蓼科、禾本科植物细胞膜对铝胁迫反应的比较研究

以4种蓼科植物(荞麦、金荞麦、虎杖、无辣蓼)和2种禾本科植物(水稻、小麦)为材料,比较研究不同科属植物的细胞膜对铝胁迫反应的差异。结果表明:(1)6种植物叶片的游离脯氨酸含量、MDA含量和根系质膜透性均随着Al3 胁迫浓度增加而增大,禾本科植物的游离脯氨酸含量高于4种蓼科植物,荞麦、金荞麦的质膜透性、MDA含量高于虎杖、无辣蓼、水稻、小麦。(2)荞麦、小麦叶片的SOD和POD活性随Al3 胁迫浓度持续增长,虎杖和水稻持续下降,金荞麦和无辣蓼在25 mg/L Al3 处理时最高,100 mg/L Al3 胁迫明显降低。综合细胞膜对铝胁迫反应的各种特征,可以说明蓼科植物细胞膜透性变化是Al3 引发氧化胁迫的一种受损表现,而禾本科植物细胞膜透性变化是对A3 胁迫的一种适应性反应。     

荞麦和金荞麦根际土壤铝形态变化及对其生长的影响

不同形态的铝对不同植物的毒害不同。以荞麦和金荞麦为实验材料,设置4个不同的土壤铝处理浓度（0,0.1,0.2,0.4 g Al^3＋/kg）,研究荞麦和金荞麦根际土壤中铝形态变化及对其生长的影响。结果表明,当土壤铝处理浓度〈0.2 g/kg时,尽管根际土壤液中铝溶出量较对照组有明显上升,毒性大的交换态铝和单聚体羟基铝（称为活性铝）占可提取铝总量的比例增加,但荞麦和金荞麦茎伸长和水分利用增强,地上部分生物积累量增多,表明荞麦和金荞麦对低铝胁迫有一定的适应;当土壤铝处理浓度达到0.4 g/kg时,荞麦和金荞麦根际土壤pH降至最低,根际土壤液中铝的溶出量增至最高,严重抑制了荞麦和金荞麦叶片光合作用的正常进行,各项指标和对照差异达到显著水平,荞麦和金荞麦的生长表现出明显的铝毒害症状。因此,我们推断在根际土壤活性铝溶出量为0.106-0.143 m g/g和0.046-0.057 m g/g间可能分别存在着荞麦和金荞麦耐受铝毒害的某个阈值。     

铝胁迫下大豆根系脱落酸累积与柠檬酸分泌的关系研究

为探讨铝(Al)胁迫条件下脱落酸(ABA)调控植物根系有机酸分泌的机制,进行了ABA与Al诱导大豆根系柠檬酸分泌的关系试验。结果表明:1)外源ABA和ABA合成抑制剂fluridone分别提高和降低了Al诱导的大豆根尖ABA含量的增加,但对根系柠檬酸分泌量均无影响,ABA对根系内源柠檬酸含量和柠檬酸合成酶的活性也没有影响;2)分根试验表明,与Al直接接触的根部(Part A)内源ABA含量发生变化,且有柠檬酸的分泌,而不与Al直接接触的根部(Part B)内源ABA含量也发生变化,但没有柠檬酸分泌;3)Al胁迫下,大豆耐Al基因型柠檬酸分泌量远高于敏感基因型,但二者的内源ABA含量却没有差异;4)30μmol AlCl3处理,在0~12 h柠檬酸分泌速率和内源ABA含量随Al处理时间增加而增加,去除Al胁迫时(12~18 h),柠檬酸分泌速率继续增加,但内源ABA含量则迅速下降。综合以上结果,推测ABA不是通过提高Al诱导柠檬酸分泌来调控大豆耐Al性。     

镉胁迫下小麦根系的生理生态变化

本文通过水培和砂培两种方法 ,研究了镉胁迫下小麦 (TriticumaestivmL .)根系的生理生态变化。通过研究镉对小麦根系生长发育状况 ,根系活力 ,根系对矿质元素的吸收 ,探讨镉胁迫下植物根系的生理生态效应。研究结果表明 :镉影响根系的长度、生物量、体积和根系活力。Cd2 + 在低浓度 (处理浓度低于 5mg/L)作用下 ,随处理浓度的升高 ,刺激小麦根系的长度、生物量、体积相应地升高 ;当处理浓度高于相应浓度时 ,根长度、生物量、体积相应随浓度升高而降低。镉胁迫下根系活力受到抑制。水培和砂培中 ,镉对根系的影响趋势一致 ,但是影响幅度有差异。砂培好于水培。镉影响小麦根对矿质元素的吸收 ,Ca、Cu、Fe、K、Mg、Mn、Na、Zn吸收情况不太一致。Ca、Cu、Fe、Mg、Mn、Na的吸收量随Cd2 + 浓度升高而增加 ,K、Zn的吸收量随Cd2 + 浓度升高而减少     

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。     

硅、钙对水土保持植物荞麦铝毒的缓解效应

采取水培法,研究了铝胁迫下不同水平的钙或硅对荞麦真叶期和初花期铝毒害的缓解效应。结果显示:在Al3 胁迫下,增加钙或硅的供应可减轻Al3 对植物的毒害,显著削弱因Al3 处理导致的根系活力、可溶性蛋白质含量和过氧化物酶(POD)活性的下降以及丙二醛含量的上升,在初花期能完全消除Al3 对可溶性蛋白质形成的抑制效应并促进其形成,有效提高植株抗逆性。但随着Al3 浓度的提高,Ca2 和硅的缓解效应有限。Ca2 的缓解效果略强于硅。     

铝毒胁迫下磷对荞麦根系铝形态和分布的影响

以2个荞麦（Fagopyrum esculentum Moench）品种＂江西荞麦＂（铝耐性）和＂内蒙荞麦＂（铝敏感）为材料,采用水培法,研究铝毒胁迫下磷对荞麦根系总铝和单核2种形态以及Al在根尖和细胞壁中的分布情况的影响。结果表明,与200μmol/L Al处理相比,1.0mmol/L磷预处理分别使江西荞麦和内蒙荞麦的相对根长增加了24.4%和35.9%,根系总Al含量分别降低了18.2%和22.5%,根系单核Al含量分别降低了95%和63.2%。根尖细胞壁荧光检测结果为在单Al胁迫下细胞壁的荧光强度最大,1.0mmol/L磷预处理大幅度减弱细胞壁的荧光强度。表明外源磷供应可降低根系总Al和单核Al含量,使毒性形态的铝转化为无毒形态,以及减少Al在根尖以及细胞壁的积累,以缓解Al对根伸长的抑制,提高荞麦根系的抗铝毒害能力。     

黑麦品种间耐铝差异性机制研究

采用室内模拟方法,研究了铝诱导黑麦根系分泌有机酸、根尖磷对铝的固定作用。结果表明,在铝胁迫下冬牧品种（Win）相对根伸长率高于King品种。在铝胁迫下,经磷预处理的根尖铝和磷含量增加,且以Win品种根尖中的Al、P含量较高,说明根尖磷对铝的固定是黑麦耐铝机制之一。另一方面,在铝胁迫下,两品种根系均分泌柠檬酸和苹果酸,且Win的分泌速率较高。有机酸的分泌随着铝处理浓度（10、30、50 mol/L）和时间（0.5、3、6、9、12 h）的增加而增加,但在低温（4C）下柠檬酸分泌量显著减少。Al处理0.5 h后苹果酸已明显分泌,而柠檬酸的分泌在铝处理6 h后才明显增加。在铝处理前,进行缺磷预处理（3 d）不能增加有机酸的分泌,10 mol/L的La3+、Cu2+、Ni3+也不能诱导根系分泌有机酸。说明铝诱导根系专一性分泌有机酸也是黑麦品种间耐铝性差异的机制。     

荞麦对酸铝胁迫生理响应的研究

铝毒害是限制酸性土壤中植物生长的重要因素,以荞麦(FagopyrumesculentumMoench.)为实验材料,在沙培条件下,用不同浓度(0,10,100,1000mg/L)、不同pH(3,4,5)的铝溶液处理,在出苗后的第14d和28d测试与铝胁迫有直接关系的5个生理指标。结果表明,溶液的铝浓度和pH的变化对荞麦生理都有明显的影响,最低浓度的铝处理10mg/L在不同pH下已经影响了荞麦的正常生长,和对照相比根系活力(RA)下降、根质膜透性(MP)增大、叶片内丙二醛(MDA)和游离脯氨酸(Pro)的含量以及过氧化物酶(POD)的活性升高,并且随着铝处理浓度的升高,荞麦体内各生理指标和对照差异性加大;同一铝浓度下pH5和pH3相比,MP降低、RA增强、叶片内MDA和Pro的含量以及POD的活性有所下降。铝胁迫下荞麦体内各生理指标的变化有显著的相关性。随着荞麦的生长,铝毒害有所缓解。     

酸性森林土壤中Ca-H-Al交换过程与铝的溶解机制研究

华南酸性森林土壤分别在pH值为3．46、4．24和4．84条件下用含不同浓度盐基离子（Ca^2＋）的酸性浸提液浸提，以查明降水中盐基离子对土壤水中Al和H^＋的影响。实验结果表明：随着Ca^2＋浓度的增加，土壤浸出液中H^＋和Al都有增加的趋势。随着Ca^2＋浓度的变化，H^＋和Al有不同的来源：当Ca^2＋〈0．5mmol L^-1，土壤主要通过Ca—H交换机制释放H^＋，浸出液中Al主要来源于土壤活性铝的溶解；当Ca^2＋〉0．5mmolL^-1时，由于Ca—Al交换反应，浸出液中Al随Ca^2＋浓度增加而显著增加，此时H^＋主要来源于Al的水解反应。浸出液中pH—pAl关系也随pH值（或Ca^2＋浓度）的变化有显著不同：当浸出液pH〉3．7（Ca^2＋〈0．5mmolL^-1）时，浸出液中Al^3＋活度随pH的变化幅度较小，这可能是酸性土壤中活性铝已显著流失的缘故；当pH〈3．7（Ca^2＋〉0．5mmol L^-1）时H^＋对于Al浓度具有较强的依赖性，故pH随Al^3＋活度增加而显著降低。因此，降水中盐基离子的增加能够引起土壤水乃至地表水中酸性阳离子（特别是Al）的迅速增加，可能造成对水生生物的突发性影响。     

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.     

籽粒苋不同富钾基因型根系分泌物中有机酸和氨基酸的变化特点

采用溶液培养试验研究了籽粒苋(Amaranthus.spp.)不同富钾基因型在不同供钾水平条件下3个不同生长时期内根系分泌物中氨基酸和有机酸的种类及含量变化情况。结果表明,1)籽粒苋根系分泌物中氨基酸和有机酸含量随着供钾水平的升高而降低,且富钾基因型始终大于一般基因型。在低钾胁迫时,根系分泌物中有10种氨基酸和5种有机酸出现,而在供钾正常时则缺少谷氨酸、甘氨酸、苯丙氨酸、草酸和柠檬酸等;酪氨酸、-氨基丁酸和丝氨酸的含量约占氨基酸分泌总量的一半以上;苹果酸含量约占有机酸分泌总量的60%以上。2)籽粒苋生长50d时,一般基因型氨基酸和有机酸的分泌总量较生长40d时迅速降低,而富钾基因型降低速度则相对较为平稳。在3个生长期内,酪氨酸、-氨基丁酸和丝氨酸均为两类基因型根系分泌物中的主要氨基酸种类,苹果酸则是主要的有机酸类型,其在氨基酸和有机酸分泌总量中所占相对比例均随生长期的延长而升高。3)籽粒苋根系分泌物处理后的土壤速效钾含量均高于清水对照处理,富钾基因型在低钾胁迫时的根系分泌物对土壤钾的活化作用明显大于一般基因型。     

铁锰营养失衡对商陆根系分泌物的影响

以商陆为实验材料,用水培方法设置了8个实验处理:Fe0Mn0(对照),Fe0Mn-,Fe0Mn ,Fe-Mn0,Fe-Mn-,Fe-Mn ,Fe Mn0,Fe Mn-,Fe Mn 。处理30 d时,对根系分泌物中可溶性糖、总氨基酸、pH值以及根系质膜透性进行测定。结果表明,Fe-Mn-的可溶性糖含量稍高于对照,其余各处理组均低于对照,Fe0Mn ,Fe Mn 达到显著水平;氨基酸含量在铁锰失衡条件下普遍有所增加,其中Fe-Mn0分泌的氨基酸含量最大,与对照差异显著;除Fe0Mn 外,各处理组的pH值与对照组相比都显著增加,其中以铁毒处理组(Fe Mn0,Fe Mn ,Fe Mn-)的增加率最高;铁毒处理组(Fe Mn0,Fe Mn ,Fe Mn-)使商陆根系质膜透性增加,对商陆根系造成一定的伤害。总体而言,铁锰的缺乏或过量都会引起商陆根系分泌物含量的变化,其中以铁胁迫和锰毒对其影响最大;另外,相对单铁或单锰处理而言,铁锰之间的交互作用对商陆根系分泌物的变化也有一定的影响。     

铝对荞麦铝和其它营养元素运输的影响

铝胁迫下铝和其它元素的吸收、运输和分布是铝毒害的基础。采用土培法。研究荞麦（Fagopyrum esculentum Moench）在不同的铝浓度水平下对铝的吸收和运输，以及铝胁迫对氮、磷、钾、钙、镁、钠、锌、铜、铁、锰等元素的吸收和运输的影响。结果表明：在铝胁迫下，养麦植株铝含量迅速上升，而其他元素的吸收均受到一定的阻碍影响，在植株各部的含量均有所下降；花期荞麦与真叶期相比，地上部分的铝含量及根部含量均大幅下降，植株的其他元素含量同阳增加，表明铝胁迫得到缓解，可见养麦作为一种铝积累植物对铝毒有较强的适应能力。     

Root exudation,organic acids,and element distribution in roots of Norway spruce seedlings treated with aluminum in hydroponics

Seedlings of Norway spruce (Picea abies [L.] Karst.), which had been grown under sterile conditions for three months, were treated for one week in a hydroculture system with either 500 μM AlCl₃ or 750 μM CaCl₂ solutions at pH 4. Organic acids were determined in hot‐water extracts of ground root tissue. Oxalate (3.3—6.6 μmol (g root dry weight)^—1) was most abundant. Malate, citrate, formate, acetate, and lactate concentrations ranged between 1—2 μmol (g root dry weight)^—1. Organic substances and phosphate found in the treatment solutions at the end of the experimental period were considered to be root exudates. Total root exudation within a 2‐day period ranged from 20—40 μmol C (g root weight)^—1. In root exudates, organic acids, and total carbohydrates, total amino acids, and total phenolic substances were quantified. Citrate and malate, although present in hot‐water extracts of root tissue, were not detected in root exudates. Phosphate was released from Ca‐treated plants. In Al treatments, there was indication of Al phosphate precipitation at the root surface. Oxalate and phenolics present in the exudates of Norway spruce seedlings are ligands that can form stable complexes with Al. However, concentrations of these substances in the treatment solutions were at micromolar levels. Their importance for the protection of the sensitive root apex under natural conditions is discussed.     

铝胁迫对油菜根系形态和生理指标的影响

为探讨油菜幼苗在不同浓度铝胁迫下的生理响应,以2个耐铝毒差异显著的油菜品种(耐铝品种R178和铝敏感品种S169)为试验材料,在营养液培养条件下,共设置0(对照)、50、100、150、200和 300 μmol·L^-1 6个铝(pH值4.5)处理,研究铝胁迫对油菜根系形态及生理指标的影响。结果表明,50 μmol·L^-1铝处理下R178各根系形态指标与对照相比均无显著差异,而S169根系各形态指标与对照均差异显著,其中总根尖数随着铝处理浓度的增加呈先升高后降低的趋势,其他根系指标均随着铝处理浓度的增加呈逐渐减少的趋势,300 μmol·L^-1铝处理下,2个品种的主根相对伸长率较对照分别减少65.7%和79.7%。随着铝处理浓度的增加,2个品种幼苗根系中可溶性蛋白和脯氨酸含量均呈先升高后降低的趋势,叶片中可溶性蛋白含量呈降低趋势,而脯氨酸含量则呈升高的趋势。铝胁迫导致2个品种幼苗根系和叶片的质膜透性显著增加,300 μmol·L^-1铝处理下R178和S169根系相对电解质外渗率较对照分别增加54%和59%,叶片中分别增加82%和90%,同一处理下R178根系和叶片电解质外渗率均小于S169。随着铝处理浓度的增加,2个品种根系中的超氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT)活性均呈先增加后降低的趋势;R178叶片中SOD活性呈增加趋势,而S169则呈先增加后降低的趋势,且在200 μmol·L^-1时达到最大值;2个品种叶片中的POD、CAT和抗坏血酸过氧化物酶(APX)活性均呈先增加后降低的趋势。综上,铝胁迫显著抑制了油菜根系生长,破坏了细胞质膜的完整性,油菜幼苗通过蛋白质和脯氨酸含量的积累以及保护酶活性的增高抵抗铝胁迫。本研究结果为耐铝油菜资源筛选和新品种选育提供了理论依据。     

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.     

Phosphorus Efficiency of Buckwheat (Fagopyrum esculentum)

The ability of buckwheat (Fagopyrum esculentum) roots to acquire phosphorus (P) was characterized by investigating P uptake, morphological features, and chemical changes in the rhizosphere. Over a range of nutrient solution P concentrations (5–500 μmol · L^?1), maximum shoot growth was achieved with a P supply between 5 and 100 μmol · L^?1. Root weight and root length, as well as length and frequency of root hairs, were higher at low P levels. Root surface and the root surface/shoot dry weight ratio reached high values. Though P uptake rates were only moderate (0.15 pmol · cm^?1 root · sec^?1), shoot P concentrations were high (1.8% of dry weight with 100 μM P) predominantly being inorganic (80%). Phosphorus efficiency was characterized by a high specific absorption rate (810 mmol P · kg^?1 root dry wt · d^?1) rather than by an efficient utilization for dry weight production. Root exudates of low-P plants had lower pH values than exudates of high-P plants and increased the solubility of FePO₄ and MnO₂ to a greater extent. Amounts of exuded organic acids and phenolics were low and could not account for the observed solubilization of FePO₄ and MnO₂. Enhanced hydrolysis of glucose-6-phosphate by exudates from low-P plants was due to an increased “soluble” acid phosphatase activity, and root surface phosphatase activity was also slightly enhanced with P deficiency. In the rhizosphere soil of buckwheat, some depletion of organic P forms was observed, and in pot trials with quartz sand, buckwheat utilized glucose- 6-phosphate as a P source at the same rate as inorganic P.     

Influence of microflora and composition of root bathing solution on root exudation of maize plants

Root exudation of carbon (C) plays a major role in processes occurring in the plant rhizosphere. Environmental factors affecting root exudation have been identified but their effects are rarely quantified. The purpose of this work was to evaluate the impact of both the microflora and the chemical composition of the growth medium on root exudation, taking into account soluble exudates and mucilage fraction. Maize plants (Zea mays L.) were grown for 12 days in hydroponic conditions and then transferred in three root bathing solutions (demineralized water, KCl or nutrient solution) during 24 hours. In each case, presence of microflora was tested with a comparison between plants inoculated with maize rhizospheric strain and axenic plants. Exudation was measured in terms of C and biomass production. A strong interaction was noticed between microflora and chemical composition of the root bathing solution. In fact, the presence of rhizospheric microflora induces a stimulation of soluble exudates only in KCl and Nutrient solutions. In demineralized water, a different response was observed with a higher C release for axenic plants, probably due to the osmotic shock induced to the roots. Concerning mucilage fractions, small quantities were recovered on all treatments. This work demonstrates that the chemical composition of the root bathing solution and presence of microorganisms significantly modify the amount of soluble exudates. Attention must therefore be paid to the cultural conditions when exudation is studied because of the sensitivity of this process to root environment.