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.

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.

Cotoneaster multiflorus is a large deciduous, ornamental shrub, suitable for landscape use. It has long arching branches and very abundant white flowers followed by scarlet-red fruit. It is low-demanding species which can grow on clay soils. As a drought tolerant species, it has potential to withstand the effect of climate change. Generative propagation of this species is difficult due to its combined embryo and seed coat dormancy. For that reason, the aim of this study was to establish quick and effective method for generative propagation of selected elite genotypes of C. multiflorus that are growing in the Belgrade area. The seeds were collected in a public green spaces in the park in Petlovo brdo, Belgrade, and after maceration, the effect of different treatments was examined. These treatments included soaking seeds in sulfuric acid at 96 % for 60 or 90 minutes, 5 months of cold stratification at 3-5oS in perlite or without substrate (naked stratification), and combinations of these treat?ments. The obtained results showed that C. multiflorus requires the combination of sulfuric acid pre?treatment and a cold stratification in perlite for germination. The seeds treated with sulfuric acid followed by 5 months of naked stratification didn?t germinate. The length of sulfuric acid treatment also influenced germination rate and better results were achieved with seeds that were soaked for 90 minutes in sulfuric acid compred to 60 minutes treatment. However, the maximum germination percentage obtained in this research did not exceed 40%, real ger?mination rate was 59%. It is necessary to perform additional research in order to improve germination.

Chinese catalpa is a medicinal and ornamental, low demanding tree which tolerates urban pollution, drought and poor soils. It should be planted more often in Serbia, and gen?erative propagation is the most suitable method for mass production of this species. The aim of this research was to investigate the effects of red and far-red light on Catalpa ovata seed germination, as well as the influence of seed storage length on germination. The seeds were collected in 2003 and 2007 from the same tree, stored for one and five years and exposed to red light (R) or far-red light (FR) before seed germination tests. After one year of storage, seed germination was high (74-82%) in a control treatment (white light conditions, 16h light and 8h dark), and the seeds did not germinate in dark conditions. Red light and a combination of red light and far red light treatments induced germination, but the obtained values varied (7 - 66%) depending on the year of seed harvesting. The seeds collected in 2003 had a higher germination percentage (51.0%) compared to the germination of seeds collected in 2007 (up to 14%) after red light treatment. The time of exposure to red light pulse (10, 15, 20 or 30 min) did not considerably affect germination rate. After 5 years of storage, germination percentage was considerably lower, reaching only 30% in white light conditions. The results obtained in this research confirmed that C. ovata seeds are photoblastic and can be stored for one year preserving a high germination rate.