Difference in Allelopathic Potential as Influenced by Root Periderm Colour of Sweet Potato (Ipomoea batatas)

Laboratory bioassay and high‐performance liquid chromatography (HPLC) analysis were conducted to determine the allelopathic potentials of aqueous or methanol extracts from three different coloured sweet potato [Ipomoea batatas L. (Lam)] cultivars by plant part. The aqueous extracts applied on filter paper significantly inhibited root growth of alfalfa (Medicago sativa L.). Aqueous leaf leachates at 40 g dry tissue l^?1 (g l^?1) from white sweet potato cultivar ‘Sinyulmi’ showed the highest inhibition against alfalfa, followed by yellow ‘Sinhwangmi’ and purple ‘Jami’. Alfalfa root growth was significantly inhibited by methanol extracts of the same plants as the concentration increased. Aqueous and methanol extracts from leaves showed the most inhibitory effect on alfalfa root growth followed by stems and roots. By means of HPLC analysis, leaf samples of sweet potato had the highest amount of phenolic compounds followed by stems and roots. Total content of these compounds was highest for leaf extracts (37.7 mg 100 g^?1), detected in EtOAc fraction, especially trans‐cinnamic acid (20.9 mg 100 g^?1). These results suggest that sweet potato plants are allelopathic and that their activities differ depending on plant part as well as root periderm colour.     

Herbicidal Potential and Quantification of Suspected Allelochemicals from Four Grass Crop Extracts

Unknown compounds in crop plants are inhibitory to seed germination and early seedling growth of weed plants. A Petri dish assay showed that barley (Hordeum vulgare L.), oats (Avena sativa L.), rice (Oryza sativa L.) and wheat (Triticum aestivum L.) extracts significantly reduced root growth of alfalfa (Medicago sativa L.), barnyard grass (Echinochloa crus‐galli, Beauv. var. oryzicola Ohwi.) and eclipta (Eclipta prostrata L.). As the concentration of crop extracts increased, root growth of the test plants were significantly reduced. A high‐performance liquid chromatography analysis with nine standard phenolic compounds showed that the concentrations and compositions of allelopathic compounds depend on the extracted plant extracts. Caffeic acid, hydro‐cinnamic acid, ferulic acid, m‐coumaric acid, p‐coumaric acid and coumarin were present in all the crop plant species, and hydro‐cinnamic acid were detected as the highest amount. Coumarin at 10^?3 m significantly inhibited root growth of alfalfa and barnyard grass more than that of eclipta. The research suggests that extracts of barley, oats, rice and wheat have an allelopathic effect on alfalfa, barnyard grass and eclipta and that the findings of bioassay were considerably correlated with the type and amount of causative allelochemicals, indicating that the allelopathic effects on three test plants were ranked in order of wheat (highest), barley, rice and oats (lowest). The results may have value in enabling weed control based on natural plant extracts or crop residues in the fields.     

Allelopathic Effects of Black Mustard (Brassica nigra) on Germination and Growth of Wild Barley (Hordeum spontaneum)

Black mustard [Brassica nigra (L.) Koch.] contains water‐soluble allelochemicals that inhibit the germination and growth of other species. This characteristic could be used in weed management programmes. Greenhouse and laboratory experiments were conducted to determine the effects on wild barley (Hordeum spontaneum Koch.) germination and seedling growth of (i) preceding crops, (ii) fresh black mustard residue incorporation, and (iii) black mustard leaf, stem, flower and root water extract concentrations. Growth of wild barley, as indicated by plant height and weight, was significantly reduced when grown in soil previously cropped to black mustard compared with that cropped to wild barley. Soil incorporation of fresh black mustard roots and both roots and shoots reduced wild barley germination, plant height and weight when compared with a no‐residue control. In bioassays, black mustard extracts reduced wild barley hypocotyl length, hypocotyl weight, radicle weight, seed germination, and radicle length by as much as 44, 55, 57, 63 and 75 %, respectively, when compared with a water control. Increasing the water extract concentrations from 4 to 20 g per 100 ml of water of all black mustard parts significantly increased the inhibition of wild barley germination, seedling length and weight. Based on 8‐day‐old wild barley radicle length, averaged across all extract concentrations, the degree of toxicity of different black mustard plant parts can be ranked in the following order of inhibition: leaves > flowers > mixture of all plant parts > stems > roots.     

Alfalfa Phytoestrogen Content: Impact of Plant Maturity and Herbage Components

Legumes contain a range of non‐nutritional phytochemicals that may have health‐promoting effects in humans. In this study, we determined the concentrations of four phytoestrogens (coumestrol, apigenin, luteolin and quercetin) in field‐grown alfalfa (Medicago sativa L.). Differences between plants of different stages of maturity, between plant parts, and different canopy segments were assessed. The concentration of individual phytoestrogen in whole herbage varied between 15 and 225 μg g^?1 dry matter (DM) and was strongly affected by stage of maturity. Coumestrol and apigenin concentrations were highest at early vegetative stages, luteolin and quercetin at early vegetative and late flowering stages. All phytoestrogens were found in lowest concentrations at the early flowering stage (average 68 μg g^?1 DM); stage at which alfalfa is usually harvested when used as a forage source for animals. At vegetative stages, apigenin was the predominant phytoestrogen in herbage followed by coumestrol, the reverse being observed upon initiation of flowering; luteolin and quercetin were found at all stages in similarly lower concentrations. Concentrations of luteolin, quercetin and apigenin were 225, 410 and 690 % greater, respectively, in flowers than in leaves or stems; coumestrol concentration was similar between plant parts. In flowers and stems the predominant phytoestrogens were apigenin and quercetin, followed by coumestrol and luteolin. Similar concentrations (average 26 μg g^?1 DM) of each of the four phytoestrogens were found in leaves. Concentrations through the herbage canopy varied and were greatest at >60 cm from the soil surface for apigenin and coumestrol, but greatest at >60 and 0–20 cm for quercetin and at 0–20 cm for luteolin. The results suggest that if alfalfa is to be used as a source of phytoestrogens and is harvested for the production of herbal supplements or nutraceuticals, management will need to be adapted.     

Allelopathic Effect of Conyza albida on Avena sativa and Spirodela polyrhiza

The allelopathic influence of four plant tissues of Conyza albida (stems, leaves and inflorescences) on oat growth were investigated using in vivo tests. Oat growth (fresh and dry weights of above and underground parts) was inhibited from phytotoxic activity of upper leaves and inflorescence tissues of C. albida in pot studies. The inhibition was significantly higher than in the other tissues studied. The inhibiting action of crude extracts and volatile compounds from young plants (rosette) and mature plants were examined using two bioassay methods: (a) seed germination and radicle growth of oat and (b) fresh weight of duckweed plants. Both bioassayed species exhibited greater phytotoxic response from the young plants, collected in winter, than from the mature ones.     

Differential Cl−/Salt Tolerance and NaCl‐Induced Alternations of Tissue and Cellular Ion Fluxes in Glycine max,Glycine soja and their Hybrid Seedlings

The salt‐sensitive Glycine max N23674 cultivar, the salt‐born Glycine soja BB52 population, and their hybrid 4076 strain (F₅) selected for salt tolerance generation by generation were used as the experimental materials in this study. First, the effects of NaCl stress on seed germination, tissue damage, and time‐course ionic absorption and transportation were compared. When qualitatively compared with seed germination appearance in culture dishes, and tissue damages on roots or leaves of seedlings, or quantitatively compared with the relative salt injury rate, the inhibition on N23674 was all the most remarkable. After the exposure of 140 mm NaCl for 1 h, 4 h, 8 h, 12 h, 2 days and 4 days, the content of Cl^? gradually increased in the roots and leaves of seedlings of BB52, 4076 and 23674. Interestingly, the extents of the Cl^? rise in roots of the three experimental soybean materials were BB52 > 4076 > N23674, whereas those in leaves were just on the contrary. Secondly, by using the scanning ion‐selective electrode technique (SIET), fluxes of Na⁺ and Cl^? in roots and protoplasts isolated from roots and leaves were also investigated among the three experimental soybean materials. After 140 mm NaCl stress for 2, 4 and 6 days, and when compared with N23674, slighter net Cl^? influxes were observed in root tissue and protoplasts of roots and leaves of BB52 and 4076 seedlings, especially at the cellular protoplast level. The results indicate that with regard to the ionic effect of NaCl stress, Cl^? was the main determinant salt ion for salt tolerance in G. soja, G. max and their hybrid, and the difference in their Cl^?/salt tolerance is mainly attributed to the capacity of Cl^? restriction to the plant above‐ground parts such as leaves.     

Root-mediated Allelopathic Interference of Nettle-leaved Goosefoot (Chenopodium murale) on Wheat (Triticum aestivum)

A study was conducted to determine the potential and nature of root‐mediated allelopathic interference of Chenopodium murale on wheat. Early growth of wheat reduced significantly in agar medium where C. murale seedlings were previously growing as well as in rhizosphere soil of C. murale. The reduction in wheat growth was due to the presence of inhibitory metabolites released by roots of C. murale in the growth media. Even the soil incorporation of root residues also reduced the wheat growth in terms of seedling length and seedling dry weight. Only a partial amelioration in growth inhibition occurred upon charcoal supplementation or nitrogen fertilization in these amended soils. Root residues did not reduce the available nutrients in the soil, which was rather nutrient rich. These results indicated the definite role of allelopathy of C. murale roots in retarding wheat growth. Root amended soils contained significantly higher amount of phytotoxic phenolics as the putative allelochemicals, which were ferulic acid, vanillic acid, p‐coumaric acid and benzoic acid. The study concluded that C. murale roots and their exudates exerted allelopathic effects on wheat by releasing water‐soluble phenolic acids as putative allelochemicals in soil.     

外来物种裂叶月见草化感作用

摘要：化感作用在植物入侵过程中具有重要意义。以裂叶月见草入侵早期直接与之竞争的草本植物（小蓬草和阿拉伯婆婆纳）以及农作物（小麦和小白菜）为材料,利用培养皿滤纸法研究裂叶月见草植株各器官浸提液对这四种受体植物种子萌发和幼苗生长的影响,探讨其化感作用的强弱、对农作物的影响以及化感作用与其入侵性的关系。结果表明,裂叶月见草具有化感物质,不同器官内化感物质含量不同,叶片和根内最多,茎次之,枯叶内含量最少;。裂叶月见草提取液对4种受体植物种子萌发和幼苗生长均有化感作用,不同浓度浸提液对植物的化感作用强度不同,高浓度时较强,低浓度时较弱,高浓度的提取液能降低种子的萌发率、发芽速率和胚根长度,其中发芽速率和胚根长度更敏感,可能是衡量化感作用的最敏感指标;不同植物对裂叶月见草化感作用的敏感程度不同,阿拉伯婆婆纳的种子萌发对化感物质最敏感,小白菜的幼苗生长对化感物质最敏感,小麦最不敏感。     

木香薷地上部位水浸液的化感作用的比较

为比较木香薷地上不同部位水浸液的化感作用强弱,以木香薷新鲜茎、叶、花序为供体,黄菖蒲种子为受体,采用3×5二因素完全随机试验设计和实验室生物测定法,测定了受不同部位不同浓度的木香薷水浸液处理后黄菖蒲种子的发芽势、发芽率、发芽指数与成苗率4项指标,并计算了化感效应指数和化感综合效应。结果表明,木香薷不同部位及不同的水浸液浓度对受体的4项指标均有极显著影响(P<0.01);且三部位中,茎和花序水浸液对受体的化感作用均表现为随浓度的升高而增强;三部位的化感综合效应值分别为：-4.60、-6.45、-4.84,表现出“叶>花序>茎”的化感抑制作用的强弱顺序。木香薷的叶、茎和花序均能释放化感物质,以叶最强。     

Differences in Ion Accumulation and Salt Tolerance among Glycine Accessions

Salinity reduces crop yield by limiting water uptake and causing ion‐specific stress. Soybean [Glycine max (L.) Merr.] is sensitive to soil salinity. However, there is variability among soybean genotypes and wild relatives for salt tolerance, suggesting that genetic improvement may be possible. The objective of this study was to identify differences in salt tolerance based on ion accumulation in leaves, stems and roots among accessions of four Glycine species. Four NaCl treatments, 0, 50, 75 and 100 mm , were imposed on G. max, G. soja, G. tomentella and G. argyrea accessions with different levels of salinity tolerance. Tolerant genotypes had less leaf scorch and a greater capacity to prevent Na⁺ and Cl^? transport from soil solution to stems and leaves than sensitive genotypes. Magnitude of leaf injury per unit increase in leaf Na⁺ or Cl^? concentrations was lower in tolerant than in susceptible accessions. Also, plant injury was associated more with Na⁺ rather than with Cl^? concentration in leaves. Salt‐tolerant accessions had greater leaf chlorophyll‐meter readings than sensitive genotypes at all NaCl concentrations. Glycine argyrea and G. tomentella accessions possessed higher salt tolerance than G. soja and G. max genotypes.     

Antioxidant capacity and phenolic content of <Emphasis Type="Italic">Rumex dentatus</Emphasis> L. Grown in Egypt

Rumex dentatus L. (Family: Polygonaceae) is a weedy plant widely distributed in many countries including Egypt. It has been used in the Mediterranean diet as a leafy vegetable and its leaves and roots exhibited various biological activities. In our study, total phenolics, antioxidant capacities assayed by 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging and β-carotene bleaching methods and reducing power were evaluated in different extracts/fractions of leaves and roots of R. dentatus grown in Egypt. In addition, their phenolic compositions were determined by GC-MS and HPLC. The results showed that total phenolic content in the ethyl acetate fractions of leaves and roots were high and measured at 169.5 and 257.4 mg gallic acid equivalent per g extract, respectively. The ethyl acetate fractions of leaves and roots exhibited strong DPPH activity and the DPPH IC₅₀ values were 0.021 and 0.012 mg mL⁻¹ of leaves and roots, respectively. Furthermore, the ethyl acetate fractions of leaves and roots showed high reducing power and antioxidant activity assayed by β-carotene bleaching method. GC-MS and HPLC analyses indicated that these fractions contained a variety of phenolic compounds including p-hydroxybenzoic acid, syringic acid, vanillin, benzoic acid, ferulic acid, and cinnamic acid. Our study verified that the ethyl acetate fractions of leaves and roots of R. dentatus have strong antioxidant activities which are correlated with its high levels of phenolic compounds and therefore, they could be utilized as a natural source of antioxidant in food industry.     

木麻黄自毒作用物对其幼苗内源激素的影响

以15年生木麻黄根系的水浸液作为他感作用物,采用水培方法研究木麻黄自毒作用对其苗木内源激素的影响。结果表明,木麻黄自毒作用主要表现在对其幼苗叶、根中生长类激素IAA、GR、iPAs和ZRs含量下降,且随自毒作用物质浓度升高下降幅度增大,ABA含量、ABA/IAA、ABA/GA、ABA/iPAs、ABA/ZRs、ABA/IAA+GA+iPAs+ZRs增加,内源激素失衡。木麻黄自毒作用对其根、茎和叶生长量和生物量下降与IAA、GR、iPAs和ZRs含量减少和ABA含量增加及内源激素失衡有密切关系。     

氩离子注入介导甘草总DNA在大叶紫花苜蓿中转化的初步研究

氩离子注入介导乌拉尔甘草总DNA在和田大叶紫花苜蓿中转化,对苜蓿正常生长和发育产生了显著的生物学效应.转基因苜蓿T1代的结实率仅有11.66%,其中发育正常的种子比例为64.29%.对种子发育良好的苜蓿T1代9个单株的根茎分别进行了天然产物的定性检识,结果表明,2个单株的根中含有皂苷类物质.用X射线衍射仪对2个处理的转基因苜蓿进行扫描,结果表明,一种图谱经寻峰处理后,d值相对偏差最大为0.67,大于本实验误差允许范围0.02,说明样品微观结构或成份发生了变化.提取并测定了转基因苜蓿与对照组茎和根中的多糖含量,结果表明,转基因苜蓿茎和根中多糖含量分别为0.890%和4.815%,对照组苜蓿多糖含量分别为1.064%和4.882%,说明转入甘草总DNA的苜蓿多糖的含量均有所降低.     

Stimulation of Rice (Oryza sativa L.) Seedling Vigour by Smoke-water and Butenolide

The newly identified smoke‐compound butenolide (3‐methyl‐2H‐furo[2,3‐c]pyran‐2‐one) can improve seedling vigour. This study highlights the effects of smoke‐water and butenolide on shoot and root elongation of a local rice variety. Smoke‐water (1 : 500) and butenolide (10^?8 m ) treatments significantly increased shoot length. A low concentration of butenolide (10^?10 m ) promoted maximum root length and seedling weight, which were significantly different from the control. Butenolide‐treated (10^?8 m ) seedlings had a significantly greater number of lateral roots than untreated seedlings. The vigour index of smoke‐water (1 : 500) and butenolide‐treated (10^?8 m ) rice seeds was significantly higher than that of untreated seeds. These findings suggest the possible use of butenolide for promoting vigorous seedlings in rice.     

Spermidine Enhances Waterlogging Tolerance via Regulation of Antioxidant Defence,Heat Shock Protein Expression and Plasma Membrane H+‐ATPase Activity in Zea mays

Polyamines (PAs) are ubiquitous biogenic amines that play important roles in the environmental stress tolerance of crops. However, the relationship between PAs and plant waterlogging (WL) tolerance has received little attention. In this study, the protective effects of spermidine (Spd) against WL stress were investigated by Zea mays. WL treatment inhibited root growth and caused a significant increase in lipid peroxidation, membrane permeability and DNA damage in maize roots. Pre‐soaking seeds with Spd markedly alleviated these effects caused by WL. Spd pre‐soaking also significantly increased the endogenous Spd content in both control and waterlogged maize roots. In addition, the activity of antioxidant enzymes (catalase, CAT; glutathione reductase, GR; superoxide dismutase, SOD; peroxidase, POD) was enhanced in Spd‐pre‐soaked maize roots under WL stress. Thus, hydrogen peroxide (H₂O₂) and superoxide‐radical () accumulation were reduced. Spd treatment also enhances the expression and protein abundance of heat shock protein (HSP) 70 and 90 during the period of WL stress. Furthermore, Spd pre‐soaking reversed the inhibition effect of WL on H⁺ efflux and K⁺ influx in maize roots. The PM H⁺‐ATPase activity in Spd‐pre‐treated seedlings exhibited less inhibitory under WL conditions. In conclusion, this study suggests that WL stress could be alleviated by priming seeds with Spd in maize species. This alleviative effect was partially attributable to (i) up‐regulated activity of antioxidant enzymes; (ii) maintained PM H⁺‐ATPase activity; and (iii) increased Hsp70 and Hsp90 gene expression and protein abundance.     

转GsPPCK1基因苜蓿植株的获得及其耐碱性分析

磷酸烯醇式丙酮酸羧化酶激酶(phosphoenolpyruvate carboxylase kinase, PPCK)是一种钙不依赖的丝氨酸/苏氨酸(Ser/Thr)类蛋白激酶, 参与碳氮代谢等多个生物学过程, 然而其在碱胁迫反应中的作用尚未见报道。本研究在前期野生大豆碱胁迫基因表达谱数据基础上, 采用同源克隆的方法分离野生大豆(Glycine soja)PPCK1基因, 该基因与大豆(Glycine max) PPCK1基因(AY374445)具有99%的相似性, 被命名为GsPPCK1。在50 mmol L^–1 NaHCO₃ 胁迫处理3 h内, 根和叶中GsPPCK1基因上调表达, 属碱胁迫早期应答基因。通过农杆菌介导法对肇东苜蓿进行遗传转化, 并对RT-PCR阳性的超表达转基因株系进行耐碱性分析表明, 在100 mmol L^–1 NaHCO₃处理15 d后转基因株系生长状态良好, 而非转基因对照株系明显萎蔫、失绿、甚至死亡; 转基因株系的丙二醛含量和相对质膜透性显著低于非转基因株系(P<0.05), 而叶绿素含量和根系活力显著高于非转基因对照(P<0.05), 说明超量表达GsPPCK1基因增强了苜蓿的耐碱能力。以上结果表明, GsPPCK1参于植物耐碱胁迫反应过程, 在碱胁迫基因工程研究领域具有良好的理论和实际应用意义。     

空心莲子草不同部位水浸液对黄瓜种子萌发及根系细胞膜透性的影响

研究了空心莲子草不同部位、不同浓度水浸液对黄瓜种子萌发、幼苗生长及幼苗根系细胞膜透性的影响.结果表明,与对照相比,空心莲子草根、茎、叶水浸液对黄瓜种子萌发及幼苗生长均表现出相同的趋势,即随着水浸液浓度的增加,黄瓜种子的发芽率、幼苗根长和苗长所受的抑制作用增强;而黄瓜幼苗根系细胞膜透性即相对电导率和丙二醛含量均呈递增的趋势;在相同浓度下,黄瓜种子萌发、幼苗生长及根系细胞膜透性对空心莲子草叶水浸液最敏感,茎次之,根最弱.     

Bermudagrass cultivar identification by use of isoenzyme electrophoretic patterns

Summary Isoenzyme analysis has been demonstrated as an effective tool for definitive identification of plant cultivars, but it has not been applied to pasture bermudagrass (Cynodon spp.) cultivars in the USA. Polyacrylamide gel electrophoresis (PAGE) was used to study five isoenzyme systems in mitochondrial, microsomal, and soluble cell fractions of actively growing leaves, stems, and roots of seven vegetatively-propagated pasture bermudagrass (Cynodon spp.) cultivars used in the southern half of the USA. Peroxidase, esterase, and, with one exception, acid phosphatase successfully differentiated between the cultivars in all leaf and stem cell fractions. Fewer cultivar differences were found for amino- and endo-peptidases. Only peroxidase and acid phosphatase were resolved from root cell fractions; and only the microsomal fraction differentiated between all cultivars. Within plant parts, cultivars were distinguishable on the basis of peptidase banding in some cellular fractions, but not in others. Plant part and subcellular fraction-specific isoenzyme variations suggest the existence of multiple molecular forms of various enzymes within the same plant.Journal Article 5746 of the Okla. Agric. Exp. Stn.     

水葫芦生物学特性的多态性

【研究目的】研究水葫芦生物学特性的多态性,以期为研究生态学特性和合理防治提供理论依据。【方法】采集来自鱼塘、污水沟、池塘和清水饲养的水葫芦植株,分别观察根、茎、叶的形态、大小,记录数据并拍照。【结果】水葫芦在有根系和不带有根系的情况下都能萌发新根。水葫芦叶片形态具有多态性,多态性的表现程度应与养殖的水质相关。水葫芦的叶片生长具有多态性,有独立成叶的或是带有包叶等,并且其中部分叶片在生长过程能形成新的根状茎,长出上长下短的新根,从而发育成新株。【结论】水葫芦具有很强的生长能力,其生物学特性具有多态性.     

Modelling Biomass Accumulation and Partitioning in Chickpea (Cicer arietinum L.)

Quantitative information regarding biomass accumulation and partitioning in chickpea (Cicer arietinum L.) is limited or inconclusive. The objective of this study was to obtain baseline values for extinction coefficient (K_S), radiation use efficiency (RUE, g MJ^?1) and biomass partitioning coefficients of chickpea crops grown under well‐watered conditions. The stability of these parameters during the crop life cycle and under different environmental and growth conditions, caused by season and sowing date and density, were also evaluated. Two field experiments, each with three sowing dates and four plant densities, were conducted during 2002–2004. Crop leaf area index, light interception and crop biomass were measured between emergence and maturity. A K_S value of 0.5 was obtained. An average RUE of 1 g MJ^?1 was obtained. Plant density had no effect on RUE, but some effects of temperature were detected. There was no effect of solar radiation or vapour pressure deficit on RUE when RUE values were corrected for the effect of temperature. RUE was constant during the whole crop cycle. A biphasic pattern was found for biomass partitioning between leaves and stems before first‐seed stage. At lower levels of total dry matter, 54 % of biomass produced was allocated to leaves, but at higher levels of total dry matter, i.e. under favourable and prolonged conditions for vegetative growth, this portion decreased to 28 %. During the period from first‐pod to first‐seed, 60 % of biomass produced went to stems, 27 % to pods and 13 % to leaves. During the period from first‐seed to maturity, 83 % of biomass was partitioned to pods. It was concluded that using fixed partitioning coefficients after first‐seed are not as effective as they are before this stage. Environmental conditions (temperature and solar radiation) and plant density did not affect partitioning of biomass.