首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 187 毫秒
1.
缺铁水稻根表铁膜对硒的转运和吸收的影响   总被引：2，自引：0，他引：2  
Under anaerobic conditions, ferric hydroxide deposits on the surface of rice roots and affects uptake and translocation of certain nutrients. In the present study, rice plants were cultured in Fe-deficient or sufficient solutions and placed in a medium containing selenium （Se） for 2 h. Then, FeSO4 was added at the various concentrations of 0, 10, 40, or 70 mg L-1 to induce varying levels of iron plaque on the root surfaces and subsequent uptake of Se was monitored. The uptake of Se was inhibited by the iron plaque, with the effect proportional to the amount of plaque induced. The activity of cysteine synthase was decreased with increasing amounts of iron plaque on the roots. This may be the important reason for iron plaque inhibition of Se translocation. At each level of iron plaque, Fe-deficient rice had more Se than Fe-sufficient rice. Furthermore, with plaque induced by 20 mg Fe L-1, plants from Fe-deficient media accumulated more Se than those from Fe-sufficient media, as the Se concentration was increased from 10 to 30 or 50 mg L^-1. We found that phytosiderophores, highly effective iron chelating agents, could desorb selenite from ferrihydrite. Root exudates of the Fe-deficient rice, especially phytosiderophores in the exudates, could enhance Se uptake by rice plants with iron plaque.  相似文献   

2.
Based on the fact that Fe toxicity which is usually characterized by leaf oranging and low yield can be obviously subdued by application of Si or Mn due to counteraction.between Fe and Si or Mn.A pot experiment was conducted with four treatments of CK,Si,Mn and Si Mn to further study the effect of combined application of Si and Mn on rice growth on red earths.Water-soluble SI,Fe and Mn were measured.and electron probe was used to study Si,Mn,Fe and Ca in root cross sections.Combined application of Si and Mn could increas water-soluble Si and Mn but reduce water-soluble Fe,thus being favorable for correctiong Fe toxicity.Electron probe study showed obvous differences of Si,Fe,Mn,and Ca in rice roots between CK and the other three treatments.The combined applicatioin of Si and Mn could reduce leaf oranging and improve rice growth.The Si Mn treatment had a higher plant height,lower number of oranging leaves and a 25.0% higher rice yield than CK and showed a better effect on rice growth than the treatment of sole Si or Mn.  相似文献   

3.
An experiment using rhizobox was conducted to study Si,Fe and Mn distributions in rice rhizosphere of red earths and paddy soils.It was found that Si,Fe and Mn diftributions in rhizosphere of the paddy soils were characterized by a depleted zone around root suface,beyond which the concentrations gradually rost.From lmm layer to 2mm layer the concentrations dropped and then rose again.Whereas Si and Fe in red earths showed no depleted zone but even accumulated zone around root surface.Mn showed an approximately even distribution in each layer and no depletion was found in root surface layers.This indicated that during rice (Oryza sativa L.)plantation,depletion and accumulation of Si,Fe and Mn in rhizosphere were important features of matured red earths by water culture.The distribution changes of Si,Fe and Mn in relation to soil-root interaction are also discussed.  相似文献   

4.
To elucidate the mechanisms of tolerance to zinc (Zn) deficiency and Zn toxicity in the root of apple trees, the apple rootstock Malus hupehensis (Pamp.) Rehd seedlings were selected to study the responses of organic acids to Zn homeostasis in roots under low Zn (0 μmol L-1 ), adequate Zn (as control, 4 μmol L-1 ) and toxic Zn (100 μmol L-1 ) treatments. The differences of Zn concentrations and accumulations in the roots were highest, compared with those in the stems and leaves, when apple seedlings were subjected to low and toxic Zn treatments for 1 d. The concentrations and accumulations of oxalic and malic acids in the roots in the low and toxic Zn treatments increased by 20% to 60% compared with those of the control treatment. Significantly negative correlations were found between the total Zn concentrations and the concentrations of oxalic and malic acids in the roots under 1 d of low Zn treatment. However, contrary correlations were found for the toxic Zn treatment. Meanwhile, the maximum influx rates of Zn 2+ under low and toxic Zn treatments increased by 30% and 20%, respectively, compared with the rate of the control treatment. Both Zn deficiency and Zn toxicity increased the concentrations of organic acids in root after short-time Zn treatment, which could resist Zn stress through balanding Zn homeostasis in M. hupehensis Rehd.  相似文献   

5.
The interaction of Pb-Cd can be observed not only in the uptake process of elements by plants and in their influence on the growth,but also in rhizosphere.The changes in extractable Cd and Pb concentrations in the rhizosphere soil of rice plants ,root exudates from wheat and wheat plant and their complexing capacity,with Pa and Cd were investigated under different Pb and Cd treatments.Results showed that the concentration of extractable Cd in the rhizosphere of rice in red soil was markedly increased by Pb-Cd interaction,It increased by 56% in the treatment with Pb and Cd added against that in the treatment with only Cd added in soil . The considerable differences in both composition and amount of root exudate from wheat and rice were found among different treatments.Pb and Cd might be complexed by root exudates ,The concentrations of free Pb and Cd in the solution were increased markedly by adding root exudate from wheat and decreased by that from rice due to Pd-Cd interaction.The distribution patterns of Pb and Cd in roots were affected by Pb-Cd interaction,which accelerated transport of Pb into internal tissue and retarded accumulation of Cd in external tissue.  相似文献   

6.
Being divided into three groups-strong,moderate and weak-according to the different kinetic parameters (Fmax,km,Cmin) of potassium uptake by crops,21 cultivars of rice have been studied to find out the relationships between their potassium nutrition and the oxidation-reduction status in the rhizosphere soils. Results show that,with no application of K fertilizer,there were higher contents of active reducing substances and ferrous iron in rhizosphere soils planted with cultivars,such as Zhongguo 91,week in absorbing potassium than in soils cropped with cultivars,Shanyou 64,stronger in absorbing potassium.As a result of K application,however,these toxic substances were decreased appreciably in the soil,particularly in the root zone where weakly K-absorbing sultivars were growing,and the parameter of soil redox (pH pE) was increased,the most striking example of this being found in the rhizosphere soil where the more strongly K-absorbing sultivars were growing.On and close to the root surface in soils where rice plants were supplied with potassium fertilizer,rather more iron oxide had been accumulated compared with rice receiving no potash,and even greater amounts of red iron oxide precipitated on the rice root in neutral paddy soils.As shown by the concentration distribution of active reducing substances and ferrous iron in a microzone of the profile,the redox range of rice roots supplied with potassium may extend as far as several centimeters from the root surface.It can thus be seen that potassium nutrition exerts its effect first on the morphological properties of rice roots and their exudation of oxygen,then on the content of soluble oxygen and the count and species of oxygen-consuming microbes in the rhizosphere soil,and finally on the redox status of the soil.  相似文献   

7.
Mn and Fe are two important micronutrients of paddy soils derived from red earths.Rice(Oryza sativa L.)oranging physiological diease in newly reclaimed red rarths is related to Fe toxicity.There have been considerable studies on Mn and Fe counteraction,but influence of Mn and Fe counteration on rice oranging physiological disease still remains unknown.This paper is to study,using two soils from USA and China respectively,the relationship between Nn and Fe counteraction and the physiological disease.Analysis for water soluble and extractable Fe and Mn showed that Mn/Fe ratios of the red earths were lower than those of the paddy soils.Fertilizing with Mn raised Mn/Fe and reduced oranging leaves,improved growth and increased yields.Analysis with electron probe showed that Mn treatment had less Fe deposit in root epidermis and more Ca and Si in roots.The results indicated that fertilizing with Mn could correct Fe toxicity.How to apply Mn and Fe counteraction in practice is worth further studying.  相似文献   

8.
Root box experiments were conducted to evaluate the effects of N and NK levels in the root zone on shoot photosynthesis and root growth of hybrid an cultivar of rice (Oryza sativa L.) on two paddy soils (clayey and silty).The results showed that dry matter yields in the hybrid and the cultivar were considerably increased by NK supply,bu the effect was greater for the hybrid.Supply of NK in the root zone significantly increased photosynthetic rate of the lower position leaf and the active green leaf area per plant,in which the effects were much more obvious in the hybrid rice than in the cultivar.High NK supply in the root zone stimulated the root growth,and decreased pH and increased the oxidation zone in the rhizosphere in both entries,but to a greater extent in the hybrid .The results indicated that higher NK levels were needed to maintain higher root activity and shoot photosynthetic capacity in rice,particularly in hybrid rice.  相似文献   

9.
水稻突变体对镉的吸收及其亚细胞分布和化学形态特点   总被引：12，自引：0，他引：12  
Wild-type （Zhonghua 11） and mutant rice （Oryza sativa L.） plants were used to investigate the effect of cadmium （Cd） application on biomass production, to characterize the influx of Cd from roots to shoots, and to determine the form, content, and subcellular distribution of Cd in the roots, leaf sheaths, and leaves of the rice plants. Seedlings were cultivated in a nutrient solution and were treated with 0.5 mmol L^-1 of Cd^2＋ for 14 d. The sensitivity of rice plants to Cd toxicity was tested by studying the changes in biomass production and by observing the onset of toxicity symptoms in the plants. Both the wild-type and mutant rice plants developed symptoms of Cd stress. In addition, Cd application significantly （P ≤ 0.01） decreased dry matter production of roots, leaf sheaths, and leaves of both types, especially the mutant. The Cd content in roots of the mutant was significantly （P ≤0.05） higher than that of the wild-type rice. However, there was no significant difference in the Cd content of roots, leaf sheaths, and leaves between the wild-type and mutant rice. Most of the Cd was bound to the cell wall of the roots, leaf sheaths, and leaves, and the mutant had greater Cd content in cell organelles than the wild type. The uneven subcellular distribution could be responsible for the Cd sensitivity of the mutant rice. Furthermore, different chemical forms of Cd were found to occur in the roots, leaf sheaths, and leaves of both types of rice plants. Ethanol-, water-, and NaCl-extractable Cd had greater toxicity than the other forms of Cd and induced stunted growth and chlorosis in the plants. The high Cd content of the toxic forms of Cd in the cell organelles could seriously damage the cells and the metabolic processes in mutant rice plants.  相似文献   

10.
Shi  W. M.  Liu  Z. Y. 《土壤圈》1991,1(1):73-81
Large amounts of phytosiderophore are detected from both the solution and the rhizosphere soil when cereal crops are under Fe deficiency stress.The extension of phytosiderophore in the rhizosphere soil is found only within 1 mm apart from the root surface.The rate of phytosiderophore secretion is negatively related to chlorophyll content in young leaves and positively related to the Fe-solubilizing capacity.Results from in vitro experiments whow 10 μmoles mugineic acid can dissolve 501 μg Fe from iron hydroxide and 146 ug from strengite.Thus,phytosiderophore can considerably enhance the soil iron availability by increasing the solubility of amorphous iron hydroxide and iron phosphate,and active Fe is consequently accumulated in the plant rhizosphere,43% higher than in the bulk soils There is evidence to support that mugineic acid chelates with Fe%3 at a rate of 1:1 in the acid condition.In addition,we observe mugineic acid has certain effects on mobilization of P as well as Fe by dissolving the insoluble iron phosphate,And phytosiderophore seems to be an effective remedy for the chlorosis of dicotyledonous plants.  相似文献   

11.
水稻根表铁氧化物胶膜对水稻吸收磷的影响   总被引：19，自引：2，他引：19  
本文采用营养液培养方法研究了根表铁氧化物胶膜对水稻吸收磷的影响。结果表明，水稻报表的铁氧化物胶膜随营养液中Fe2+浓度的增加而增加。铁氧化物胶膜可富集生长介质中的磷，根表铁膜数量越多，富集的磷量也越多。根表铁股可促进水稻对磷的吸收，但这种促进作用的大小依赖于根表铁膜数量。根表铁膜数量为24570mp／kg时，促进作用达到最大，此后随着铁膜数量的增加，水稻吸收磷的数量下降，但仍高于根表没有铁膜的水稻。因此，水稻根表形成的铁氧化物胶膜在一定程度上是一个磷富集库，对水稻吸收磷起促进作用。在此过程中，缺铁条件下水稻根分泌物中的植物铁载体对淀积铁氧化物胶膜的水稻根系吸收磷没有明显的作用。  相似文献   

12.
Roots of rice (Oryza sativa L.) exposed to 25, 50, and 100 ppm concentrations of manganese (Mn2+) in solution culture at pH 4.0, 5.0, 6.0, 7.0, and 8.0 for 48 hours developed visible brown coatings (plaque) of oxidized Mn. Most plaque was deposited on a region of the root 1–6 cm long above the root tip. Manganese in root plaque was removed by dithionite‐bicarbonate‐citrate extraction and internal root Mn released by pressure digestion. Concentrations of Mn were determined by atomic absorption spectrometry. Mean concentrations of Mn in plaque exceeded concentrations of Mn remaining in roots after the DCB wash in all treatment conditions. Concentrations of plaque and internal Mn increased with increasing pH and Mn2+ concentration in the treatment solution. Significant positive correlations existed between plaque and internal Mn concentrations at high pH. A larger percentage of total root metal remains in Mn plaqued roots after DCB treatment than has been previously observed in similarly treated iron (Fe) plaqued roots.  相似文献   

13.
Iron toxicity is a syndrome of disorder associated with large concentrations of reduced iron (Fe2+) in the soil solution. It only occurs in flooded soils and hence affects primarily the production of lowland rice. The appearance of iron toxicity symptoms in rice involves an excessive uptake of Fe2+ by the rice roots and its acropetal translocation into the leaves where an elevated production of toxic oxygen radicals can damage cell structural components and impair physiological processes. The typical visual symptom associated with these processes is the “bronzing” of the rice leaves and substantial associated yield losses. The circumstances of iron toxicity are quite well established. Thus, the geochemistry, soil microbial processes, and the physiological effects of Fe2+ within the plant or cell are documented in a number of reviews and book chapters. However, despite our current knowledge of the processes and mechanisms involved, iron toxicity remains an important constraint to rice production, and together with Zn deficiency, it is the most commonly observed micronutrient disorder in wetland rice. Reported yield losses in farmers' fields usually range between 15% and 30%, but can also reach the level of complete crop failure. A range of agronomic management interventions have been advocated to reduce the Fe2+ concentration in the soil or to foster the rice plants' ability to cope with excess iron in either soil or the plant. In addition, the available rice germplasm contains numerous accessions and cultivars which are reportedly tolerant to excess Fe2+. However, none of those options is universally applicable or efficient under the diverse environmental conditions where Fe toxicity is expressed. Based on the available literature, this paper categorizes iron‐toxic environments, the steps involved in toxicity expression in rice, and the current knowledge of crop adaptation mechanisms in view of establishing a conceptual framework for future constraint analysis, research approaches, and the targeting of technical options.  相似文献   

14.
In the present study, the sodium citrate, sodium bicarbonate, and ethylenediaminetetraacetate (CBE) method was evaluated for iron (Fe) extraction from plant root surfaces and compared with the dithionite-citrate-bicarbonate (DCB) method. Iron plaque on root surfaces was induced by growing rice seedlings in soil with 1.8 mM Fe2+. Iron plaque was extracted following CBE and DCB methods. The effects of pH, temperature, and incubation time of these methods on Fe extraction from root surfaces were also examined. Iron extraction of CBE and DCB methods did not differ significantly (P < 0.05) at pH between 6 and 8, whereas Fe extraction decreased substantially for further increase of the pH of CBE and DCB solution. In some instances, there were significant differences between CBE and DCB methods in extracellular Fe extraction for temperature and incubation time. The average Fe extraction of CBE and DCB methods were 94% and 81%, respectively, indicating that CBE method would be a better choice for Fe extraction from plant roots. The recommended optimal conditions for CBE method are pH 8, volume of the solution 30 mL, incubation time 30 min, and solution temperature 22 ± 2 °C.  相似文献   

15.
铁肥根系输液矫正果树缺铁失绿症机理   总被引：3，自引：0，他引：3  
邻二氮杂啡铁示踪结果表明 ,铁肥根系输液处理时铁以二价态由根被动吸收 ,并运输到根、茎、和叶的主脉内。运输部位都是靠近形成层的木质部 ,运输速度每小时可达数十厘米。室内营养液培养的八棱海棠苗用59Fe示踪结果表明 ,断根中分配的59Fe为 18.1% ,叶中分配的59Fe占 70 .9% ;断 1、2、3条根的植株59Fe在叶中的分配比例分别为 57.9%、63.6 %、68.0 %。  相似文献   

16.
Toxicity of Fe2+ is one of the major constraints for lowland rice production in tropical and subtropical areas. The root tip is a primary site of iron (Fe2+) toxicity in rice. To explore the effects of iron toxicity on the morphological and biological characteristics on the border cells in rice (Oryza sativa L.), experiments were carried out using the border cells in two cultivars. The experimental results revealed the following properties of border cells shared by both rice cultivars: the first border cells appeared almost synchronously with the emergence of the primary root tip; the number of border cells reached maximum when the root was 25 mm long; the border cells were most viable when the root length was 20 mm; and the relative activity of pectin methylesterase (PME) was the highest when the root length was 2 mm. The two rice cultivars exhibited different trends in their response to Fe2+ toxicity: the number of root border cells in Fe2+-resistant Zhongyou 9288 increased when experiencing low levels of Fe2+ treatment, but then declined at higher Fe2+ levels. The number of root border cells in Fe2+-sensitive Shanyou No. 10, however, declined rapidly when the concentration of Fe2+ increased. The results also showed that Fe2+ toxicity hindered the development of root border cells of both rice cultivars, but the Fe2+ sensitive variety experienced thickened the root cap cell walls that led to programmed cell death.  相似文献   

17.
Silicon (Si) is the second most abundant element in the soil and can alleviate several abiotic stresses in many plant species. However, the mechanisms involved in alleviating ferrous iron (Fe2+) toxicity by Si are still largely unknown, and no study has investigated the role of Si on the Fe2+‐induced oxidative stress and antioxidant system in rice. Four cultivars of Asian and African rice (Oryza sativa L. and Oryza glaberrima Steud) were grown for 4 weeks under hydroponic conditions with or without Fe2+ (250 mg Fe2+ L?1) and with or without Si (250 mg SiO2 L?1). The plants that were treated with Fe2+ suffered Fe2+ toxicity, and Si helped to alleviate the toxicity symptoms. The bronzing index and the Fe concentration in the foliar tissue increased in the presence of Fe2+ but decreased significantly with the application of 250 mg SiO2 L?1. The concentration of malonyldialdehyde, that is commonly used as an indicator of oxidative stress, increased in the foliar tissue in the presence of 250 mg Fe2+ L?1 in the nutrient solution. The application of 250 mg SiO2 L?1 in the plant nutrient solution treated with Fe2+ considerably limited the increase of malonyldialdehyde. However, no significant effect of Si application on the activities of antioxidant enzymes (catalase and ascorbate peroxidase) and non‐enzymatic antioxidants (total ascorbate, reduced ascorbate, oxidized ascorbate, and the ratio of the reduced to oxidized forms) was observed in the rice plants that were grown in the presence of Fe2+. These results suggest that Si does not act directly on the antioxidant defense system of rice but reduces the plant Fe2+ concentration, which reduces the oxidative stress.  相似文献   

18.
In iron toxic wetlands, ferric hydroxide is commonly deposited on rice roots. This study aims to to evaluate the differences in iron plaque formation in rice cultivars from different cropping systems. Thirty days old seedlings of Brazilian rice cultivars from the lowland cropping system (‘BRS Atalanta’ and ‘Epagri 107’) and upland cropping system (‘Canastra’) or both systems (‘BRSMG Curinga’) and the cultivar ‘Nipponbare’ were exposed to iron excess [4 mM iron sulfate heptahydrate (FeSO4.7H2O)] for seven days in nutrient solution. It was observed iron plaque formation and ruptures of the root epidermal cells. The lowland cultivars showed higher Fe content in iron plaque. Iron stain was detected in the root hairs, epidermis, hypodermis, and exodermis. The root exodermis may be contributed to prevent the deposit of iron in the cortex of the lowland cultivars and in the cultivar ‘BRSMG Curinga’. It was observed in plants with iron plaque formation significant reductions in the shoot content of phosphorous, manganese and magnesium due to different causes. The differences in iron plaque formation among the cultivars might be an indicative of variations in exodermis selectivity, root oxidative capacity, and iron nutrition mechanisms.  相似文献   

19.
硒(Ⅳ)预处理下根表铁膜对水稻幼苗吸收和转运汞的影响   总被引：1，自引：0，他引：1  
采用水培试验的方法研究硒(Se,Ⅳ)预处理下,根表铁膜对水稻幼苗吸收和转运汞(Hg)的影响。将水稻幼苗置于Se0和Se0.5(mg L-1)培养液中培养2周,再用4种不同浓度的Fe2+溶液(0、25、50和100 mg L-1即Fe0、Fe25、Fe50、Fe100)诱导水稻根表形成不同数量的铁膜,随后置于0.3 mg L-1的Hg Cl2培养液中继续培养72 h。结果表明,根表铁膜对水稻幼苗生长无显著影响,但硒可以增加其生物量。碳酸氢钠―柠檬酸三钠―连二亚硫酸钠(DCB)提取液(即根表铁膜)中含铁比例(57.3%~96.2%)显著高于水稻幼苗地上部(1.1%~17.5%)和根部(2.7%~25.9%),水稻幼苗的大部分铁被积累至DCB提取液中。随着根表铁膜数量的增加,根和地上部汞含量均显著降低。在Fe50和Fe100处理中,硒的加入显著减少了地上部和根部的汞含量,也显著降低了汞的分配系数,Se(Ⅳ)预处理能明显提高铁膜固持汞的量。综上所述,Se(Ⅳ)预处理和根表铁膜均能阻碍水稻幼苗对汞的吸收和向地上部的转运,减轻水稻汞胁迫,从而起到保护水稻避免汞毒害的作用。本研究对于提高汞污染区稻米质量和保证粮食安全具有一定的现实意义。  相似文献   

20.
磷饥饿诱导水稻根表铁膜形成机理初探   总被引：11，自引：1，他引：10  
采用溶液培养的方法,初步探索了磷饥饿诱导水稻根表铁膜形成的机理。磷饥饿24h后水稻的根表出现了明显的红棕色物质的沉积,扫描电镜的能谱分析结果显示,红棕色物质是铁的氧化物。针对这一现象,首先研究了没有水稻生长的正常磷营养液和缺磷营养液的变化,结果表明二者之间全波长的扫描图谱没有出现差异。采用酸碱混合指示剂的琼脂染色方法,观察了水稻根系表面及根际pH值的变化情况,并分别测定了正常磷营养（P）和缺磷（P0）2种条件下水稻的根系活力。结果看出,缺磷时水稻根系活力高于磷营养正常的处理,尤其是基因型Jin23A,其P和P0处理间根系活力差异极显著。水稻根表三价铁的浓度高于二价铁,并且缺磷根系表面三价铁和二价铁浓度均明显高于供磷处理;缺磷处理水稻根质外体沉积的铁浓度也明显高于供磷处理。因此,初步确定磷饥饿诱导水稻根表铁膜形成是生物学基础上的化学反应过程。  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号