Fe Translocation Research Articles

Comparative investigation on the susceptibility of faba bean (Vicia faba L.) and sunflower (Helianthus annuus L.) to iron chlorosis

Comparative physiological studies on iron (Fe) chlorosis of Vicia faba L. and Helianthus annuus L. were carried out. High internal Fe contents in Vicia cotyledons (16–37 μg) were completely used for plant growth and Fe chlorosis was not inducible by the application of nitrate (with or without bicarbonate). In Helianthus, low quantities of Fe in the seeds (4 μg) were insufficient for normal growth and without Fe in the nutrient solution, Fe chlorosis was obtained in all treatments. This chlorosis was an absolute Fe deficiency. Also, the treatment with 1 μM Fe in the nutrient solution and nitrate (with or without bicarbonate) led to severe chlorotic symptoms associated with low leaf Fe concentrations and high Fe concentrations in the roots. In contrast, Helianthus grown with NH4NO3 and 1 μM Fe had green leaves and high leaf Fe concentrations. However, with NO3 supply (with or without bicarbonate), Fe translocation from the roots to the upper plant parts was restricted and leaves were chlorotic. Chlorotic and green sunflower leaves may have the same Fe concentrations, leaf Fe concentration being dependent on Fe translocation into the leaf at the various pH levels in the nutrient solution. At low external pH levels (controlled conditions) more Fe was translocated into the leaf leading to similar leaf Fe concentrations with higher chlorophyll concentrations (NH4NO3) and with lower chlorophyll concentrations (NO3). This indicates a lower utilization of leaf Fe of NO3 grown sunflower plants. Utilization of Fe in faba bean leaves is presumably higher than in sunflower leaves. In Vicia xylem sap pH was not affected by nitrate. In contrast, the xylem sap pH in Helianthus was permanently increased by about 0.4 pH units when fed with nitrate (with or without bicarbonate) compared with NH4NO3 nutrition. The xylem sap pH is indicative of leaf apoplast pH. From our earlier work (Mengel et al., 1994; Kosegarten und Englisch, 1994) we therefore suppose that in Helianthus, Fe immobilization occurs in the leaf apoplast due to high pH levels when grown with nitrate (with or without bicarbonate).

Cryptopodzolic Soils in Switzerland

SummaryCryptopodzolic Soils are characterized by a thick blackish‐brown mineral horizon rich in organic matter, the dark colour of which masks the morphological characteristics of podzolization. Little is known about the specific site factors that lead to the formation of these soils. Four representative soil profiles from a typical toposequence between 1700 and 500 m above sea level in southern Switzerland, embracing Haplic Podzols, Humic Cambisols and Cryptopodzolic Soils, are described morphologically, chemically and physically. The Cryptopodzolic Soils in this region are characterized by weak to moderate A1 and Fe translocation, and by a uniform incorporation of organic matter deep into the soil. The most prominent feature is the exceptional stability of the soil organic matter with a maximum in the spodic horizon. All these characteristics can be explained by the unique combined effect of a mild, wet climate, an Fe‐ and Al‐rich acid bedrock and a litter layer providing dissolved organic matter rich in polyphenolic substances with strong metal‐binding properties.

CONCURRENT STABILIZATION OF SOME INTERIOR DUNE FIELDS IN MICHIGAN

Inland dunes occur over a large part of east-central lower Michigan, where they mantle glaciolacustrine and outwash surfaces that were exposed around 12,000 yrs. B.P. The dunes are parabolic, with northwest-oriented limbs, and occur in swampy landscapes, suggesting that paleoclimatic conditions at the time of their formation were much drier and possibly windier. In order to determine whether the dunes stabilized concurrently or randomly in time and space, surface soils were studied on 30 dunes in the area and quantitatively analyzed for relative differences. Soils data from the dunes indicate concurrent stabilization, following a period of regional mobilization of aeolian sand. Surface soils have formed by podzolization, in uniform parent materials, and are morphologically similar throughout the area. All the soils are weakly developed, with subtle variations on a A-E-Bs-BC-C horizonation sequence. Munsell colors of Bs horizons are remarkably uniform, with 27 of 30 sites exhibiting values of 4 and chromas of 6. Chemical data suggest that Fe and Al translocation has been uniform throughout the region. When compared with soils of known age in northwest lower Michigan, the data indicate that dunes in the region had stabilized at least by 4000 yrs. B.P., leaving an approximately 8000-yr. interval in which they could have formed. In contrast to the prevailing southwesterly winds of today, dune-forming winds were dominantly from the northwest. [Key words: aeolian sedimentation, dunes, soil, Great Lakes, Michigan.]

Direct Measurement of 59Fe-Labeled Fe2+ Influx in Roots of Pea Using a Chelator Buffer System to Control Free Fe2+ in Solution.

Fe2+ transport in plants has been difficult to quantify because of the inability to control Fe2+ activity in aerated solutions and non-specific binding of Fe to cell walls. In this study, a Fe(II)-3-(2-pyridyl)-5,6-diphenyl-1,2,4-triazine-4[prime]4"-disulfonic acid buffer system was used to control free Fe2+ in uptake solutions. Additionally, desorption methodologies were developed to adequately remove nonspecifically bound Fe from the root apoplasm. This enabled us to quantify unidirectional Fe2+ influx via radiotracer (59Fe) uptake in roots of pea (Pisum sativum cv Sparkle) and its single gene mutant brz, an Fe hyperaccumulator. Fe influx into roots was dramatically inhibited by low temperature, indicating that the measured Fe accumulation in these roots was due to true influx across the plasma membrane rather than nonspecific binding to the root apoplasm. Both Fe2+ influx and Fe translocation to the shoots were stimulated by Fe deficiency in Sparkle. Additionally, brz, a mutant that constitutively exhibits high ferric reductase activity, exhibited higher Fe2+ influx rates than +Fe-grown Sparkle. These results suggest that either Fe deficiency triggers the induction of the Fe2+ transporter or that the enhanced ferric reductase activity somehow stimulates the activity of the existing Fe2+ transport protein.

Effects of Pb and Cd on Cucumber Depending on the Fe-Complex in the Culture Solution

Summary Modifying effects of EDTA and citrate as Fe(III)-complexes on Pb-and Cd-toxicity were investigated with cucumber ( Cucumis sativus L.) grown in culture solution. Pb and Cd were applied in lO μM concentration. Pb and Cd inhibited the growth of plants with Fe-citrate but with Fe-EDTA only Cd did. Chlorophyll content of Cd-treated plants-independently on the Fe-complex-was very low similarly to the iron deficient plants. Pb is proved to inhibit the chlorophyll accumulation only in plants supplied with Fe-citrate. Photosynthetic activity of 6-week-old plants was characterized by in vivo CO 2 fixation. The highest activities were observed in the middle (third-fourth) leaf storeys, and decreased in the lower and higher leaf storeys. Cd caused more than 50 % inhibition of the photosynthetic activity when applied with Fe-EDTA. With Fe-citrate, the inhibition exceeded 90 %. The photosynthetic activities in the Pb-treated plants were not significantly different from the control plants. The amount of chlorophyll containing complexes, especially that of PS I was highly affected by Cd particularly in the lower leaves. The results correlate with 59 Fe translocation into the shoot. Fe translocation was stimulated by Pb in the presence of Fe-EDTA but it was inhibited in the presence of Fe-citrate. Cd completely inhibited Fe translocation from the root to the shoot with both chelators. It is concluded that strong iron deficiency has a great but not exclusive role in the observed symptoms, and that the quality of the chelator strongly influences the effects of these polluting metals.

Mycorrhizal dependency of micropropagated argan tree (Argania spinosa): II. Mineral nutrition

The influence of V.A. mycorrhization on mineral nutrition of 2 clones ofArgania spinosa was studied with in-vitro micropropagated plantlets grown in confined medium under controlled conditions. Inoculation, which increased dry matter production by a factor of 4.5, also increased P concentration in the plant, especially in the leaves, and the mycorrhizal plants mobilized 15 times more P than control plants. N concentration was slightly lower in mycorrhizal plants, but total N content was 3 times higher. Uptake of micro elements was also affected, inoculation increasing plant Fe, Zn and Cu content. Mineral nutrition in the test clones seemed affected by root/shoot ratio and other genetically-related characteristics, such as Fe translocation efficiency. These results help us to understand how its deep mycorrhizal root system might allowArgania spinosa not only to grow in infertile arid areas but also to improve top-soil fertility by a litter effect.

Assessment of Fe status of peach rootstocks by techniques used to distinguish chlorotic and non‐chlorotic leaves1

Abstract Peach rootstocks Lovell, GF677, Siberian‐C and Nemaguard were grown for Fe efficiency evaluation under high nutrient solution pH. Various techniques were employed to assess the Fe status of plants. Total leaf and 2% acetic acid extracted Fe concentration were not able to distinguish between chlorotic and non‐chlorotic leaves. O‐Phenanthroline extraction does not seem to be sufficiently sensitive to distinguish between moderately chlorotic and green leaves. Xylem sap Fe concentration did not correspond with the leaf Fe concentration of the same rootstock which indicates its non‐suitability for the assessment of Fe translocation ability of rootstocks. P/Fe and K/Ca ratios were not found to be good indicators of Fe deficiency. Leaf chlorophyll content increased as the Fe concentration in the nutrient solution increased. Leaf chlorophyll content was a reliable criterion for assesssing the active Fe status of the plants. On the basis of the correlation between leaf chlorophyll content and Fe treatment...

Enhanced Mn accumulation by snapbean cultivars under FE stress

Abstract Iron deficiency in dicots is accompanied by an increased potential for Fe uptake and translocation. The mechanisms responsible for these changes in metabolism (Fe‐stress response) provide for the adaptation of Fe‐efficient genotypes to conditions which limit the availability of Fe. Previous studies indicated that when Fe‐stress response is initiated, the uptake of Mn, as well as Fe, is enhanced in Fe efficient species such as sunflower. The present study was conducted to determine the relationship between Fe‐stress response and Mn uptake in snapbean (Phaseolus vulgaris L., cvs. Bush Blue Lake 290, Bush Blue Lake 274). The plants were grown in complete nutrient solutions containing 0.02 to 0.52 mg L‐1 Mn, at acid or alkaline pH. Iron stress was induced with 0.22 mg l‐1 Fe(EDDHA) (molar ratio 1:1 or 1:2), high P (14.3 mg L‐1) and excess CaCO3. Bush Blue Lake 290 ('BBL 290') was more sensitive than Bush Blue Lake 274 ('BBL 274') to Mn toxicity in acid (pH 5.2) nutrient solutions with adequate Fe. Un...

Nitrate/ammonium ratio effects on mineral element uptake by sorghum1

Abstract Experiments were conducted using different NO3 –/NH4 + ratios to determine the effects of these sources of N on mineral element uptake by sorghum [Sorghum bicolor (L.) Moench] plants grown in nutrient solution. The NO3 –/NH4 + ratios in nutrient solution were 200/0, 195/5, 190/10, and 160/40 mg N L–1. Nutrient solutions were sampled daily and plants harvested every other day during the 12‐day treatment period. Moderately severe Fe deficiencies were observed on leaves of plants grown with 200/0 NO3 –/NH4 + solutions, but not on the leaves of plants grown with the other NO3 –/NH4 + ratios. As plants aged, less Fe, Mn, and Cu were translocated from the roots to leaves and leaf/root ratios of these elements decreased dramatically in plants grown with 200/0 NO3 –/NH4 + solutions. Extensive amounts of Fe, Mn, and Cu accumulated in or on the roots of plants grown with 200/0 NO3 –/NH4 + solutions. Manganese and Cu may have interacted strongly with Fe to inhibit Fe translocation to leaves and to induce Fe deficiency. As the proportion of NH4 + in solution increased, K, Ca, Mg, Mn, and Zn concentrations decreased in the leaves, and Ca, Mg, Mn, and Cu concentrations decreased in roots. Potassium and Zn tended to increase in roots as NH4 + in solution increased.

MICRONUTRIENT UPTAKE AND TRANSLOCATION BY MACROCYSTIS PYRIFERA (PHAEOPHYTA)1

ABSTRACTRadionuclides of the micronutrients (Mn, Co, Cu, Zn, Mo, and I) of Macrocystis pyrifera (L.) C. Ag. and the nonnutrient Ni were concentrated in sieve tube sap. Micronutrient uptake rates of mature blade tissue were determined using the appropriate radionuclide in artificial seawater. Cellular uptake was distinguished from free space uptake by the use of suitable wash solutions. The uptake rates were then transposed to conditions in the sea, with several assumptions being made. Micronutrient content was determined for mature blade tissue before and after treatment to remove extracellular micronutrients. A mathematical description of frond growth was developed from previously published data and used to derive equations relating micronutrient assimilation (tissue incorporation) and uptake by fronds, both expressed in mg·d−1, to frond length. Calculations revealed that at a certain frond length xi assimilation equaled uptake for Mn, Co, and Fe. Uptake was greater than assimilation for fronds longer than xi and less than assimilation for fronds shorter than xi. This indicated that Mn, Co, and Fe translocation was required from fronds longer than xi to fronds shorter than xi. The large assimilation values at xi for Mn and Co further indicate that these elements, at times, may limit Macrocystis growth. Calculations also showed that Cu, Zn, Mo, I, and Ni uptake was greater than their assimilation for all frond lengths, which suggested that these elements are transported to other tissues for storage (e.g. in holdfast) or release (e.g. from frond apices).

Problems of iron deficiency in different crop plants in India: Causative factors and control measures

Abstract The problem of Fe‐deficiency chlorosis in different parts of India, particularly in Maharashtra and Tamil Nadu States is described. The most affected crops are sugarcane, sorghum, groundnut and legumes. The soils in these affected areas are calcareous with pH above 8. The general method for correcting chlorosis has been the application of Fe salts through the soil or as foliar sprays. In Tamil Nadu, an “organically complexed Fe”; has been tested and is found to increase Fe translocation and increase crop yield in sorghum. Several cultivars of sorghum and chickpea were tested for Fe‐deficiency stress tolerance in solution culture, in the last few years and tolerant ones have been identified. It is suggested that Fe‐deficiency stress tolerance should be included as a criterion along with traits like high yields, in plant breeding and agronomy program.

Alcuni aspetti del metabolismo di piante coltivate sia su un terreno serpentinoso sia in presenza di nichel

Abstract Effects of serpentine and Ni on some aspects of plant metabolism. — Results are here reported of a series of experiments on the metabolism of plants grown on a serpentine soil and in sand and water cultures with the addition of Ni. Variations in the content of citric and malic acid, chlorophylls, P, Ni, Fe (total and HCl soluble), Mn and Cu have been followed during plant growth in the leaves and roots. In Avena and Phaseolus the citric acid content greatly increases in both treatments (serpentine and Ni); the chlorophylls (a+b) markedly decrease; HCl sol. Fe is always reduced, particularly in the serpentine plants, total Fe accumulates in the roots in both treatments. The P content is particularly high in the Ni-treated plants, whilst on serpentine oats are always P-deficient, showing also a lower Mn and Cu content than plants grown in water cultures plus Ni. The relationships between citrate accumulation and scarce Fe translocation are discussed.

Physiological Aspects of Iron‐Phosphorus Nutrition in Two Varieties of Maize: I. Uptake and Accumulation Characteristics Under Greenhouse and Field Conditions

AbstractTwo varieties of corn (Zea mays L.) showed differences in efficiency of Fe utilization when grown in hydroponic solutions and under field conditions. Under hydroponic conditions, ‘Seneca XX155’ showed greater susceptibility to P‐induced Fe stress than ‘Wisconsin 335A’, although its foliage contained more Fe. This susceptibility was related to reduced Fe translocation caused by relatively high P concentrations. Levels of P > 22 ppm in the nutrient solution produced significant reduction in foliage Fe of both varieties. Field studies showed significant reduction of tissue Fe at a fertilization level of 50 kg/ha compared to controls. Unlike results from hydroponic studies, no change in Fe status occurred at progressively higher rates of applied P (50–400 kg/ha) under field conditions. Levels of tissue Fe were never < 160 ppm following soil P applications.

Effects of Season, Night Temperature, and Potassium on the Absorption and Translocation of Iron in Centipede Grass (Eramochloa ophluroides [Munro] Hock)

Mild winter daytime greenhouse temperatures (maximum temperatures from 20 to 28 C) favored absorption and translocation of Fe in centipede grass. Increasing rates of K fertilization decreased Fe absorption but stimulated Fe translocation once both were in the plant tissues. Elevating night temperatures tended to lower grass root cation exchange capacity (CEC). Roots with low CEC absorbed less Fe than roots of grass grown at low night temperatures. Chlorosis associated with low night temperatures and high K levels was not the result of a deficiency in concentration or total uptake of Fe.