4种植物幼苗根茎叶及根系分泌物中低分子量有机酸的特征

该研究建立了植物根茎叶及根系分泌物中有机酸的离子色谱分析测定方法,并测定了4种不同植物幼苗根茎叶及根系分泌物中低分子量有机酸的组成,为揭示逆境胁迫下植物体内有机酸的作用提供依据。结果表明:离子色谱分析法对植物有机酸的加标回收率为91.10%~105.42%,检测限为0.12~0.36mg/L,方法线性关系良好(R2=0.965 3~0.998 8);4种植物根茎叶及根系分泌物中都可以检测出草酸、柠檬酸、苹果酸、丁二酸和酒石酸,其中草酸、柠檬酸和苹果酸为优势酸;有机酸的组成和含量具有物种以及器官的差异性;根系分泌物中的有机酸与根茎叶中有机酸的相关性也因种属差异而不同。这为研究逆境胁迫下植物器官及根系分泌物提供了可靠方法。     

双向标记培养植物测定大气二氧化碳稳定碳同位素组成

基于植物能够利用体内的碳酸酐酶来催化碳酸氢根离子生成二氧化碳和水作为底物进行光合作用的特性,采用两种δ13CPDB值差值大于10‰的碳酸氢钠分别作为外源碳酸氢根离子的碳同位素标记物,通过室内双向水培诸葛菜和芥菜型油菜实验,分别向水培处理液里添加已知δ13CPDB值的碳酸氢钠并培养24 h,利用同位素比值质谱(IRMS)技术,测定并计算了两个时间、两种环境下的大气二氧化碳稳定碳同位素日平均组成。结果表明:在环境1(不同浓度的Na HCO3处理液)下所得到的δCa值与添加到处理液中的碳酸氢根离子的浓度有关;在环境2(不同浓度的PEG处理液)下所得到的δCa值与添加到处理液中的PEG的浓度无关;两种环境下所测得的大气二氧化碳稳定碳同位素日平均组成δCa值与实验中培养的植物种类无关,而与添加到培养液中碳酸氢根离子的浓度及植物的生长速率有关。数据重现性好,结果准确可靠,可以高精度的测定不同待测环境下大气二氧化碳稳定碳同位素比值,其可为以后监测不同时间、不同地点的大气二氧化碳碳同位素组成及来源提供非常有效的方法和信息。     

不同供Zn水平下HCO3^-对小麦幼苗生长和活性氧代谢的影响

采用营养液培养法,研究了不同pH条件下高浓度HCO3^-(10mmol／L)在缺Zn和正常供Zn时对小麦幼苗生长,尤其是对活性氧自由基代谢的影响。结果表明,在酸性或碱性营养液中,HCO3^-在缺Zn时均显著降低小麦根系生长量,正常供Zn时HCO3^-对后者的影响则不明显。缺Zn条件下,HCO3^-在pH为6的营养液中使小麦根系和叶片中活性氧产生速率分别上升9．9％和3．9％,在pH为8的营养液中分别上升10．9％和5．7％;正常供Zn时HCO3^-虽使根系和叶片中活性氧产生速率增加,但幅度有所降低。缺Zn时HCO3^-大幅度降低小麦根系中POD、CAT、SOD3种保护酶的活性,而正常供Zn在一定程度上则能缓解HCO3^-对小麦根系组织中膜脂的过氧化作用。正常供Zn与缺Zn相比,后者显著增加小麦根系和叶片中的自氧化速率。     

不同供Zn水平下HCO3-对小麦幼苗生长和活性氧代谢的影响

采用营养液培养法,研究了不同pH条件下高浓度HCO3- (10 mmol/L) 在缺Zn和正常供Zn时对小麦幼苗生长,尤其是对活性氧自由基代谢的影响.结果表明,在酸性或碱性营养液中,HCO3- 在缺Zn时均显著降低小麦根系生长量,正常供Zn时HCO3-对后者的影响则不明显.缺Zn条件下,HCO3- 在pH为6的营养液中使小麦根系和叶片中活性氧产生速率分别上升9.9%和3.9%,在pH为8的营养液中分别上升10.9%和5.7%;正常供Zn时HCO3-虽使根系和叶片中活性氧产生速率增加,但幅度有所降低.缺Zn时HCO3-大幅度降低小麦根系中POD、CAT、SOD 3种保护酶的活性,而正常供Zn在一定程度上则能缓解HCO3-对小麦根系组织中膜脂的过氧化作用.正常供Zn与缺Zn相比,后者显著增加小麦根系和叶片中的自氧化速率.     

荞麦、高粱根系分泌物对玉米根边缘细胞和根生长的影响

植物的根系分泌物是植物根系与周围环境之间的化学媒介,通过传递特定的信息,调节根际微环境,影响周围植物的生长。玉米(Zea mays L.)和荞麦(Fagopyrum esculentum Moench)是农作物间套作体系中典型的不能搭配的组合,其障碍因素尚不清楚。以玉米为受体植物,采用根悬空培养的方法,研究了荞麦、高粱(Sorghum bicolor(L.) Moench)根系分泌物对玉米根边缘细胞和根生长的影响。结果发现,玉米根边缘细胞离体培养条件下,用荞麦根系分泌物中的小分子物质处理4、8 h显著诱导边缘细胞凋亡、死亡,细胞活率分别比对照降低了71.6%和72.3%;荞麦根系分泌物中的小分子物质对玉米根产生氧化胁迫,诱导根SOD、POD和CAT活性分别比对照高22.6%、33.9%和107.2%,根中超氧阴离子(O₂^-·)和脯氨酸含量分别比对照高33.9%和49.8%;荞麦根系分泌物中小分子物质的胁迫使根细胞膜透性增大,与对照相比升高80.0%,丙二醛(MDA)含量比对照升高31.5%;荞麦根系分泌物中小分子物质诱导根内源激素(IAA)含...     

丛枝菌根真菌对三叶草根系分泌的有机酸组分和含量的影响

比较洗根法、层析纸法和琼脂膜法收集土培条件下生长的菌根化和非菌根化三叶草根分泌物的效果。试验采用三室根箱装置 ,将根系与菌丝生长空间分开 ,三叶草生长 5 6d后 ,打开三室根箱装置 ,由于尼龙网的阻挡作用使根系均匀垫积在尼龙网内侧并形成根垫。分别采用洗根法、层析纸法和琼脂膜法 3种方法收集三叶草根系分泌物 ,并通过高效液相色谱方法测定分泌物中草酸、酒石酸、苹果酸、乳酸、乙酸、顺丁烯二酸、反丁烯二酸、柠檬酸、丁二酸等有机酸的含量。结果表明 :3种收集方法收集的三叶草分泌的有机酸无论在种类上还是在数量上都存在相当大的差别。从检测到的有机酸种类来看 ,琼脂膜法收集检测到苹果酸、乙酸、顺丁烯二酸、柠檬酸、丁二酸和乳酸 6种有机酸 ;洗根法收集的分泌物检测到酒石酸、苹果酸、乙酸、顺丁烯二酸、柠檬酸、丁二酸和乳酸 7种有机酸 ;层析纸法收集的分泌物检测到酒石酸、苹果酸、柠檬酸和乳酸 4种有机酸。从收集到的有机酸数量来看 ,洗根法收集到的有机酸总量为 2 9.97～ 2 32 .7μg/( gfw· 2 h) ;琼脂膜法集到的有机酸总量为 1 .5～ 7.3μg/( cm2· 2 h) ;层析纸法收集的有机酸总量为0 .2 3～ 6.5 8μg/( cm2 · 2 h)。丛枝菌根真菌侵染对三叶草根系分泌的有机酸的组分和含量都有一     

根系分泌物生态学研究

在植物生长过程中 ,由根系的不同部位分泌或溢泌一些无机离子及有机化合物 ,这些物质统称为根系分泌物。植物在其生长过程中不断地分泌无机离子及有机化合物 ,这是植物长期适应外界环境而形成的一种适应机制。早在 2 0世纪 5 0年代就有人对植物根系分泌物进行了研究 ,Ｒｏｖｉｒａ等[4 3] 和Ｖａｎｃｕｒａ等[4 7] 对根土界面根系分泌物进行了系统的研究 ,切尔诺布里维卡[2 6 ] 研究了植物根系分泌物的生物学作用 ,揭示了其在间作中的作用 ,直到 70年代对根系分泌物的研究才出现了蓬勃发展的趋势。近年来的研究表明 ,根系分泌物是保持根际微…     

锌和铁缺乏对枳生理指标、矿物质含量及叶片超微结构的影响

采用营养液培养法,研究了缺锌(0μmol·L-1 Zn2+)、缺铁(0μmol.L-1 Fe-EDTA)条件下柑橘砧木枳的生理胁迫反应.结果表明:1)锌、铁缺乏使枳生物量与根系活力均显著下降,叶片与根系中的SOD活性明显上升;叶片与根系中的POD活性在缺锌下显著增高,但在缺铁胁迫下显著降低;缺锌处理的根系CAT活性显著上升,但缺铁处理下的CAT活性与对照无显著差异.2)缺铁处理的根部K、Mg、P含量及缺锌处理的地上部K含量均显著降低;缺铁处理的根部和地上部Zn、Cu含量以及缺锌处理的根部Fe、Mn及地上部Mn含量均显著增高.3)叶肉细胞超微结构变化显著,缺铁胁迫下细胞器受损程度较重,如叶绿体、线粒体空泡化严重,叶绿体膜及类囊体片层模糊,质体小球明显增多,无淀粉粒;而缺锌处理时叶绿体基粒片层排列松散、数目明显减少,质体小球明显增多.     

外源水杨酸对铝胁迫下菊芋根系分泌物的影响

为探究铝胁迫对菊芋根系分泌物的影响以及外源水杨酸(SA)的缓解作用,该文以耐铝型南京菊芋和铝敏感型资阳菊芋为试验材料,采用土培法,设置铝浓度500 μmol·L^-1,分析了不同浓度(10、100、1 000 μmol·L^-1)SA对铝胁迫下菊芋根系分泌物中有机酸、氨基酸以及根尖相关代谢酶活的影响。结果表明:(1)单铝胁迫会导致菊芋根系分泌物中柠檬酸、草酸、苹果酸浓度升高,且南京菊芋升高幅度大于资阳菊芋; 柠檬酸合酶和苹果酸脱氢酶在单铝胁迫下活性增强; 脯氨酸含量显著提升,总氨基酸浓度均显著减少。(2)外源SA加入后,南京菊芋根系分泌的柠檬酸、草酸、苹果酸浓度均得到不同程度提高,但经高浓度(1 000 μmol·L^-1)SA处理后资阳菊芋根系分泌草酸显著降低,且在各浓度SA处理下苹果酸浓度均无明显变化; 柠檬酸合酶活性出现不同程度的增强,但对南京菊芋根尖中苹果酸脱氢酶活性影响不大,且高浓度(1 000 μmol·L^-1)SA处理后显著降低了资阳菊芋根尖中苹果酸脱氢酶活性; 脯氨酸含量显著下降,从总氨基酸浓度变化来看,南京菊芋在高浓度(1 000 μmol·L^-1)SA、资阳菊芋在低浓度(10 μmol·L^-1)SA处理下得到最大缓解效果。因此,菊芋通过分泌有机酸应对铝毒侵害,外源SA可促进菊芋根系有机酸代谢速率,分泌更多的有机酸来缓解铝胁迫,这种缓解效果在耐铝性相对较强的南京菊芋中表现更好。     

营养元素亏缺对人参根分泌物主成分的影响

采用营养液培养的方法,研究了氮、磷、钾元素亏缺对生长发育初期人参根系分泌物组成的影响.结果表明：氮、钾元素亏缺处理的人参根系分泌物组分与对照相当,分别检测到28、29和27个强色谱峰,磷元素缺失处理人参根系分泌物组分相对较少,检测到22种强色谱峰.用化学标准品分别对上述4种处理的根系分泌物中的14、14、11和10个化合物进行了鉴定.与对照相比,氮、磷元素亏缺处理人参根系分泌物有机酸和酚酸类化合物种类增多,磷元素缺失处理人参根系分泌物种类减少.说明人参生长发育初期对氮、钾元素需求比较旺盛,而对磷元素需求较少,氮、钾元素亏缺会促进根对有机酸和酚酸物质的分泌.     

Strain-specific salt tolerance and chemotaxis ofAzospirillum brasilense and their associative N-fixation with finger millet in saline calcareous soil

Three salt-tolerantAzospirillum brasilense strains were isolated from the roots of finger millet grown in saline calcareous soil and characterized. The effect of various salts on growth and N₂ase activity of these strains was tested and strain STR1 was found more tolerant at higher concentrations of Cl^-, SO₄ ² and HCO₃ ^-. Bicarbonate was found to be the most toxic. The content and concentrations of root exudates of finger millet genotypes were different and chemotaxis to sugars, amino acids, organic acids and root exudates was strain specific. Under salt stress, significant interactions between strains and genotypes of finger millet resulted in different responses of N₂ase activity, endo- and exorhizospheric population, dry weight of root, shoot and grain yield.     

Root exudates as mediators of mineral acquisition in low-nutrient environments

Plant developmental processes are controlled by internal signals that depend on the adequate supply of mineral nutrients by soil to roots. Thus, the availability of nutrient elements can be a major constraint to plant growth in many environments of the world, especially the tropics where soils are extremely low in nutrients. Plants take up most mineral nutrients through the rhizosphere where micro-organisms interact with plant products in root exudates. Plant root exudates consist of a complex mixture of organic acid anions, phytosiderophores, sugars, vitamins, amino acids, purines, nucleosides, inorganic ions (e.g. HCO₃ ^–, OH^–, H⁺), gaseous molecules (CO₂, H₂), enzymes and root border cells which have major direct or indirect effects on the acquisition of mineral nutrients required for plant growth. Phenolics and aldonic acids exuded directly by roots of N₂-fixing legumes serve as major signals to Rhizobiaceae bacteria which form root nodules where N₂ is reduced to ammonia. Some of the same compounds affect development of mycorrhizal fungi that are crucial for phosphate uptake. Plants growing in low-nutrient environments also employ root exudates in ways other than as symbiotic signals to soil microbes involved in nutrient procurement. Extracellular enzymes release P from organic compounds, and several types of molecules increase iron availability through chelation. Organic acids from root exudates can solubilize unavailable soil Ca, Fe and Al phosphates. Plants growing on nitrate generally maintain electronic neutrality by releasing an excess of anions, including hydroxyl ions. Legumes, which can grow well without nitrate through the benefits of N₂ reduction in the root nodules, must release a net excess of protons. These protons can markedly lower rhizosphere pH and decrease the availability of some mineral nutrients as well as the effective functioning of some soil bacteria, such as the rhizobial bacteria themselves. Thus, environments which are naturally very acidic can pose a challenge to nutrient acquisition by plant roots, and threaten the survival of many beneficial microbes including the roots themselves. A few plants such as Rooibos tea (Aspalathus linearis L.) actively modify their rhizosphere pH by extruding OH^– and HCO₃ ^– to facilitate growth in low pH soils (pH 3 – 5). Our current understanding of how plants use root exudates to modify rhizosphere pH and the potential benefits associated with such processes are assessed in this review.     

GISH and AFLP analyses of novel Brassica napus lines derived from one hybrid between B. napus and Orychophragmus violaceus

New Brassica napus inbred lines with different petal colors and with canola quality and increased levels of oleic (∼70%, 10% higher than that of B. napus parent) and linoleic (28%) acids have been developed in the progenies of one B. napus cv. Oro × Orychophragmus violaceus F₅ hybrid plant (2n=31). Their genetic constituents were analyzed by using the methods of genomic in situ hybridization (GISH) and amplified fragments length polymorphism (AFLP). No intact chromosomes of O. violaceus origin were detected by GISH in their somatic cells of ovaries and root tips (2n=38) and pollen mother cells (PMCs) with normal chromosome pairing (19 bivalents) and segregation (19:19), though signals of variable sizes and intensities were located mainly at terminal and centromeric parts of some mitotic chromosomes and meiotic bivalents at diakinesis or chromosomes in anaphase I groups and one large patch of chromatin was intensively labeled and separated spatially in some telophase I nuclei and metaphase II PMCs. AFLP analysis revealed that substantial genomic changes have occurred in these lines and O. violaceus–specific bands, deleted bands in ‘Oro’ and novel bands for two parents were detected. The possible mechanisms for these results were discussed.     

Production and characterization of intergeneric somatic hybrids between <Emphasis Type="Italic">Brassica napus</Emphasis> and <Emphasis Type="Italic">Orychophragmus violaceus</Emphasis> and their backcrossing progenies

Alien chromosome addition lines have been widely used for identifying gene linkage groups, assigning species-specific characters to a particular chromosome and comparing gene synteny between related species. In plant breeding, their utilization lies in introgressing characters of agronomic value. The present investigation reports the production of intergeneric somatic hybrids Brassica napus (2n = 38) + Orychophragmus violaceus (2n = 24) through asymmetric fusions of mesophyll protoplasts and subsequent development of B. napus-O. violaceous chromosome addition lines. Somatic hybrids showed variations in morphology and fertility and were mixoploids (2n = 51–67) with a range of 19–28 O. violaceus chromosomes identified by genomic in situ hybridization (GISH). After pollinated with B. napus parent and following embryo rescue, 20 BC₁ plants were obtained from one hybrid. These exhibited typical serrated leaves of O. violaceus or B. napus-type leaves. All BC₁ plants were partially male fertile but female sterile because of abnormal ovules. These were mixoploids (2n = 41–54) with 9–16 chromosomes from O. violaceus. BC₂ plants showed segregations for female fertility, leaf shape and still some chromosome variation (2n = 39–43) with 2–5 O. violaceus chromosomes, but mainly containing the whole complement from B. napus. Among the selfed progenies of BC₂ plants, monosomic addition lines (2n = 39, AACC + 1O) with or without the serrated leaves of O. violaceus or female sterility were established. The complete set of additions is expected from this investigation. In addition, O. violaceus plants at diploid and tetraploid levels with some variations in morphology and chromosome numbers were regenerated from the pretreated protoplasts by iodoacetate and UV-irradiation. Z. Zhao and T. Hu make equal contributions to this work.     

Effect of bicarbonate on root growth and accumulation of organic acids in Zn-inefficient and Zn-efficient rice cultivars (Oryza sativa L.)

Bicarbonate has been regarded as a major factor for inducing Zn deficiency in lowland rice, but the mechanisms responsible for this effect are not yet fully understood. The objective of the present study was to test whether early effects of bicarbonate (HCO₃ ⁻)are inhibition of root growth due to the accumulation of organic acids induced by HCO₃ ⁻. Solution culture experiments were conducted using two rice cultivars differing in susceptibility to Zn deficiency, and four bicarbonate concentrations (0, 5, 10, 20 mM). Bicarbonate (5–20 mM) strongly inhibited root growth of the Zn-inefficient cultivar within 4 days of treatments. In contrast, root growth of the Zn-efficient cultivar was slightly stimulated with bicarbonate at 5–10 mM and not affected at 20 mM. The inhibitory effect of bicarbonate on root growth in the Zn-inefficient cultivar was mainly that of impairment of new root initiation rather than suppression of elongation of individual roots. Bicarbonate (5–20 mM) increased the concentrations of malate, succinate and citrate in the roots of both cultivars, but to a greater extent for the Zn-inefficient than for the Zn-efficient cultivars. The results suggest that the impairment of root growth was likely to be the initial action of bicarbonate in inducing Zn deficiency in lowland rice, and the inhibitory effect of bicarbonate on root growth of the Zn-inefficient cultivar might result from high accumulation and an insufficient compartmentation of organic acids in the root cells.     

Comparison of photosynthetic activity of <Emphasis Type="Italic">Orychophragmus violaceus</Emphasis> and oil-seed rape

Orychophragmus violaceus, Brassica campestris cv. Chuanyou No.8, and Brassica juncea cv. Luzhousileng diurnal changes of net photosynthetic rate (P _N) and activities of carbonic anhydrase (CA) of leaves were studied. One uni-modal curve occurred at the diurnal changes of P _N in O. violaceus, but bimodal curves were found in B. campestris and B. juncea. Thus photosynthetic midday depression was not found in O. violaceus but in both Brassica species. Midday depression of P _N in O. violaceus was not related to high temperature or low humidity at midday but to the activity of CA.     

Metabolomic Responses of Guard Cells and Mesophyll Cells to Bicarbonate

Anthropogenic CO₂ presently at 400 ppm is expected to reach 550 ppm in 2050, an increment expected to affect plant growth and productivity. Paired stomatal guard cells (GCs) are the gate-way for water, CO₂, and pathogen, while mesophyll cells (MCs) represent the bulk cell-type of green leaves mainly for photosynthesis. We used the two different cell types, i.e., GCs and MCs from canola (Brassica napus) to profile metabolomic changes upon increased CO₂ through supplementation with bicarbonate (HCO₃ ^-). Two metabolomics platforms enabled quantification of 268 metabolites in a time-course study to reveal short-term responses. The HCO₃ ^- responsive metabolomes of the cell types differed in their responsiveness. The MCs demonstrated increased amino acids, phenylpropanoids, redox metabolites, auxins and cytokinins, all of which were decreased in GCs in response to HCO₃ ^-. In addition, the GCs showed differential increases of primary C-metabolites, N-metabolites (e.g., purines and amino acids), and defense-responsive pathways (e.g., alkaloids, phenolics, and flavonoids) as compared to the MCs, indicating differential C/N homeostasis in the cell-types. The metabolomics results provide insights into plant responses and crop productivity under future climatic changes where elevated CO₂ conditions are to take center-stage.     

不同氮处理下速生柳对水体氮的吸收、分配及生理响应

采用水培法,研究了旱柳苗在外源添加不同氮水平(贫氮、中氮、富氮、过氮)的铵态氮(NH+4-N)和硝态氮(NO-3-N)的生长、氮吸收、分配和生理响应。结果表明:一定范围氮浓度的增加能够促进旱柳苗的生长,但过量氮会抑制其生长,且NH+4-N的抑制作用大于NO-3-N;两种氮处理下,旱柳表现出对NH+4-N的吸收偏好,在同一氮水平时,旱柳各部位氮原子百分含量Atom%15N(AT%)、15N吸收量和来自氮源的N%(Ndff%)均为NH+4-N处理大于NO-3-N处理,且随着氮浓度的增加,差异增大,且在旱柳各部位的分布为根﹥茎﹥叶;2种氮素过量和不足均会对旱柳根和叶生理指标产生不同的影响,其中在过氮水平时,NH+4-N和NO-3-N处理下根系活力比对照减少了50.61%和增加了19.53%;在过氮水平时,NH+4-N处理柳树苗根总长、根表面积、根平均直径、根体积和侧根数分别对照下降了30.92%、29.48%、19.44%、27.01%和36.41%,NO-3-N处理柳树苗相应的根系形态指标分别对对照下降了1.66%、5.65%、1.49%、5.06%和25.72%。可见,高浓度NH+4-N对旱柳苗的胁迫影响大于NO-3-N,在应用于水体氮污染修复时可通过改变水体无机氮的比例,削弱其对旱柳的影响,从而提高旱柳对水体氮污染的修复效果。     

碳酸氢盐处理下桑树和构树的生长、光合和抗逆性差异

为探究喀斯特生境中,在碳酸氢盐的胁迫下HCO^-₃对植株生长及生理特性的影响,该文以构树和桑树幼苗为研究对象,对不同浓度NaHCO₃溶液(0、15、30 mmol·L^-1)处理下植株的生长情况、光合能力、抗氧化酶活性、渗透调节物质含量和细胞膜系统损伤情况进行研究。结果表明:(1)在HCO^-₃处理下,构树和桑树的生长和光合能力均受到抑制,叶片细胞内均发生显著的抗氧化和抗渗透胁迫生理响应。(2)HCO^-₃对构树和桑树生长的抑制作用与其浓度有关,并有显著差异性(P<0.05)。(3)30 mmol·L^-1 HCO^-₃处理对植株生长、光合、抗氧化酶系统和渗透调节系统的抑制作用以及植物细胞的损伤情况要显著强于15 mmol·L^-1 HCO^-₃处理的效果。(4)同等浓度的HCO^-₃处理下,构树的生长、光合能力、抗氧化酶活性、渗透调节物质含量显著高于桑树,其叶片细胞损伤情况显著低于桑树。综上结果均表明,构树对碳酸氢盐胁迫的耐受能力要优于桑树。该研究为阐明桑科植物对喀斯特环境适应机制提供科学支撑。     

Mobilization of Cu and Zn by root exudates of dicotyledonous plants in resin-buffered solutions and in soil

It has been frequently suggested that root exudates play a role in trace metal mobilization and uptake by plants, but there is little in vivo evidence. We studied root exudation of dicotyledonous plants in relation to mobilization and uptake of Cu and Zn in nutrient solutions and in a calcareous soil at varying Cu and Zn supply. Spinach (Spinacia oleracea L.) and tomato (Lycopersicon esculentum L.) were grown on resin-buffered nutrient solutions at varying free ion activities of Cu (pCu 13.0–10.4) and Zn (pZn 10.1–6.6). The Cu and Zn concentrations in the nutrient solution increased with time, except in plant-free controls, indicating that the plant roots released organic ligands that mobilized Cu and Zn from the resin. At same pCu, soluble Cu increased more at low Zn supply, as long as Zn deficiency effects on growth were small. Zinc deficiency was observed in most treatment solutions with pZn ≥ 9.3, but not in nutrient solutions of a smaller volume/plant ratio in which higher Zn concentrations were observed at same pZn. Root exudates of Zn-deficient plants showed higher specific UV absorbance (SUVA, an indicator of aromaticity and metal affinity) than those of non-deficient plants. Measurement of the metal diffusion flux with the DGT technique showed that the Cu and Zn complexes in the nutrient solutions were highly labile. Diffusive transport (through the unstirred layer surrounding the roots) of the free ion only could not explain the observed plant uptake of Cu and of Zn at low Zn²⁺ activity. The Cu and Zn uptake by the plants was well explained if it was assumed that the complexes with root exudates contributed 0.4% (Cu) or 20% (Zn) relative to the free ion. In the soil experiment, metal concentrations and organic C concentrations were larger in the solution of planted soils than in unplanted controls. The SUVA of the soil solution after plant growth was higher for unamended soils, on which the plants were Zn-deficient, than for Zn-amended soils. In conclusion, root exudates of dicotyledonous plants are able to mobilize Cu and Zn, and plants appear to respond to Zn deficiency by exuding root exudates with higher metal affinity.