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1.
Hydroponically grown barley plants ( Hordeum vulgare L. cv. Minorimugi) under iron-deficient (–Fe) and high phosphorus (P) conditions (500 µmol L−1) showed Fe chlorosis and lower growth compared with plants grown in –Fe and low P conditions (50, 5 and 0.5 µmol L−1). To understand the physiological role of P in regulating the growth of plants in –Fe medium, we carried out an Fe feeding experiment using four P levels (500, 50, 5 and 0.5 µmol L−1) and phytosiderophores (PS), mugineic acid. Our results suggest that plants grown in a high P medium had higher absorption activity of 59Fe compared with plants grown in low P media, irrespective of the presence or absence of added PS. Translocation of 59Fe from roots to shoots was not affected by the P level. The relative translocation rate of 59Fe increased with decreasing levels of P in the medium. In general, the addition of PS enhanced the absorption of 59Fe and its translocation. Taken together these results suggest that the lower relative translocation rate of Fe in high P plants may be induced by the physiological inactivation of Fe in the roots, and the higher absorption activity of Fe in high P conditions possibly results from the response of barley plants to Fe deficiency.  相似文献   

2.
Abstract

A hydroponic experiment was conducted to observe the effect of arsenic (As) on a number of physiological and mineralogical properties of rice (Oryza sativa L. cv. Akihikari) seedlings. Seedlings were treated with 0, 6.7, 13.4 and 26.8 µmol L?1 As (0, 0.5, 1.0 and 2.0 mg As L?1) for 14 days in a greenhouse. Shoot dry matter yield decreased by 23, 56 and 64%; however, the values for roots were 15, 35 and 42% for the 6.7, 13.4 and 26.8 µmol L?1 As treatments, respectively. Shoot height decreased by 11, 35 and 43%, while that of the roots decreased by 6, 11 and 33%, respectively. These results indicated that the shoot was more sensitive to As than the root in rice. Leaf number and width of leaf blade also decreased with As toxicity. Arsenic toxicity induced chlorosis symptoms in the youngest leaves of rice seedlings by decreasing chlorophyll content. Concentrations and accumulations of K, Mg, Fe, Mn, Zn and Cu decreased significantly in shoots in the 26.8 µmol L?1 As treatment. However, the concentration of P increased in shoots at 6.7 and 13.4 µmol L?1 As levels, indicating a cooperative rather than antagonistic relationship. Arsenic and Fe concentration increased in roots at higher As treatments. Arsenic translocation (%) decreased in the 13.4 and 26.8 µmol L?1 As treatments compared with the 6.7 µmol L?1 As treatment. Arsenic and Fe were mostly concentrated in the roots of rice seedlings, assuming co-existence of these two elements. Roots contained an almost 8–16-fold higher As concentration than shoots in plants in the As treatments. Considering the concentration of Mn, Zn and Cu, it was suggested that chlorosis resulted from Fe deficiency induced by As and not heavy-metal-induced Fe deficiency.  相似文献   

3.
The release of phytosiderophore (PS) from roots of Fe-deficient graminaceous plants follows a distinct diurnal rhythm with maximum release rates occurring usually 3 to 4 hours after the onset of light. However, it remains to be determined whether absorption of the PS-Fe3+ complex shows a diurnal rhythmicity similar to that of PS release, Barley plants grown with or without 10 µM FeEDTA for 7 days were fed with ferreted PS (10 µM labelled with 59Fe) at 4-h intervals to study the diurnal variations in the absorption and transloca tion of 59Fe, The absorption of 59Fe, irrespective of the Fe nutritional status of the plants, was higher during the day and lower during the night but did not show any peak throughout the day-night cycle. On the other hand, the translocation of 59Fe into shoots of Fe-deficient plants was lower than that of Fe-sufficient plants, while the Fe nutritional status of the plants did not affect the absorption of 59Fe by roots, The formation of root apoplastic 59Fe was lower during the day and higher during the night, regardless of the Fe nutritional status of plants. Our results showed that the absorption of the PS-Fe3+ complex by roots did not follow the PS release pattern.  相似文献   

4.
Barley (Hordeum vulgare L.) plants were grown hydroponically in a greenhouse for 14 d under Fe-deficient conditions before treatment for 3 h with excess Mn (25 µM) and equimolar amounts of plant-borne (phytosiderophores, PS) or synthetic (ethylene diamine tetraacetic acid, EDTA) metal chelators. The xylem sap was collected for 3 h and analyzed for PS, Fe, Mn, Zn, Cu, and citrate concentrations. Excess Mn in the feeding medium decreased the concentrations of PS, Fe, Zn, and Cu in the xylem sap. Addition of 25 µM Mn and an equimolar amount of PS to the feeding medium increased the concentrations of PS, Fe, and Cu in the xylem sap, while EDTA decreased the concentrations of PS and the above nutrients. Excess Mn in the feeding medium increased the Mn concentration in the xylem sap and this increase was more pronounced with the addition of PS to the feeding medium, while EDTA had a depressing effect. These findings suggested that the roots of Fe-deficient barley plants can enhance the absorption and/or translocation of both Mn2+ and a PS-Mn complex. Addition of excess Mn to the feeding medium, irrespective of chelators, did not affect the xylem citrate concentration, indicating that citrate may not contribute to the translocation of metal micronutrients. In the xylem sap of Fe-deficient barley plants, the concentrations of metal micronutrients were positively correlated with the concentrations of PSG  相似文献   

5.
The mechanisms of iron (Fe) absorption and translocation in plants have received much study because they are the key processes in the supply of Fe to plants. The objective of this research was to study the effectiveness of phytosiderophore (PS) in the absorption and translocation of 59Fe in Fe-deficient barley (Hordeum vulgare L. cv. ‘Minorimugi’) plants in the presence of plant-borne, synthetic, or microbial chelators. Plants grown under Fe-deficient conditions in a phytotron at pH 5.5 for 7–18 d were fed with Fe3+ (10 μ M labeled with 59Fe) in the presence of 10 μ M of different chelators with or without 10 μ M PS for 4 h starting at 2 p.m. (6 h after the onset of light period). The absorption and translocation of 59Fe in plants treated with PS and Fe3 + were increased relative to plants fed solely with Fe3 + (control). There was no effect found on absorption and translocation of 59Fe in plants treated with EDTA or p-coumarate relative to the control, but a differential increase was observed in 59Fe absorption and translocation in plants treated with EDTA or p-coumarate in the presence of PS. In comparison with the control, a decrease in 59Fe absorption and translocation was observed in plants treated with HEDTA or EDDHA or FOB, but this decrease was avoided in plants treated with HEDTA or EDDHA or FOB in the presence of PS. The enhancement of 59Fe absorption and translocation in plants treated with citrate, and the highest 59Fe absorption and translocation in plants treated with citrate and PS, indicated that citrate had an additive effect on Fe absorption and translocation in plants. Our results showed that PS effectively played a role in Fe absorption and translocation in plants in the presence of other chelators. Plants treated with any chelators had lower extracellular 59Fe in the roots compared with the control.  相似文献   

6.
《Journal of plant nutrition》2013,36(12):2067-2083
Abstract

Information is desired on plant species that have a great potential in phytoremediation of copper (Cu) contaminated soils. Two contrasting ecotypes of Elsholtzia argyi were comparatively studied using nutrient solution culture for their growth response and uptake, distribution, and translocation of Cu. The results show that the ecotype from an old mined area (Sanmen-ecotype) had greater tolerance to Cu than that from the nonmined area (Jiuxi-ecotype) based on dry matter yield at different Cu supply levels. Inhibited root and leaf growth was noted at the external Cu levels > 50 µmol L?1 for the Sanmen-ecotype, and at the Cu supply levels > 5 µmol L?1 for the Jiuxi-ecotype. Stem growth was most sensitive to Cu toxicity in E. argyi, and was inhibited at the Cu levels ≥ 2.5 µmol L?1 for Jiuxi-ecotype and ≥ 25 µmol L?1 for Sanmen-ecotype. Root Cu concentrations were higher in Sanmen-ecotype than in Jiuxi-ecotype, but leaf, especially stem Cu concentrations were much lower in the former than in the latter. Furthermore, Jiuxi-ecotype was much more efficient than Sanmen-ecotype in the translocation of Cu from root to the shoot, and it had higher ratios of stem/root and leaf/root Cu concentration. At the Cu supply levels higher than 10 µmol L?1, root concentrations of potassium (K), calcium (Ca), magnesium (Mg), manganese (Mn), and zinc (Zn) considerably decreased in Jiuxi-ecotype, but were not affected or even increased in Sanmen-ecotype. Zinc concentrations in the stems, particularly in the leaves of Sanmen-ecotype increased by 3 folds, but were hardly changed in Juixi-ecotype when grown at the Cu levels higher than 10 µmol L?1. These results indicate that the Sanmen-ecotype of E. argyi is a Cu-tolerant ecotype, and its tolerance to high Cu levels was mainly related to its extraordinary capability to restrict Cu uptake, especially Cu translocation from root to the shoot, probably by competitive uptake and translocation of Zn.  相似文献   

7.
Abstract

To clarify the mechanism of Magnesium (Mg) in alleviating cadmium (Cd) phytotoxicity, Japanese mustard spinach (Brassica rapa L. var. pervirdis) was grown for 10 days after treatment in hydroponics in a growth chamber under natural light. The treatments were: (1) nutrient solution alone (Control), (2) 10 mmol L?1 Mg (High-Mg), (3) 2.5 µmol L?1 Cd (Cd-toxic), (4) 2.5 µmol L?1 Cd plus 10 mmol L?1 Mg (Mg-alleviated). The Cd-toxic treatment showed substantial growth retardation and chlorosis of young leaves, such symptoms were not observed in Mg-alleviated plants. Magnesium-alleviated plants showed higher shoot growth, more than twofold, and decreased shoot Cd concentration, approximately 40%, compared with Cd-toxic plants. This increase in shoot growth and simultaneous decrease in shoot Cd concentration may explain the alleviation of Cd toxicity with Mg in Japanese mustard spinach. In Cd-toxic plants, concentrations of K in shoots and Zn in both shoots and roots increased compared with the other three treatments. Concentrations and accumulations of Fe and Mn in shoots decreased significantly in the Cd-treated (Cd-toxic and Mg-alleviated) plants compared with the control and High-Mg plants. Thus, the application of high amounts of Mg in the nutrient solution can alleviate Cd toxicity in plants.  相似文献   

8.
Abstract

Phytoremediation is a good technique for removing cadmium (Cd) from farmland soils. To remove Cd from these soils effectively, it is necessary for Cd ions to be transported to the shoot organs for later harvest. However, the mechanism of Cd translocation to shoot organs via xylem vessels has not yet been elucidated. We selected oilseed rape plants (Brassica napus L.) and established a method to collect xylem exudates from these plants. After 3 days of Cd treatment (10 µmol L?1 and 30 µmol L?1) the Cd concentrations in the xylem exudates were approximately 6.5 µmol L?1 and 16 µmol L?1, respectively. The detection of Cd in the xylem exudate indicated that Cd was moving to shoot organs via xylem vessels. The effect of these Cd treatments on the amino acid, organic acid and protein composition of xylem exudates from oilseed rape plants was investigated. The level of amino acids and organic acids detected was enough to bind Cd transported via the xylem. Sodium dodecylsulfate-polyacrylamide gel electrophoresis analysis revealed that proteins with molecular weights of 36 kDa and 45 kDa clearly increased in the exudates with Cd treatment. The possibility that these compounds are binding Cd in the xylem exudates was discussed.  相似文献   

9.
《Journal of plant nutrition》2013,36(12):2745-2761
ABSTRACT

Effect of cadmium (Cd) on biomass accumulation and physiological activity and alleviation of Cd-toxicity by application of zinc (Zn) and ascorbic acid in barley was studied, using semisolid medium culture including 15 treatments [four Cd concentration treatments: 0.1, 1, 5, 50?µmol?L?1, four treatments with addition of 300?µmol?L?1 Zn or 250?mg?L?1 ascorbic acid (ASA) based on these four Cd concentrations, respectively, and three controls: basic nutrient medium, and with Zn or ASA, respectively]. Cadmium addition to semisolid medium, at a concentration of 1, 5, and 50?µmol?L?1, inhibited biomass accumulation and increased malondialdehyde (MDA) content of barley plants, while the addition of 0.1?µmol?L?1 Cd increased slightly dry mass. There was a tendency to a decrease in Zn, copper (Cu) concentrations both in shoots and roots and iron (Fe) in shoots of barley plants exposed to 1 to 50?µmol?L?1 Cd. In addition, there were indications of a stress repose characterized by increased superoxide dismutase (SOD) and peroxidase (POD) activities relative to plants not subjected to Cd. The physiological changes caused by Cd toxicity could be alleviated to different extent by application of 300?µmol?L?1 Zn or 250?mg?L?1 ASA in Cd stressed plants. The most pronounced effects of adding Zn or ASA in Cd stressed medium were expressed in the decreased MDA and increased biomass accumulation, e.g., MDA contents were reduced (p≤0.01) by 4.8%–17.8% in shoots and 0.5%–19.7% in roots by adding 300?µmol?L?1 Zn, in 50?µmol?L?1 Cd stressed plants, and by 1.3%–7.4% in shoots and 2.6%–4.5% in roots by application of 250?µmol?L?1 ASA, respectively. However, ASA addition may enhance Cd translation from root to shoot, accordingly, ASA would be unsuitable for the edible crops grown in Cd contaminated soils to alleviate phytotoxicity of Cd.  相似文献   

10.
Abstract

The effect of additional iron (Fe) on arsenic (As) induced chlorosis in barley (Hordeum vulgare L. cv. Minorimugi) was investigated. The treatments were: (1) 0?μmol?L?1 As?+?10?μmol?L?1 Fe3+ (control), (2) 33.5?μmol?L?1 As?+?10?μmol?L?1 Fe3+ (As-treated) and (3) 33.5?μmol?L?1 As?+?50?μmol?L?1 Fe3+ (additional-Fe3+) for 14?days. Arsenic and Fe3+ were added as sodium-meta arsenite (NaAsO2) and ethylenediaminetetraacetic acid-Fe3+, respectively. Chlorosis in fully developed young leaves was observed in the As-treated plants. The chlorophyll index and the Fe concentration decreased in shoots of the As-treated plants compared with the control plants. Arsenic reduced the concentration of phosphorus, potassium, calcium, magnesium, manganese, zinc and copper. The additional-Fe3+ treatment increased the chlorophyll index in plants compared with the As-treated plants. Among the elements, Fe concentration and accumulation specifically increased in the shoots of additional-Fe3+ plants compared with As-treated plants, indicating that As-induced chlorosis was Fe-chlorosis. Arsenic and Fe were mostly concentrated in the roots of the As-treated plants. Despite inducing chlorosis in the As-treated plants, phytosiderophores (PS) accumulation in the roots and release from the roots did not increase, rather PS accumulation decreased, indicating that As toxicity hindered PS production in the roots. The PS accumulation in the roots was further reduced in the additional-Fe3+ treatment.  相似文献   

11.
In order to clarify the mechanism by which calcium (Ca) alleviates manganese (Mn) phytotoxicity, barley plants were grown under the following conditions: (1) nutrient solution alone (control), (2) nutrient solution + 25 μM Mn (Mn-toxic), and (3) nutrient solution + 25 μ M Mn + 20 mM Ca (Ca-alleviated). Feeding experiments using 54Mn and 59Fe (iron) with 2.0 or 20 mM Ca to the plant roots were also conducted. The absorption and translocation of 54Mn in the control plants were lowered by the high-Ca (20 mM) feeding condition. The translocation of 54Mn to shoots of Mn-toxic or Ca-alleviated plants was also lowered by the high-Ca feeding condition, but 54Mn absorption by roots of the plants was unaffected. The absorption and translocation of 59Fe in the plants was unaffected by the high-Ca feeding condition. Calcium alleviation of Mn phytotoxicity in barley may be induced mainly by the inhibition of Mn translocation to shoots.  相似文献   

12.
Radioactively labeled iron (59Fe) was used to study differential uptake in sorghum plants in the recovery stage of chlorosis. Radio-labeled 59Fe was supplied through root feeding in nutrient solution experiment (48 hrs, pH 6.2) to non-chlorotic and chlorotic plants. Chlorotic plants were further treated with foliar spray [ferrous sulfate (FeSO4), FeSO4 + thiourea (TU), FeSO4 + citric acid (CA), FeSO4 + thioglycollic acid (TGA)] to study the uptake of radio-labeled 59Fe through root feeding during recovery process of chlorosis. Under iron deficiency, the differential uptake of 59Fe was markedly increased in leaves and stem of chlorotic control (-Fe) sorghum plants as compared to non-chlorotic control (+Fe) and foliar sprayed (FeSO4, FeSO4 + TU, FeSO4 + CA, and FeSO4 + TGA) plants. The lowest uptake of 59Fe was observed in younger leaves (24.33 nmol, g?1 fresh weight h?1) and stem (1.98 nmol, g?1 fresh weight h?1) of non-chlorotic control followed by foliar sprayed plants in comparison to chlorotic control, respectively. Similarly less 59Fe uptake was observed in the older leaves of FeSO4 + CA sprayed (21.70 nmol, g?1 fresh weight h?1) plants in comparison to chlorotic control (35.60 nmol, g?1 fresh weight h?1). The highest differential 59Fe uptake through nutrient medium was in the roots of plants, which were foliar sprayed with FeSO4 along with TU. The role of iron alone and along with citric acid and thiol compounds is discussed in recovery of chlorosis.  相似文献   

13.
Micronutrient deficiency in cultivable soil, particularly that of iron (Fe) and zinc (Zn), is a major productivity constraint in the world. Low Fe availability due to the low solubility of the oxidized ferric forms is a challenge. An experiment was, thus, executed to assess the performance of eight genetically diverse rice genotypes on Fe-sufficient (100 µM) and Fe-deficient (1 µM) nutrient solution, and their ability to recover from Fe deficiency was measured. Fe efficiency under Fe deficiency in terms of biomass production showed a significant positive correlation with the root release of phytosiderophore (PS) (R2 = 0.62*). This study shows that the Fe deficiency tolerance of Pusa 33 was related to both a high release of PS by the root and an efficient translocation of Fe from the root to the shoot as the Fe–PS complex, which could be useful for improving the Fe nutrition of rice particularly under aerobic conditions.  相似文献   

14.
Iron (Fe) nanoparticles (NPs), with 30–40 nm diameter, were stabilized on sand. The resulting synthesized Fe/SiO2 NPs, with different Fe contents (0–25 mg kg?1) were employed as fertilizers in probing the mean germination time (MGT), growth and dry matter of barley and maize and their comparison with common Fe/SiO2 in a completely randomized design (CRD) experiment. The results showed that our fertilizers had significant effects on MGT, with the lowest of 0.58 day for barley and 0.79 day for maize; at 15 and 5 mg kg?1 nano Fe/SiO2, respectively. Application of 15 mg kg?1 of nano Fe/SiO2 increased the shoot length: 8.25% and 20.8% for barley and maize, respectively. However, the concentration of 25 mg kg?1 had a negative impact on shoot length in barley. Increasing the concentrations of both nano and common Fe/SiO2 particles, increased the root lengths in both plants, however this increase was higher with the application of nano Fe/SiO2. Likewise, seedling length enlarged with the concentration increase of both Fe/SiO2 particles and was more pronounced with nano Fe/SiO2. The application of nano Fe/SiO2 was more effective compared with the common Fe/SiO2 in encouraging barley and maize growth. The positive impact was higher in maize than barley.  相似文献   

15.
Abstract

Studies examining iron (Fe) toxicity and zinc (Zn) deficiency in rice have shown that screening experiments in nutrient solutions are of limited use because the rankings of genotypes as tolerant or intolerant can be very different from the results obtained in field-screening experiments. A possible reason for such deviation is that crucial rhizosphere processes cannot be reproduced in nutrient solutions. The objective of the present study was to evaluate the suitability of low-concentration agar nutrient solutions (ANS) as an alternative screening tool. Agar was dissolved in boiling water and mixed with nutrient solution to achieve a final agar concentration of 0.1% (w/v). Zinc deficiency was induced by supplying Zn at a low concentration (0.1 × 10?3 µmol L?1), while Fe toxicity was induced by supplying excess Fe2+ (200 mg L?1). Three-week-old seedlings were transplanted into this medium. Symptoms of Zn deficiency and Fe toxicity developed more rapidly in ANS compared with conventional nutrient solutions (CNS). For Zn deficiency this was probably because of the development of Zn depletion zones as a result of the reduced convection in the viscous agar medium. In the case of Fe toxicity we observed far less Fe precipitation in ANS compared with CNS. Genotypic comparisons showed that the tolerance rankings obtained in ANS were very similar to the field tolerance rankings, whereas this was not the case in CNS. This was particularly evident with regard to the considerable root growth inhibition detected in intolerant genotypes when stress treatments were imposed in ANS.  相似文献   

16.
The increasing number of cases of soil contamination by heavy metals has affected crop yields, and represents an imminent risk to food. Some of these contaminants, such as cadmium (Cd) and lead (Pb), are very similar to micronutrients, and thus can be absorbed by plants. This study evaluated the translocation of increasing amounts of cadmium and lead and the effects of these metals in the production of beans. Bean plants were grown in nutrient solution Clark and subjected to increasing levels of Cd (from 0 to 0.5 mg L?1) and Pb (from 0 to 10 mg L?1). Cadmium concentration of 0.1 mg L?1 translocated 39.8% to the shoot, and dry matter production was reduced by 45% in shoots and 80% in roots, compared to the control treatment. Lead showed impaired movement in the plant, however the concentration of 1.0 mg L?1 was observed in 5.7% of metal translocation to the leaves. The concentration of 10 mg L?1 Pb reduced dry matter production of roots and shoots in 83% and 76%, respectively, compared to the control treatment.  相似文献   

17.
EDTA-enhanced phytoremediation by corn (Zea mays L.) of soil supplemented with 500 mg L?1 lead (Pb) was examined. The chelate EDTA was used in order to increase Pb bioavailability at four levels: 0 (control), 0.5 (low), 1.0 (medium), and 2.5 mmol kg?1 (high). Plants were grown under controlled conditions in a growth-chamber with supplementary light. An EDTA concentration of 5.0 mmol kg?1 was lethal to plants. At high and medium EDTA levels plants grew significantly less than control ones. Lead concentrations in corn leaves increased with increased EDTA levels. Plants subjected to medium EDTA level had the greatest root to shoot Pb translocation. Plants subjected to high EDTA level showed high phosphorus (P) uptake and translocation within plants. Therefore, possibly it was not only Pb that caused toxic effect on plants, but also the high internal concentration of P that in turn could have complexed active Fe.  相似文献   

18.
Abstract

It has been showed that Chao’s method [extraction with 0.1 mol L?1 hydroxylamine hydrochloride (NH2OH-HCl) at pH 2.0 for 30 min], which is commonly used to extract manganese (Mn) oxides and occluded heavy metals from soil samples, is not suitable for Andisols because of low solubility, and thus low extractability, of Mn oxides in such soils. Therefore, a new method is evaluated here, for extracting Mn oxides and occluded heavy metals from Andisols, Entisols and Inceptisols. The method has three steps: (1) reduction of Mn oxides with 0.01 mol L?1 NH2OH-HCl (pH 5.0) for 16 h, (2) recovery of re-adsorbed metals by short-time extraction with 0.5 mol L?1 ammonium chloride in 0.02 mol L?1 hydrochloric acid, and (3) washing with ultrapure water. This method achieves a higher rate of extraction of Mn oxides than does Chao’s method, especially from Andisol samples. Standard addition experiments showed that both the new method and Chao’s method can successfully extract released cadmium (Cd), cobalt (Co), nickel (Ni) and zinc (Zn) from Mn oxides with little re-adsorption. The selectivity of Mn oxide extraction by the new method, indicated by the rate of extraction of iron (Fe) oxides and the aluminum (Al)/Mn and silicon (Si)/Mn extraction ratios, is comparable to that of Chao’s method. Thus, the new method should be useful for extracting Mn oxides and occluded Cd, Co, Ni, and Zn from soil samples. Moreover, because the new method achieved nearly complete extraction of NH2OH-HCl reactive Mn oxides even from Andisol samples, the method is more applicable to Andisol samples than Chao’s method.  相似文献   

19.
《Journal of plant nutrition》2013,36(10-11):2231-2242
Abstract

Radioactively labeled iron (59Fe) was used to study iron retranslocation from mature leaves of Broad bean (Vicia faba L. var. Scirocco). Our experiments offered the possibility to detect and quantify the translocation of foliar applied iron by imaging technique in combination with tissue analysis. 59Fe labeled solution was placed as a droplet onto the leafs upper surface of intact plants. Distribution of 59Fe was analyzed after 0.5 h up to 2 days. Iron was translocated acropetally (towards the tip of the treated leaf) as well as basipetally. Movement in the apical direction was predominant, amounting to about 65% of 59Fe translocated from the application site. About 35% of 59Fe were transported basipetally, corresponding to absolute amounts of 2.8–53.6 pmol h?1. After 30 min, it was detectable in the petiole, which included a translocation of 20 mm basipetal from the application site. A mean of 15% of the iron retranslocated from a leaflet was detected in non‐treated leaflets of the same leaf. This iron was supposed to have been exchanged from the phloem into the xylem pathway, probably within the petiole. When the loading rate into the phloem was estimated on basis of the sum of retranslocated 59Fe per time and per area of the leaf treated, a range of 0.031–2.21 pmol h?1 mm?2 (mean: 0.62 pmol h?1 mm?2) was obtained. This was not sufficient to meet an estimated demand for iron in the growing terminal bud, but could cover about 25% of it. In conclusion, average iron retranslocation from leaves of Fe‐sufficient plants was not large enough to meet the iron demand of the growing shoot. This was not due to a limitation in iron availability for transport, as an excess amount of iron was supplied which was not biologically bound, but a limitation due to transport facilities, probably in the phloem, seemed to be more likely in this case.  相似文献   

20.
Abstract

To assess soil-to-plant transfer of various elements more precisely, the concentrations of the elements extracted from soil samples using eight chemical solutions were compared with the results of a pot cultivation experiment of komatsuna (Brassica rapa L. var. perviridis) or buckwheat (Fagopyrum esculentum M.) using the soils. From agricultural fields in Aomori, Japan, 16 soil samples were collected. Elements in the samples were extracted using acids (1 mol L?1 HNO3, 0.1 mol L?1 HNO3, 0.01 mol L?1 HNO3), chelating agents (0.05 mol L?1 EDTA), neutral salt solutions (1 mol L?1 NH4OAc, 1 mol L?1 NH4NO3, 0.01 mol L?1 CaCl2) and pure water. The 28 elements in the extracted solutions and plant samples were determined. The extractability of many metals was higher in 1 mol L?1 HNO3, 0.1 mol L?1 HNO3 and the 0.05 mol L?1 EDTA solutions than in the other extractants. Higher extractability using the NH4OAc solution than the NH4NO3 solution was observed for some elements, in particular U. Extractability by pure water was not always lowest among these methods, probably because of dispersion of colloidal substances in the extracted solution. The pot cultivation experiment showed that the concentrations in soil and in the extracted fraction using 1 mol L?1 HNO3, 0.1 mol L?1 HNO3 or the EDTA solution did not correlate with the concentration in plant samples for most elements. Plant uptake of Zn, Y and La by komatsuna correlated well with their concentrations in extracts with neutral salt solutions or 0.01 mol L?1 HNO3. Concentrations of Al, Cu and Cd in buckwheat were also correlated with the concentrations in the extracts.  相似文献   

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