The effects of iron deficiency on lead accumulation in Ailanthus altissima (Mill.) Swingle seedlings.

Understanding the effects of root Fe deficiency on the uptake and translocation of toxic metals can be important for improving the phytoremediation strategies of polluted soils. The present study investigated how Fe nutritional status affects the uptake and root-to-shoot-translocation of Pb in hydroponically grown seedlings of (Mill.) Swingle. The interactions of Fe deficiency and Pb were assessed by measuring the root Fe(III) reductase activity, carboxylic acids concentration in root exudates, root and shoot biomass, and accumulation of Pb and other metals (Fe, Zn, Mn, and Cu) in roots and leaves of Fe-sufficient (+Fe) and Fe-deficient (-Fe) plants. The results indicate that Fe deficiency induced 18-fold higher Fe(III) reductase activity in roots compared with +Fe plants, which was followed by increased root exudation of citric acid (28.2 ± 1.39 in +Fe and 498 ± 256.4 µmol g DW 2 h in -Fe plants). Iron deficiency also induces a significant decrease of root and shoot dry weight compared with the control +Fe plants, whereas 2-wk Pb (20 µM) treatment did not influence root and shoot growth. Iron-sufficient plants accumulated more Pb (56.8 ± 17.29 µg g) in leaves than -Fe plants (21.5 ± 8.10 µg g). Two weeks of exposure to Pb significantly decreased Fe(III) reductase activity and accumulation of Fe, Zn, and Mn in the roots of -Fe plants. It is hypothesized that 2 wk of root exposure to Pb blocks functioning of a specific Fe transport system activated under Fe deficiency.

Factors Affecting Seed Germination of the Invasive Species Symphyotrichum lanceolatum and Their Implication for Invasion Success.

Invasive species Symphyotrichum lanceolatum (Willd.) G. L. Nesom is spreading uncontrollably along wet habitats as well as in disturbed ecosystems. All those habitats function as corridors that facilitate seed dispersal. One way to prevent the spread of invasive species is to know their reproductive ecology. The present study evaluates the potential for generative reproduction of S. lanceolatum and determines how different temperatures, amounts of nutrients, and light regimes, affect seed germination. Seeds collected from 13 natural populations were germinated at four fluctuating temperature regimes (15/6, 20/10, 30/15, and 35/20 °C). To test the influence of nitrate on seed germination, two KNO3 concentrations were used (5 mM and 50 mM solution). For each treatment, three replicates of 30 seeds were placed in complete darkness or a 14 h photoperiod. The results showed that the germination increased with increasing temperature. The optimal temperature regimes were 30/15 °C and 35/20 °C with approximately 88% germination. The overall effect of KNO3 on germination was positive. The concentration of 50 mM KNO3 had a less stimulating effect compared to 5 mM KNO3. Seeds showed sensitivity to lack of light during germination but were able to germinate in a significant percentage in such conditions. Considering that S. lanceolatum often occurs in disturbed sites, these results suggest that seed reaction to alternating temperature, nutrients concentration, and light can be determining factors that affect seed germination of this species and, thus, its spread.

Analysis of Phenolic Compounds for the Determination of Grafts (in) Compatibility Using In Vitro Callus Cultures of Sato-Zakura Cherries.

The aim of this study was to prove that under in vitro conditions, the adhesiveness of the callus between rootstock and scion, the development of callus cells at the points of fusion, and the presence of phenolic components are closely related to the level of (in) compatibility of the grafting combinations between Sato-zakura cherry cultivars ('Amanogawa', 'Kanzan', and 'Kiku-shidare-zakura') and commercial rootstocks. Prunus avium, Prunus 'Colt', Prunus mahaleb and Prunus serrulata were used as compatible and Prunus serotina and Pyrus communis 'Pyrodwarf' were used as two potentially incompatible rootstocks. The results indicated the significant manifestations of the early signs of the incompatibility on the callus junction. Phenols, as well as tissue senescence, were very precisely localized by toluidine blue and alcian blue as well as safranin staining, which can indicate the early signs of the callus incompatibility in some grafting unions. In the callus unions of Prunus avium with 'Amanogawa' and 'Kiku-shidare-zakura' the results of chemical analyses indicated that the existence of several flavonols, flavones and phenol acids could be involved in the incompatibility process in grafted combination. The detection of flavonol astragalin in the unions can be a biomarker of compatibility between scion and the rootstock, while some polyphenols, such as neochlorogenic acid, sinapic acid, ellagic acid, caffeic acid, baicalein, naringenin, apigenin and luteolin can be used as the indicators of graft incompatibility. p-coumaric acid and ferulic acid could be used for detection of delayed incompatibility.