Allelopathic Effects of Water Extracts of Sweet Potato (Ipomoea batatas) on Seed Germination of Ageratum conyzoides

Sustainable weed management strategies are essential to reduce chemical and labor inputs. This study aimed to evaluate the effect of water extracts from sweet potato [Ipomoea batatas (L.) Lamarck] on seed germination of Ageratum conyzoides L. under controlled conditions. The aqueous was produced from plant parts i.e., roots, stems, and leaves of sweet potato at concentrations of 0.025, 0.050, 0.075, and 0.100 g·mL-1. The results showed that the plant parts of sweet potato all contained allelopathic substances, which showed high-concentration inhibition and low-concentration promotion of seed germination of A. conyzoides. When the aqueous extract concentrations were 0.050, 0.075, and 0.100 g·mL-1, the germination of A. conyzoides seeds was inhibited, while the germination was promoted at a concentration of 0.025 g·mL-1. This shows that when the planting density of sweet potato is large, it can form an obvious prevention and control effect on A. conyzoides, and thus improve herbicide resistance management.

Cellular Growth Dynamics Affects Allelopathic Activity in Coffee Cell Culture

Cellular growth dynamics and allelopathic activity in coffee cell cultures were examined as follows: First, we compared allelopathic activity of seven woody plant calli, Coffea canephora, Derris indica, Ficus carica L., Juniperus conferta, Prunus persica, Punica granatum, and Sonneratia ovata, using a modified “sandwich method bioassay” and found that coffee callus showed the strongest growth inhibition to lettuce seedling nearly 90% of hypocotyl and 96% of root. This coffee callus actively proliferated, with a 21-fold increase during five weeks of subculture, with a growth curve comprising two typical phases: a lag phase of 0 - 2 weeks of culture and an exponential phase of 3 - 5 weeks of culture. Allelopathic activity varied depending on the growth phase of the coffee callus. The strongest allelopathic activity was detected in 1 - 2-week-old callus showing nearly 100% inhibitory effect on lettuce seedling growth. As the allelopathic activity of coffee calli is extremely high, beyond the natural level in coffee leaves and green beans, we focused on analyzing the allelopathic activity of its aqueous extracts using high-performance liquid chromatography. Several prominent peaks, including two reference alkaloids, theobromine and caffeine, which are known allelochemicals in coffee plants, and three distinct unknown peaks were identified at 270 nm in coffee calli during the lag phase (1 - 2 weeks of culture). The higher value of the total phenolic content in the lag phase also suggested a key biosynthetic pathway in relation to the allelopathic activity of coffee callus will be activated in the lag phase.

Effect of Potato Extract on its Phenolic Metabolism,SAGs Accumulation and Allelopathic Autotoxicity

[Objective] The paper was to study the effect of potato extract on its phenolic metabolism,SAGs accumulation and allelopathic autotoxicity.[Method] With water treatment as control,the effects of aqueous extracts of potato bud,leaf-stem and tuber on its morphological characteristics,phenolic metabolism,glycoside alkaloids accumulation and allelopathic autotoxicity were studied.[Result] After the treatment of aqueous extract,the germination rate of potato reduced,germination was delayed,the plants became smaller,and the growth of root slowed down;the content of phenolic substances in roots,stems and leaves of potato increased,glycoside alkaloids accumulated,the activity of PPO and PAL increased.The effects of aqueous extract treatment on germination,growth,phenolic metabolism,glycoside alkaloid content and allelopathic autotoxicity successively were bud extractleaf-stem extracttuber extractcontrol.Treatment of aqueous extract did not affect the distribution of phenolic substances and glycosidic alkaloid in potato.[Conclusion] Phenolic substances and glycosidic alkaloid involved in the allelopathic autotoxicity of aqueous extract of potato,which had inhibition effect on germination and growth of potato.

Phenolic Acids in Plant-Soil-Microbe System: A Review

Phenolic acids are very common compounds in pedosphere. Theobjective of this review was to summarize the current knowledge ofthe behaviors of phenolic acids in plant-soil microbe system. Whenphenolic acids originated form leaching, decomposition and exudationof living and dead plant tissues enter soils, they can reactphysiochemically with soil particle surfaces and/or incorporate intohumic matter. Phenolic acids desorbed from soil particle surfaces andremained in solution phase can be utilized by microbe as carbonsources and absorbed by plants.

Study on the Allelopathic Effects of Alien Invasive Species Cenchrus echinatus on Seed Germination and Seedling Growth of Solanaceae Crops

[Objective] This study aimed to investigate the potential ecological dam- ages of alien invasive species Cenchrus echinatus. [Method] By using seed germi- nation method, the effects of different concentrations of C. echinatus aqueous extracts on seed germination and seedling growth of three Solanaceae crops were investigated. [Result] After incubated for 5 d, no significant differences were observed in germination speed indices of Lycopersicum esculentum seeds between aqueous extract groups and control groups; germination speed indices of Solarium melongena seeds were significantly reduced with the increasing concentration of Cenchrus echinatus aqueous extracts; however, Capsicum frutescens seeds in various groups were not germinated. After incubated for 7 d, root lengths of Lycopersicum esculentum seedlings were inhibited with the increasing concentration of Cenchrus echinatus aqueous extracts, while stem lengths and comprehensive allelopathic effects were promoted; germination rates of Solanum melongena seeds in various groups were all significantly lower than control groups; root length, stem length and comprehen- sive allelopathic effects in higher concentration groups were inhibited; germination rates of Capsicum frutescens seeds were significantly inhibited, and those in the highest concentration group were not generated. After incubated for 14 d, all indica- tors of Solanum melongena were significantly inhibited; various indicators of Capsicum frutescens in the highest concentration group were significantly inhibited. [Conclusion] The sensitivity of three Solanaceae crops to Cenchrus echinatus aqueous extracts presented an overall order of Solanum melongena 〉 Capsicum frutescens 〉 Lycopersicum esculentum, suggesting that Cenchrus echinatus can to some extent inhibit the growth of several crops, which should be strictly prevented and controlled in agricultural production.

Allelopathic Effects of Aqueous Extracts of Different Tissues and Rhizosphere Root of Adzuki Bean on Growth of Wheat Seedlings

Seedlings of wheat were used as receptor plants to study the allelopathic effects of Adzuki Bean aqueous extracts from different organs and rhizosphere soil at different concentrations （0, 10, 40 and 160 g/L） using sand culture of pot method. The results indicated that root aqueous extract of adzuki bean presented promotion effects at low concentrations and inhibition effects at the high concentra- tion on the growth of height and young leaf length of wheat seedlings, but inhibition effects at low concentrations and promotion effects at the high concentration on the growth of root length, the number of lateral roots and dry weigh of underground part of wheat seedlings. With the concentrations of rhizosphere soil, root, stem and leaf aqueous extracts of adzuki bean increasing, their inhibitory allelopathic effects on the growth of height and young leaf of wheat seedlings increased; the physiological parameters of wheat seedlings studied at the low concentrations of aqueous extracts, indicated that root and rhizosphere soil aqueous extracts of adzuki bean improved the activities of hyperoxid dismutase （SOD） and peroxide enzyme（POD）, but reduced the contents of chlorophyll and malonaldehyde （MDA）; the physiological parameters of wheat seedlings studied at the high concentration of aqueous extracts indicated that the leaf aqueous extract of adzuki bean inhibited root vigor, and reduced the contents of Chlorophyll and MDA, but it was found that the aqueous extract significantly improved the activities of SOD and POD; and as to the synthetic allelopathic effect （SE）, the allelopathic effects of different tissues and rhizosphere soil of adzuki bean on wheat seedlings were in order of leaf〉stem〉soil〉root.

Application of Box-Behnken Design in Optimization of Allelopathic Effects of Potamogeton Pectinatus Against Microcystis Aeruginosa

Allelopathic effects of submerged macrophytes against algae are affected by many environmental factors which can only be measured one by one by traditional methods. Box-Behnken design of response surface methodology was used to optimize three environmental factors （temperature, light intensity and total dissolved solids） of allelopathic effects of Potarnogeton pectinatus against Microcystis aeruginosa at the same time. By solving the regression equation and analyzing the response surface contour plots, the optimal conditions of the relatively inhibitory rate of Microcystis aeruginosa were that the temperature was 23℃, the light intensity was 2 700 lx and the total dissolved solids were 4 415 mg/L. Under these conditions, the optimal value of relatively inhibitory rate of Microcystis aeruginosa was 81.9%. According to validation experiments, the results of analysis indicated that the experimental values fitted well with the predicted ones.

Allelopathic Effects of Aqueous Extract of Torreya fargesii Aril on Seed Germination and Seedling Growth of Radish, Mustard and Cabbage

[Objective] This study aimed to investigate the allelopathic effects of Torreya fargesii aril. [Method] By indoor bioassay, the effects of different con-centrations （10, 20,40, 80 g/L） of aqueous extract of T. fargesii aril on seed germination rate, seedling root length, seedling height, fresh weight, chlorophyll content, malondialdehyde （MDA） content and anti oxidative enzyme activities of radish, mustard and cabbage were analyzed and compared. [ Result] Different concentrations of aqueous extract of T. fargesii aril inhibited seed germination and seedling growth of three crops, and the inhibitory effects were enhanced with the increase of concentration. Seedling height and fresh weight of three crops were improved by low concentrations of aqueous extract of T. fargesii aril and inhibited by high concentrations of aqueous extract. Overall, aqueous extract of T. fargesii aril exhibited allelopathic inhibitory effects on three crops, and the level of allelopath-ic inhibitory effects demonstrated a descending order of radish 〉 mustard 〉 cabbage. Compared with the control group, 80 g/L aqueous extract of T. fargesii aril almost significantly reduced seed germination rate, seedling root length, seedling height, fresh weight and chlorophyll content, and significantly improved MDA con-tent and antioxidative enzyme （SOD, CAT, POD） activities of radish, mustard and cabbage （P 〈 0 .0 5 ） . [ Conclusion] Aqueous extract of T. fargesii aril exhibited remarkable allelopathic inhibitory effects on seed germination of radish, mustard and cabbage, which indicated that there might be dormancy-associated germination in-hibiting allelochemicals in T. fargesii aril. This study provided theoretical basis for subsequent clarification of the mechanism of seed dormancy of T. fargesii.

Allelopathic eff ects of macroalga Corallina pilulifera on the red-tide forming alga Heterosigma akashiwo under laboratory conditions

Over the past few years, harmful algal blooms （HABs）, such as red tides, have been frequently observed in coastal zones worldwide. The natural allelopathic interactions among macroalgae and red tide microalgae can alter the structure and succession of aquatic ecosystems. We investigated the influence of four environmental factors （temperature, salinity, light, and pH） on the allelopathic effects of the macroalgae Corallina pilulifera on red-tide forming Heterosigma akashiwo under laboratory conditions. Each of the factors had four levels： temperature （15, 20, 25, and 30℃）, salinity （10, 20, 30, and 40）, light （20, 100, 200 and 400 gmol/（m2.s））, and pH （5.5, 7, 8.5, and 10. Two-factor experiments were designed for each two environmental factors, with six combination treatments （temperature-salinity, temperature-light, temperature-pH, salinity-light, salinity-pH, and light-pH）. Results showed that the allelopathic effect was significantly influenced by temperature, salinity, light, and pH. As single factors, the low temperature （15 ℃）, low salinity （10）, high-intensity light （400umol/（m2.s））, and high pH （10） treatments substantially enhanced the allelopathic effect. The strongest allelopathic effect of C. pilulifera on H. akashiwo was observed under the following treatments： 15℃ and salinity of 40, 25℃ and pH 10, 25℃ with medium- to high-intensity light at 200-400 umol/（m2.s）, 400umol/（m2.s） and salinity of 10, 400 gmol/（m2·s） and pH 10, and pH 10 with a salinity of 40.

Identification of the toxic compounds produced by Sargassum thunbergii to red tide microalgae

The inhibitory effects of methanol extracts from the tissues of three macroalgal species on the growths of three marine red tide microalgae were assessed under laboratory conditions.Extracts of Sargassum thunbergii(Mertens ex Roth) Kuntz tissue had stronger inhibitory effects than those of either Sargassum pallidum(Turner) C.Agardh or Sargassum kjellmanianum Yendo on the growths of Heterosigma akashiwo(Hada) Hada,Skeletonema costatum(Grev.) Grev,and Prorocentrum micans Ehrenberg.Methanol extracts of S.thunbergii were further divided into petroleum ether,ethyl acetate,butanol,and distilled water phases by liquid-liquid fractionation.The petroleum ether and ethyl acetate fractions had strong algicidal effects on the microalgae.Gas chromatography-mass spectrometry analyses of these two phases identified nine fatty acids,most of which were unsaturated fatty acids.In addition,pure compounds of four of the nine unsaturated fatty acids had effective concentrations below 5 mg/L.Therefore,unsaturated fatty acids are a component of the allelochemicals in S.thunbergii tissue.

Inhibitory effects of Albizia lebbeck leaf extracts on germination and growth behavior of some popular agricultural crops

An experiment was conducted to observe the inhibitory effects of the leaf extracts derived from Albizia lebbeck （L.） Benth. On germination and growth behavior of some popular agricultural crops （receptor） of Bangladesh. Experiments were set on sterilized petridishes with a photoperiod of 24 h at room temperature of 27-30℃. The effects of the different concentrations of aqueous extracts were compared to distil water （control.）. The aqueous extracts of leaf caused significant inhibitory effect on germination, root and shoot elongation and development of lateral roots of receptor plants. Bioassays indicated that the inhibitory effect was proportional to the concentrations of the extracts and higher concentration （50%-100%） had the stronger inhibitory effect whereas the lower concentration （10%-25%） showed stimulatory effect in some cases. The study also revealed that, inhibitory effect was much pronounced in root and lateral root development rather than germination and shoot growth.

Influence of Treatment of <i>Jatropha curcas</i>L. Leachates and Potassium on Growth and Phytochemical Constituents of Wheat (<i>Triticum aestivum</i>L.)

Jatropha curcas L. commonly known as “physic nut” is an exotic species that shows invasive characters. Plantation of Jatropha species is being undertaken at a large scale for biodiesel production. The plants defoliate their leaves twice a year and have been shown to possess certain antinutritional factors. Seeds of Jatropha are removed from mature dried fruits for oil extraction and ovary walls are discarded. For the present experiments leachates from sun dried leaves and ovary walls of Jatropha curcas L. were used for analyzing their possible allelopathic effects on the growth of wheat (Triticum aestivum L. cultivar, MP-4010). Leachate treatments result in slight decrease in growth in terms of plant height, leaf area, biomass, spike length and 100 seed weight of wheat and increase in total phenols, tannins, phytic acid and free amino acids. Results suggest that the leachates of leaf and ovary wall of Jatropha curcas are slightly inhibitory, however the impact does not last long. Nevertheless, continuous plantation may lead to accumulation of damaging constituents which reflects the need for further analysis and experimentation.

Effect of border planting of Eucalyptus citriodora Hook. on the growth and biomass production performance of Cymbopogon winterianus Jowitt ex Bor Grass at Wondo Genet,Southern Ethiopia

The use of Eucalyptus trees, in association with other plants, has the potential to reduce the growth of neighbouring plants or grasses by competing for resources or releasing allelochemicals that may cause other plants to grow slowly. Our purpose here is to assess whether border planting of Eucalyptus is harmful to the establishment,growth, and production of Cymbopogon winterianus at various distances from tree lines in the Wondo Genet Agricultural Research Center in Southern Ethiopia. Several factors were studied: growth performances and yield of aromatic grasses; soil properties, including total nitrogen,organic carbon, and moisture content; and plant leaf nutrient content(NPK) at various distances away from the Eucalyptus citriodora border line were studied. Chemical compositions of hydro-distilled essential oils obtained from selected C. winterianus grasses leaves were analysed by gas chromatography. Plant height, biomass yield, amount of essential oil yield, and essential oil composition all were significantly affected due to Eucalyptus effect in the first10-m distance as compared to beyond 10 m from the tree border line. There were increases in soil total nitrogen,organic carbon, and moisture content with decreasing distances to the Eucalyptus tree border. The result of plant leaf nutrient content(NPK) differed across treatment and distance. The pot experiment(15 cm 9 20 cm), shoot length,and number of leaves of aromatic plants varied in the degree of inhibition based on the concentration of the aqueous extract. Significantly higher inhibitions of the shoot length and number of leaf parameters were observed when using 25% fresh leaf extract compared to other extract levels.

Effect of UV-B irradiation on interspecific competition between Ulva pertusa and Grateloupia filicina

We report the effect of UVoB irradiation （9.6 kJ m-2 day^-） on interspecific competition between two species of macroalgae, Ulva pertusa （U） and Grateloupiafilicina （G）, in co-culture. Growth of U. pertusa and G. filicina was inhibited by UV-B irradiation in mono-culture and specific growth rate （μ） declined as a result. Interspecific competition between U. pertusa and G filicina was closely related to the initial weights when co-cultured. When initial ratios of U. pertusa （U） to G filicina （G） were U：G=I.2：I and 1：1, U. pertusa was the dominant algae. When the initial U：G ratio was 1：1.2, G. filicina was competitively dominant in the earlier stage, but U. pertusa grew faster, superseding G. filicina in the later stage. At initial ration U：G = 1：1.4, G. filicina was predominant. Under UV-B irradiation, the competitive ability of G filicina was weakened and the interspecific competitive balance favored U. pertusa, which suggests that G. filicina was more sensitive to UV-B irradiation. We also probed the potential allelopathic effects between the two species, which led to mutual growth inhibition.

Studies on the Allelopathic Potential of Corn （Zea mays L.） Aqueous Extracts and Root Exudates

This investigation was carried out at Faculty of Agriculture and Forestry-University of Duhok/Kurdistan-Iraq. Three experiments were included in this investigation： （1） First experiment was a bioassay related to the germination performance, shoot and root development of corn （Zea mays L.） and peanut （Arachishypogaea） at two concentrations of root （3% and 1.5%） and shoot （12% and 6%） aqueous extracts of corn medium; （2） The second experiment dedicated to the intercropping of corn and peanut at four treatments; （3） While the third experiment involved the effect of peanut root exudation on growth of corn. Experiment results revealed that corn shoot and root water extracts highly inhibited seed germination of both corn and peanut, the inhibitory of shoot extract was more than root aqueous extract. While its effect on the seedling growth was vice versa as compared with control treatment, there was an increase in root and shoot length of both corn and peanut when grown in corn aqueous extracts. Intercropping experiment results has stimulated most traits of peanut under studying. Also for corn, there was apparent and significant increase in all characteristics as compared with control. It was further confirmed from the results of peanut root exudates that had all studied characters of corn were stimulated than the control treatment.

Allelopathic Effects of Eichhornia crassipes on the Growth of Microcystis aeruginosa

Algal blooms caused by eutrophication in fresh water are one of the major environmental problems in the world. Using biological methods to control algal growth, especially based on allelopathic inhibitory effects of aquatic macrophytes on phytoplankton growth, have been received world-wide attention. In this study, the allelopathic activity of the invasive macrophyte, Eichhornia crassipes （water hyacinth）, on blue-green algae, Microcystis aeruginosa （PCC7806） was investigated using coexistence assay. Our results showed that water hyacinth had disparate effects on the growth ofM~ aeruginosa （PCC7806） under different initial algal densities. Under lower initial algal density （OD650 = 0.10 and OD650 = 0.05）, the algal growth was significantly inhibited by water hyacinth （inhibition ratio was 95.6% and 97.3%, respectively）. While it was stimulated at higher initial algal densities （OD650 = 0.20）. Water hyacinth inhibited the growth of algae mainly through its root system. Culture water from water hyacinth and aqueous methanol extracts from dry roots samples also showed inhibition effects on algal growth. The inhibition effects increased as the increase of crude extract concentration, suggest that water hyacinth may excrete inhibitory substances from root system and show allelopathic inhibitory potential to the growth ofM. aeruginosa.

A New Bioassay Method for Evaluation Allelopathic Potential of Rice Germplasm

Allelopathy was defined in 1996 by IAS （international allelopathy society） as any process involving secondary metabolites produced by plant, algae, bacteria and fungi that influences the growth and development of agricultural and biological systems. Rice allelopathy against weeds was reported since 1989, which offers an integrated weed management with substantially reduced herbicide usage. Application of allelopathic rice cultivars is thought a resources conservation and environmental friendly way of weed bio-control, and could promote the sustainable development of agriculture. Screening or evaluating the allelopathic potential rice variety is the first step. In this paper, a new bioassay method was set up by the allelopathic potential of 9 rice lines on the target weed barnyardgrass （Echinochloa crusgalli）, and comparing with bioassay methods such as relay seeding in filter paper （RSF） and relay seeding in agar （RSA）. The results indicated that three methods had a same tendency in evaluating the allelopathic potential of rice; there existed a significant difference among different bioassay methods, and an interaction between bioassay methods and rice lines. The method of root exudates （RE） with the highest value and a correlation efficiency of 0.98 was considered as ideal bioassay method for evaluation of allelopathic potential.

Advances of Allelopathic Autotoxicity in Rehmannia glutinosa L.

Allelopathic autotoxicity occurs when a plant releases toxic chemical substances into the environment which inhibits development and growth of the same plant species.Rehmannia glutinosa L.( R.glutinosa ) is one of the most common traditional Chinese medicines,whose productivity and quality,however,are seriously impacted by consecutive monoculture obstacle.Allelopathic autotoxicity is one reason for consecutive monoculture obstacle.In this paper,we reviewed the categories of allelochemicals,the methods of allelochemicals identification,and the mechanisms of allelopathic autotoxicity,which provides clues for further study of the molecular mechanisms of allelopathic autotoxicity and consecutive monoculture obstacle.

Allelopathy of the Leaf Extract of Eucalyptus Genetic Material on the Physiological Performance of Millet Seeds

This study aims to evaluate the possible allelopathic effects of young and mature leaf extract from of two eucalyptus genetic materials on the physiological performance of millet seeds. The experiment was carried out in a completely randomized design, in a 5 × 2 × 2 factorial arrangement [five concentrations of the extract (0, 25%, 50%, 75%, and 100%) × two genetic materials (1 - Eucalyptus grandis × Eucalyptus urophylla and 2 - Eucalyptus grandis × Eucalyptus camaldulensis) × two maturation stages of leaves (young and mature leaves)] with four replicates, each one with 25 seeds. Seeding was performed on the germitest paper substrate distributed in Petri dishes, moistened with the extract according to the treatments, being allocated in biochemical oxygen demand (B.O.D) adjusted at 25°C and 12 h photoperiod. Percentage, speed index, mean germination time, aerial part and primary root length, and dry matter weight of aerial part and root system of seedlings were evaluated. The leaf extracts of the two eucalyptus clones had all the analyzed variables changed with effect more evident on young leaf extract of the genetic material 1. It can be concluded that the tested genetic materials have a detrimental effect on the physiological performance of millet seeds.

Research on the allelopathic potential of wheat

Objective: This paper mainly discusses the Allelopathic potential of Wheat. Methods: This paper is prepared by reviewing the latest academic literatures. Result: The green revolution in the 1960s caused an increase in the demand for food. The agricultural sector and farmers tended to spend more time on the agricultural work but the crop yield was suppressed by the weeds. Hence, the usage of herbicide insecticides, fungicides and others chemicals had been increased. Although herbicides are efficient for weed controls, the continuous uses had gradually stimulated the weeds developing an effecttive resistance to the chemicals. Wheat (Triticum aestivum L.) is known as allelopathic against crops and weeds. Allelopathy of wheat (Triticum aestivum L.) has been extensively examined for its potentials in weeds management. The allelopathic activity of wheat has been attributed to hydroxamic acids, the related compounds and phenolic acids. Therefore, it could effectively reduce herbicide uses in order to maintain an eco-friendly environment and a cost-effective weed control.