enriched with 5 mg dm −3 AgNPs. The diameter of trichomes formed on the abaxial surface was largest in plants exposed to 1, 2, 5 and 10 mg dm −3 AuNPs, 1 mg dm −3 AgNPs, and smallest in plants exposed to 5 mg dm −3 AgNPs. Key message Silver and gold nanoparticles had a significantly improved the growth and development of narrow-leaved lavender propagated in vitro. The number and size of secretory trichomes formed on the leaves of narrow-leaved lavender grown in in vitro cultures depends on the concentration of silver or gold nanoparticles in the media. Keywords Micropropagation • Metal nanoparticles • Oil glands • Nanosilver • Nanogold Abbreviations NPs Nanoparticles AgNPs Silver nanoparticles AuNPs Gold nanoparticles MS Murashige and Skoog medium KIN Kinetin IAA 3-Indoleacetic acid Narrow-leaved lavender (Lavandula angustifolia Mill.) belonging to Lamiaceae family is an evergreen perennial plant with a high number of beneficial properties. The herb is native to the Mediterranean region, but is also grown in many other countries in the world (Wesołowska et al. 2019). Lavender infusions show carminative, diuretic, antirheumatic and anti-epileptic properties, and are effective painkillers, especially for nervous headaches and migraines (Gilani et al. 2000). Essential oils and extracts of the plant demonstrate antibacterial and antifungal properties (D'Auria et al. 2005). Apart from medicinal applications, lavender is Communicated by Nokwanda Pearl Makunga.