氧化石墨烯对多年生黑麦草逆境生理及光合特征的影响

为探讨不同浓度氧化石墨烯（GO）对多年生黑麦草生长、生理及光合特征的影响,该文采用盆栽试验,在土壤中添加0、10、20、30、40、50 mg·g^-1 GO进行多年生黑麦草培养,并测定植物生长指标、光合色素含量、保护酶活性、丙二醛（MDA）含量、叶片质膜透性、可溶性蛋白含量和光合参数。结果表明：（1）10、20 mg·g^-1 GO处理对多年生黑麦草生长无显著影响;30～50 mg·g^-1 GO处理对多年生黑麦草生长具有抑制作用,在50 mg·g^-1 GO浓度下多年生黑麦草株高和生物量均最小,较对照分别降低了16.8%和27.1%。（2）当GO浓度达到30 mg·g^-1时,总叶绿素和类胡萝卜素的含量显著降低,在50 mg·g^-1 GO处理时达到最低。（3）高浓度的GO处理(40、50 mg·g^-1)虽降低了多年生黑麦草的叶片净光合速率（P_n）、气孔导度（G_s）和蒸腾速率（T_r     

纳米铁联合氧化石墨烯对垃圾堆肥基质高羊茅生理生态的影响

通过室内盆栽试验,在生活垃圾堆肥中按质量比添加1%氧化石墨烯(GO)和不同比例的纳米铁(nZVI,1%、3%、5%),研究了GO和nZVI对高羊茅生长和生理特性的影响。结果表明:单独添加GO及共同添加GO和nZVI促进了高羊茅种子萌发,发芽率和发芽指数均在GO+5%nZVI处理达到最大。除1%nZVI处理外,其他添加剂处理显著提高了高羊茅地上生物量和叶绿素含量,在GO+5%nZVI处理达到最大,较对照分别提高25%和31%。添加3%、5%nZVI显著提高了超氧化物歧化酶(SOD)和过氧化物酶(POD)活性,且随nZVI添加比例的增加而升高。与对照相比,单独添加nZVI以及联合GO处理过氧化氢酶(CAT)与丙二醛(MDA)含量显著降低,随nZVI添加比例的增加而减少,分别在GO+5%nZVI和GO+3%nZVI处理中达到最低,较对照分别降低52%和48%。高羊茅地上部重金属含量随nZVI添加比例的增加而降低,在共同添加GO和nZVI的处理中效果显著,均显著低于对照。可见,nZVI和GO两种材料对堆肥重金属具有固定作用,减少了植物对重金属的吸收,促进了草坪植物的生长。     

外源褪黑素对干旱胁迫下黑麦草和苜蓿抗氧化能力及养分吸收的影响

以黑麦草和苜蓿为对象,分别叶面喷施和根施100 μmol·L^-1的褪黑素溶液,在干旱胁迫下测定了生物量、丙二醛(MDA)含量、相对电导率、超氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT)活性、养分含量(有机碳C、全氮N、全磷P)等指标,研究外源褪黑素对干旱胁迫下植物抗氧化能力及养分吸收的影响。结果表明: 干旱胁迫下,黑麦草和苜蓿的地上、地下生物量显著降低,外施褪黑素能够有效缓解干旱胁迫对黑麦草和苜蓿生长的抑制作用,叶面喷施和根施褪黑素使干旱胁迫下黑麦草的生物量分别增加14.5%和29.6%,苜蓿的生物量分别增加36.6%和49.1%。干旱胁迫下,黑麦草的SOD、POD活性和苜蓿的SOD活性显著降低,外施褪黑素显著提高黑麦草和苜蓿的SOD、POD、CAT活性,减少叶片中MDA的积累,使叶片相对电导率显著下降,抗氧化能力显著提高。干旱和外施褪黑素对黑麦草和苜蓿有机碳含量无显著影响。干旱胁迫下,黑麦草叶片和根中的N、P含量以及苜蓿根中的N含量降低,外施褪黑素提高黑麦草和苜蓿根和叶片中的N、P含量,这表明褪黑素对干旱胁迫下黑麦草和苜蓿的养分吸收有一定的调节作用。施用褪黑素不仅能改善植物的抗氧化能力,还能调节养分吸收以增强植物对干旱胁迫的适应性,而且叶面喷施褪黑素效果好于根施。     

放线菌对干旱胁迫下黑麦草生长及抗氧化特性的影响

采用菌剂接种及盆栽生物实验,研究了干旱缺水条件下放线菌对黑麦草生长和抗氧化特性的影响。结果显示:(1)干旱胁迫下,土壤中接种放线菌显著促进黑麦草的生长,其中根分蘖及根部生物量分别显著增加35.00%和37.47%;(2)接种放线菌后,黑麦草叶片的叶绿素总量和类胡萝卜素含量分别显著增加了12.02%和10.38%;(3)加菌后3种主要的抗氧化酶超氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT)较不加菌对照均增加,其增率分别为12.72%、2.38%和24.83%,其中SOD和CAT的活性增加显著。研究表明,干旱胁迫下放线菌接种土壤后,提高了黑麦草叶绿素含量和类胡萝卜素含量,增强了黑麦草抗干旱胁迫的抗氧化酶活性,可显著促进黑麦草的生长,增加其生物量。     

干旱胁迫对蒙古黄芪生长及根部次生代谢物含量的影响

以山西道地药材黄芪一年生幼苗为试验材料,设置常规水分条件(CK)、轻度干旱胁迫(A1)、中度干旱胁迫(A2)、重度干旱胁迫(A3)4个不同处理,研究土壤干旱胁迫对黄芪生长及生理的影响。结果表明:黄芪茎叶快速生长集中在出苗后80—120d,以后生长减缓;当茎叶枯萎时,根中生物量短期快速积累。与常规水分条件相比,干旱胁迫处理显著降低了黄芪苗高及茎叶生物量,但对抗氧化能力、根系生长及次生代谢物积累产生了不同的影响。轻度干旱胁迫下SOD、POD、CAT 3种抗氧化酶活性升高,丙二醛(MDA)含量和细胞膜透性降低,同时根长与根生物量增加、多糖与皂苷两种次生代谢物积累增多,黄芪药材的质量得到显著提高(P0.05);胁迫上升到中度、重度时,SOD酶活性逐渐降低,重度胁迫下低于对照,而POD及CAT酶活性、MDA含量、细胞膜透性均随胁迫增强而升高,相反,根长、根生物量、多糖与皂苷含量降低,导致黄芪药材的质量显著降低(P0.01)。综上表明,干旱胁迫下,SOD酶表现较为敏感,可能在清除活性氧中起主要作用;轻度水分胁迫能有效启动黄芪体内抗氧化酶系统和次生代谢,它们相互协作共同对抗胁迫对细胞产生的伤害,通过降低地上部分的生长,将营养物质优先运往根部,促进根产量及药材质量的提高。这一结论,可在黄芪多糖和皂苷次生代谢物定向培育的水分管理中加以利用。     

天竺桂凋落叶添加对凤仙花生理特性的影响

采用盆栽试验,通过向土壤(每盆8kg)中添加0(CK)、20(L20)、40(L40)和80g·pot-1(L80)天竺桂(Cinnamomum japonicum)凋落叶,模拟其自然分解对凤仙花(Impatiens balsamina)生理特性的影响。结果显示:(1)天竺桂凋落叶处理显著增加了凤仙花现蕾前期和现蕾期叶片H2O2含量,同时显著抑制了凤仙花现蕾前期、现蕾期和盛花期超氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT)活性。(2)凋落叶添加处理显著增加了凤仙花现蕾前期抗坏血酸(ASA)含量,但现蕾期和盛花期ASA含量却显著下降。(3)添加凋落物处理显著降低了现蕾前凤仙花叶片MDA含量,但显著增加了现蕾期MDA含量,而盛花期MDA含量在L20、L80处理下显著降低,在L40处理下则显著增加。(4)天竺桂凋落叶添加对可溶性蛋白和可溶性糖两种渗透调节物质含量影响不显著。(5)凋落叶处理显著抑制了凤仙花地径生长和地上生物量积累。(6)天竺桂凋落叶中主要化感物质可能有香豆素、桉叶油醇、肉桂醛、反式石竹烯和松油醇等。研究认为,非酶促活性氧清除系统可能在凤仙花抵御化感物质氧化胁迫过程中发挥着比酶促系统更为重要的作用,其中的ASA在氧化胁迫的早期过程扮演着重要角色;天竺桂凋落叶添加处理所造成的氧化胁迫可能超过了两类活性氧清除系统的清除能力,对凤仙花膜系统造成明显伤害,导致其地径和生物量积累显著降低。     

水分胁迫对春播玉米苗期生长及其生理生化特性的影响

采用盆栽试验,以‘蠡玉18'玉米单交种为供试材料,设置充分供水(CK)、轻度水分胁迫(LS)、中度水分胁迫(MS)和重度水分胁迫(SS)4个水分处理水平,研究了水分胁迫对春播玉米苗期保护酶活性和生长的影响,以探讨土壤水分胁迫对玉米苗期生长发育及其生理过程的影响机制.结果表明:(1)随着水分胁迫程度的加剧,玉米幼苗的生物量显著下降,根冠比、根系活力和脯氨酸含量增加,且水分胁迫对玉米幼苗地上部生物量的抑制作用更大;可溶性蛋白含量差异不明显,MDA含量波动变化.(2)随着水分胁迫时间的延长,根冠比、根系活力和植株脯氨酸含量先升高后降低,可溶性蛋白含量呈先下降后升高的趋势;玉米幼苗叶片和根系MDA积累波动变化,而叶片MDA含量始终高于根系.(3)在水分胁迫初期,玉米叶片中CAT活性较SOD、POD响应更敏感;玉米苗期根系在中度水分胁迫下主要依赖CAT来降低氧化危害,而在重度水分胁迫下前期主要依赖CAT、后期通过CAT和POD的共同作用来降低氧化伤害;水分胁迫条件下,叶片和根系POD同步降低氧化伤害,而SOD和CAT在叶片和根系间存在互补作用.研究表明,在不同程度的水分胁迫条件下,玉米幼苗的生长受到一定程度的抑制,但其能够通过调节自身的保护酶活性和渗透调节物质含量来减轻干旱伤害,维持植株的正常生理代谢功能.     

低温胁迫下玉米幼苗根系受外源海藻糖调控的生理表现

为了探究海藻糖对增强玉米幼苗抗低温能力的生理表现,以玉米"先玉335"为试验材料,采用盆栽试验,分析12 mmol·L-1外源海藻糖对低温胁迫不同时间(0、2、4、6和8d)下玉米幼苗根系生物量、抗氧化酶活性及渗透调节物质的影响。结果表明:低温胁迫显著抑制玉米幼苗根系生长及干物质累积,诱导抗氧化酶活性增加,破坏细胞渗透调节水平;低温胁迫后应用外源海藻糖,玉米幼苗根系根表面积、根长及鲜干重显著增加,根系内SOD、POD和CAT活性呈现先升高后降低趋势,MDA含量及相对电导率在玉米幼苗根系内显著降低,脯氨酸、可溶性蛋白、可溶性糖含量也呈现先升高后降低趋势;在低温胁迫第6天时,T+L处理的根系根表面积、根长及鲜干重分别较CK+L增加了18.25%、4.73%、2.48%和21.43%;T+L处理后根系内SOD、POD和CAT活性分别较CK+L处理提升17.26%、23.79%和30.78%;T+L处理后根系内MDA含量和相对电导率值分别较CK+L处理降低45.13%和63.25%;T+L处理后的脯氨酸、可溶性蛋白和可溶性糖含量在低温胁迫第6天时最高,与CK+L处理相比差异显著,且分别较CK+L高出2.93、0.51和2.58倍。可见,海藻糖能够调控低温胁迫下玉米幼苗根系生理水平,提高玉米幼苗抗逆能力,促进玉米根系生长及生物量增加,海藻糖对作物生长的生理调控能力与低温存在协同作用,在低温环境下,海藻糖对作物体内抗氧化系统酶活表达及渗透物质的积累有显著提升效果。     

外源NO对盐胁迫下黑麦草幼苗根生长抑制和氧化损伤的缓解效应

研究了外源一氧化氮(nitric oxide, NO)对盐胁迫下黑麦草幼苗根生长和氧化损伤的影响。结果表明,5~100 μmol·L^-1的NO供体硝普钠(sodium nitroprusside, SNP)处理显著减轻100mmol·L^-1 NaCl胁迫对黑麦草幼苗根生长的抑制效应,其中50 μmol·L^-1的SNP效果最明显,150 μmol·L^-1以上的SNP处理则抑制根的生长。50 μmol·L^-1 SNP处理提高了100 mmol·L^-1 NaCl胁迫下黑麦草幼苗根组织中超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、过氧化物酶(POD)和抗坏血酸过氧化物酶(APX)及液泡膜上H⁺-ATP酶(H⁺-ATPase)和H⁺焦磷酸酶(H⁺-PPase)的活性,使谷胱甘肽(GSH)、抗坏血酸(ASA)和脯氨酸含量及K⁺/Na⁺、(Spd+Spm)/Put比值和根干物质积累量增加,超氧阴离子(O^-₂)、H₂O₂和丙二醛(MDA)含量降低,而1mmol·L^-1NO清除剂PTIO和1 μmol·L^-1 NaNO₂处理(对照)的效果则不明显。由此推断,NO通过提高根组织的抗氧化和渗透调节能力,促进根系对K⁺的选择性吸收及Put向Spd和Spm的转化,降低Na⁺的吸收并加强在液泡中的区隔化缓解盐胁迫对黑麦草幼苗根生长的抑制和膜脂过氧化损伤。     

黄土性土壤固化对黑麦草生长和根系活力的影响

采用盆栽试验,研究了安塞黄绵土不同容重、不同固化剂(路邦EN-1固化剂)掺量对黑麦草生长和根系活力的影响.结果表明:黄绵土容重在1.2～1.4 9·cm-3范围内,随土壤容重的增加,黑麦草叶绿素含量、根系活力、根冠比、根生物量和植株生物量均降低;各土壤容重条件下,黑麦草叶绿素含量、根系活力、根冠比、根生物量和植株生物量均高于对照,且随着固化剂掺量的增加均呈先增加后降低的趋势.土壤容重和固化剂掺量交互作用对根生物量和总生物量的影响均显著(P＜0.05).总体来看,土壤容重1.3 g·cm-3、固化剂掺量0.15％处理下,各指标值均最高.     

Effect of carbon dioxide on antioxidant enzymes and ginsenoside production in root suspension cultures of Panax ginseng

The aim of this study was to investigate the effect of CO₂ at various concentrations (1, 2.5 and 5%) on antioxidant enzymes and ginsenoside accumulation in Panax ginseng roots in 5 l airlift bioreactors (working volume 4 l). One and 2.5% CO₂ was beneficial for root biomass accumulation, but 5% CO₂ decreased the biomass. Ginsenoside concentration decreased with increasing concentration of CO₂. No significant difference was observed in the malondialdehyde (MDA) content and lipoxygenase (LOX) activity between respective controls and CO₂ treated roots. Antioxidant enzymes such as ascorbate peroxidase (APX), monodehydroascorbate reductase (MDHAR), glutathione reductase (GR), catalase (CAT), guaiacol peroxidase (G-POD) including reduced ascorbate and total glutathione were induced in CO₂ exposed roots which emphasized the protective role of antioxidants against CO₂ induced stress. Superoxide dismutase activity (SOD) which was induced after 15 days was significantly inhibited after 45 days. Glutathione-S-transferase (GST) and glutathione peroxidase (GPX) activities also increased when the roots were subjected to 1 and 2.5% CO₂ compared to the respective controls but not at 5%. A higher reduced ascorbate to oxidized (ASC/DHA) ratio in CO₂ treated root indicates the plant's ability to tolerate CO₂ stress. These observations suggest that an increase in antioxidant enzymes may affect a defense response to the cellular damage induced by CO₂. Probably, this increase could not stop the deleterious effects of CO₂ concentration on ginsenoside concentration, but reduced stress severity and thereby allowing root growth to occur.     

Effects of the coordination mechanism between roots and leaves induced by root-breaking and exogenous cytokinin spraying on the grazing tolerance of ryegrass

The grazing tolerance mechanism of ryegrass was investigated by examining the effects of roots on leaves under frequent defoliation. The study consisted of four treatments: (1) with root breaking and cytokinin spraying, (2) root breaking without cytokinin spraying, (3) cytokinin spraying with no root breaking, and (4) no root breaking and no cytokinin spraying. Results showed that root breaking or frequent defoliation inhibited the ryegrass regrowth, which resulted in low biomass of the newly grown leaves and roots, as well as low soluble carbohydrate content and xylem sap quantity in the roots. Spraying with exogenous cytokinin promoted the increase in newly grown leaf biomass, but decreased root biomass, root soluble carbohydrate content, and root xylem sap quantity. Determination of gibberellic acid, indole-3-acetic acid, abscisic acid, and zeatin riboside (ZR) in roots, newly grown leaves, and stubbles showed that cytokinin is a key factor in ryegrass regrowth under frequent defoliation. Root breaking and frequent defoliation both decreased the ZR content in roots and in newly grown leaves, whereas spraying with exogenous cytokinin increased the ZR content in roots and in newly grown leaves. Therefore, cytokinin enhances the above ground productivity at the cost of root growth under frequent defoliation.     

蚯蚓-秸秆及其交互作用对黑麦草修复Cu污染土壤的影响

以高沙土为供试土壤,加入Cu^2＋以模拟成：0,100,200,400mg／kgCu^2＋的Cu污染土壤,设置接种蚯蚓（E）、表施秸秆（M）,同时加入蚯蚓和秸秆（ME）及不加蚯蚓和秸秆的对照（CK）4个处理,并种植黑麦草。研究蚯蚓、秸秆相互作用对黑麦草吸收、富集铜的影响。结果表明：加入秸秆显著提高了蚯蚓的生物量,一定程度上缓解了重金属对蚯蚓的毒害,同时蚯蚓显著提高了秸秆的分解率,较无蚯蚓对照提高了58．11％～77．32％。接种蚯蚓（E,ME）还提高了土壤有效态重金属（DTPA-Cu）含量,秸秆处理（M）则降低了土壤有效态重金属含量。研究还发现,E处理促进了黑麦草地上部生长,而M和ME处理均显著提高了黑麦草地下部的生物量。E和ME处理同时提高了植物地上部和地下部的Cu浓度及Cu吸收量,M处理则只对植物的地下部Cu浓度和Cu吸收量有显著促进作用。总体来看,E处理、M处理及ME处理分别使黑麦草地上部Cu富集系数提高了31．22％～121．07％．2．12％～61．28％和25．56％～132．64％。     

Sex-Related Responses of Populus cathayana Shoots and Roots to AM Fungi and Drought Stress

We investigated the impact of drought and arbuscular mycorrhizal (AM) fungi on the morphological structure and physiological function of shoots and roots of male and female seedlings of the dioecious plant Populus cathayana Rehder. Pot-grown seedlings were subjected to well watered or water-limiting conditions (drought) and were grown in soil that was either inoculated or not inoculated with the AM fungus Rhizophagus intraradices. No significant differences were found in the infection rates between the two sexes. Drought decreased root and shoot growth, biomass and root morphological characteristics, whereas superoxide radical (O₂–) and hydrogen peroxide content, peroxidase (POD) activity, malondialdehyde (MDA) concentration and proline content were significantly enhanced in both sexes. Male plants that formed an AM fungal symbiosis showed a significant increase in shoot and root morphological growth, increased proline content of leaves and roots, and increased POD activity in roots under both watering regimes; however, MDA concentration in the roots decreased. By contrast, AM fungi either had no effect or a slight negative effect on the shoot and root growth of female plants, with lower root biomass, total biomass and root/shoot ration under drought. In females, MDA concentration increased in leaves and roots under both watering regimes, and the proline content and POD activity of roots increased under drought conditions; however, POD activity significantly decreased under well-watered conditions. These findings suggest that AM fungi enhanced the tolerance of male plants to drought by improving shoot and root growth, biomass and the antioxidant system. Further investigation is needed to unravel the complex effects of AM fungi on the growth and antioxidant system of female plants.     

Graphene Oxide Regulates Root Development and Influences IAA Concentration in Rice

Researchers have found that graphene oxide (GO) has significant effects on plant growth and development. The effects of GO on plants are variable and influenced by many factors, including GO concentration and genotype. Five rice varieties, Huanghuazhan (HHZ), Jinghuazhan (JHZ), Shenyou9521 (SY9521), Jingyouhuazhan (JYHZ), and Jingchuxiang (JCX), were treated with different concentrations of GO (0, 5, 15, 25, and 50 mg/L), and their physiological response was measured. The results demonstrate that GO had significant effects on the development of HHZ, JCX, JHZ, JYHZ, and SY9521 roots, but the effect varied by GO concentration and rice variety. The highest concentration of GO (50 mg/L) reduced the root length, fresh weight, and dry weight for all five rice species. The GO treatment also affected the levels of abscisic acid (ABA), indole-3-acetic acid (IAA), and malondialdehyde (MDA) and the activity of superoxide dismutase (SOD) and catalase (CAT) enzymes. The correlation analysis indicates that GO could affect the IAA content to modulate rice root growth.

     

The Application of Fertilizer and AMF Promotes Growth and Reduces the Cadmium and Lead Contents of Ryegrass (<i>Lolium multiflorum</i> L.) in a Copper Mining Area

Heavy metal-polluted soil was collected from the Pulang copper mine in Shangri-La City, Yunnan Province, Southwest China. The effects of fertilizer (organic and inorganic) and arbuscular mycorrhizal fungi (AMF) on ryegrass (Lolium multiflorum L.) growth, root morphology, mineral nutrition and cadmium (Cd) and lead (Pb) contents were investigated by pot experiments. The results showed that both fertilizer and AMF significantly ameliorated the root morphology and mineral nutrition, reduced the Cd and Pb contents, and promoted the growth of ryegrass. Among all treatments, the combined application of organic–inorganic compound fertilizer with AMF had the highest effect, resulting in increases in root length, surface area and branch number by 2.3, 1.1, and 3.9 times, respectively; an 88% increase in plant biomass; a nitrogen content increase of 2.3 and 1.2 times, and phosphorus content increase of 62% and 68% in shoots and roots, respectively was also recorded as well as decreases in Cd content by 34% and 62% and Pb content by 47% and 34% in shoots and roots, respectively. Two-factor analysis showed that both fertilizer and AMF significantly promoted ryegrass growth (plant height, biomass, chlorophyll content, root length, nitrogen and phosphorus content) and reduced the Cd and Pb contents in roots, and there was a synergistic effect between them. Moreover, the nitrogen and phosphorus contents were very significantly positively correlated with the shoot and root biomasses but very significantly negatively correlated with the Cd and Pb contents of ryegrass. Thus, the application of fertilizer and AMF synergistically improved ryegrass growth on polluted soils in the copper mining area.     

Role of earthworm-straw interactions on phytoremediation of Cu contaminated soil by ryegrass

It is well known that the earthworm's activities can increase the availability of soil nutrients, improve soil structure, and enhance the biomass of plants in uncontaminated soil. Recently, many researchers found that some metal-tolerant earthworms can survive and even change the fractional distribution of heavy metals in contaminated soil. Furthermore, it has been revealed that earthworms are able to increase metal availability, and therefore, accumulate more metals in plants through their burrowing and casting activity. It is clear that the influence of soil animals is an important factor for phyto-remedation that must be taken into account. ~In this article, the authors studied some effects of addition of earthworms (Metaphire guillelmi), corn straw, and in combinations of earthworms and corn straw on the growth and Cu uptake by ryegrass in Cu contaminated pot soils. The experiment consisted of four levels of Cu addition (0, 100, 200, 400 mg·kg?1) and four treatments. The treatments were 1. control (CK); 2.straw mulching only (M); 3. earthworm additions to soil only (E); and 4.straw mulching plus earthworm additions (ME). Each treatment had three replicates. 10 seeds of ryegrass (Lolium multiflorum) were sowed in each pot and harvested after 30 days. After 30 days of incubation, all earthworms were found to be alive and the pot soils were burrowed through by earthworms. Results showed that the biomass of earthworm declined with the increase of the dosage of Cu additions. The biomass of earthworm increased significantly in treatment 4 (ME) as compared with treatment 3 (E). Not only the earthworms could get more food from the straw, but also could counteract some negative effects of Cu on the earthworms. The rates of straw decomposition in ME treatment increased by about 58.11% ?77.32%. The earthworm activities increased root biomass of ryegrass significantly, but did not show the effect on plant root growth. On the contrary, straw enhanced roots biomass significantly instead of shoots biomass. It was also found that the concentration of Cu in the plant shoot and the plant root, as well as plant Cu uptake were enhanced by earthworm's activities and straw mulching. The increased amount by straw mulching was lower than that of earthworms (E). The treatment of the earthworm–straw mulching combinations enhanced plant Cu concentration, and the amount increased by it was lower than that of the earthworm treatment (E) but higher than that of straw mulching treatment (M). The accumulation factors of copper in the shoots of ryegrass were increased by 31.22% ?121.07%, 2.12% ?61.28% and 25.56% ?132.64%, respectively, in treatment 3(E), 2(M), and 4(ME), respectively. In conclusion, the earthworm activities, straw-mulching and their interactions may have potential roles in elevating phyto-extraction efficiency in low to medium level Cu contaminated soil.     

Effect and mechanism of endophytic bacteria on growth and secondary metabolite synthesis in Salvia miltiorrhiza hairy roots

Our study found that except Novosphingobium resinovorum (B5) Salvia miltiorrhiza root endophytic bacteria Pseudomonas brassicacearum sub sp. neoaurantiaca (B1), Rhizobium radiobacter (B2), Pseudomonas thivervalensis (B3), Pseudomonas frederiksbergensis (B4) significantly improved the activity of key enzymes 3-hydroxy-3-methyglutary1-CoA reductase and 1-deoxy-d-xylulose-5-phosphate synthase in the biosynthetic pathway of tanshinones. Specifically, HMGR activity with B1 treatment increased 2.1-fold that of control, 1-deoxy-d-xylulose-5-phosphate synthase activity with B2 treatment increased 5.0-fold that of control, which caused a significant increase in tanshinone content in the hairy roots. The dihydrotanshinone I and cryptotanshinone content under B1 treatment increased 19.2-fold and 11.3-fold, respectively, and total tanshinone content increased 3.7-fold that of control. The five endophytic bacteria B1, B2, B3, B4 and B5 all significantly decreased phenylalanine ammonia-lyase and tyrosine aminotransferase activity in hairy roots, of which, B3 treatment decreased phenylalanine ammonia-lyase activity by 46.2 %, and B2 treatment decreased tyrosine aminotransferase activity by 44.7 % compared with the control. Each of the five endophytic bacteria decomposed rosmarinic acid and salvianolic acid B, which caused a significant decrease in rosmarinic acid and salvianolic acid B content in hairy roots, with B2 treatment decreasing rosmarinic acid and salvianolic acid B content by 94.5 and 89.0 %, respectively, compared with the control. The five endophytic bacteria also inhibited the growth of S. miltiorrhiza hairy roots, of which, B2 and B4 treatment decreased hairy root biomass by 55.2 and 51.3 %, respectively, compared with the control, while hairy roots promoted the growth of B4 and B5 and inhibited the growth of B1 and B3.