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。     

籽粒苋富钾基因型的生理生化基础研究

通过不同供钾水平的溶液培养试验和缺钾土培试验,研究了籽粒苋富钾基因型的生理生化特性。结果表明,籽粒苋富钾基因型(R104、K12)叶绿素含量和光合速率,以及脯氨酸、游离氨基酸和可溶性糖含量高于一般基因型(M9)。籽粒苋叶片POD、SOD及ATP酶活性因器官、叶位、供钾水平和生育阶段不同而不同,富钾基因型3种酶活性高于一般基因型;叶片SOD酶和ATP酶活性显著高于根部,而POD、SOD酶活性下部叶明显低于上部叶。叶片POD、SOD及ATP酶活性随供钾水平的增加而提高,且随着生长期的延长而降低。     

籽粒苋不同富钾基因型根际钾营养与根系特性研究

在缺钾土培和水培条件下,研究了籽粒苋不同基因型根际和非根际土壤速效钾、缓效钾和全钾含量的变化,以及根际微生物数量、根系主要分泌物、根系质子分泌量和根系CEC的变化。结果表明,籽粒苋根际土壤速效钾和缓效钾含量明显高于非根际土壤,且在根际形成钾的相对富集区,富钾基因型R104和K12根际钾的富集能力明显高于一般基因型;籽粒苋根际土壤的全钾含量却低于非根际土壤,富钾基因型的降低幅度大于一般基因型。富钾基因型根际微生物数量和根系分泌能力显著高于一般基因型,且根际细菌和真菌数量与主要根系分泌物的分泌量变化基本保持一致。富钾基因型R104和K12根系CEC和H 分泌量高于一般基因型M9和Cr047,而相同基因型内各品种间的变化不显著。     

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。     

富钾植物籽粒苋(Amaranthus spp.)对土壤矿物钾的吸收利用研究

运用土培、石英砂培、有机酸释钾实验及矿物X衍射分析研究了不同基因型籽粒苋(Amaranthusspp.)对土壤矿物钾的吸收利用及其机制。结果表明,籽粒苋能有效地利用土壤和云母(黑云母和金云母)中的钾;籽粒苋品种R104、CX4对钾的吸收量高于一般型品种(CX77);籽粒苋根系能引起云母矿物向蛭石转化;籽粒苋根系分泌物中的草酸比一般有机酸具有更高的释放矿物中钾素的能力。     

化肥有机肥配施对油菜营养生长期根系分泌物的影响

探讨油菜营养生长期根系分泌有机酸和氨基酸对不同施肥处理的响应,为油菜安全高效生产提供理论依据。盆栽试验设置5 个化肥有机肥不同配施比例,分析油菜根系和地上部的干重及其根系分泌的有机酸和氨基酸的种类和含量。研究结果表明,油菜根系分泌有机酸以丙二酸、乙酸和柠檬酸为主,其中丙二酸和乙酸受施肥影响最为显著,有机肥配施显著降低二者分泌量。与单施化肥相比,有机肥配施显著减少了油菜根系分泌有机酸总量,并不同程度降低了地上部和根系生物量。化肥有机肥配施比例为1∶3 时有机酸总量降低最明显,但生物量与单施化肥无明显差异。油菜根系分泌氨基酸以谷氨酸和γ- 氨基丁酸为主,不同配施比例对油菜根系分泌35 种氨基酸种类的影响不大,但对氨基酸分泌总量影响显著。随有机肥配比的增加,氨基酸总量呈现先减少后增加的趋势。根系干重与有机酸分泌总量呈极显著正相关关系,但与氨基酸分泌总量无关,后者与土壤可溶性有机碳含量和细菌数量显著相关。油菜根系分泌有机酸和氨基酸所起的生态作用可能不同,前者可能是植物受到养分胁迫时的应激反应,后者可能是为了增强土壤活性。化肥有机肥1∶3 配比为油菜生长提供最均衡养分,为油菜施肥管理提供参考。     

籽粒苋不同富钾基因型矿质营养元素含量的研究

采用水培试验,研究了在两种供钾水平(K,0.5mmolL-1和5.0mmolL-1)条件下4个不同籽粒苋品种植株体内矿质营养元素的含量及其变化。同时,还在低钾条件下,测定了不同籽粒苋品种根、茎、叶中矿质营养成分的含量和构成情况,结果表明:(1)籽粒苋各品种氮、钾含量随着供钾水平降低而减少,一般基因型氮钾含量降幅大于富钾基因型;在相同供钾水平条件下,富钾基因型的氮钾含量均高于一般基因型,而相同基因型的不同品种间氮钾含量则相近。籽粒苋各品种氮主要分布在根和叶中,其次是茎;磷大量分布在根,其次是叶,再次是茎;钾主要存在于茎中,根和叶次之。(2)籽粒苋钙、镁、硫含量随着供钾水平的升高而降低,富钾基因型镁、硫含量低于一般基因型。籽粒苋不同品种的钙、镁主要分布在叶片中,其次是茎和根;硫在根中的分布最少,叶中最多。(3)不同品种B、Cu、Fe、Mn、Zn等微量元素含量随着供钾水平的降低而升高,灰分含量则降低。富钾基因型B、Fe、Zn及灰分含量都高于一般基因型,而Cu的含量则是一般基因型高于富钾基因型。4个籽粒苋品种的硼、铜主要存在于叶片中,其次是根,茎含量相对前两者要小;铁、锰、锌在根的含量最高,叶片次之,茎最低,根系中铁的含量分别是叶和茎的7倍左右和10倍以上。     

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。     

施氮和干湿灌溉对水稻抽穗期根系分泌有机酸的影响

以水稻品种‘连粳7号’为试验材料进行盆栽试验,设置不施氮(0N,0 kg?hm-2)、中氮(MN,240 kg?hm-2)和高氮(HN,360 kg?hm-2)3种施氮水平及浅水层灌溉(0 k Pa)、轻度干湿交替灌溉(-20 k Pa)和重度干湿交替灌溉(-40 k Pa)3种灌溉方式,研究不同水氮处理对水稻抽穗期根系分泌有机酸总量和组分变化、氨基酸含量及水稻氮肥农学利用率与偏生产力的影响及其耦合效应,探索水氮耦合机理,为水稻氮素高效利用及根际生态提供理论及科学依据。结果表明:轻度干湿交替灌溉增加了水稻根系酒石酸、柠檬酸、草酸、苹果酸、琥珀酸、总有机酸、氨基酸分泌量,分别较浅水层灌溉增加13.2%、8.7%、27.3%、40.0%、6.7%、6.3%及6.4%,水稻氮肥农学利用效率及偏生产力分别增加4.1%及1.7%,显著提高根系分泌有机酸及氨基酸含量;重度干湿交替灌溉减少水稻根系酒石酸、柠檬酸、草酸、苹果酸、琥珀酸的分泌量,显著降低根系分泌有机酸总量、氨基酸含量及水稻的氮肥利用效率。同一水分条件下,施氮显著促进根系酒石酸、乙酸、苹果酸、琥珀酸的分泌,降低了草酸和柠檬酸的分泌量。根系分泌的酒石酸和琥珀酸含量在MN与HN间差异较小。分析表明,根系分泌有机酸总量、氨基酸、苹果酸及琥珀酸的供氮效应为正效应,轻度干湿交替灌溉效应及与供氮的耦合效应为正效应,而重度干湿交替灌溉效应及其与供氮的耦合效应则为负效应。根系分泌的柠檬酸、草酸与氮肥利用率呈显著与极显著正相关,乙酸与氮肥利用间呈显著负相关。结果表明通过轻度干湿交替灌溉与中等施氮调控发挥水肥耦合效应,可以促进水稻根系酒石酸、苹果酸、琥珀酸及氨基酸分泌,提高氮肥利用效率,从而促进水稻高产。     

Cd胁迫下长白落叶松幼苗根系有机酸的分泌研究

用A1层暗棕壤栽植长白落叶松幼苗(1 a生和2 a生),1个月后用CdCl2溶液对土壤进行Cd胁迫处理,使土壤Cd2+浓度分别达1、2、4、8 mg kg-1,在胁迫处理后第3 d、10 d和30 d,分别采集上述两种幼苗的根际土壤样品,研究不同Cd胁迫程度(水平)和胁迫时间处理后,长白落叶松幼苗根系分泌的有机酸种类和数量,以期为系统研究有机酸在森林生态系统中的作用提供理论依据。结果表明,Cd胁迫促进1 a生苗根系分泌有机酸种类和数量增加,增加量因胁迫时间和胁迫程度而异;增加有机酸种类数量的胁迫时长顺序为30 d 3 d 10 d,即在一定胁迫程度范围内,苗木受胁迫时间较短、胁迫较重时新检出有机酸的种类较多。同样,在一定胁迫程度和胁迫时长内,苗木根系分泌有机酸总量随胁迫程度提高而增加,达到最大值后胁迫程度继续提高则分泌有机酸的总量降低。在其它条件一定时,随胁迫时间延长,根系有机酸分泌总量降低。在不同的胁迫时间,有机酸分泌量大多以3 d增幅最大;对于不同种类有机酸,苹果酸分泌量增幅最大,其次为柠檬酸或草酸。对于2 a生苗,大多数Cd胁迫处理也增加其根系分泌的有机酸种类数量,且在一定胁迫程度内有机酸分泌总量随胁迫程度增加而增加。     

Soluble root exudates of maize: Influence of potassium supply and rhizosphere microorganisms

Maize was grown for 36 days in solution culture with roots either under axenic conditions or in the presence of rhizosphere organisms. In other experiments with sterile roots the plants were grown with different concentrations of potassium. At the end of the experiments sugars, organic acids and amino acids in the nutrient solutions were determined. Under axenic conditions the exudates consisted of up to 65% sugars, up to 33% organic acids and only up to 2% amino acids. The same substances were detected in non-sterile nutrient solutions. In the presence of microorganisms fructose, arabinose and the predominating glucose decreased to almost one half, while sucrose was not affected. The amounts of organic acids were not changed by microbial growth. The main amino acid, glutamic acid, was nearly doubled by the presence of microorganisms, whereas other amino acids remained unchanged. The lower O₂ content of the nutrient solutions of non-sterile roots suggested microbial decomposition of monosaccharides. In another experiment with roots grown under axenic conditions and with different K treatments low K supply significantly increased the total amounts of sugars, organic acids and amino acids exuded g^?1 root dry matter. As in the previous experiment glucose, fumaric and oxalacetic acid as well as glutamic and aspartic acid dominated in the respective fractions. Again sugars and organic acids represented the major quantity of exudates, while amino acids amounted to less than 2%. In an additional experiment with another cultivar, with nitrate as N source and a 5-day longer growth period, somewhat different results were obtained. In the exudates sugars were found in lower amounts, probably due to a higher growth rate. Under these conditions organic acids were the prevailing root exudates. Unlike sugars and amino acids, their total quantity was not affected by K nutrition, but the proportion of malic acid increased with increasing K supply, while oxalacetic acid dominated at low K nutrition. Similarly the total amount of organic acids within the root was independent of K nutrition. However malic acid content increased with increasing K application, while the likewise dominating citric and oxalacetic acid decreased.     

Root exudation of sugars,amino acids,and organic acids by maize as affected by nitrogen,phosphorus, potassium,and iron deficiency

Root exudates play a major role in the mobilization of sparingly soluble nutrients in the rhizosphere. Since the amount and composition of major metabolites in root exudates from one plant species have not yet been systematically compared under different nutrient deficiencies, relations between exudation patterns and the type of nutrient being deficient remain poorly understood. Comparing root exudates from axenically grown maize plants exposed to N, K, P, or Fe deficiency showed a higher release of glutamate, glucose, ribitol, and citrate from Fe‐deficient plants, while P deficiency stimulated the release of γ‐aminobutyric acid and carbohydrates. Potassium‐starved plants released less sugars, in particular glycerol, ribitol, fructose, and maltose, while under N deficiency lower amounts of amino acids were found in root exudates. Principal‐component analysis revealed a clear separation in the variation of the root‐exudate composition between Fe or P deficiency versus N or K deficiency in the first principal component, which explained 46% of the variation in the data. In addition, a negative correlation was found between the amounts of sugars, organic and amino acids released under deficiency of a certain nutrient and the diffusion coefficient of the respective nutrient in soils. We thus hypothesize that the release of dominant root exudates such as sugars, amino acids, and organic acids by roots may reflect an ancient strategy to cope with limiting nutrient supply.     

Differences in Root Exudation Among Phosphorus‐Starved Genotypes of Maize and Green Gram and Its Relationship with Phosphorus Uptake

Abstract

Availability of phosphorus (P) in soil and its acquisition by plants is affected by the release of high and low molecular weight root exudates. A study was carried out to ascertain the qualitative and quantitative differences in root exudation among the genotypes of maize (Zea mays L.) and green gram (Vigna radiata L.) under P‐stress. Results showed that both inter‐ and intra‐species differences do exist among maize and green gram in terms of root exudation, P uptake, and shoot and root P content. In general, green gram, a legume crop, had greater root exudation compared to maize. However, the amino acid content of the total root exudates in maize was two‐fold as compared to green gram. The maize and green gram genotypes possessed genetic variability in root exudation. Irrespective of the species or genotypes, a positive relationship was found among P uptake rates, total root exudation, and shoot and root ³²P content. The amount of sugars and amino acid present in the root exudates of P‐starved seedlings also add to the variation in P uptake efficiency of genotypes.     

Analysis of wild sunflower (Helianthus annuus L.) root exudates using gas chromatography‐mass spectrometry

Plant root systems mediate ecological processes in the rhizosphere through the exudation of organic compounds. Although exudate composition is thought to depend strongly on plant nutrient status, little is known about the influence of multi‐nutrient stresses. In this study, we examined responses to short‐term (3 d) nutrient limitation in Helianthus annuus (common sunflower), and root exudates were collected for 2, 4, or 6 h with the trap‐solution method. Root exudates, analyzed by means of gas chromatography‐mass spectrometry, consisted of over 60 sugars, sugar alcohols, amino acids, organic acids, and phosphates, with sugars and organic acids generally detected in the highest quantities. Twenty‐five of the detected metabolites, including half of the organic acids, sugars, and sugar alcohols, differed in relative abundance among the three sampling intervals, exhibiting higher abundance in sampling intervals greater than 2 h. Similarly, 24 of the detected metabolites, including half of the amino acids, phosphates, and sugar alcohols, were affected by nutrient supply, with 20 exhibiting higher abundance in the high‐nutrient treatment. Fumaric acid, quinic acid, and glucose were detected at significantly higher levels in the low‐nutrient treatment, potentially representing an adaptive response to nutrient limitation in sunflower. However, as sampling interval exerted a strong influence on the apparent effects of nutrient supply, future studies should consider the potential impacts of sampling‐interval length in comparative analyses of genotypes or treatments.     

Variation of wheat root exudates under aluminum stress

The wheat (Triticum aestivum L.) cultivar Yangzhou 158 was used as a reference. The wheat root exudates were collected using a hydroponic mode. The changes of the electrolytes, H+, sugar, organic acids, amino acids, and secondary metabolites in wheat root exudates induced by aluminum (Al) were studied. The research results show that Al stress affects wheat root exudation. The secreted electrolytes and sugar increase with the increasing of the external Al3+ concentration. The total amount of secreted amino acids has a specific correlation with the external Al3+ concentration. At first, the amino acids secrete normally, but when Al3+ concentration is over 10 mg.L-1, the amino acid constitution varies obviously. Under Al stress, some original secondary metabolites disappear gradually, and other new secondary metabolites release simultaneously. Increasing the external Al3+ concentration gradually stimulates the exudation of organic acids. The organic acid levels in the wheat root zone increase in response to Al treatments. Active Al ions are accumulated in wheat roots. This Al-dependent variation in wheat root exudates suggests a specific Al-induced response of the wheat.     

氮素对不同大豆品种根系分泌物中有机酸的影响

采用室内溶液培养方法,分别研究了接种根瘤菌处理下,两种氮源和两种氮浓度对两个大豆品种根系分泌物中有机酸的影响。结果表明,合丰25号根系分泌的有机酸种类和数量无论苗期或花期,接种或不接种根瘤菌,均表现为硝态氮处理高于酰胺态氮处理,表明合丰25号大豆更喜硝态氮,硝态氮促进了有机酸的分泌。绥农10号在酰胺态氮下的有机酸种类和数量均高于硝态氮处理,表明其更喜酰胺态氮,酰胺态氮下根瘤菌的存在增加其根系分泌物中有机酸种类和数量。可见,大豆根系分泌物中有机酸的种类和数量因品种而异,因品种对氮源的喜好而变化;根瘤菌在不同程度上增强或减弱根系有机酸的分泌作用。柠檬酸受氮素供应浓度影响很大,当氮素供应浓度较低时,大豆根系分泌物中可检测到柠檬酸,供氮浓度升高则检测不到。     

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。     

The effects of Fe deficiency on low molecular weight organic acid exudation and cadmium uptake by Solanum nigrum L.

Abstract

The influence of Fe-deficiency on the root exudation of low molecular weight organic acids (LMWOAs), pH alteration and cadmium (Cd) accumulation and translocation were investigated in morel (Solanum nigrum L.) in hydroponic culture experiments. Tartaric, citric, malic and acetic acids were monitored because these acids were abundant and often detected as root exudates. Results showed that Fe-deficient plants excreted large amounts of LMWOAs in comparison with Fe-sufficient plants across all Cd treatments (p <0.05). In both cases the concentrations of the four organic acids were tartaric > citric > malic > acetic. The results showed that the Fe-deficient plants with higher concentrations of LMWOAs accumulated more Cd (p <0.05) and induced a decrease in solution pH compared with the Fe-sufficient plants. Cadmium accumulation in the Fe-deficient and Fe-sufficient plants had significant positive correlations with the exudation of malic and acetic acids (p <0.05 and p<0.01). Cadmium accumulation in the Fe-sufficient plants had a significant (p<0.01) positive correlation with the exudation of tartaric acid, whereas there was a negative correlation (p<0.01) between Cd accumulation and the exudation of tartaric acid in the Fe-deficient plants. No significant correlation between the exudation of citric acid and Cd accumulation was obtained. Our results indicate that Fe-deficiency could induce Cd accumulation and translocation through an increase of LMWOAs exudation and pH alteration, both of which enhance Cd bioavailability.