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1.
For better understanding of mechanisms responsible for differences in uptake and distribution of cadmium (Cd) and nickel (Ni) in different plant species, nutrient solution experiments were conducted with four plant species [bean (Phaseolus vulgaris L.), rice (Oryza saliva L.), curly kale (Brassica oleracea L.) and maize (Zea mays L.)]. The plants were grown in a complete nutrient solution with additional 0.125 and 0.50 μM Cd or 0.50 and 1.00 μM Ni. Large differences in Cd and Ni concentrations in shoot dry matter were found between plant species. Maize had the highest Cd concentration in the shoots, and bean the lowest. Contrary to Cd, the Ni concentrations were highest in the shoots of bean and the lowest in maize. A gradient of Cd concentrations occurred in bean and rice plants with the order roots > > stalk base >> shoots (stems/sheaths > leaves). A similar gradient of Ni concentrations was also found in maize and rice plants. In the xylem sap, the Cd and Ni concentrations were positively correlated with Cd and Ni concentrations in the shoot dry matter. In the roots of maize, about 60% of Cd could be extracted with Tris‐HCl buffer (pH 8.0), while in roots of other plant species this proportion was much lower. This higher extractability of Cd in the roots of maize is in accordance with the higher mobility as indicated by the higher translocation of Cd from roots to shoots and also the higher Cd concentrations in the xylem sap in maize than in the other plant species. Similarly, a higher proportion of Ni in the soluble fraction was found in the roots of bean compared with maize which is in agreement with the higher Ni accumulation in the shoots of bean. The results of gel‐filtration of the soluble extracts of the roots indicated that phytochelatins (PCs) were induced in the roots upon Cd but not Ni exposure. The higher Cd concentrations and proportions of Cd bound to PC complexes in the roots of maize compared with the other plant species suggest that PCs may be involved in the Cd trans‐location from roots to shoots. 相似文献
2.
Cadmium (Cd) is toxic to plants, animals, and humans. However, different plant species growing on the same soil may have very different shoot Cd concentrations depending on properties such as size of the root system, Cd net influx, shoot‐growth rate, Cd translocation from root to shoot, and the ability to affect Cd availability in the soil. To investigate possible reasons for different shoot Cd concentrations maize, sunflower, flax, and spinach were grown on an acid sandy soil (pH<$>_{{\rm{(CaCl}}_{\rm{2}} {\rm)}<$> 4.5, and Corg 2.8%) in a growth chamber with Cd additions as Cd(NO3)2 of none, 14, and 40 μmol (kg soil)–1 resulting in Cd soil‐solution concentrations of 0.04, 0.68, and 2.5 μM. Only the high Cd addition caused a significant growth reduction of flax and spinach. The shoot Cd concentration was up to 30 times higher in spinach than in maize; the other species were intermediate. Of the plant properties studied only the variation of the Cd net influx explained the differences in shoot Cd concentrations. This was due to a decreased (maize, sunflower) or increased (flax) Cd concentration in soil solution or more effective uptake kinetics (spinach). 相似文献
3.
Cadmium (Cd) uptake by lettuce (Lactuca sativa L.) was studied in a hydroponic solution study at concentrations approaching the total concentration in contaminated soil solutions. Four cultivars of lettuce were tested (Divina, Reine de Mai, Melina, and J.44). Ten 12‐day old seedlings, pretreated in 0.5 μM CdCl2 solution, were labelled with carrier free 109CdCl2 (from 0.05 μM to 5 μM Cd in nutrient solution) in the presence and absence of metabolic inhibitors, DNP and DCCD. Cadmium taken up by the roots was determined after a 30 min desorption in unlabelled CdCl2 solution. In the absence of metabolic inhibitors and at 5 μM Cd, root absorbed from 2.5 to 8 mg Cd/g root dry weight. Exchangeable Cd measured after desorption represented less than 1% of the total Cd absorbed by the root. Cadmium absorption in presence of DNP showed that approximately 80% of the Cd enters the cell through an active process. This mechanism seems to be directly associated with H+‐ATPase as observed with DCCD inhibition. Varietal differences in shoot Cd uptake were only demonstrated at concentrations below 0.1 μM. Screening lettuce cultivars only by the Cd level in the tissue seems not to be possible for these cultivars except at concentrations close to that in the soil solution. But differences in relative contribution of uptake mechanisms in total Cd absorption were observed. High levels of Cd in roots were correlated with high contri‐ butions from H+‐ATPase in the active process of Cd uptake. 相似文献
4.
Net release and net uptake of sugars by roots of intact maize (Zea mays cv. Blizzard) and field bean (Vicia faba L. cv. Alfred) were studied at micromolar external sugar concentrations that are relevant to the rhizosphere. Besides various sugars not further characterized there was net release of glucose, fructose, sucrose, arabinose, ribose, and galactose. The net release of these sugars into the root medium (0.1 mM CaSO4) was stimulated by the protonophore CCCP (10 μM), the sulfhydryl reagent NEM (300 μM), the specific inhibitor of plasmalemma H+ ATPase vanadate (0.5 mM), and by the inhibitor of the glucose carrier phlorizin (2 mM). Net uptake of glucose, fructose, and arabinose from 10 μM external concentrations was inhibited by these substances. Stimulation of net release and inhibition of net uptake was most pronounced for glucose. Sucrose added to the root medium was hydrolyzed by invertase activity leading to glucose and fructose uptake by roots. It is concluded that the retention of sugars by plant roots is not only determined by plasmalemma permeability but is also controlled by the H+ electrochemical gradient established by ATPase activity (retrieval mechanism). The proton gradient drives a sugar/H+ cotransport system that is selective for glucose but may also transport other sugars, particularly in the absence of glucose. 相似文献
5.
For better understanding of mechanisms responsible for genotypic differences in uptake and translocation of cadmium (Cd) in different plant species, two maize (Zea mays L.) inbred lines (B37 and F2) and a bean (Phaseolus vulgaris L.) cultivar (Saxa) were grown in a complete nutrient solution with additional 0.5 μM Cd and 250 μM buthionine sulfoximine (BSO), an inhibitor of PC synthesis, alone or in combination. The maize line B37 had a much higher Cd content in shoots (116.2 mg Cd kg?1 dry wt.) than F2 (32.7 mg Cd kg?1 dry wt.) and bean (1.83 in leaves, and 2.85 mg Cd kg?1 dry wt. in stems), whereas in roots the Cd content was much higher in bean (602.6 mg Cd kg?1 dry wt.) than in maize (427.1 mg Cd kg?1 dry wt. in B37, and 428.2 mg Cd kg?1 dry wt. in F2). Application of BSO markedly decreased Cd contents in roots of bean and maize lines, and also Cd contents in shoots and stem basis of both maize lines, while Cd contents in leaves, stems and stem basis of bean were not reduced by BSO. In root extracts (Tris-HCl buffer, pH 8.0) the proportion of Cd in the soluble fraction was much lower in bean (29.6%) than in the maize lines B37 (58.6%) and F2 (60.1%). Compared with the whole root tissue, Cd contents in the stele of the roots were much lower, especially in bean, and decreased by BSO in both maize lines, but not in bean. Gel-chromatography of root extracts strongly suggested that in the soluble fraction about 80% of the Cd was present as Cd-phytochelatin (PC) complexes in B37, whereas in F2 this Cd fraction accounted for about 50%, and in bean only for a few percent in the soluble fraction, Our results suggest that Cd-PC complexes constitute a mobile form in plants. The lower proportion of Cd in the soluble fraction as well as lower PC production in roots of bean compared to maize lines may be the main reasons for the very low Cd translocation from roots to shoots in bean plants. 相似文献
6.
Cadmium (Cd) uptake by white lupin (Lupinus albus) was studied at low Cd concentrations (0.05nM to 5 μM) in hydroponic solution. Ten 12‐day old seedlings were pretreated in 0.5 mM CaCl2 solution in presence and absence of metabolic inhibitors (DCCD, DNP or NaN3). Cadmium solutions were labelled with carrier free 109CdCl2. Cadmium uptake was measured after a 2 h desorption in unlabelled CdCl2 solution. In the absence of any metabolic inhibitor and at 5 [μM Cd, roots absorbed 235.23 μg Cd/g root dry weight. Over the range of lnM to 5 μM Cd, exchangeable Cd represented approximately 5% of the absorbed fraction, and about 25 % of the total absorbed Cd was adsorbed to the root. Cadmium was passively absorbed to about 30% as observed in the presence of the inhibitor (DCCD). Ative absorption which represented 70% of Cd uptake involved H+‐ATPase carriers. Cadmium absorption was reduced to 30 and 20% in presence of lanthanum (La3+) and zinc (Zn2+), respectively which suggested that calcium (Ca), Cd, and Zn use the same carriers. Cadmium uptake in presence of DNP or NaN3 was approximately 4‐ fold that in control. Data showed presomption for an excretion of Cd out of root cells which could be the expression of a detoxification process limiting cell contamination. 相似文献
7.
《Communications in Soil Science and Plant Analysis》2012,43(9-10):1517-1531
Abstract A pot experiment was conducted to investigate the effects of different cadmium (Cd) concentrations of phaeozem on growth and uptake of Cd and mineral nutrient copper (Cu) and zinc (Zn) by three maize genotypes in the mature stage. The results showed that the dry‐matter accumulation of shoots was inhibited by added Cd for Jidan209 and Jitian6, but this did not influence Chunyou30. The root biomasses decreased significantly for Jitian6 and stimulated Jidan209 and Chunyou30. Yields of three genotypes of maize were decreased by increasing soil Cd concentrations. Among them, Chunyou30 had a high tolerance and Jitian6 was most sensitive to Cd. The accumulation order of Cd in different parts of plants was root > leaf > stem > grain. The percentage of absorbed Cd by roots was 70–85% of total absorbed amount. Cadmium uptake by maize in the mature stage had a significant genetic variation: Jitian6 > Jidan209 > Chunyou30 for root, stem and leaf, and Jidan209 > Jitian6 > Chunyou30 for grain, respectively. Increase of soil Cd had no significant effect on Zn concentration of leaves, but there was a significant genetic variation: Chunyou30 > Jidan209 > Jitian6 (P=0.023). Cu concentration of leaves was increased significantly with increase of soil Cd (P<0.01), but no genetic variation was observed. 相似文献
8.
不同积累型苋菜(Amaranthus mangostanus L.)镉吸收转运特征差异性研究 总被引：1，自引：1，他引：0
9.
Maize (Zea mays L.) and sunflower (Helianthus annuus L.) grown on a calcareous soil showed poor growth and/or were chlorotic in spite of abundant Fe in the roots. It has been
hypothesized that microbial siderophores chelate Fe (III) in the soil, and that in this form Fe is transported towards the
root apoplast. On the calcareous soil, total and apoplastic root Fe concentrations were high, probably because of a high apoplastic
pH depressing Fe (III)-reductase activity and thus the Fe2+ supply to the cytoplasm. On the acidic soil, total and apoplastic root Fe concentrations were low, probably because of a
low apoplastic pH favouring Fe (III) reduction, hence plants showed no Fe-deficiency symptoms. The main objective of the present
work was to investigate the role of microbial soil activity in plant Fe acquisition. For this purpose, plants were grown under
sterile and non-sterile conditions on a loess loam soil. Plants cultivated under non-sterile conditions grew well, showed
no Fe-deficiency symptoms and had fairly high Fe concentrations in the roots in contrast to plants grown in the sterile medium.
Low root and leaf Fe concentrations in the axenic treatments indicated that the production of microbial siderophores was totally
suppressed. Accordingly, sunflowers were severely chlorotic and this was associated with very poor growth, whereas in maize
only growth was drastically reduced. In maize under sterile conditions, root apoplastic and total Fe concentrations were not
as low as in sunflowers, which may have indicated that phytosiderophores produced in maize partly sustained Fe acquisition,
but due to poor growth were not as efficient in supplying Fe as microbial activity under natural conditions. It may be therefore
assumed that in natural habitats soil microbial activity is of pivotal importance for plant Fe acquisition.
Received: 11 March 1999 相似文献
10.
The effect of local nutrient supply to maize roots (Zea mays L. cv. Blizzard) on net proton release was studied using the split root technique (SRNS, SRCa) to compare plants that were cultivated with their roots completely in either nutrient solution (NS) or 0.1 mM CaSO4 (Ca). Roots in NS released more protons than roots in Ca. This higher net proton release was associated with significantly higher ATP concentrations in the root tissue. Higher net proton release and ATP concentrations were also observed after a 4 h lag phase when 20 μM abscisic acid were exogenously applied to roots in 0.1 mM CaSO4. It is suggested that higher metabolic activity in roots supplied with nutrients increased ATP concentrations and thus the substrate supply of the plasma membrane H+ ATPase. When only half of the root system was supplied with nutrient solution with the other half bathed in 0.1 mM CaSO4, the roots in the SRNS compartment released significantly higher amounts of protons relative to the NS control plants. Conversely, roots in the SRCa compartment showed net proton uptake in contrast to the roots of control plants in 0.1 mM CaSO4 which significantly acidified the root medium. These differences in proton release by roots in the split root system and control roots could not be explained in terms of differences in ATP concentrations. It is therefore suggested that an internal signal may lead to a modification of the plasma membrane H+ ATPase as shown earlier during plant adaptation to low pH in the root medium. 相似文献
11.
The objective of this study was to evaluate if amino acids in roots and/or in root exudates play a role in cadmium (Cd) stress. Lettuce (Lactuca sativa L. cv. Reine de Mai) and white lupin (Lupinus albus L. cv. lublanc) were grown for 19 to 21 days with axenic roots in a hydroponic system. After treatment with various concentrations of Cd (0, 0.01, 0.1, 1, 10, and 100 μM Cd) per nine days, roots and root exudates were collected. The stress did not result in significant dry weight (DW) differences between Cd‐treated and control plants, but Cd induced decreases in relative water content (RWC) and water potential (Pm). Amino acid levels and carbon (14C) incorporation into amino acids increased at low Cd concentrations in roots. However, 100 μM Cd induced a decrease of amino acid levels and an equally significant reduction of 14C incorporation, suggesting a decreased plant metabolism. Moreover, a higher Cd concentration induced increased levels of specific amino acids, for instance asparagine and lysine in lettuce and asparagine and hydroxylysine in lupin roots. Amino acids in root exudates corresponded less than 1% of the amounts found in root cells suggesting that amino acids could not be the major Cd chelators. Amino acid accumulation in root exudates differed than that found in roots except for asparagine. In conclusion, Cd induces in the root and root exudates increased levels of specific amino acids, such as Asn, Lys and HLys similarly to other environmental stresses. Although the amino acids could not participate in Cd chelation, lysine and its derivatives, such as hydroxylysine, could be used as stress markers for Cd in higher plants. 相似文献
12.
菌根对紫色土上间作玉米生长及磷素累积的影响 总被引：6，自引：2，他引：4
丛枝菌根真菌(arbuscular mycorrhizal fungi,AMF)在土壤与植物系统的磷素循环中发挥着关键的作用。本文通过盆栽模拟试验研究了不同AMF接种状况[不接种(NM)、接种Glomus mosseae(GM)、接种G.etunicatum(GE)]和玉米/大豆间作体系不同根系分隔方式(不分隔、尼龙网分隔、塑料膜分隔)对间作玉米植株生长及磷素吸收累积的影响。研究结果表明:GM处理下的间作玉米根系侵染率在不同根系分隔方式之间的差异不显著,而GE处理则在塑料膜分隔处理下对玉米的侵染率最高。接种不同AMF对间作玉米促生效果不同,GM和GE处理在不同根系分隔情况下表现出各自的优势,与未接种处理相比,GM处理能使玉米生物量、株高有一定程度增加并在根系不分隔处理下玉米磷吸收较多、生长较好;GE处理能使植株生物量有一定程度增加并在尼龙网分隔处理下的玉米磷吸收较多、生长较好。间作体系不同根系分隔方式对玉米的影响也不同,其中玉米地上部生物量在根系分隔处理下普遍小于不分隔处理,但根系生物量的大小情况则刚好相反。另外,无论何种接种状况,玉米根系磷含量及吸收量均以尼龙网分隔处理显著较高。而根系磷吸收效率则以接种G.mosseae且不分隔根系处理显著高于分隔处理。所有复合处理中,以接种G.etunicatum与尼龙网分隔根系组合处理对间作玉米的生长及磷素累积的促进作用最好,若应用于滇池流域,可望有效控制坡耕地土壤磷素的迁移。 相似文献
13.
Bülent E. Erenoglu Hemanta K. Patra Hicham Khodr Volker Römheld Nicolaus von Wirén 《植物养料与土壤学杂志》2007,170(6):788-795
Increasing the mobilization and root uptake of chromium (Cr) by synthetic and plant‐borne chelators might be relevant for the design of phytoremediation strategies on Cr‐contaminated sites. Short‐term uptake studies in maize roots supplied with 51CrCl3 or 51Cr(III)‐EDTA led to higher apoplastic Cr contents in plant roots supplied with 51CrCl3 and in Fe‐sufficient plants relative to Fe‐deficient plants, indicating that Fe stimulated co‐precipitation of Cr. Concentration‐dependent retention of Cr in a methanol:chloroform‐treated cell‐wall fraction was still saturable and in agreement with the predicted tendency of Cr(III) to precipitate as Cr(OH)3. To investigate a possible stimulation of Cr(III) uptake by phytosiderophores, Fe‐deficient maize roots were exposed for 6 d to Cr(III)‐EDTA or Cr(III)‐DMA (2'‐deoxymugineic acid). Relative to plants without Cr supply, the supply of both chelated Cr species in a subtoxic concentration of 1 µM resulted in alleviation of Fe deficiency–induced chlorosis and higher Cr accumulation. Long‐term Cr accumulation from Cr(III)‐DMA was similar to that from Cr(III)‐EDTA, and Cr uptake from both chelates was not altered in the maize mutant ys1, which is defective in metal‐phytosiderophore uptake. We therefore conclude that phytosiderophores increase Cr solubility similar to synthetic chelators like EDTA, but do not additionally contribute to Cr(III) uptake from Cr‐contaminated sites. 相似文献
14.
Effect of supplying P to a portion of the soybean root system on root growth and P uptake kinetics 1
Abstract Knowledge of the effect of supplying P to portions of the soybean (Glycine max L. Merr) root system on P influx kinetics and root growth is important in developing P fertilizer placement practices for efficient fertilizer use. The objective of this research was to determine the effect of restricting P supply to portions of the root system on plant P status, root growth, and P influx kinetics. Two solution experiments were conducted in a controlled climate chamber. Phosphorus influx kinetics were determined on 25‐day‐old soybean plants that had been grown with 100, 75, 50, 25, and 12.5% of their roots initially exposed to P. Phosphorus influx kinetics were also measured on 25‐day‐old plants that had been P‐starved for the last 1, 2, 4, and 6 days prior to the determining P influx kinetics in order to relate plant P status to P influx kinetics. Reducing the portion of the roots supplied with P reduced P uptake. This resulted in a reduction in plant P concentration and was related to a 3.41‐fold increase in maximum P influx measured on 25‐day‐old plants. Restricting the proportion of roots supplied with P had no significant effects on the Michaelis‐Menten constant or on the concentration in solution where net influx was zero. Root growth rate of the roots in the P containing solution was not significantly different from those in the ‐P solution. Phosphorus uptake was correlated with final root surface area exposed to P (r2 = 0.88??). Starving the plants for P reduced P concentration in the shoot and root and this resulted in as much as a 1.68‐fold increase in maximum influx. 相似文献
15.
Abstract A solution culture study was conducted to determine the genotypic difference in the effects of cadmium (Cd) addition on growth and on the uptake and distribution of Cd and other 11 nutrients in wheat plants. Cadmium addition at a rate of 1 mg L?1 significantly reduced root and shoot dry matter production, shoot height, root length, chlorophyll content, and tillers per plant. On the average of 16 wheat genotypes used in study, Cd concentrations of Cd‐treated plants were 48.1 and 459 μg g?1 dry weight (DW) in shoots and roots, respectively, and retained 77.91% of total Cd taken up in the roots. On the whole, Cd addition reduced the concentration of sulfur (S), phosphorus (P), magnesium (Mg), molybdenum (Mo), manganese (Mn), and boron (B), and increased iron (Fe), irrespective of the plant parts. The effect of Cd on the concentration of potassium (K), calcium (Ca), and copper (Cu) differed in shoots and roots. The significant difference existed among 16 wheat genotypes in their response to Cd in terms of growth and nutrient concentrations. Genotype E81513, which showed relatively less inhibition in growth, had the lowest shoot Cd concentration and more Cd accumulation in roots, while Ailuyuang had the highest Cd concentration and accumulation in shoot with lower Cd concentration in root. The significant interaction was found between Cd treatment and genotype for all nutrient concentrations in both shoot and root, except S and Zn in root. 相似文献
16.
Roghieh Hajiboland Sara Bahrami Rad Juan Barceló Charlotte Poschenrieder 《植物养料与土壤学杂志》2013,176(4):616-625
Beneficial effects of aluminum (Al) on plant growth have been reported for plant species adapted to acid soils. However, mechanisms underlying the stimulatory effect of Al have not been fully elucidated. The aim of this study was to determine the possible contribution of photosynthesis, antioxidative defense, and the metabolism of both nitrogen and phenolics to the Al‐induced growth stimulation in tea (Camellia sinensis [L.] Kuntze) plants. In hydroponics, shoot growth achieved its maximum at 50 μM Al suply (24 μM Al3+ activity). A more than threefold increase of root biomass was observed for plants supplied with 300 μM Al (125 μM Al3+ activity). Total root length was positively related to root Al concentrations (r = 0.98). Chlorophyll a and carotenoid concentrations and net assimilation rates were considerably enhanced by Al supply in the young but not in the old leaves. Activity of nitrate reductase was not influenced by Al. Higher concentrations of soluble nitrogen compounds (nitrate, nitrite, amino acids) and reduction of protein concentrations suggest Al‐induced protein degradation. This occurred concomitantly with enhanced net CO2‐assimilation rates and carbohydrate concentrations. Aluminum treatments activated antioxidant defense enzymes and increased free proline content. Lowering of malondialdehyde concentrations by Al supply indicates that membrane integrity was not impaired by Al. Leaves and roots of Al‐treated plants had considerably lower phenolic and lignin concentrations in the cell walls, but a higher proportion of soluble phenolics. In conclusion, Al‐induced growth stimulation in tea plants was mediated by higher photosynthesis rate and increased antioxidant defense. Additionally, greater root surface area may improve water and nutrient uptake by the plants. 相似文献
17.
Silicon (Si)‐induced cadmium (Cd) tolerance in rice (Oryza sativa L.) was investigated by analyzing Cd uptake, growth, and physiological parameters. Silicon treatments (0.0, 0.2, or 0.6 mM) were added to 6 d–old seedlings, and Cd treatments (0.0 or 5.0 μM) were added to 20 d–old seedlings. Parameters determined included: maximum net CO2 assimilation (Amax), stomatal conductance (gsmax), and transpiration (Emax) rates at varying intercellular CO2 concentrations (Ci). Also measured were chlorophyll fluorescence, growth, and Cd‐uptake parameters. Results showed a Si‐induced inhibition of Cd uptake. However, 0.2 mM or 0.6 mM Si treatment concentrations did not differentially inhibit Cd uptake or differentially alleviate Cd‐induced growth inhibition, despite a significant increase in tissue Si concentration due to 0.6 mM Si treatment compared to 0.2 mM Si treatment. Additionally, photosynthesis and chlorophyll‐fluorescence analysis showed that treatment with Cd significantly inhibited photosynthetic efficiency. Interestingly, the addition of 0.2 mM Si, more so than the addition of 0.6 mM Si, significantly alleviated the inhibitory effects of Cd toxicity on photosynthesis and chlorophyll‐fluorescence parameters. Our results suggest that 0.2 mM Si could be close to an optimum Si‐dose requirement for the alleviation of toxicity symptoms mediated by moderate (5 μM) Cd exposure. 相似文献
18.
Salicylic acid alleviates the toxicity effect of cadmium on germination,seedling growth,and amylase activity of rice 总被引：1，自引：0，他引：1
Cadmium (Cd) is a toxic heavy‐metal pollutant in the environment. Salicylic acid (SA) is an essential component of plant resistance to pathogens and also plays an important role in mediating plant responses to some abiotic stresses. In the present investigation, the potential effects of SA in alleviating Cd toxicity during seedling stage of rice were studied. Seeds of rice (Oryza sativa L. cv. Xiushui 11) were sterilized and divided into two groups. Half of the seeds were presoaked in 0.1 mM SA solution for 24 h, then both groups were allowed to germinate under various Cd concentrations for 7 d. Cadmium treatments caused a gradual decrease in vigor index, root length, α‐amylase activity, and the mitotic index of root tips. However, pretreatment with SA partially alleviated the negative effect of Cd on germination parameters and increased enzyme activity and mitotic index. Cadmium uptake by seedlings increased with increasing Cd concentration and followed Michaelis‐Menten kinetics. Salicylic acid pretreatment of seeds influenced the Cd level in the seedlings by decreasing Vmax. The results suggest that SA plays a positive role in rice‐seed germination and early seedling growth by protecting it against Cd toxicity. 相似文献
19.
Nitrogen nutritional status of young maize plants (Zea mays) is not limited by NaCl stress 
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下载免费PDF全文 Maize plants (Zea mays L. cv. Pioneer 3906) were grown in hydroponics with four different NaCl treatments (control, 50, 100, 150 mM NaCl). Nitrogen (N) was supplied as 2 mM Ca(NO3)2 in the fully concentrated nutrient solution. Plants of half of the pots were treated with additional 1 mM NH4NO3 2 d after start of the NaCl application. After 23 d, the maize plants were harvested and contents and concentrations of nitrate, reduced N as well as chloride were determined in shoots and roots. With increasing NaCl stress net nitrate uptake and net root‐to‐shoot translocation of total N decreased significantly. Under salt stress, decreased nitrate concentrations in shoots probably caused substrate limitation of nitrate reductase. However, the concentrations of reduced N in shoots were not affected by salt stress and no N deficiency was observed. Additional N application to the 100 and 150 mM NaCl treatments did not improve plant growth. A Cl?/NO antagonism was only weakly pronounced, probably because of the Cl? exclusion ability of maize. Thus, although net uptake and net translocation of total N were markedly decreased by NaCl application, the smaller maize plants nevertheless took up enough N to meet their demand pointing to other growth‐limiting factors than N nutrition. 相似文献
20.
《Pedobiologia》2014,57(4-6):223-233
Mycorrhizal fungi and earthworms can individually or interactively influence plant growth and heavy metal uptake. The influence of earthworms and arbuscular mycorrhizal (AM) fungi either alone or in combination on maize (Zea mays L.) growth and cadmium (Cd) uptake was investigated in a calcareous soil artificially spiked with Cd. Soils were contaminated with Cd (10 and 20 mg Cd kg−1), inoculated or un-inoculated with the epigeic earthworm Lumbricus rubellus and two AM fungal species (Rhizophagus irregularis and Funneliformis mosseae) for two months of growth under greenhouse conditions. Generally, earthworms alone increased both shoot P uptake and biomass but decreased shoot Cd concentration and root Cd uptake. AM fungi individually often increased total maize P uptake, declined shoot Cd concentration, and consequently produced higher total biomass. However, R. irregularis enhanced shoot Cd uptake at low Cd level and root Cd uptake at high Cd level. In plants inoculated with F. mosseae species, earthworms increased shoot biomass and Cd uptake, decreased root biomass and Cd uptake at all Cd levels, and increased shoot Cd concentration at low Cd level. In plants colonized by R. irregularis species, however, earthworm addition decreased maize biomass only at high Cd level and root Cd concentration and total maize Cd uptake at both Cd levels. Earthworm activity decreased Cd transfer from the soil to maize roots at low Cd level, but this was counterbalanced in the presence of F. mosseae. Mycorrhizal symbiosis significantly reduced the transfer of Cd from roots to shoots, independence of earthworm effect. Overall, it is concluded that L. rubellus and AM fungi, in particular F. mosseae isolate, improved maize tolerance to Cd toxicity both individually and interactively by increasing plant growth and P nutrition, and restricting Cd transfer to the aboveground biomass. Consequently, the single and interactive effects of the two soil organisms might potentially be important not only in protecting maize plants against Cd toxicity, but also in Cd phytostabilization in soils polluted by this highly toxic metal. 相似文献