Polyphenolic compounds on leaves limit iron availability and affect growth of epiphytic bacteria

Polyphenolic compounds produced by plants can chelate iron, reducing its bioavailability to plant‐associated bacteria. In response to limited iron levels, most bacteria produce siderophores to acquire needed iron quantities. The amount of phenolic compounds detected in methanolic washings of leaves of different plant species varied greatly, being nearly sevenfold higher in Viburnum tinus than in Phaseolus vulgaris. In species with high levels of total phenolics (e.g. Pelargonium hortorum), tannin concentration of leaf washings was also high and accounted for up to 85% of total phenolics. Both stimulation of production of the siderophore pyoverdine in Pseudomonas syringae strain B728a and inhibition of growth of an isogenic mutant I‐1, deficient in pyoverdine production were associated with plants harbouring high levels of leaf surface phenolics. Levels of tannic acid sufficient to inhibit growth of the pyoverdine mutant in culture in an iron‐reversible fashion were similar to tannin levels found on leaves of plants such as P. hortorum. Additionally, the amount of pyoverdines produced by P. syringae and quantified in leaf washings from a variety of plants was directly related to the concentration of tannins released from the leaf, indicating that tannins were responsible for sequestering iron. Phenolic compounds, principally tannins, may thus play an important role in plant–microbe interactions.     

The Structure of Muta-aspergillic Acid

Iron is one of the essential trace elements for humans. In this study, the iron contents in fresh, dried, and toasted nori (Pyropia yezoensis) were analyzed. The mean iron content of fresh, dried, and toasted nori were 19.0, 22.6, and 26.2 mg/100 g (dry weight), respectively. These values were superior to other food of plant origin. Furthermore, most of the iron in nori was maintained during processing, such as washing, drying, and toasting. Then, the form of iron in fresh, dried, and toasted nori was analyzed. As a result, an iron storage protein ferritin contributed to iron storage in raw and dried nori, although the precise rate of its contribution is yet to be determined, while ferritin protein cage was degraded in the toasted nori. It is the first report that verified the ferritin contribution to iron storage in such edible macroalgae with commercial importance.     

喀斯特高原峡谷优势种叶片功能性状分析

该研究对喀斯特石漠化高原峡谷地区优势种的叶片功能性状进行了分析,调查了17种植物的叶片厚度、叶面积、叶片鲜重、叶片干重、叶干物质含量、比叶面积、叶组织密度等能反映植物生存策略且易于测量的叶片功能性状,并采用逐步回归的方法探究了叶片功能性状与土壤养分之间的关系。结果表明:(1)不同优势种叶片功能性状差异明显,叶片的厚度为0.18～0.78 mm、鲜重为0.07～6.51 g、干重为0.04～3.19 g、叶面积为3.07～325.64 cm~2、叶干物质含量为318.61～573.22 mg·g~(-1)、比叶面积为60.98～236.90 cm~2·g~(-1)、叶组织密度为0.022 1～0.036 g·cm~(-3)。(2)植物通过较小的比叶面积与较大的叶干物质含量来减少水分散失、增加养分储存,以适应高温、缺水少土的环境。(3)叶片功能性状之间存在广泛的相关关系,且均达到极显著水平。叶片厚度对鲜重、干重均表现为促进效应,比叶面积与叶干物质含量及叶组织密度之间均存在极显著的抑制效应。(4)叶片功能性状随土壤养分的变化产生规律性变化。土壤全氮、全钾和有机碳对叶片功能性状产生显著影响,尤以土壤有机碳的影响更为显著。进一步分析发现,喀斯特高原峡谷地区植被恢复及重建的优势种或建群种为翅荚香槐、清香木、枇杷等;施用有机肥能够提高花椒、金银花等经济林树种的适应能力。     

Iron toxicity and stress-induced ethylene production in rice leaves

The relationship among iron toxicity, bronzing symptom, and stress-induced ethylene production (SEP) was investigated in detached rice (Oryza sativa L.) leaves during the vegetative-ripening stage and in whole plants during the vegetative stage. When Fe²⁺ (200 mg L^-1) was applied to the detached leaf through a transpiration stream, SEP was higher in the first leaf than in the second and third leaves from the top and maximal around the panicle primordia initiation stage. The genotype difference in SEP was more pronounced in the second and third leaves than in the first leaf. Bronzing intensity increased as SEP increased; iron concentration increase during treatment in the tissue did not correlate with bronzing intensity or with SEP among the 16 genotypes tested. When the roots of an intact plant were exposed to 300 mg L^-1 of Fe²⁺ in culture solution little stress-induced ethylene was produced. By partially or totally derooting the plant, however, stress-induced ethylene was evoked, indicating that roots reduced the Fe²⁺ uptake so that little stress ethylene is produced in the intact plant. Leaf tissue tolerance for Fe²⁺ may contribute to genotype differences in iron toxicity tolerance of rice plants when roots are injured during transplanting or exposed to toxic substances in the soil.     

The Effect of Soil Water Regimes on Leaf Water Potential, Growth and Development of Soybeans

The growth and development of soybeans (Glycine max L. cv. Amsoy) was studied at soil matric potentials of ?0.1 to ?1.0 bars. Chlorophyll, photosynthesis, and leaf nitrogen per plant was greatest at ?4 bars leaf water potential. Leaf area, number of internodes, plant height and dry weight of vegetative parts declined as leaf water potential decreased from ?2 to ?19 bars. Nitrogen content and nitrate reductase activity per g fresh weight determined the percentage protein of individual seeds but nitrogen content and nitrate reductase activity per plant determined the amount of total seed protein. The protein synthesized in the seed changed little in amino acid composition with changes in leaf water potential. Leaf water potentials above or below ?4 bars decreased yield, total protein and total lipid but plants produced the largest percentage of individual seed protein at ?19 bars leaf water potential.     

Fusarinines and dimerum acid, mono- and dihydroxamate siderophores from Penicillium chrysogenum, improve iron utilization by strategy I and strategy II plants

Cucumber, as a strategy I plant, and Maize as a strategy II plant, were cultivated in hydroponic culture in the presence of a ferrated siderophore mixture (1 M) from a culture of Penicillium chrysogenumisolated from soil. The siderophore mixture significantly improved the iron status of these plants as measured by chlorophyll concentration to the same degree as a 100-fold higher FeEDTA supply. Analysis of the siderophore mixture from P. chrysogenum by HPLC and electrospray mass spectrometry revealed that besides the trihydroxamates, coprogen and ferricrocin, large amounts of dimerum acid and fusarinines were present which represent precursor siderophores or breakdown products of coprogen. In order to prove the iron donor properties of dimerum acid and fusarinines for plants, purified coprogen was hydrolyzed with ammonia and the hydrolysis products consisting of dimerum acid and fusarinine were used for iron uptake by cucumber and maize. In short term experiments radioactive iron uptake and translocation rates were determined using ferrioxamine B, coprogen and hydrolysis products of coprogen. While the trihydroxamates revealed negligible or intermediate iron uptake rates by both plant species, the fungal siderophore mixture and the ammoniacal hydrolysis products of coprogen showed high iron uptake, suggesting that dimerum acid and fusarinines are very efficient iron sources for plants. Iron reduction assays using cucumber roots or ascorbic acid also showed that iron bound to hydrolysis products of coprogen was more easily reduced compared to iron bound to trihydroxamates. Ligand exchange studies with epi-hydroxymugineic acid and EDTA showed that iron was easily exchanged between coprogen hydrolysis products and phytosiderophores or EDTA. The results indicate that coprogen hydrolysis products are an excellent source for Fe nutrition of plants.     

Iron nutrition of a hydroponic strawberry culture (Fragaria vesca L.) supplied with different Fe chelates

Several indexes are used to determine the iron nutritional status of plants, but their effectiveness depends either on the plant growth conditions in natural environments or on the assay conditions. This research was conducted to test different indexes of the iron nutritional status of a hydroponic strawberry culture where treatments mainly differed in the source of the iron applied: Fe-EDTA, Fe-EDDHA and Fe-polyflavonoid. Macro and micronutrient concentrations in the nutrient solutions, leaf and vascular tissues were measured. Fe concentration in the nutrient solution during the course of the experiment was considered in relation to the stability of the different chelates. Both Fe concentration and total Fe content of leaves reflected the effect of the treatments; Fe/Mn ratio was significant as a diagnosis index. Other element ratios as P/Fe and K/Ca are not well related with the iron nutrition symptoms observed. Fe²⁺ concentration measured in leaves was not directly affected by the different chelate treatments.     

Compartmentation of Cadmium and Iron in Mesembryanthemum crystallinum Plants during the Adaptation to Cadmium Stress

The common ice plants (Mesembryanthemum crystallinum) at the stage of five leaf pairs were exposed to cadmium chloride solutions (1, 0.1, and 0.01 mM) under the conditions of water culture. After five days, the partition of cadmium and iron in the plant organs and in the cell structures of the apical root region were investigated. Plant adaptation to excess cadmium in the environment was assessed by an increase in the leaf and root weight, a change in peroxidase activity, and an accumulation of proline. The common ice plant accumulated cadmium mainly in the root system. At a high concentration of cadmium in the nutrient solution (1 mM), its content in the root exceeded 2 g/kg fr wt, while at a concentration of 0.01 mM, it was as low as 10 mg/kg. Dithizone staining of transverse sections of the root apical region showed that, after a 48-h-long exposure of plants to 0.1 mM cadmium chloride, cadmium was localized in the cell walls of endodermis and metaxylem. The level of cadmium in leaves varied from 0.5 to 18 mg/kg fr wt. However, there was only a weak correlation between cadmium accumulation and the extent of a biomass decrease in the leaves of various stories, when cadmium concentration in the medium (1 mM cadmium chloride) was toxic. This fact could be related to a marked efflux of endogenous iron from old leaves into the young ones and to a change in the cadmium/iron ratio in the tissues. Proline accumulation in the third leaf pair and in the roots occurred at a relatively low cadmium content (10–12 mg/kg fr wt) in these organs. Maxima of activity of all three forms of peroxidase, viz., soluble, ionically-bound, and covalently-bound peroxidases, in roots were found at a high accumulation of cadmium in these organs (45 mg/kg fr wt). These maxima exceeded 3–4-fold the activity in aging leaves containing 5 mg cadmium/kg fr wt. A decrease in peroxidase activity in leaves was accompanied by a 3.3-fold decrease in iron content; thus, it could be caused by a deficiency of available iron necessary for the enzyme functioning. It was concluded that the resistance of Mesembryanthemum crystallinum, a halophyte, to excess cadmium content in the medium was achieved by its predominant accumulation in roots, where excess cadmium is compartmentalized in the apoplast and seems to be subjected to detoxification through pectate formation. Moreover, the leaves and, particularly, the roots are characterized by a high activity of the antioxidant systems, such as guaiacol-dependent peroxidases, and an occurrence of proline at modest cadmium concentrations.     

Some problems associated with determining iron in plants

Summary 1. Iron which is shown to be present as a contaminant on leaf surfaces of tomato can be removed completely by washing the leaves for 30 sec in 0.3% teepol and water followed by a 30 sec rinsing in distilled water.2. By using radioactive iron it is shown that there was no loss of the metal from within the plants during leaf washing. Agreement between chemical and radioassay data for iron showed that the metal was completely removed by the wash procedure.3. In tomato grown in the glasshouse consistent differences between the iron contents of normal and chlorotic leaves were obtained after leaf washing. When the plants were grown in a dustproof chamber differences in iron status of green and chlorotic leaves were obtained without washing.4. Added radioactive and carrier iron was fully recovered from acid digests of a variety of plant material, specially chosen to represent a range of silica contents.     

Activation of rice Yellow Stripe1-Like 16 (OsYSL16) enhances iron efficiency

Graminaceous plants release ferric-chelating phytosiderophores that bind to iron. These ferric-phytosiderophore complexes are transported across the plasma membrane by a protein produced from Yellow Stripe 1 (YS1). Here, we report the characterization of OsYSL16, one of the YS1-like genes in rice. Real-time analysis revealed that this gene was constitutively expressed irrespective of metal status. Promoter fusions of OsYSL16 to β-glucuronidase (GUS) showed that OsYSL16 was highly expressed in the vascular tissues of the root, leaf, and spikelet, and in leaf mesophyll cells. The OsYSL16-green fluorescence protein (GFP) fusion protein was localized to the plasma membrane. From a pool of rice T-DNA insertional lines, we identified two independent activation-tagging mutants in OsYSL16. On an Fe-deficient medium, those mutants retained relatively high chlorophyll concentrations compared with the wild-type (WT) controls, indicating that they are more tolerant to a lack of iron. The Fe concentration in shoots was also higher in the OsYSL16 activation lines than in the WT. During germination, the rate of Fe-utilization from the seeds was higher in the OsYSL16 activation lines than in the WT seeds. Our results suggest that the function of OsYSL16 in Fe-homeostasis is to enable distribution of iron within a plant.     

Iron reductase systems on the plant plasma membrane—A review

Higher plant roots, leaf mesophyll tissue, protoplasts as well as green algae are able to reduce extra-cellular ferricyanide and ferric chelates. In roots of dicotyledonous and nongraminaceous, monocotyledonous plants, the rate of ferric reduction is increased by iron deficiency. This reduction is an obligatory prerequisite for iron uptake and is mediated by redox systems localized on the plasma membrane. Plasma membrane-bound iron reductase systems catalyze the transmembrane electron transport from cytosolic reduced pyridine nucleotides to extracellular iron compounds. Natural and synthetic ferric complexes can act as electron acceptors.This paper gives an overview about the present knowledge on iron reductase systems at the plant plasma membrane with special emphasis on biochemical characteristics and localisation.     

濒危种观光木小枝生物量分配与功能性状的纬度变异规律及其影响因素

为了探讨观光木当年生枝条生物量的分配规律和叶片功能性状的变化规律及其影响因素,该研究以濒危物种观光木(Michelia odora)为对象,测定了广西地区5个不同纬度上观光木当年生小枝及叶片功能性状.结果表明:(1)随着纬度的增加小枝总重和总叶重总体呈异速生长关系,其生物量更多趋于对小枝的构建.(2)观光木叶功能性状呈...     

亚适温条件下缺铁和硝酸盐胁迫对番茄幼苗生长及铁吸收的影响

研究亚适温(昼/夜18 ℃/12 ℃)条件下缺铁和硝酸盐胁迫对番茄幼苗生长及铁吸收的影响.结果表明: 与适温对照相比,亚适温条件下番茄幼苗生长受到明显的抑制,株高、叶面积显著变小,干物质积累下降;亚适温下缺铁对番茄幼苗生长的影响比适温下缺铁的影响大.亚适温条件下,缺铁、硝酸盐胁迫及二者同时胁迫的番茄幼苗株高与无胁迫处理差异不显著,但幼苗叶面积明显变小,电解质渗漏率、根系活力和三价铁还原酶活性明显增加,叶绿素含量降低;根总长、根表面积、根体积及根尖数明显减小;幼苗根、茎、叶中铁含量明显降低.亚适温下硝酸盐胁迫以及缺铁与硝酸盐二者同时胁迫加重了番茄幼苗干物质积累的减少、电解质渗漏率的增加,以及减少了对铁离子的吸收.Fe²⁺对K⁺和Ca²⁺吸收具有拮抗作用,不同器官中的表现有所差异;降低营养液中的Fe²⁺浓度可使番茄幼苗的缺铁症状更加严重.     

The relation between nitrogen deficiency and second leaf senescence in wheat plants

Life span of the second leaf of wheat(Triticum aestivum L., cv. Grana) plants was studied from day 8 to day 50 of plant age in a variant with nitrogen (+N) and in a variant in which plant senescence was induced by the omission of nitrogen from the nutrient solution (−N). Seed protein was the sole source of nitrogen for these plants. Specific leaf mass (SLM) in the −N variant, and specific leaf area (SLA), the mass of fresh leaf, soluble protein content and total nitrogen content in the +N variant peaked by day 22 of plant age (that is by day 19 of leaf age). Dry matter content, leaf length and leaf area, and SLM in the +N variant peaked by day 29 of plant age (that is by day 26 of leaf age). The ontogeny of the second leaf in the variant with enhanced senescence was shorter by at least 14 days. Plants from this variant showed typical symptoms of N deficiency, that is yellowing of leaves, tip burn, and lack of tillering. However, the growth and biochemical characters studied did not indicate an earlier onset of the senescence of the second leaf of −N plants. Both +N and −N variants reached their peaks (with the exception of an earlier peak by day 12 in case of total nitrogen content in the −N variant) on the same day of leaf age. Thus the first part of the leaf life span from leaf growth initiation to full expansion was of the same length in both the control and N-def icient plants. The stage of the proper senescence of the second leaf of −N plants was very short; the leaf completely died away within 7 days after senescence onset.     

Effects of waterlogging on growth and some physiological parameters of four Brassica species

Waterlogging tolerance of four Brassica species, Brassica campestris L., B. carinata A. Br., B. juncea (L.) Czern and Coss., and B. napus L. was assessed after 4 weeks growth in greenhouse at two waterlogging treatments, unflooded control soil, and fully waterlogged soil.Shoot fresh and dry biomass, in both mean and relative terms, was highest in B. juncea and lowest in B. napus at waterlogging treatment. B. carinata was as good as B. juncea in mean shoot fresh and dry matter but it had almost same relative shoot fresh matter as that in B. campestris, but was second highest in relative shoot dry weight.Waterlogging treatment caused a marked reduction in chlorophyll content in all four species but the species difference was not evident. However, B. juncea and B. napus had lower relative total chlorophyll than the other species.A marked increase in soluble protein content of B. juncea and a significant increase in total amino acids in B. carinata was observed under waterlogged conditions as compared to the other species.At the waterlogging regime, an increase in iron content in both shoots and roots was observed in all four species. B. juncea accumulated lower amount of iron in both shoots and roots as compared to the other species, whereas B. carinata had also lower iron in the roots. The species did not differ for shoot manganese content but B. carinata had significantly higher manganese in the roots as compared to the other species.     

Inductive responses of some organic metabolites for osmotic homeostasis in peanut (Arachis hypogaea L.) seedlings during salt stress

The salt tolerance of peanut (Arachis hypogaea L.) seedlings was evaluated by analyzing growth, nutrient uptake, electrolyte leakage, lipid peroxidation and alterations in levels of some organic metabolites under NaCl stress. The plant height, leaf area and plant biomass decreased significantly in salt-treated seedlings as compared with control. The relative water content (RWC %) of leaf decreased by 16 % at high concentrations of NaCl. There was an increase in the lipid peroxidation level and decrease in the electrolyte leakage at high concentrations of NaCl. The total free amino acid and proline contents of leaf increased by 5.5- and 43-folds, respectively in 150 mM NaCl-treated plants as compared with control. Total sugar and starch content increased significantly at high concentrations of NaCl. Chl a, Chl b, total chlorophyll and carotenoid contents decreased significantly at high salinity. Na⁺ contents of leaf, stem and root increased in dose-dependent manner. K⁺ content remained unaffected in leaf and root and decreased in stem by salinity. The results from present study reveal that the peanut plants have an efficient adaptive mechanism to tolerate high salinity by maintaining adequate leaf water status associated with growth restriction. In order to circumvent the stress resulting from high salinity, the levels of some organic metabolites such as total free amino acids, proline, total sugars and starch were elevated. The elevated levels of the organic metabolites may possibly have some role in maintenance of osmotic homeostasis, nutrient uptake and adequate tissue water status in peanut seedlings under high-salinity conditions.     

Proline protects <Emphasis Type="Italic">Atropa belladonna</Emphasis> plants against nickel salt toxicity

Atropa belladonna L. plants were grown in water culture for 8 weeks before the nutrient medium was supplemented with NiCl₂ to final concentrations of 0 (control treatment), 50, 100, 150, 200, 250, and 300 μM. After 4 days of plant growing in the presence of nickel chloride, the content of water, proline, Ni, Fe, free polyamines, as well as lipid peroxidation rates were measured. The addition of 100–150 μM Ni to the medium significantly reduced the fresh weight increments and water content in comparison with these parameters for untreated plants; 200 μM Ni caused serious, although nonlethal damage to the plants, whereas 250 and 300 μM Ni proved to be lethal. In the aboveground organs, the major part of Ni was accumulated in the apical leaves. When the plants were treated with 200 μM Ni, the Ni content in apical leaves was 220 μg/g dry wt, while Ni content in roots reached 1500 μg/g dry wt. The treatment of plants with proline in the presence of 200 μM Ni inhibited Ni accumulation in tissues. The proline-treated plants exhibited elevated iron content in leaves and especially in roots and were characterized by comparatively low rates of lipid peroxidation and by sustained leaf water status. When 200 μM Ni was applied, the content of free putrescine decreased, while the contents of spermine and spermidine in leaves increased appreciably with respect to the control values. The toxic effect of nickel was accompanied not only by an enhanced accumulation of high- molecular-weight polyamines but also by their oxidative degradation, which was evident from the 14-fold increase in the content of 1,3-diaminopropane. The protective effect of exogenous proline in the presence of high nickel concentrations was manifested in lowered lipid peroxidation rates, alleviation of iron deficiency, and in retarded oxidative degradation of polyamines.     

The influence of dietary iron on zinc in rat

The purpose of this study was to clarify the influence of iron on zinc status. The animals were divided into four groups, consisting of five rats in each group. The control group was fed on basal diet with adequate levels of zinc and iron, whereas the experimental group was fed diets containing different levels of iron ad libitum for 15 d. Low levels of iron (LFe) significantly increased the zinc absorption percentage but there was a decrease in high (HFe) and very high iron (VHFe) level groups (p<0.001). The retention percentage changes were found to be parallel to the changes in the absorption percentage curve. It was found that zinc (per total dry tissue) and Zn-65 (per total tissue) increased in the rats fed the LFe, whereas in general they decreased in the rats fed the HFe and VHFe diets. Significant changes were found in the duodenum and liver. Zn-65 (per g wet tissue) significantly increased in the brain and liver in the LFe group, but there was a decrease in the duodenum, ileum, kidney, liver, and brain in the HFe and VHFe groups. Changes in the level of zinc (per g dried tissue) were found to be parallel to the changes in Zn-65 in all the groups. The dietary proportions of iron appear to influence zinc metabolism at the intestinal and cellular transport levels over a given period of time.     

Expression of a single-chain Fv antibody fragment specific for the Hepatitis B surface antigen in transgenic tobacco plants

An anti-Hepatitis B virus surface antigen (HBsAg) single chain Fv (scFv) antibody fragment was expressed in Nicotiana tabacum transgenic plants. The 6-histidine tagged scFv was targeted to either the cytosol, apoplast, and vacuole, or for retention in the endoplasmic reticulum. Expression of active scFv was detected by ELISA in fresh leaf material from F1 transgenic plant lines representative of the genetic constructs targeting the antibody fragment to the apoplastic fluid (AF-12, 0.031% of the total soluble protein), vacuole (V-20, 0.032% of the total soluble protein), and endoplasmic reticulum (ER-52, 0.22% of the total soluble protein). No scFv was detected by ELISA or western blot in the plants transformed with the cytosol construct. The biologically active scFv was easily purified (to 94–95% purity) from ER-52 and AF-12 plant material using immobilized metal ion affinity chromatography. Recovery estimated from the ER-52 plant line indicates that 15–20g of pure active scFv can be obtained per gram of fresh leaf material, on a laboratory scale.     

Alterations of iron distribution in Arabidopsis tissues infected by Dickeya dadantii

Dickeya dadantii is a plant‐pathogenic enterobacterium responsible for plant soft rot disease in a wide range of hosts, including the model plant Arabidopsis thaliana. Iron distribution in infected A. thaliana was investigated at the cellular scale using the Perls'–diaminobenzidine–H₂O₂ (PDH) method. Iron visualization during infection reveals a loss of iron from cellular compartments and plant cell walls. During symptom progression, two distinct zones are clearly visible: a macerated zone displaying weak iron content and a healthy zone displaying strong iron content. Immunolabelling of cell wall methylated pectin shows that pectin degradation is correlated with iron release from cell walls, indicating a strong relationship between cell wall integrity and iron in plant tissues. Using a D. dadantii lipopolysaccharide antibody, we show that bacteria are restricted to the infected tissue, and that they accumulate iron in planta. In conclusion, weak iron content is strictly correlated with bacterial cell localization in the infected tissues, indicating a crucial role of this element during the interaction. This is the first report of iron localization at the cellular level during a plant–microbe interaction and shows that PDH is a method of choice in this type of investigation.