Dormant, intact Avena fatua L. (wild oat) seeds germinate poorly at 20°C. Removing the hulls slightly increased germination. Treatment with smoke solutions increased the germination of both intact seeds and caryopses. Exogenous GA 3 , alone or in the presence of smoke solution, increased the germination of caryopses, while ACC shows a tendency to increase germination of caryopses only when applied in combination with smoke solution. Results suggest that GA 3 and ethylene, but not smoke solutions, are involved in the regulation of a-amylase activity during germination. However, the participation of smoke solutions in the control of ACC oxidase activity cannot be excluded.

Methyl jasmonate (JA-Me) inhibited or retarded germination of Amaranthus caudatus seeds in darkness at 24'C, Ethephon, ACC and gibberellins (GA 3 or GA4+7) partially or completely reversed this inhibition depending on the concentration of JA-Me applied . Both ethephon and the gibberellins were more effective than ACC . Both GA3 and GA 4+7 enhanced the stimulatory effect of ethephon or ACC on germination of seeds inhibited by JA-Me .Abbreviations : ACC = 1-aminocyclopropane-l-carboxylic acid ; JA = jasmonic acid ; JA-Me = methyl jasmonate . 211

Amaranthus caudatus L. seed germination was studied under different levels of water deficit induced by PEG 6000 in laboratory conditions. PEG at osmotic potentials -0.2 to -0.3 MPa at 24°C in darkness delayed germination and reduced final germination percentage. PEG solutions at osmotic potential lower than -0.3 MPa almost totally blocked seed germination. Ethephon was much more effective than GA 3 in reversing PEG-caused inhibition of A. caudatus seed germination. PEG decreased α-amylase activity after 14 h incubation. It decreased β-amylase activity after 14 and 20 h, and caused an increase in total dehydrogenase activity only after 20 h of incubation. Unlike GA 3 , ethephon increased α-amylase activity in seeds after 12 and 14 h of incubation under water deficit. After 20 h of incubation there was no difference in α-amylase activity in any of the treatments. Neither ethephon nor GA 3 affected the activity of β-amylase and dehydrogenase.K Ke ey y w wo or rd ds s: : Amaranthus caudatus seeds, α-, β-amylase, dehydrogenase, ethylene, gibberellin A 3 , polyethylene glycol.

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;

In this paper the authors present studies on the effect of auxin precursors and chemical analogues on the growth and biochemical composition in Chlorella pyrenoidosa (Chlorophyceae). Among auxin precursors tryptamine exhibited slightly higher stimulative activity in regard to fresh and dry weight, mineral substances, chlorophylls, carotenoids, monosaccharides (aldohexoses) and water-soluble proteins content in Ch. pyrenoidosa cells as compared to anthranilic acid. Among auxin analogues used phenoxyacetic acid and naphthyl-3-acetic acid had the strongest stimulative effect of the above-mentioned parameters. Their activity was significantly higher than that of auxin precursors. The activity of naphthyl-3-sulphonic acid was slightly lower than that of tryptamine, whereas the stimulation by 2,4-dichlorophenoxyacetic acid was similar to that of anthranilic acid. In Ch. pyrenoidosa cells 2,4-dichlorophenoxyacetic acid and naphthyl-3-sulphonic reached their maximum activity at the latest (between the 15th or 16th day) of the culturing, whereas tryptamine, phenylacetic acid, naphthyl-3-acetic acid and indolyl-3-acetic acid - at the earliest (between the 8th or 12th) day