Archives - Allelopathy Journal

We investigated the chemical composition, herbicidal and fumigant insecticidal activities of essential oil from the flowers of Buddleja alternifolia Maxim. The main constituents of the oil were: ketoisophorone (21.89 %), (Z, E)-Geranyl linalool (3.61 %), dihydrooxoiso-phorone (7.76 %), p-vinyl guaiacol (5.15 %), phenethyl alcohol (3.40 %), safranal (3.25 %) and pentacosane (3.23 %). The fumigant insecticidal activity was investigated by exposing the 7-day-old adults of Callosobruchus maculatus and Sitophilus oryzae for 24 h at 20 to 320 μL/L air oil concentrations. The concentrations < 20 μL/L air were also assayed to interpolate the lethal concentration of 50 % (LC50). The herbicidal effects of essential oil were evaluated on seed germination and seedling growth of 4-weeds [Bidens pilosa, Lolium perenne L., Echinochloa crusgalli (L.) Beauv. and Plantago asiatica L.]. The lowest concentrations of oil causing 100 % mortality of C. maculatus were 20 μL/L and S. oryzae 40 μL/L, after exposure times of 21 h and 18 h, respectively. The susceptibility of these insects was same at concentrations < 20 μL/L with LC50 values of 9.97-12.03 μL/L. The oil at 0.08 % concentration, completely inhibited (100 % Inhibition) the seed germination of 4- test weed species. Its phytotoxic effects on the seedling growth were species specific and B. pilosa proved most sensitive weed. Hence, the flower oil may be developed as herbicide or insecticide after more research.

We studied the effects of ozone (O3) on the allelopathic medicinal trees/shrubs that influenced other species growing under their canopy in National Park Sochi, Russia (Caucasus region). Using model reactions, the action of rain leachates from these allelopathic trees/shrubs on the plants growing under their canopy was determined. Depending on the duration and intensity of exposure, the O3 treatment of test woody plants changed their (i) characteristics of leaves and their water extracts, (ii) colour and (iii) autofluorescence of secretory cells. Water extracts from the allelopathic woody donor plants served as model of rain leachates, and their effects were tested on the seeds and pollens germination of acceptor plants (Lavatera trimestris L. var.Rubin and Hippeastrum (Herb.) hybridum ). The effects of water extracts from the ozone treated plants differed from the untreated plants. The allelochemicals in donor plants stimulated, inhibited or had no effects on the recipient plants compared with control. The test-reactions in tropospheric ozone stress should be used in Modelling System of tree/shrub-herbaceous plants interactions, to find the allelopathic interactions in urban conditions.

We studied the allelopathic effects of phenolic acids in the Eucalyptus plantations soil on Eucalyptus seedlings growth. Based on the actual content of p-hydroxybenzoic acid, vanillic acid, ferulic acid, coumaric acid, benzoic acid and salicylic acids in soil of Eucalyptus grandis × Eucalyptus urophylla plantations (X), concentration gradients of each phenolic acid (0.5X, 1.0X, 2.0X) were prepared to apply in potted Eucalyptus seedlings. The results showed that each of the 6-phenolic acids significantly (p < 0.05) promoted or inhibited the stomatal conductance, intercellular CO2 concentration, transpiration rate, chlorophyll fluorescence (minimal fluorescence of dark-adapted leaves, maximal fluorescence of dark-adapted leaves, variable fluorescence of dark-adapted leaves, maximum quantum yield of PSII photochemistry). These treatments also influenced the water-use efficiency and growth parameters (height, root biomass, stem biomass, leaf biomass, shoot biomass, total biomass and root/shoot ratio) of Eucalyptus seedlings. Whereas, none of the test phenolic acids affected the ground diameter or net photosynthetic rate of seedlings. This study indicated that further experiments in Eucalyptus plantations are required to find, whether phenolic acids in Eucalyptus plantations soil significantly affected the growth of Eucalyptus trees under natural conditions and how to regulate the phenolic acids contents in forest soil?

We studied the nematicidal effects of olive pomace (OP) and green walnut husk (GWH) on root-knot nematode (Meloidogyne incognita) in tomato. We determined under in-vitro conditions, the efficacy of OP and GWH extracts (0, 25, 50, 75 and 100%) against the second stage juvenile of M. incognita. Then, GWH and OP were mixed with sandy loam soil at rates of 0 %, 0.5 %, 1 %, 1.5 % and 2 % w/w under controlled atmosphere conditions. Tomato seedlings (Solanum lycopersicum L. cv Troy) were transplanted in pots and inoculated by second stage juveniles of M. incognita. Gall index (GI), egg mass index, root and shoot development of tomato plants were determined 60 days after inoculation. GWH (2 %) application reduced the GI of tomato seedlings by 85 % while OP (2 %) reduced it by 53 % than unamended control. Mortality rates of J2 were significantly affected by type of material, concentrations and the exposure time. GWH had higher juglone (5-hydroxy-1,4- naphthoquinone) concentration which suppressed the root knot nematodes as compared to OP. Higher rates of GWH and OP added into the soil resulted into healthy and much longer root systems. Plant fresh and dry weight increased in all treatments than control. Use of GWH and OP suppressed the root-knot nematodes without causing phytotoxicity to tomato plants.

We investigated the herbicidal activity of ethanolic extracts of Veronica persica (Lour.) Merr. against four weeds (Echinochloa crusgalli (L.) Beauv., Beckmannia syzigachne (Steud.) Fern., Leptochloa chinensis (L.) Nees and Lindernia procumbens (Krock.). The chemical constituents of V. persica were identified using gas chromatography-mass spectrometry (GC-MS). The possible inhibitory mechanisms of the ethanolic V. persica (Lour.) Merr. extracts to E. crusgalli (L.) Beauv. were evaluated by comparing the activities of catalase (CAT), peroxidase (POD) and superoxide dismutase (SOD) enzymes. Lower extract concentrations (50 and 100 μg/mL) were less inhibitory than higher concentrations (150 and 300 μg/mL). The allelopathic herbicidal effects of V. persica (Lour.) Merr. on the 4-test weeds followed the order: L. chinensis (L.) Nees, L. procumbens (Krock.) Philcox, B. syzigachne (Steud.) Fern., E. crusgalli (L.) Beauv.. Twenty-one compounds were identified in the ethanolic extracts, of which 9,12,15-octadec-atrienoic acid (EC50=0.65 μg/mL) was the major component, followed by 4-compounds [9,12-octadecadienoic acid, hexadecanoic acid (EC50=7.13 μg/mL) and decanoic acid (EC50=0.48μg/mL)]. All these compounds were herbicidal. The CAT, POD and SOD activity of E. crusgalli (L.) Beauv. leaves increased at lower concentrations of V. persica (Lour.) Merr. extracts, but decreased at higher concentrations. It was concluded that V. persica (Lour.) Merr. had strong allelopathic herbicidal activity, thus a standard herbicide against weeds can be developed from its major components.

We assessed the effects of allelochemicals present in in Eucalyptus urophylla S.T. Blake on two legume species: Albizia julibrissin Durazz. and Acacia mearn De Wilde. and their symbiotic relationship with rhizobia. Addition of E. urophylla leaves or eucalypt soil increased the total soil phenolics and soil N, and the total soil phenolics were negatively correlated with root nodulation of these two legumes. The test phenolic compounds and those found in Eucalyptus plant significantly reduced the number of root nodules in A. julibrissin. However, these phenolic compounds had no effect on the rhizobia growth, but significantly inhibited the legume-rhizobium symbiosis by reducing the seedling root hairs deformation.