Supply and uptake of potassium,calcium and magnesium of spray carnations (Dianthus caryophyllus) grown in rockwool

Summary In two experiments with carnations grown in rockwool the effects of different cation ratios in the nutrient solution were studied. The results showed that carnations need a high calcium supply. The crop did not appear to be sensitive to different potassium-magnesium ratios in the nutrient solution. In the nutrient solution added mole ratios K∶Ca∶Mg=55∶35∶10 seemed to be optimal. Such ratios in addition led to ratios of 55∶30∶15 in the root environment. Tissue analysis showed that in younger leaves of peduncles harvested a potassium content of 900 mmol per kg dry matter was optimal. For calcium a content of 350 and for magnesium 100–150 mmol per kg was needed. Analytical data of plant-sap analyses were closely correlated with data gained by digestion of dried material. For potassium and magnesium the relationships were linear. However, for calcium a curvilinear relationship was found. In the experiments indications were obtained that a sufficient calcium supply suppressed foot rot in carnations.     

岩棉育苗对番茄幼苗生长发育的影响

采用岩棉和营养土方作育苗基质,观测了基质对番茄幼苗各时期生长的影响。其试验结果是：以岩棉作基质培育功苗能增加番茄幼苗全株的干重,其中幼苗根系的干重增加较为显著。在播种２４ｄ内,岩棉育苗的幼苗高度、茎干重、叶面积和干重的增长略低于营养土方育苗,２４ｄ以后,岩棉育苗则增长迅速,说明岩棉育苗具有增加幼苗干物质累积、培育壮苗的特点,证实岩棉是一种良好的育苗基质。     

Iron plaque enhances phosphorus uptake by rice (Oryza sativa) growing under varying phosphorus and iron concentrations

Both solution culture and pot experiments were performed to investigate (a) the effects of external Fe (II) concentrations and forms on the formation of iron plaque on the roots of rice (Oryza sativa) and subsequent P adsorption on iron plaque and shoot P concentrations and (b) the effects of soil moisture regimes on the formation of iron plaque and P adsorption on root surfaces and P accumulation in shoots. The results showed that iron plaque was significantly increased with increasing Fe²⁺ concentrations in the solution culture. The amounts of P adsorbed on the iron plaque were increased significantly with external Fe²⁺ concentrations. Although shoot P concentration was not significantly affected by Fe²⁺ treatment after incubation for 2 days, it was significantly increased in the Fe‐treated plants compared with Fe‐deprived ones after incubation for 4 days. Soil culture experiment showed that the formation of iron plaque on root surfaces was promoted by exogenous iron, with greater amount of iron plaque being formed by addition of ferric hydroxide than of ferric oxide. Phosphorus adsorption on iron plaque also increased with the addition of iron oxides, and increasing soil P increased the amounts of P associated with the iron plaque and shoot P concentration. The amounts of iron plaque were almost sixfold higher under flooding condition than under field capacity condition. Plants pretreated under flooding condition generally had higher shoot P concentrations when they were transplanted to solutions with varying P levels, and this was most pronounced in the treatment with highest solution P concentration. The results suggest that iron plaque acts as a nutrient reservoir for phosphorus in the rhizosphere and helps enhance P acquisition by rice.     

Effects of external iron concentration upon seedling growth and uptake of Fe and phosphate by the common reed, Phragmites australis (Cav.) Trin ex. Steudel

The objectives of this study were to determine whether, and to what degree, the aqueous iron concentration in the growing medium affects the growth of, and Fe uptake by, Phragmites australis, and whether the presence of iron in the growing environment affects the uptake of the essential element phosphate. The wetland macrophyte P. australis was grown under laboratory conditions in nutrient solution (0.31 mg L(-1) phosphate) containing a range of iron concentrations (0-50 mg L(-1) Fe). A threshold of iron concentration (1 mg L(-1)) was found, above which growth of P. australis was significantly inhibited. No direct causal relationship between iron content in aerial tissues and growth inhibition was found, which strongly suggests that iron toxicity cannot explain these results. Phosphate concentrations in aerial tissues were consistently sufficient for growth and development (2-3 % d. wt) despite significant variation in concentration of phosphate associated with roots. External Fe concentration had a significant effect on the growth of P. australis and on both Fe and phosphate concentrations associated with roots. However, neither direct toxicity nor phosphate deficiency could explain the reduction in growth above 1 mg L(-1) external Fe concentration     

铁对小麦吸收不同形态镉的影响

采用营养液培养方法,研究了在供铁与铁与缺铁条件下小麦对不同镉化合物和镉污染土壤中镉的吸收和转移,同时不他陪伴阴离子对小麦吸收镉的影响。结果表明：缺铁培养小麦植株地上部及根中的含镉量均显著高于下沉供铁培养的小麦,小麦对小同化合物的吸收量不同,其吸收的多寡顺序依次为：Ｃｄ（ＮＯ３）２〉ＣｄＳＯ４〉ＣｄＯ。     

作物种植前后土壤有机质及养分因子的空间变异分析

以作物土壤试验数据为基础,结合多年的农户调查数据,采用Moran's I指数分析、Pearson相关系数分析和Kriging插值3种地统计学方法,探讨了浙江省浦江县作物种植前后土壤有机质及氮磷钾等养分因子的空间演化规律。研究发现Moran's I指数分析证实随着区域范围的加大,各因子间自相关程度产生较大差异。这一点在Pearson相关系数分析中也得到证实,并在kriging插值图中直观表达。结果还表明:有机质和碱解氮的形成与水的关系较为密切,水源区两因子的含量较周边高,且会促进前者向后者转化。养分投入后,过多的养分在土壤中降解过程与区域自然环境条件的关系较密切。同一作物的农户养分投入在不同区域差异较大,不同作物的农户养分投入在区域内却存在量的相关。     

山东小麦地方品种资源铁和锌含量分析

利用等离子体发射光谱仪,对426份山东小麦地方品种资源进行了铁和锌微量元素含量的测定,摸清了山东省小麦地方品种资源铁和锌含量的分布情况。结果表明,山东小麦地方品种资源铁含量的分布范围为5.2～44.1mg/kg,锌含量的分布范围为6.2～50.4mg/kg。铁含量最高的种质是土耳其和落麦,分别为44.1mg/kg和41.8mg/kg;锌含量最高的种质是大青芒,为50.4mg/kg。利用这些铁锌含量高、子粒商品性及面制品口味好的小麦地方品种作育种亲本,对培育子粒中富含铁锌微量元素的高营养小麦新种质,具有十分重要的意义。     

Response of rice (Oryza sativa) with root surface iron plaque under aluminium stress

BACKGROUND AND AIMS: Rice (Oryza sativa) is an aquatic plant with a characteristic of forming iron plaque on its root surfaces. It is considered to be the most Al-tolerant species among the cereal crops. The objective of this study was to determine the effects of root surface iron plaque on Al translocation, accumulation and the change of physiological responses under Al stress in rice in the presence of iron plaque. METHODS: The japonica variety rice, Koshihikari, was used in this study and was grown hydroponically in a growth chamber. Iron plaque was induced by exposing the rice roots to 30 mg L(-1) ferrous iron either as Fe(II)-EDTA in nutrient solution (6 d, Method I) or as FeSO(4) in water solution (12 h, Method II). Organic acid in root exudates was retained in the anion-exchange resin and eluted with 2 m HCl, then analysed by high-performance liquid chromatography (HPLC) after proper pre-treatment. Fe and Al in iron plaque were extracted with DCB (dithionite-citrate-bicarbonate) solution. KEY RESULTS AND CONCLUSIONS: Both methods (I and II) could induce the formation of iron plaque on rice root surfaces. The amounts of DCB-extractable Fe and Al on root surfaces were much higher in the presence of iron plaque than in the absence of iron plaque. Al contents in root tips were significantly decreased with iron plaque; translocation of Al from roots to shoots was significantly reduced with iron plaque. Al-induced secretion of citrate was observed and iron plaque could greatly depress this citrate secretion. These results suggested that iron plaque on rice root surfaces can be a sink to sequester Al onto the root surfaces and Fe ions can pre-saturate Al-binding sites in root tips, which protects the rice root tips from suffering Al stress to a certain extent.     

Effect of iron chlorosis-inducing factors on the pH of the cytoplasm of sunflower (Helianthus annuus)

Summary Growth chamber experiments with sunflower in nutrient solution were performed to investigate the effect of phosphorus and bicarbonate in inducing iron chlorosis.Iron chlorosis as proved by lower dry matter yield and reduced chlorophyll content was induced by bicarbonate alone and more pronounced by a combination of bicarbonate and phosphate, but not by phosphate alone.Iron content of roots and aerial plant parts was reduced by bicarbonate in all experiments, but only in one experiment by phosphate alone.Bicarbonate in the nutrient medium increased the pH of the cytoplasm in leaf cells, while phosphate had no effect.A daily adjustment of the pH in the nutrient medium to a value comparable to that in the bicarbonate trial, did not affect the pH of the cytoplasm.It is concluded that the pH of the cytoplasm plays an important role in establishing plant resistance or susceptibility to Fe chlorosis.     

Physiological responses and differential gene expression in Prunus rootstocks under iron deficiency conditions

Two Prunus rootstocks, the Myrobalan plum P 2175 and the interspecific peach-almond hybrid, Felinem, were studied to characterize their biochemical and molecular responses induced under iron-Deficient conditions. Plants of both genotypes were submitted to different treatments using a hydroponic system that permitted removal of Fe from the nutrient solution. Control plants were grown in 90 μM Fe (III)-EDTA, Deficient plants were grown in an iron free solution, and plants submitted to an Inductor treatment were resupplied with 180 μM Fe (III)-EDTA over 1 and 2 days after a period of 4 or 15 days of growth on an iron-free solution. Felinem increased the activity of the iron chelate reductase (FC-R) in the Inductor treatment after 4 days of iron deprivation. In contrast, P 2175 did not show any response after at least 15 days without iron. The induction of the FC-R activity in this genotype was coincident in time with the medium acidification. These results suggest two different mechanisms of iron chlorosis tolerance in both Strategy I genotypes. Felinem would use the iron reduction as the main mechanism to capture the iron from the soil, and in P 2175, the mechanism of response would be slower and start with the acidification of the medium synchronized with the gradual loss of chlorophyll in leaves. To better understand the control of these responses at the molecular level, the differential expression of PFRO2, PIRT1 and PAHA2 genes involved in the reductase activity, the iron transport in roots, and the proton release, respectively, were analyzed. The expression of these genes, estimated by quantitative real-time PCR, was different between genotypes and among treatments. The results were in agreement with the physiological responses observed.     

FURTHER ASPECTS OF THE RELATIONSHIP BETWEEN NICKEL TOXICITY AND IRON SUPPLY

Absorption of nickel by oat plants increased with increasing pH for a fixed iron supply. Nickel uptake and toxicity symptoms (necrosis and chlorosis) were both reduced when the concentration of iron in the nutrient solution was high. Nickel-iron ratio in the nutrient solution. For solutions with the same nickel-iron ratio, toxicity symptoms increased with increase in the absolute amount of nickel. There was a linear relationship between the degree of necrotic symptoms and the nickel-iron ratio in the plant.
Nickel consistently reduced the iron content of roots and tops. In the absence of nickel, the iron content of the roots but not of the tops, increased with iron supply. In nickel-toxic plants, the magnesium, calcium and phosphorus contents of the tops and the potassium, calcium and phosphorus contents of the roots were higher than in healthy plants, but the potassium content of the tops and the magnesium content of the roots were lower.
Similar results were found with tomato.     

The role of nodules in the tolerance of common bean to iron deficiency

Iron is vital for the establishment and function of symbiotic root nodules of legumes. Although abundant in the environment, Fe is often a limiting nutrient for plant growth due to its low solubility and availability in some soils. We have studied the mechanism of iron uptake in the root nodules of common bean to evaluate the role of nodules in physiological responses to iron deficiency. Based on experiments using full or partial submergence of nodulated roots in the nutrient solution, our results show that the nodules were affected only slightly under iron deficiency, especially when the nodules were submerged in nutrient solution in the tolerant cultivar. In addition, fully submerged root nodules showed enhanced acidification of the nutrient solution and showed higher ferric chelate reductase activity than that of partially submerged roots in plants cultivated under Fe deficiency. The main results obtained in this work suggest that in addition to preferential Fe allocation from the root system to the nodules, this symbiotic organ probably develops some mechanisms to respond to iron deficiency. These mechanisms were implied especially in nodule Fe absorption efficiency and in the ability of this organ to take up Fe directly from the medium.     

The effect of different iron concentrations on lead accumulation in hydroponically grown <Emphasis Type="Italic">Matthiola flavida</Emphasis> Boiss

The general relationship between heavy metals and mineral nutrition of plants grown in polluted environments is one of the most important factors for modifying the toxic properties of these metals. To study the effect of iron and lead pollution on the growth of Matthiola flavida a factorial research was undertaken in the form of a completely randomized design with four replications in hydroponic culture. After germination, seedlings were transferred to a hydroponic culture. During the pre-treatment step, a series of plants contained enough iron (+Fe), whereas the second series was without iron (?Fe). After the pre-treatment step, both series of plants were treated with three levels of iron as FeEDDHA and two levels of lead as Pb(NO₃)₂. The results showed that in both series of plants, lead reduced the root growth, shoot height, shoot and root dry weight. For 5 µM lead concentration, with increasing concentration of iron in the nutrient solution, concentration of lead in the roots and shoots decreased. For 1 µM concentration of lead, increasing the iron concentration in the nutrient solution reduced the concentration of lead in the roots, but had no significant effect on the amount of lead in shoots. Lead accumulation in shoots and roots of plants with Fe was more than plants without Fe. Also, in low concentrations of iron, the amount of iron in shoot increased with the increase of lead concentration in the nutrient solution. The results showed that in lead pollution, iron has a positive effect on investigated traits.     

Iron toxicity to rice in an acid sulfate soil as influenced by water regimes

Summary The effects of two water regimes: Continuous flooding and flooding with soil drying on iron toxicity to rice in an acid sulfate soil was studied by continuously growing 7 crops of IR-32 rice in pots under the two water treatments. There was no plant growth upto the second crop under both water treatments due to iron toxicity. But there was good growth of rice under the continuous water regime from third cropping onwards, however, there was no growth of rice in the flooding with soil drying treatment even upto the seventh crop due to iron toxicity.The results of the study bring out that keeping an acid sulfate soil flooded for a few weeks and then planting rice when iron in soil solution has dropped below toxicity level may be a possible management practice for lowland rice culture on such soils. Drying and reflooding an acid sulfate soil on the other hand aggravates soil acidity and keeps iron in solution in high amounts to be toxic to rice plant.     

Iron-mediated effect of alcohol on hepatocyte differentiation in HepaRG cells

The development of alcoholic liver diseases depends on the ability of hepatocyte to proliferate and differentiate in the case of alcohol-induced injury. Our previous work showed an inhibitory effect of alcohol on hepatocyte proliferation. However, the effect of alcohol on hepatocyte differentiation has not yet been precisely characterized. In the present study, we evaluated the effect of alcohol on hepatocyte differentiation in relationship with changes of iron metabolism in HepaRG cells. This unique bipotent human cell line can differentiate into hepatocytes and biliary epithelial cells, paralleling liver development. Results showed that alcohol reduced cell viability, total protein level and enhanced hepatic enzymes leakage in differentiated HepaRG cells. Moreover, it caused cell enlargement, decreased number of hepatocyte and expression of C/EBPα as well as bile canaliculi F-actin. Alcohol increased expression of hepatic cell-specific markers and alcohol-metabolizing enzymes (ADH2, CYP2E1). This was associated with a lipid peroxidation and an iron excess expressed by an increase in total iron content, ferritin level, iron uptake as well as an overexpression of genes involved in iron transport and storage. Alcohol-induced hepatoxicity was amplified by exogenous iron via exceeding iron overload. Taken together, our data demonstrate that in differentiated hepatocytes, alcohol reduces proliferation while increasing expression of hepatic cell-specific markers. Moreover, iron overload could be one of the underlying mechanisms of effect of alcohol on the whole differentiation process of hepatocytes.     

Interpreting changes in stem diameter in rose plants

Sixteen adult rose plants ( Rosa hybrida cv. Sweet Promise) were grown in rockwool in a phytotron. Water uptake was estimated by computing the difference between the rate of nutrient solution supply and the rate of leaching, continuously measured using a high-precision flowmeter. Transpiration was measured using a balance continuously recording the loss of weight in the entire system. Changes in stem diameter were recorded using linear variable differential transducers placed at the base of four developing shoots and on their corresponding basal stems. Changes in stem diameter were related to changes in the water content of 16 plants. The amplitude of shrinkage in daytime stem diameter and daily increase in stem diameter was lower in basal stems. Radial hydraulic resistance to water diffusion in stems seems to be very low and stem reservoirs appear to be very early sensors of water depletion. When the nutrient solution supply was suppressed, the amplitude of the daily increase in stem diameter and transpiration rates were reduced one and one-and-a-half days later, respectively. When water depletion became more severe, stem diameter decreased from one day to another. The amplitude of daily stem shrinkage increased sharply for 6 days after watering was stopped, while the bulk modulus of elasticity of leaves decreased, probably as a result of damage to the cell wall.     

THE RELATIONSHIP BETWEEN NICKEL TOXICITY AND IRON SUPPLY

The influence of varying levels of iron and substrate pH on the uptake of nickel and the intensity of toxicity symptoms in oat plants have been investigated using sand-and water-culture techniques.
Nickel-toxicity symptoms (both necrosis and chlorosis) are less severe when the concentration of iron in the nutrient solution is high. The reduction in degree of necrosis is related to a reduced content of nickel in the leaf blades, whilst that of chlorosis is related to the Ni/Fe ratio in the leaf blades—an internal antagonism being indicated in the latter case.
A reciprocal relationship exists between the nickel and iron contents of the leaf blades; the nickel content is materially reduced by high concentrations of iron in the nutrient solution, and the iron content by nickel, the former being the more pronounced effect.
Uptake of nickel increases with increasing pH for a constant iron level in the substrate, although the degree of necrotic symptoms is similar over pH range 4–7. Iron uptake is reduced by both nickel and increasing pH and results in chlorosis at pH values of 5·5 and above.
For a constant level of iron supply the phosphate content of the stem extracts is higher the greater the degree of nickel toxicity; the phosphorus status of the plant may be a factor in producing nickel toxicity but if so, it has to be considered in relation to other factors.     

A comparative study of the effects of natural and synthetic ligands on iron uptake by plants

Summary The uptake of iron by wheat seedlings was investigated using half-strength Hoagland's nutrient solution containing 2.0 M ferric chloride labelled with⁵⁹Fe. The iron content of root tissue, which includes adsorbed iron, was depressed by the presence in the solution of the synthetic ligands EDTA and polymaleic acid (PMA) and by the natural ligands, humate, fulvate and a water-extractable soil polycarboxylate. The patterns of change in iron content of the shoots were in all cases different from those of the roots and were of two types. EDTA and humate increased the iron content of the shoots to maximum values, at ligand concentrations of 5.0 M and 2.5 mg l^–1 respectively, and decreased it at higher concentrations. Fulvate, water-extractable soil polycarboxylate and PMA increased the iron content of the shoots up to the maximum ligand concentrations tested (25 mg l^–1). These results are discussed in the light of the likely solution chemistry of iron and the various ligands.     

Response of tomatoes (Lycopersicon esculentum) to an unequal distribution of nutrients in the root environment

Tomato (Lycopersicon esculentum Mill.) plants were grown in a split root system. The plants were rooted in two separate cubes of rockwool, which were subsequently irrigated with nutrient solution of equal (control) or different EC values. Besides optimal values, too low and too high values for maximal production were included.The yield was determined by the EC value considered optimal for plant nutrition if present in one of both rockwool cubes. The quality of the fruits was primarily determined by standard EC values available in part of the root environment. Water was preferably taken up from the low EC compartment, nutrients from the high EC compartment. Samples of leaves and fruits were analyzed to get information about uptake and translocation of nutrients in the plant.     

Influence of nutrient solution pH on N2O and N2 emissions from a soilless culture system

The influence of nutrient solution pH on the emission of N2O and N2 was investigated during cultivation of cucumbers in a closed-loop rockwool system. Between pH 4 and 7 these gaseous nitrogen losses increased from 1.6 to 21.1% of the N fertilizer input. This was equivalent to average flux rates of 0.06 and 0.85 kg nitrogen per hectare greenhouse area and day, respectively. The N2O/N2 ratio was inversely related to the total gaseous nitrogen losses. At neutral pH dinitrogen was the main emission product, whereas more acidic conditions favoured the emission of nitrous oxide. The pH effects were probably not indirectly affected by root respiration or exudation as much as by a direct inhibition of the activity of denitrifying microorganisms due to high H+ concentrations since similar results were obtained in unplanted nutrient solution systems with the addition of glucose as carbon source. Despite the low microbial denitrification activity under acidic conditions, nitrogen balance deficits of up to one-fifth of the N input still occurred. It is suggested these losses were predominantly caused by chemodenitrification.