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1.
间作对玉米根系分泌物及团聚体稳定性的影响   总被引：8，自引：1，他引：7  
通过田间小区试验种植玉米(玉米单作、玉米∥大豆、玉米∥马铃薯),测定3个生育期(拔节期、大喇叭口期、抽雄期)玉米根系分泌总糖含量、总有机酸含量和土壤团聚体状况,分析间作对玉米根系分泌物及团聚体稳定性的影响。结果表明:玉米根系分泌总糖含量和总有机酸含量随生育期的推移而增加,间作显著提高玉米根系分泌总糖含量和总有机酸含量,玉米∥马铃薯玉米∥大豆。在抽雄期,玉米∥大豆、玉米∥马铃薯相比玉米单作0.25mm水稳性团聚体含量(R_(0.25))分别显著提高6.19%,8.17%;平均质量直径(MWD)分别提高5.04%,10.08%;几何平均直径(GMD)分别提高6.12%,12.24%;分形维数(D)分别显著降低0.72%,1.09%;团聚体破坏率(PAD)分别显著降低16.77%,26.08%。在根系分泌物最大的抽雄期,玉米根系分泌总糖含量、总有机酸含量与R_(0.25),GMD,D,PAD呈极显著相关关系(P0.01)。因此,间作可通过增加玉米根系分泌总糖含量和总有机酸含量,进而提高土壤团聚体的稳定性。  相似文献   

2.
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.  相似文献   

3.
The soil organic matter plays a key role in ecological soil functions, and has to be considered as an important CO2 sink on a global scale. Apart from crop residues (shoots and roots), left over on the field after harvest, carbon and nitrogen compounds are also released by plant roots into the soil during vegetation, and undergo several transformation processes. Up to now the knowledge about amount, composition, and turnover of these root‐borne compounds is still very limited. So far it could be demonstrated with different plant species, that up to 20 % of photosynthetically fixed C are released into the soil during vegetation period. These C amounts are ecological relevant. Depending on assimilate sink strength during ontogenesis, the C release varies with plant age. A large percentage of these root‐borne substances were rapidly respired by microorganisms (64—86 %). About 2—5 % of net C assimilation was kept in soil. The root exudates of maize were mainly water‐soluble (79 %), and in this fraction about 64 % carbohydrates, 22 % amino acids/amides and 14 % organic acids could be identified. Plant species and in some cases also plant cultivars varied strongly in their root exudation pattern. Under non‐sterile conditions the exuded compounds were rapidly stabilized in water‐insoluble forms and bound preferably to the soil clay fraction. The binding of root exudates to soil particles also improved soil structure by increasing aggregate stability. Future research should focus on quantification and characterization of root‐borne C compounds during the whole plant ontogenesis. Apart from pot experiments with 14CO2 labeling, it is necessary to conduct model field experiments with 13CO2 labeling in order to be able to distinguish between CO2 originating from the soil C pool and rhizosphere respiration, originating from plant assimilates. Such a separation is necessary to assess if soils are sources or sinks of CO2. The incorporation of root‐borne C (14C, 13C) into soil organic matter of different stability is also of particular interest.  相似文献   

4.
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.  相似文献   

5.
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。  相似文献   

6.
Field and pot experiments showed that the P demand of wheat is highest in early stages of growth (up to 1.67 μg P per cm2 root surface and day). The needed orthophosphate ions H2PO4? and HPO42-move from soil to the root by diffusion. This process is controlled by the concentration gradient of the diffusible phosphate and the effective diffusion coefficient according to Pick's first law. Root excretions (rhizodeposition) are able to affect both characteristics. The water soluble portion of rhizodeposition contains more than 50% of up to 8 different sugars, 10–40% carboxylic acids and 10–15 amino acids and amides. The composition varies in dependence on the age of the root parts and on nutrition (Zea mays L., Brassica napus L., Pisum sativum L.). Diffusion experiments using small soil blocks showed that 50–75% of the root exudates were decomposed by respiration within 3 days. The rest was largely chemically converted. Originally present sugars disappeared. Due to the biosynthesis of different organic acids from the individual sugars the mobilisation of Ca3(PO4)2 by Pantoea agglomerans increased when the sugar mixture was derived from the rhizodeposition of P deficient plants with more pentoses instead of glucose and fructose (mainly effect of anions). In the rhizosphere therefore a mixture of rhizodeposition and its conversion products exists which affects the binding of phosphorus in soil and the P transport to the root. This should be considered both for the development of new soil extractants and for modelling the P supply to plants.  相似文献   

7.
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.  相似文献   

8.
The methods used for estimating below‐ground carbon (C) translocation by plants, and the results obtained for different plant species are reviewed. Three tracer techniques using C isotopes to quantify root‐derived C are discussed: pulse labeling, continuous labeling, and a method based on the difference in 13C natural abundance in C3 and C4 plants. It is shown, that only the tracer methods provided adequate results for the whole below‐ground C translocation. This included roots, exudates and other organic substances, quickly decomposable by soil microorganisms, and CO2 produced by root respiration. Advantages due to coupling of two different tracer techniques are shown. The differences in the below‐ground C translocation pattern between plant species (cereals, grasses, and trees) are discussed. Cereals (wheat and barley) transfer 20%—30% of total assimilated C into the soil. Half of this amount is subsequently found in the roots and about one‐third in CO2 evolved from the soil by root respiration and microbial utilization of rootborne organic substances. The remaining part of below‐ground translocated C is incorporated into the soil microorganisms and soil organic matter. The portion of assimilated C allocated below the ground by cereals decreases during growth and by increasing N fertilization. Pasture plants translocated about 30%—50% of assimilates below‐ground, and their translocation patterns were similar to those of crop plants. On average, the total C amounts translocated into the soil by cereals and pasture plants are approximately the same (1500 kg C ha—1), when the same growth period is considered. However, during one vegetation period the cereals and grasses allocated beneath the ground about 1500 and 2200 kg C ha—1, respectively. Finally, a simple approach is suggested for a rough calculation of C input into the soil and for root‐derived CO2 efflux from the soil.  相似文献   

9.
Estimation of the amount of root exudates and simultaneous identification of their composition in non‐sterile soil is a challenging objective in rhizosphere research. We coupled 3 methods: (1) labeling of corn in 14CO2 atmosphere to separate root‐derived and soil‐derived organic substances in the rhizosphere, (2) a previously developed leaching method to collect rhizodeposits, and (3) pyrolysis field ionization mass spectrometry (Py‐FIMS) to investigate the molecular‐chemical composition of rhizodeposits. Eluted rhizodeposits accounted for 2.8 % (Loam) and 0.97 % (nutrient solution in quartz sand) of recovered 14C and showed clear differences in composition between the growth substrates. The 14CO2 evolved mostly by root respiration accounted for 3.5–4.0 % without significant differences according to growth substrate or diurnal dynamics. Principal component analysis of the Py‐FI mass spectra of leachates showed a clear diurnal dynamics of the amount and the composition of corn rhizodeposits collected during day‐time and night‐time. Differences originated mostly from signals assigned to carbohydrates, sterols, and peptides. This approach is recommended for forthcoming studies of rhizodeposition in different soil substrates, crops grown, and time‐series of exudate sampling.  相似文献   

10.
This study assesses the influence of saccharides in the rhizodeposition on the phosphate solubilizing ability of rhizosphere bacteria. Water‐soluble rhizodeposits were analyzed of 14C‐labeled pea plants (Pisum sativum, cv. ‘Grapis’) which were grown at two different levels of P‐nutrition. The sugars produced were fed in vitro either as single compounds or as synthetic mixtures to three bacterial strains and the ability of the bacteria to mobilize Ca3(PO4)2 was measured. The relative glucose proportion of pea exudates decreased under P deficiency while the content of galactose, ribose, xylose and fucose increased. In vitro feeding of single sugars and sugar mixtures showed that the ability of Pseudomonas fluorescens (PsIA12) to dissolve tertiary calcium phosphate was lower with pentoses and the mixed sugars of the P‐deficient plants than with glucose. On the other hand, the shifted sugar pattern observed under P deficiency increased the phosphate mobilization ability of Pantoea agglomerans (D5/23) and Azospirillum sp. (CC 322) considerably. This observation can only partly be explained by the acidification of the nutrient medium. Bacteria also produced different carboxylic anions depending on sugar supply. In addition to low‐molecular mono‐, di‐, and tricarboxylic acids which are known as P‐solubilizing substances, sugar acids also played an important role in cultures D 5/23 and CC 322.  相似文献   

11.
Various methods have been suggested to separate root and microbial contributions to soil respiration. However, to date there is no ideal approach available to partition below-ground CO2 fluxes in its components although the combination of traditional methods with approaches based on isotopes seems especially promising for the future improvement of estimates. Here we provide evidence for the applicability of a new approach based on the hypothesis that root-derived (rhizomicrobial) respiration, including root respiration and CO2 derived from microbial activity in the immediate vicinity of the root, is proportional to non-structural carbon contents (sugars and organic acids) of plant tissues. We examined relationships between root-derived CO2 and non-structural carbon of rice (Oryza sativa) seedlings using 14C pulse labelling techniques, which partitioned the 14C fixed by photosynthesis into root-derived 14CO2, and 14C in sugars and organic acids of roots and shoots. After the 14C pulse 14C in both sugars and organic acids of plant tissues decreased steeply during the first 12 h, and then decreased at a lower rate during the remaining 60 h. Soil 14CO2 efflux and soil CO2 efflux strongly depended on 14C pools in non-structural carbon of the plant tissues. Based on the linear regression between root-derived respiration and total non-structural carbon (sugars and organic acids) of roots, non-rhizomicrobial respiration (SOM-derived) was estimated to be 0.25 mg C g−1 root d.w. h−1. Assuming the value was constant, root-derived respiration contributed 85–92% to bulk soil respiration.  相似文献   

12.
Root exudates comprising soluble low‐molecular‐weight organic compounds (LMWOCs) play a crucial role in the rhizosphere processes. Therefore, accurate determination of the composition and quantity of these compounds is of importance. A continuous trapping system (CTS) with XAD‐4 macroporous resin is widely used for collecting root exudates in hydroponics, and ion exchange resins are used in the separation of root exudates into neutral, acid and basic fractions. Here, we studied the adsorption equilibrium isotherms and dynamic adsorption properties of 27 standard LMWOCs on XAD‐4 resin. The adsorption isotherms of most LMWOCs matched the Langmuir isotherm equations. Furthermore, we investigated the adsorption efficiency of the CTS for LMWOCs and the recovery ratios during fractionation by ion exchange resins. The adsorption capacities of the CTS for LMWOCs which are non‐polar or having large non‐polar moieties were higher. The recovery ratios of most LMWOCs were larger than 80% during fractionation. The overall recovery ratios of LMWOCs were ca. 10, 20, and 30% for sugars, organic acids, and amino acids, respectively. Using this collection method, we present the composition and quantity of root exudates of cucumber (Cumumis sativus L.) at four different growth stages. The major components of root exudates were similar to previous works, whereas the quantities were different. The various collection methods may be the main reason for these differences. Therefore, it is necessary to study the overall recovery ratios when the compositions of root exudates via different collection methods are compared.  相似文献   

13.
Previous studies describe the suitability of a new type of phosphorus (P) fertilizer, called “rhizosphere‐controlled fertilizer” (RCF), to supply available P to plants while reducing soil phosphorus fixation. In order to explore the involvement of organic acid root exudation in P uptake from RCF, we investigated the relationship between shoot and root P concentrations, and the concentration of the main polycarboxylic organic acids in roots, shoots, and plant exudates. Plant species with different P‐acquisition efficiency (low: maize; medium: chickpea; high: lupin) were grown in hydroponics with three different P fertilizers: The water‐insoluble P fraction of RCF (RCF); Phospal, a slow‐release source of phosphate composed of calcium and aluminum phosphates (PH); monopotassiumphosphate (KP), and a control treatment without P (P–). RCF was as efficient as KP in supplying P to plants in the case of chickpea and lupin, and slightly less efficient than KP in maize. However, P from PH was not available for maize and less available compared to KP and RCF in chickpea and lupin. This variation reflects the different efficiencies in P acquisition for the three plant species. Except in the case of maize, plants receiving KP presented the lowest concentration of organic acids in roots and exudates, while those plants suffering severe P deficiency (P– and PH) showed the highest organic acid concentration. However, RCF had a high concentration of organic acids in roots and exudates, as well as a high P concentration in the shoot indicating that P uptake from RCF is enhanced due to root release and action of specific organic acids.  相似文献   

14.
In leguminous root nodules, bacteroids are differentiated from rhizobia and are surrounded by a peribacteroid membrane (PBM) forming an intracellular structure designated as symbiosome. Through the peribacteroid space (PBS) between the PBM and bacteroids, metabolic substances and signal compounds are exchanged between two symbionts. In this study, organic compounds with low molecular weight in the PBS were collected from isolated symbiosomes of soybean (Glycine max L.) root nodules, and their composition was analyzed and compared with that of the organic compounds in whole root nodules and bacteroids. Major differences were detected in the molar percentages of amino and organic acids, and sugars, to the total low molecular weight organic compounds among whole root nodules, PBS, and bacteroids. The PBS composition was characterized by abundant sugars and poor amino acids. Also the composition of the amino acids, organic acids, and sugars in the PBS was clearly different from that in whole root nodules and bacteroids. The PBS sugar composition was characterized by the predominance of inositols, especially myo-inositol at the 5th and 7th weeks of the host plant growth stages. Changes in the myo- and D-chiro- inositol balance at the host plant growth stages occurred and a syntony was observed between the PBS and bacteroids. The localization of myo-inositol in the PBS accounted for almost 70% of the total myo-inositol in root nodules. A small difference in the PBS composition between two soybean cultivars was recorded but it varied with the growth stages. It was tentatively concluded that the PBS sugar composition affected the bacteroidal sugar composition in soybean plants, and that inositol utilization in the bacteroids could be a factor controlling the bacteroidal function level which varied with the host plant growth stages.  相似文献   

15.
We conducted a 13CO2 pulse-chase labelling experiment in a drained boreal organic (peat) soil cultivated with perennial crop, reed canary grass (RCG; Phalaris arundinacea) to study the flow of carbon from plants to soil microbes. Both limed and unlimed soils were studied, since liming is a common agricultural practice for acidic organic soils. Soil samples taken within three months after the labelling and three times in the following year were used for the δ13C analysis of microbial phospholipid fatty acids (PLFAs), root sugars and root lipids. We estimated the contribution of carbon from root exudates to microbial PLFA synthesis. The flow of carbon from plants to microbes was fast as the label allocation in PLFAs had a peak 1–3 days after labelling. The results showed that fungi were important in the incorporation of fresh, plant-derived carbon, including root sugars. None of the main microbial PLFA biomarker groups (fungi, Gram-positive bacteria, Gram-negative bacteria, arbuscular mycorrhizal fungi) was completely lacking label over the measurement period. One year after the labelling, when the labelled carbon was widely distributed into plant biomass and soil, bacterial biomarkers increased their share of the label allocation. Liming had a minor effect on the label allocation rate into PLFAs. The mixing model approach used to calculate the root exudate contribution to microbial biomass resulted in a highly conservative estimate of utilization of this important C-source (0–6.5%, with highest incorporation into fungi). In summary, the results of this study provide new information about the role of various microbial groups in the turnover of plant-derived, fresh carbon in boreal organic soil.  相似文献   

16.
Most studies showing potential organic nitrogen uptake were conducted with amino acids. They conclude that, in some ecosystems, amino acids significantly contribute to the N demand of plants and that roots have special transporters to re-uptake amino acids released into the rhizosphere. However, the relevance of the uptake of organic N compounds can only be evaluated by comparing the uptake of N-containing and N-free organic substances. We compared the uptake of alanine, glucose and acetate labelled with 14C by maize. Additionally, the N uptake was estimated by 15N labelled alanine and KNO3. We found a similar uptake of 14C from alanine, glucose and acetate, amounting for the whole plant less than 1% of 14C input. These results show that maize did not prefer N-containing to N-free organic substances. The uptake of 15N by maize exceeded that of 14C (10- to 50-fold), irrespective of the 15N source. However, plant uptake of nitrate (23.6–35.2% of 15N input) always exceeded the uptake of N from alanine (9.6–28.8%). The uptake of organically bound N by maize growing in soil occurred mainly by transpiration flow – as dissolved organics. The contribution of specific amino acid transporters was minor.  相似文献   

17.
《Journal of plant nutrition》2013,36(12):2391-2401
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.  相似文献   

18.
In an effort to improve our understanding of the specific apple replant disease (SARD), direct and indirect effects of phytohormones and related compounds (abscisic acid, 6‐benzyladenine, indole‐3‐acetic acid, 1‐naphthaleneacetic acid, and gibberellins GA3 or GA4) on root exudates of apple seedlings were evaluated as a potential mediating factor in the infection process. In the first type of experiments, radioactively labeled hormonal substances were applied to the stumps of decapitated apple‐seedlings and the occurrence of radioactivity in root exudates and their qualitative characterization were examined (direct influence). In another set of experiments, the effects of leaf‐applied plant growth regulators on the amount and composition of the predominant organic acids, carbohydrates, and amino acids/amides were studied. Cherry seedlings resistant to SARD and apple seedlings with dormant apical buds and, thus, not susceptible to infection were used for comparison. The results showed no differences in exudation of applied plant growth regulators between growing cherry and apple seedlings. Thus, a direct effect of plant hormones on the infection process is unlikely. However, leaf treatments with growth regulators, in particular with auxin‐type compounds and abscisic acid, increased exudation of alditols. This may indicate that plant hormones are, to some degree, indirectly involved in the infection process.  相似文献   

19.
ABSTRACT

The effect of cadmium (Cd) on root exudates of sorghum and maize was investigated in order to get further insight into the mechanisms of plant tolerance to Cd. Plants were grown hydroponically and supplemented with: 0, 0.5, and 5.0 mg Cd L? 1. Hydroponic solutions containing exudates were analyzed by high performance liquid chromatography (HPLC). The results showed different exudation patterns by sorghum and maize with cadmium supply. While sorghum enhanced malate exudation over the entire range of applied Cd in the uptake solutions, maize increased mainly citrate. Moreover, malate concentration exuded in sorghum rhizosphere presented higher values than citrate (from maize). With the aid of the HYPERQUAD speciation program, a significant decrease in the bioavailable Cd (free Cd plus Cd chloro-complexes) was found due to the increase of Cd organic complexation in the hydroponic solution. Furthermore, similar metal organic complex concentrations were obtained for both plants, which turned the maize and sorghum overall detoxification process equivalent. Exudation of malate and citrate should contribute to tolerance mechanisms of these plants, reducing deleterious effects of free Cd on root growth. These findings support the idea that the metal-binding capabilities of root exudates may be an important mechanism for stabilizing metals in soil.  相似文献   

20.
为探讨马铃薯连作障碍的可能机理,在大田条件下,以轮作为对照(CK),收集连作5年(CP5)马铃薯植株在不同生育期的根系分泌物,采用GC-MS对根系分泌物的主要成分进行了鉴定,并通过生物检测验证了根系分泌物的自毒效应。结果表明:CK和CP5处理的马铃薯在不同生育期的根系分泌物均鉴定出糖类、酸类、胺类、脂类、醇类和嘧啶类等成分,以糖类和酸类物质居多;CP5处理根系分泌物的成分较CK复杂,酸类物质含量有升高的趋势。连作改变了马铃薯根系分泌物的化学组成和含量:CP5处理在苗期、现蕾期和开花期的根系分泌物中均鉴定出邻苯二甲酸二丁酯,相对含量分别为0.16%、0.21%和0.24%,CK处理未检测到;CP5处理在苗期、现蕾期和开花期的根系分泌物中均鉴定出棕榈酸,相对含量分别为0.34%、1.12%和0.47%,CK处理仅在现蕾期和开花期鉴定出棕榈酸的存在,但相对含量仅为0.56%和0.24%。生物检测试验结果表明,棕榈酸和邻苯二甲酸二丁酯显著抑制了马铃薯生长,1 mmol·L-1棕榈酸和邻苯二甲酸二丁酯对马铃薯生长的抑制作用远远大于0.5 mmol·L-1的抑制作用。棕榈酸和邻苯二甲酸二丁酯是马铃薯根系分泌的自毒物质,但二者未表现出物质的叠加效应。现蕾期马铃薯根系分泌物所含的物质最多,是马铃薯根系分泌物收集的适宜时期。  相似文献   

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