富钾植物籽粒苋根系分泌物及其矿物释钾作用的研究

应用１４ Ｃ 同位素示踪技术研究了籽粒苋品种根系分泌物的动态、构成以及对含钾矿物钾素释放的作用。结果表明,具有高效富钾特性的籽粒苋品种, Ｃ Ｏ２ 同化能力强,光合产物向根外分泌的比例大。籽粒苋根系分泌物中的有机酸主要是草酸,占有机酸总量的９５ ％ 以上。不同种属的籽粒苋分泌有机酸的能力不同,一般是 Ａ Ｄｕｂｉｓ＞ Ａ Ｒｅｔｒｏｆｌｅｘｕｓ ＞ Ａ Ｃｒｕｅｎｔｕｓ 。同一种内,则钾素利用高效型品种一般型品种。钾亏缺处理显著提高光合产物向根外的分泌量。钾利用高效型籽粒苋品种的草酸分泌量明显增加。根系分泌物对含钾矿物有明显的解钾作用。草酸含量与根系分泌物解钾量显著相关,籽粒苋的草酸分泌能力是籽粒苋高效吸收利用土壤钾及富钾特性的重要机理之一。     

分层供水和表层施锌对玉米植株生长和锌吸收的影响

进行分层水分隔离盆栽试验,模拟田间不同层次土壤中水分含量分布不均条件,研究表层土壤施锌情况下,玉米植株生长和锌吸收以及根系在表层和底层土壤中的分配。结果表明,施锌明显促进了玉米地上部生长。在土壤表层水分充足时,施锌对植株增长效果较明显,有利于玉米利用土壤水分。缺锌条件下,改善土壤水分并未显著提高玉米生物量。表层土壤干旱时,上下层土壤中根系干物重之比减小,底层土壤中根系分布相对增加,当表层土壤水分增加时,根系在表层土壤中干物重显著增加,分布相对增多。施锌并没有影响根系在不同层次土壤中的分配。表层土壤水分对苗期玉米植株锌吸收总量有显著影响,干旱条件下,玉米植株锌吸收总量下降;底层土壤水分供应状况对玉米锌浓度影响不大,但植株中锌向地上部运转增加。尽管施锌没有提高生长早期玉米根系生长和对底层土壤水分的利用,但本研究表明缺锌旱地土壤上如通过灌溉等措施增加了耕层土壤水分,应该注意施用锌肥,否则严重影响玉米生物量和玉米对土壤水分的利用效率。     

水稻氮高效基因型根系分泌物中有机酸和氨基酸的变化特征

采用溶液培养试验,研究水稻氮高效基因型在不同供氮水平下,根系分泌物中有机酸和氨基酸种类及含量的变化情况,并探讨其与氮素利用效率之间的关系。结果表明: 1）水稻氮高效基因型氮积累量随着供氮水平的降低明显下降,而氮素利用效率显著提高; 在供氮水平为20 mg/L时,高效基因型具有较高的氮积累量,且氮素利用效率较低效基因型高42.9%（分蘖期）和21.4%（拔节期）。 2）草酸为高效基因型根系分泌的主要有机酸种类,其分泌量占有机酸总量的80%以上,其次是乙酸和柠檬酸; 有机酸分泌总量和草酸分泌量在分蘖期和拔节期随供氮水平的降低而降低,乙酸和柠檬酸分泌量在拔节期也呈相同趋势; 相同供氮水平下,高效基因型有机酸分泌总量均显著低于低效基因型,且在20 mg/L时差异明显。 3）丙氨酸为高效基因型根系分泌的主要氨基酸种类,其分泌量占氨基酸总量的50%以上,其次是丝氨酸、 谷氨酸、 天冬氨酸、 苯丙氨酸、 甘氨酸和苏氨酸,且氨基酸分泌总量和各组分氨基酸分泌量均随供氮水平的降低而降低; 在低氮水平（10 mg/L和20 mg/L）下,高效基因型氨基酸分泌总量均显著低于低效基因型。4）在分蘖期和拔节期,水稻根系分泌有机酸和氨基酸总量与氮素利用效率均呈显著或极显著负相关,有机酸分泌组分中的草酸和氨基酸分泌组分的天冬氨酸分泌量与氮素利用效率也呈显著或极显著负相关。以上结果表明,低氮条件下水稻氮高效基因型氮效率优势明显,高效基因型氮素利用效率高,有利于体内同化物质的合理分配。     

水稻耐低锌基因型的生长发育和若干生理特性研究

在不同Zn2+活度（pZn2+9.7,pZn2+11.0和pZn2+＞11.5）的溶液培养条件下,研究了水稻耐低锌基因型的生长发育和若干生理特性。结果表明:水稻锌营养存在明显的基因型差异,降低锌离子活度会增加地下部于物质的积累,当Zn2+活度从pZn2+9.7下降到pZn2+11.0时,耐低锌品种的地上部干重虽下降,但因地下部干重显著增加,故总干重相近;锌敏感品种则地上部干重显著下降,而地下部干重增加不明显,总干重显著下降。当严重缺锌（pZn2+＞11.5）时,所有基因型水稻的干重构极显著地下降,但锌敏感品种比耐低锌品种下降得更多。降低Zn2+活度使水稻秧苗的出叶速度减慢,在极度缺锌条件下,敏感品种只能生长到3.5叶,而耐低锌品种能生长到4.5叶左右。对叶绿素和根系氧化力的测定结果表明,轻度缺锌或缺锌初期会使叶绿素含量上升和根系氧化力下降,但严重缺锌时,则使叶绿素含量显著降低,而使根系氧化力明显增加。锌敏感品种比耐缺锌品种的变化更为明显。锌离子活度对秧苗的含水量也有明显的影响。因此,耐低锌基因型在低Zn2+活度条件通过保持较低的根氧化作用,促进根系生长以维持地上部新叶生长,达到低锌适应稳态。     

缺锌玉米植株的傅立叶变换红外光谱研究

【目的】傅里叶变换红外光谱（fourier transform infrared spectroscopy, FTIR）是一种基于化合物中官能团和极性键振动的结构分析技术。本文利用傅立叶变换红外光谱仪检测缺锌和正常供锌玉米植株不同器官的组分变化,同时比较两个玉米品种植株不同部位的生物量和锌含量,以期为缺锌影响玉米生长与生理代谢的机理研究提供参考。【方法】选取农大108和郑单958两个玉米品种,利用营养液培养方式,设置缺锌和正常处理。1）当玉米出现缺锌症状后,将地上部和根系分开,测量株高和根长,烘干至恒重测干重。2）烘干至恒重的植株样品用HNO3-HClO4（3∶1）消煮,原子吸收分光光度计（型号WFX-120C,北京瑞利分析仪器公司）测定消煮液中锌浓度,计算植株中锌含量和锌积累量。3）收获玉米根系放入FAA固定液（70%酒精∶38%甲醛∶乙酸体积=90∶5∶5）中,利用扫描仪（EsponV700）扫描根系样品获取数字化图像,利用WinRHIZO根系分析软件（Regent Instruments Inc., Canada）对图像进行分析,获得根长、 根面积、 根体积等指标。4）取玉米根、 茎、 叶部分烘干样品,磨碎过0.2 mm筛,采用溴化钾压片法,利用傅立叶变换红外光谱仪（VERTEX 70,Bruker）检测不同部位的光谱特性,OPUS 6.5软件采集数据并进行基线校正。【结果】缺锌胁迫下, 植株地上部锌含量明显下降,低于临界水平（20 g/g）,生物量降低; 缺锌根系面积与体积变小,总根长变小。用缺锌与施锌植株生物量比来表征玉米对缺锌敏感性,品种农大108较郑单958对缺锌更为敏感。缺锌玉米根系和叶片FTIR谱在波数3410、 2920、 1650、 1380、 1055 cm-1附近处透过率较高,茎FTIR谱在这些波数处透过率较低,表明缺锌导致根系和叶片中碳水化合物、 脂类、 蛋白质及核酸含量下降,而在茎中有所积累。农大108植株中各组分变化受缺锌影响较大。【结论】缺锌导致玉米植株生长受抑,利用FTIR技术研究发现缺锌植株中碳水化合物、 脂类、 蛋白质及核酸组分发生变化,农大108植株中各组分变化受缺锌影响较大,品种农大108可能较郑单958对缺锌更为敏感。     

不同抗性蚕豆品种根系分泌物对枯萎病菌的化感作用及根系分泌物组分分析

蚕豆枯萎病是土传病害,其发生与蚕豆根系分泌物有密切关系。本文以3个枯萎病不同抗性蚕豆品种——‘89-147’(高抗)、‘8363’(中抗)和‘云豆324’(感病)为材料,通过水培试验收集根系分泌物,测定根系分泌物对镰刀菌孢子萌发和菌丝生长的影响,分析对枯萎病表现出不同抗性的蚕豆品种根系分泌物中糖、氨基酸和有机酸的含量,分离鉴定了根系分泌物中氨基酸和有机酸的组分。结果表明,抗病品种的根系分泌物抑制了尖孢镰刀菌的孢子萌发和菌丝生长,在加入5 mL中抗品种根系分泌物时,显著促进尖孢镰刀菌孢子萌发,但对菌丝生长无显著影响;而在加入1 mL感病品种根系分泌物时,就能显著促进尖孢镰刀菌孢子萌发和菌丝生长。不同抗性蚕豆品种根系分泌物中氨基酸总量和总糖含量随抗性的降低而升高,有机酸分泌总量则随蚕豆品种对枯萎病的抗性增加而升高。感病品种和中抗品种中检出15种氨基酸,而高抗品种中检出14种,组氨酸只存在于中抗品种中,脯氨酸仅在感病品种中检出,3个蚕豆品种根系分泌物中均未检出精氨酸。蚕豆根系分泌物中天门冬氨酸、谷氨酸、苯丙氨酸、酪氨酸和亮氨酸含量高,可能会促进枯萎病的发生,而蛋氨酸、赖氨酸和丝氨酸含量高可能抑制枯萎病发生。酒石酸仅在抗病品种中存在,根系分泌物中有机酸种类丰富,有助于提高蚕豆对枯萎病的抗性。蚕豆对枯萎病的抗性不同,根分泌物对镰刀菌孢子萌发和菌丝生长的影响也不同,而这种抗病性差异与蚕豆根系分泌物中糖、氨基酸、有机酸的含量和组分密切相关。     

植物根系活性对菲浓度的响应——以栾树、樟树为例

[目的]分析栾树、樟树根系分泌物在菲胁迫下的变化特征,为筛选抗多环芳烃污染树种,进一步开展植物修复多环芳烃污染提供科学依据。[方法]设置3种菲处理浓度[L_0(CK, 0 mg/kg);L_1(100 mg/kg);L_2(1 000 mg/kg)],通过盆栽试验的方法,对栾树、樟树的根系分泌物中总有机碳(TOC)、全碳(TC)、全氮(TN)含量及根系活性进行测定。[结果]①随着菲浓度的升高,栾树与樟树根系分泌物中TOC与TC含量均呈下降趋势,TN含量则呈先升后降的趋势;②随着菲浓度的升高,栾树和樟树根系的总吸收面积和活跃吸收面积总体呈下降趋势;③3个处理水平下,栾树根系分泌物中TC,TOC,TN含量均高于樟树,且栾树根系总吸收面积和活跃吸收面积也高于樟树。[结论]通过菲胁迫下栾树与樟树根系分泌量和根系活性的比较,表明栾树相较于樟树对菲具有更好的耐受性。     

外源有机酸对两种生态型东南景天吸收和积累锌的影响

通过溶液培养试验,比较研究了外源有机酸对两种生态型东南景天生长和锌吸收与积累的影响。结果表明,外加柠檬酸或草酸能明显增强非超积累生态型东南景天的耐锌毒能力,叶片、茎和根系的生物量均有增加;而对锌超积累生态型东南景天的生长没有显著性影响。外加柠檬酸、草酸或柠檬酸+草酸,锌超积累生态型根系Zn含量显著增加,但叶片和茎组织中Zn含量无明显变化;而非超积累生态型叶片、茎和根系Zn含量均显著增加,尤其是根系Zn含量,与单独Zn处理相比外源有机酸处理增加4～5倍。同样,外加柠檬酸、草酸或柠檬酸+草酸明显提高Zn在非超积累生态型根系和地上部的积累量,且对地上部Zn积累量的促进程度大于根部;柠檬酸的促进作用又比草酸及2种酸混合处理高1倍。然而,有机酸处理对Zn超积累生态型根系Zn积累量有所增加,但对叶片和茎中Zn积累量无影响。叶片和茎中水溶态Zn含量也受外源有机酸的影响,2种生态型叶片、茎中水溶态Zn含量均受有机酸处理而提高。Zn超积累生态型叶片和茎中水溶态Zn含量占总Zn含量比例也受有机酸处理而增大,但非超积累生态型则显著降低。上述结果表明,柠檬酸和草酸可能作为其Zn吸收的配基,促进根系对Zn吸收与积累,叶片和茎中的Zn可能与可溶性有机化合物或无机盐结合。     

缺锌对玉米根系发育、生长素含量及生长素转运基因表达的影响

【目的】研究缺锌对玉米根系生长及根系中生长素含量与生长素运输关键基因表达的影响,揭示缺锌胁迫下玉米根系生长与生长素响应特征。【方法】以郑单958玉米为材料,进行营养液培养试验,设置Zn 0缺锌 (0 μmol/L) 和正常供锌 (1 μmol/L) 两个处理。植株干样经硝酸–过氧化氢消煮,利用原子吸收分光光度计测定消煮液锌浓度。保存于FAA溶液 (70% 乙醇︰38% 甲醛︰乙酸 = 90︰5︰5,体积比) 中的根系样品,经洗涤扫描获得数字图像,利用WinRHIZO软件分析得到根长、根表面积、根体积等指标;采用气相色谱-质谱联用仪检测根系中生长素吲哚乙酸含量;采用实时荧光定量PCR技术对玉米根系生长素转运基因ZmAUX1和ZmPIN1c表达进行定量分析。【结果】缺锌胁迫下,植株地上部锌含量低于20 μg/g,生物量显著降低;缺锌根系表面积与体积变小,总根长、侧根总长度与侧根平均长度变短,侧根密度增大,直径变细。缺锌条件下,距根尖2 cm的区域中生长素较正常供锌处理降低近30%。缺锌根系中ZmAUX1和ZmPIN1c基因表达明显受抑。【结论】缺锌胁迫下玉米根系中生长素转运关键基因表达降低,生长素含量下降,生长素分布改变,影响根系生长发育。     

激光剥蚀–电感耦合等离子体质谱分析缺锌胁迫玉米根尖微量元素空间分布

【目的】激光剥蚀?电感耦合等离子体质谱 (laser ablation inductively coupled plasma mass spectrometry,LA-ICP-MS) 法是一种利用聚焦激光扫描激发固体样品,并经电感耦合等离子体质谱离子化,以分析样品元素含量及分布的新兴技术。本文利用LA-ICP-MS技术研究缺锌 (Zn) 胁迫下玉米根尖铁 (Fe)、锰 (Mn)、铜 (Cu)、Zn元素的分布定位,以期从组织水平揭示作物中Zn的转运富集规律及缺Zn对微量金属元素吸收转运的影响。【方法】以玉米‘郑单958’为试材,用不同加锌浓度营养液进行培养,获得根系样品烘干后磨碎、混匀、压片,取适量混匀的根系样品消煮,利用液体进样系统ICP-MS检测得到样品中实际元素含量,并与样品压片LA-ICP-MS检测信号值间进行线性回归分析,标准曲线相关性良好 (R2 = 0.9995),从而获得可适用于LA-ICP-MS定量分析的自制根系标准样品。将此标准样品与待测根尖样品放入LA样品池中,13C作为内标元素,进行缺锌胁迫下玉米根尖中锌元素分布特征的定量成像研究。【结果】缺锌胁迫下玉米根系锌元素含量显著降低,仅为正常植株的27.78%;缺锌根系中Mn和Cu含量升高。LA-ICP-MS系统定量成像显示,玉米根尖顶端Zn含量较高,由表皮向内锌含量逐渐增加;缺Zn处理根系Zn含量降低,根尖顶端Zn分布明显减少。利用LA-ICP-MS检测信号强度值对Fe、Mn、Cu元素进行定性分布,成像显示在正常根系中Fe、Mn、Cu元素在根尖前端信号强度较高,由表向内逐渐增加;缺锌处理下,根系中Fe、Mn、Cu信号强度均有不同程度增加。【结论】正常施锌玉米根尖中锌、铁、锰、铜分布呈现由表皮向中柱增加的趋势;缺锌胁迫下根系锌含量显著降低,铁、锰、铜均有不同程度积累。     

不同Zn浓度对黑麦草根分泌物、根际Zn形态及植物Zn蓄集的影响

A glasshouse experiment was conducted using a root-bag technique to study the root exudates, rhizosphere Zn fractions, and Zn concentrations and accumulations of two ryegrass cultivars (Lolium perenne L. cvs. Airs and Tede) at different soil Zn levels (0, 2, 4, 8, and 16 mmol kg-1 soil). Results indicated that plant growth of the two cultivars was not adversely affected at soil Zn level≤8 mmol kg-1. Plants accumulated more Zn as soil Zn levels increased, and Zn concentrations of shoots were about 540 /μg g-1 in Aris and 583.9μg g-1 in Tede in response to 16 mmol Zn kg-1 soil. Zn ratios of shoots to roots across the soil Zn levels were higher in Tede than in Airs, corresponding with higher rhizosphere available Zn fractions (exchangeable, bound to manganese oxides, and bound to organic matter) in Airs than in Tede. Low-molecular-weight (LMW) organic acids (oxalic, tartaric, malic, and succinic acids) and amino acids (proline, threonine, glutamic acid, and aspartic acid, etc.) were detected in root exudates, and the concentrations of LMW organic acids and amino acids increased with addition of 4 mmol Zn kg-1 soil compared with zero Zn addition. Higher rhizosphere concentrations of oxalic acid, glutamic acid, alanine, phenylalanine, leucine, and proline in Tede than in Airs likely resulted in increased Zn uptake from the soil by Tede than by Airs. The results suggested that genotypic differences in Zn accumulations were mainly because of different root exudates and rhizosphere Zn fractions.     

Low molecular weight organic acids released from roots of durum wheat and flax into sterile nutrient solutions

Knowledge of the composition and quantity of organic substances released from roots of different plant species is necessary for understanding the chemical and biological processes in the rhizosphere. The present study was undertaken to quantify low molecular weight organic acids (LMWOAs) released from roots of five cultivars/lines of durum wheat (Triticum turgidum var. durum L.): Kyle, Sceptre, DT618, DT627, and DT637 and four cultivars/ lines of flax (Linum usitatissiumum L.): Somme, Flanders, AC Emerson, and YSED 2. Plants were grown in sterile nutrient solution cultures and amounts of organic acids exuded by roots were analyzed by gas chromatography. The LMWOAs varied significantly among both durum wheat and flax cultivars and oxalic, malonic, fumaric, succinic, acetic, malic, citric and tartaric acids were detected in root exudates of both species. Generally, oxalic and acetic acids were predominant in durum wheat exudates and oxalic, acetic and malic acids were predominant in flax root exudates. High oxalic acid concentrations occurred in root exudates of durum wheat cultivars DT627 and DT637, and flax cultivar YSED 2. Compared with the other durum wheat cultivars, Kyle released the lowest total amount of LMWOAs, whereas among the flax cultivars, YSED 2 had the highest total amount of acids secreted from roots. The data showed that the release of LMWOAs from roots was cultivar dependent. The results provide valuable background information for studying the role of root exudates in soil‐plant relationships.     

Bioavailability of Zn as affected by root-induced changes of pakchoi cultivars with different Zn efficiencies

Background, aim, and scope  The Zn content in the human body is tremendously higher than that in the plant. It is vulnerable to Zn nutrition deficiency in the human body. Those who consume less animal products are subject to Zn deficiency and mainly live in the developing regions. The preventive measures against Zn deficiency in the human body, for example, Zn supplements from chemicals and Zn-fortified food, are expensive and often unattainable. We have been working on finding solutions to Zn malnutrition by screening Zn-efficient varieties of crops which can absorb more Zn from Zn-deficient soils and transfer more Zn to the edible part of crops. Pakchoi is a popular vegetable in many parts of the world. The Zn deficiency in the human body could be rectified by consuming Zn-efficient pakchoi cultivars. Rhizosphere is the ‘hotspot’ for plant–soil–microbe interactions, and the rhizospheric interactions play a key role in the micronutrient acquisition. However, little attention has been paid to the rhizosphere effects of different plant genotypes on the expression of nutrient efficiency. The aim of this study was to examine the difference of rhizosphere effect between two pakchoi cultivars with different Zn efficiencies. Materials and methods  A Zn-deficient calcareous purple soil was collected from central China. There were two Zn treatments, one with Zn addition (5 mg kg⁻¹ soil) and the other, which acts as a control, with no Zn addition. Two pakchoi cultivars were Wuyueman of Zn-efficient and Heiyoubaicai of Zn-inefficient plants. Ten seeds of each pakchoi cultivar were sown in the rhizobag. The plastic pot was filled with 0.8 kg soil with 37% of the soil in the rhizobag. The seedlings were harvested on day 45 after planting. The rhizosphere and bulk soil samples were analyzed for their physical and chemical properties, microbial biomass, and Zn concentrations. Zn in the plants was also determined. Results  The cultivar Wuyueman demonstrated a much higher depletion rate of available Zn in the rhizosphere than did the cultivar Heiyoubaicai. The available Zn in the rhizosphere of Wuyueman was lower in the rhizosphere soil (0.47 mg kg⁻¹) compared with that in the bulk soil (1.08 mg·kg⁻¹), and the depletion rate of available Zn was 56.5% under Zn deficiency. This was closely associated with the capacity of cultivar Wuyueman to take up more Zn from the soil, especially under Zn-limiting conditions. The rhizosphere pH of pakchoi cultivars was lower than that in the bulk soil, while the microbial biomass carbon in the rhizosphere was significantly higher than that in the bulk soil. Under Zn-deficient conditions, the rhizosphere pH of the cultivar Wuyueman was lower but the microbial biomass carbon was higher than those of the cultivar Heiyoubaicai. Discussion  Soil-available Zn was substantially depleted in the rhizosphere of two pakchoi cultivars, with the greater depletion rate being found in the cultivar Wuyueman rather than in the cultivar Heiyoubaicai, especially under Zn-deficient conditions. This was related to the mobilization of Zn induced by the plants with different Zn efficiencies and, thus, Zn bioavailability in the rhizosphere. The pH decrease and the increase of microbial biomass carbon in the rhizosphere of the cultivar Wuyueman might have contributed to the translocation of Zn in its rhizosphere, which allows Zn to be absorbed more easily by Wuyueman than by Heiyoubaicai. This suggests that root-induced changes in the rhizosphere of pakchoi have a certain effect on the expression of zinc efficiency. Conclusions  Root-induced changes mobilized Zn in the rhizosphere of two pakchoi cultivars and increased its bioavailability. The rate of Zn mobilization was higher in the rhizosphere of the Zn-efficient cultivar than that of the Zn-inefficient cultivar at low Zn levels. Recommendations and perspectives  Root-induced changes in the rhizosphere are important factors for the nutrient dynamics and, thus, also for the mineral nutrition of plants. Soil conditions near the roots are different from those in the bulk soil. Many results have shown that these differences depend on soil properties, fertilizer application, plant species, and other factors. Further research should focus on the environmental effects of the rhizosphere on nutrient availability.     

不同白菜品种对锌的响应及锌利用效率研究

采用盆栽试验研究了白菜[Brassica campestris L.ssp.Chinensis(L.)Makino]4个品种对不同浓度锌(Zn 0、1、10 mg/kg)的响应.结果表明,白菜的生物量及体内锌含量随锌水平的增加而增加;但白菜品种对锌营养反应的敏感性不同.地上部锌含量、锌积累量和锌吸收效率均以日本华冠(J...     

铅胁迫下小花南芥与玉米间作对根系分泌物 有机酸的影响

为了揭示Pb胁迫对间作和单作的超累积植物和作物根系分泌低分子有机酸的影响,研究设置400 mg·L?1Pb胁迫,采用水培曝气法试验,以玉米和小花南芥单作为对照处理,研究Pb胁迫下玉米和小花南芥间作对植物根系形态、根系分泌有机酸及Pb吸收的影响。结果表明:与单作相比,间作小花南芥情况下,玉米根系分泌物检测到乳酸;玉米分根条数、根表面积和根密度与单作相比分别增加60%、15%和42%,地下部和地上部干重生物量分别增加108%和75%,玉米地下部Pb含量下降44%;与单作相比,间作玉米条件下,小花南芥根系分泌物检测到乙酸和乳酸,小花南芥根系分泌物量与单作相比增加103%~1 700%,小花南芥地下部和地上部Pb累积量分别比单作增加49%和75%,转运系数增加22%。相关分析结果表明,单作小花南芥只有地上部Pb累积量与草酸显著相关,而间作小花南芥地下部和地上部Pb累积量与草酸、柠檬酸和苹果酸显著相关。研究表明超富集植物小花南芥与玉米间作体系,根系分泌的有机酸改变了Pb在小花南芥和玉米体内的累积特征,促进超累积植物小花南芥累积Pb,减少农作物玉米植株体内Pb含量。Pb胁迫下超累积植物小花南芥与玉米间作是一种可行的修复模式。     

Effect of zinc deficiency in wheat on the release of zinc and iron mobilizing root exudates

The effect of Zn deficiency in wheat (Triticum aestivum L. cv. Ares) on the release of Zn mobilizing root exudates was studied in nutrient solution. Compared to Zn sufficient plants, Zn deficient plants had higher root and lower shoot dry weights. After visual Zn deficiency symptoms in leaves appeared (15–17 day old plants) there was a severalfold increase in the release of root exudates efficient at mobilizing Zn from either a selective cation exchanger (Zn-chelite) or a calcareous soil. The release of these root exudates by Zn deficient plants followed a distinct diurnal rhythm with a maximum between 2 and 8 h after the onset of light. Re-supply of Zn to deficient plants depressed the release of Zn mobilizing root exudates within 12 h to about 50%-, and after 72 h to the level of the control plants (Zn sufficient plants). The root exudates of Zn deficient wheat plants were equally effective at mobilizing Fe from freshly precipitated Fe^III hydroxide as Zn from Zn-chelite. Furthermore, root exudates from Fe deficient wheat plants mobilized Zn from Zn-chelite, as well as Fe from Fe^III hydroxide. Purification of the root exudates and identification by HPLC indicated that under Zn as well as under Fe deficiency, wheat roots of the cv. Ares released the phytosiderophore 2′-deoxymugineic acid. Additional experiments with barley (Hordeum vulgare L. cv. Europa) showed that in this species another phytosiderophore (epi-3-hydroxymugineic acid) was released under both Zn and Fe deficiencies. These results demonstrate that the enhanced release of phytosiderophores by roots of grasses is not a response mechanism specific for Fe deficiency, but also occurs under Zn deficiency. The ecological relevance of enhanced release of phytosiderophore also under Zn deficiency is discussed.     

蚕豆根系分泌物中氨基酸含量与枯萎病的关系

通过田间试验研究不同品种蚕豆枯萎病病情指数的差异,并通过水培试验鉴定蚕豆根系分泌物中氨基酸组分并测定氨基酸的含量,分析各氨基酸组分与蚕豆枯萎病病情指数的相关性。结果表明:根系分泌物中氨基酸总量随着蚕豆枯萎病抗性的降低而升高。感病品种和中抗品种中检出15种氨基酸,而抗病品种中检出14种,组氨酸只存在于中抗品种中,脯氨酸仅在感病品种中检测到,3个蚕豆品种根系分泌物中均未检出精氨酸。丝氨酸(Ser)、蛋氨酸(Met)和赖氨酸(Lys)与枯萎病病指呈负相关关系,以Ser的相关系数最高,其他13种氨基酸含量与蚕豆枯萎病的病情指数呈正相关。蚕豆根系分泌物中Ser、Met和Lys含量及Ser/Gly、Ser/Ala比值高能抑制枯萎病的发生与发展,而天门冬氨酸(Asp)、苏氨酸(Thr)、甘氨酸(Gly)、丙氨酸(Ala)、缬氨酸(Val)、酪氨酸(Tyr)、苯丙氨酸(Phe)含量高时能促进枯萎病的发生。不同蚕豆品种根系分泌的氨基酸含量与组分的差异是影响蚕豆对枯萎病抗性差异的重要原因之一。     

Release of phytosiderophores from roots of wheat and triticale under nickel‐deficient conditions

Despite numerous studies on phytosiderophores (PS) there is still an open question whether nickel (Ni) deficiency induces release of PS from graminaceous plant roots. Seedlings of two wheat cultivars (Triticum aestivum L. cvs. Rushan and Kavir) and a triticale cultivar (X. triticosecale) were grown in Ni‐free nutrient solution (Ni‐deficient, Ni–) and with 10 µM NiSO₄ (Ni‐sufficient, Ni+, control). Root exudates were collected weekly for 4 weeks and the amount of PS in the root exudates was measured. The response to Ni deficiency on the release of PS differed between species. Roots of Rushan and triticale exuded higher PS in response to Ni‐deficient conditions. Nickel deficiency significantly enhanced shoot Fe and Zn concentrations in wheat, while it decreased shoot Fe and Zn concentrations in triticale. In Kavir, PS exudation was decreased by Ni deficiency at weeks 3 and 4 and the reduced release of PS from roots of Kavir was accompanied by lower concentrations of Fe and Zn in plant roots but higher Fe and Zn concentrations in shoot tissue. The PS release by Kavir was triggered by a Ni‐induced Zn deficiency particularly in the shoots. According to the results, it is suggested that in the studies concerning the phytosiderophore release under Ni deficiency, special attention should be given to different responses among and within cereals and to the plant Zn or Fe nutritional status.