Comparison of the Vegetative Growth,Eco-Physiological Characteristics and Mineral Nutrient Content of Basil Plants in Different Irrigation Ratios of Hydroponic:Aquaponic Solutions

Aquaponics is the combined culture of fish and plants in recirculating systems. This experiment was conducted to evaluate the production of basil out of the aquaponic system by irrigation of the plants with different ratios of hydroponic and aquaponic solutions. Basil seedlings were irrigated three times day^?1 with 200 mL aquaponic-aquaponic-aquaponic (AAA), aquaponic-hydroponic-aquaponic (AHA), hydroponic-aquaponic-hydroponic (HAH), and hydroponic-hydroponic-hydroponic (HHH) solutions, respectively. Fresh and dry mass of shoots and roots of basil decreased at AAA treatment significantly. The plants were slightly less green at AHA treatments, and a visible chlorosis appeared in the leaves of AAA-treated plants. This chlorosis resulted lower net carbon dioxide (CO₂) assimilation rate, transpiration rate, and stomatal conductance in AAA treatment. Iron (Fe), manganese (Mn), and potassium (K) concentrations in leaves decreased and zinc (Zn) concentration increased in higher ratios of aquaponic:hydroponic solution. Lower Fe, Mn, and K concentrations in aquaponic solution may be a main part of the reason for growth reduction.     

Nutrient Dynamics in Orange Trees: The Effect of Soil Fertility

Lime-induced iron (Fe) chlorosis is a nutritional disorder common in calcareous soils, which may result from a low level of Fe available or adverse factors that inhibit Fe mobilization and uptake by plants. Organic-matter amendments can prevent or correct Fe chlorosis in plants but the effect of endogenous soil organic matter (SOM) on this disorder is not known. The main subject of this work was to investigate the consequence of two contrasting levels of soil fertility on the nutritional status of an orange grove [Citrus sinensis (L.) Osb. cv. Valencia Late]. The field experiment was conducted in a commercial citrus grove using mature trees distributed in two plots with different values of SOM, phosphorus (P), and potassium (K), but with the same level of active lime. The concentration of nitrogen (N), P, K, magnesium (Mg), calcium (Ca), Fe, copper (Cu), zinc (Zn), and manganese (Mn) in young and mature leaves and flowers was evaluated. The level of Mg and the Mg/Zn ratio in flowers from both plots, although significantly different, only indicated moderate Fe chlorosis, as predicted by a previously developed model, and was consistent with the amount of chlorophyll present in the leaves. However, nutrient partitioning between leaves of contrasting age was very different. Mature leaves from trees grown in the high-fertility plot (HF) had larger concentrations of N, P, and K but lower concentrations of Ca, Fe, and Mn than did those from the low-fertility plot (LF). Young leaves from the LF had more N, P, Mg, Cu, and Mn and less Ca and Fe than did those from the HF. Flower analysis, although useful to predict Fe chlorosis, failed to detect differences in the nutritional status of plants resulting from contrasting levels of soil fertility. Furthermore, endogenous SOM had only a marginal effect on Fe chlorosis.     

Determination of iron chlorosis with extractable iron analysis in peach leaves

Iron (Fe) though indispensable for the biosynthesis of chlorophyll, but its total content in the plant was not associated with the occurrence of chlorosis. Iron, which is the ferrous‐iron (Fe²⁺) form—termed “active”; Fe— and extracted with weak acids and some chelating agents, has been closely related to Fe chlorosis. In this study, three different methods were tested in order to determine suitable methods for extractable‐Fe analysis in a Dixired peach cultivar. In the first two methods, o‐phenantroline (o‐Ph) and 1N hydrochloric acid (HCl) were used to extract Fe²⁺ from fresh leaves. In the third method, 1N HCl were used as an extractant on dried leaf samples. The relationship between chlorophyll content of the leaves and Fe extracted by the three methods, was statistically significant. Hydrochloric acid extraction with dried leaves which gave the highest significant correlation (r = 0.930) with chlorophyll content, can be used for the determination of Fe²⁺ ("active”; Fe) status in peach trees.     

Genetic Differences in Resistance to Iron Deficiency Chlorosis in Peanut

Iron (Fe) deficiency has been a widespread problem in peanut (Arachis hypogaea L.) grown on calcareous soils of northern China and has resulted in significant yield losses. Field observations showed considerable variability in visual chlorosis symptoms among peanut cultivars in the same soil. The objective of this study was to confirm the genetic differences in resistance to Fe-deficiency chlorosis in peanut and to identify feasible indicators for screening Fe-efficient genotypes. Resistance to Fe chlorosis of sixteen peanut cultivars grown on calcareous soil was evaluated in the field and physiological responses to Fe-deficiency stress were studied in nutrient solution. There were significant differences in resistance to Fe-deficiency chlorosis among the sixteen peanut cultivars tested, which was identified with SPAD readings, active Fe concentrations in young leaves in the early growth stages, and the pod yield. For Fe-resistant peanut cultivars, Fe-reduction capacity and quality of releasing hydrogen ions from roots increased under Fe-deficiency stress. Highly correlated relationships were observed between the summation of root Fe reduction and field chlorosis scores for sixteen cultivars (r² = 0.79). It was concluded that Fe-reduction capacity was a better physiological indicator for screening Fe-efficient peanut genotypes of the mechanisms measured.     

Comparison of Various Analysis Methods for Determination of Iron Chlorosis in Apple Trees

Abstract

The objective of this study was to compare iron (Fe) concentrations (mg kg^?1) of the leaves measured by different methods and to determine the most suitable method to be used in evaluation of iron chlorosis in apple trees. For this purpose, green and chlorotic leaves were collected from 76 apple orchards in 1998 and 1999. Iron concentrations (mg kg^?1) of dried leaf samples were measured with 4 different methods, 1 N HCl (Method 1), 0.1 N HCl (Method 2), 0.005 M DTPA (Method 3), and 1.5% o-phenanthroline (Method 4). Total Fe concentrations (mg kg^?1) of dried leaf samples were also analyzed. Total chlorophyll and peroxidase enzyme activity in fresh leaf samples were measured. The total chlorophyll, peroxidase enzyme activity, Fe concentrations (mg kg^?1) determined by Method 1, Method 3, Method 4, and total Fe concentrations (mg kg^?1) of green leaves were higher than those of chlorotic leaves. On the other hand, no significant difference was found between Fe concentrations (mg kg^?1) of green and chlorotic leaves, measured with Method 2. Significant relationship observed amongst chlorophyll concentrations, peroxidase enzyme activity, and Fe concentrations (mg kg^?1) of samples suggests that 1 N HCl method was the most suitable method amongst the methods used in this study for apple trees.     

Iron chlorosis in macadamia as affected by phosphate‐iron interactions 1

Iron (Fe) chlorosis induced by heavy phosphate (P) fertilizations is a serious problem for macadamia (Macadamia integrifolia) in Hawaii. To address this problem, a study was conducted to quantify the effects of P‐Fe interaction on macadamia leaf composition and chlorosis. The soil used was a limed Oxisol (Tropeptic Eutrustox, Wahiawa Series), pH 5.5. Phosphate was added as treble superphosphate at 0, 150 and 500 mg P/kg. The 150 mg P/kg rate was designed to yield approximately 0.04 mg P/L in the soil solution, a level considered adequate for macadamia growth. The 500 mg P/kg rate was intended to produce approximately 0.2 mg P/L, a level required by many horticultural crops but considered excessive for macadamia. Iron was added as Fe‐DTPA at 0, 5 and 10 mg Fe/kg soil, and factorially imposed on the P treatments. Color Index, a numerical rating based on hue, value and chroma from a Munsell Color Chart for Plant Tissues, was correlated with leaf chlorophyll concentration and used as an indicator of chlorosis.

Phosphate concentrations in leaves increased with increasing P application rates as expected, but decreased remarkably with increasing Fe rates (at a constant P rate). Plant Fe unexpectedly remained unchanged with increasing Fe rates but decreased with increasing P rates. The results suggest that (1) soil‐solution Fe was not a limiting factor to macadamia growth as is often incorrectly assumed for high P‐fertilized soils, (2) Fe uptake was restricted not because soil‐solution Fe was low but because plant P was excessively high, and (3) Fe translocation from roots to leaves may have been hampered by high P in the plants. Consequently, Fe chlorosis was intensified primarily by P fertilization (actually, by high plant P concentrations) and secondarily by P‐Fe interactions. Chlorosis, as measured by Color Index, can be diagnosed by a leaf Fe/P ratio < 0.06, and predicted by a soil‐solution ³√Fe/P ratio < 15.     

On‐farm diagnosis and management of iron chlorosis in groundnut

Abstract

Iron (Fe) chlorosis is a major nutritional constraint to groundnut (Arachis hypogaea L.) productivity in many parts of the world. On‐farm research was conducted at a Fe‐chlorotic site to evaluate the performance of three genotypes (TMV‐2, ICGS‐11, and ICGV‐86031), three fertilizer practices [no fertilizer control, fanners practice (125: 200: 0 kg NPK ha^?1), recommended practice (20: 50: 30 kg NPK ha^?1)], and two Fe treatments (non‐sprayed control and foliar FeSO₄ sprays) for their effect on Fe‐chlorosis and haulm and pod yields. These treatments were tested in a strip‐split plot design with four replicates. Results revealed that TMV‐2 and ICGS‐11 were susceptible to Fe‐chlorosis and produced significantly smaller haulm and pod yield, whereas, ICGV‐8603 1 was tolerant to Fe‐chlorosis. Farmer's fertilizer practice had the highest incidence of Fe‐chlorosis. Extractable Fe and chlorophyll content in the fresh leaves were the best indices of Fe‐status and were significantly (P<0.01) correlated with visual chlorosis ratings. Foliar application of FeSO₄ (0.5 w/ v) was effective in correcting Fe‐chlorosis and increased pod yield by about 30 to 40% in susceptible genotypes. These results suggests that use of tolerant genotypes such as ICGV‐86031 or foliar application of FeSO₄ in susceptible genotypes such as TMV‐2 and ICGS‐11 in combination with recommended fertilizer levels is an effective management package for alleviating Fe‐chlorosis in groundnut.     

Iron treatment of lime‐induced chlorosis: Implications for chlorophyll,Fe2 +, Fe3 + and K+ in leaves 1

This study addressed some complementary aspects related to plant Fe nutrition. A field and a greenhouse experiment were conducted to monitor changes in chlorophyll, Fe³⁺, Fe²⁺, Ca²⁺ and K⁺ along with the progressive evolution of lime‐induced chlorosis, and following soil (Fe‐EDDHA, Fe‐EDTA, Fe‐DTPA, DTPA) and foliar (Fe‐EDDHA, FeSO₄, “Fe‐Metalosate") treatments, in a chlorosis‐susceptible ornamental plant, Hydrangea macrophylla, over a year's growing period. Though soil Fe‐EDDHA was the most effective compound in alleviating chlorosis symptoms, it became less so with time and was only partly effective as a foliar spray. Leaf analysis showed that as chlorosis intensified and chlorophyll content decreased, phenanthroline ‐ Fe (Fe²⁺) decreased with corresponding increases in total iron (Fe³⁺) and K⁺ concentrations. The reliability of these chlorosis‐indicators was confirmed as the reverse changes occurred upon chlorosis plant recovery.     

Soil Properties Influencing Iron Chlorosis in Grapevines Grown in the Montilla‐Moriles Area,Southern Spain

Abstract

Iron (Fe) chlorosis, an Fe deficiency commonly observed in grapevines cultivated on calcareous soils, generally inhibits plant growth and decreases yield. The objective of this research was to relate the incidence of Fe chlorosis in vines of the Montilla‐Moriles area, southern Spain, to indigenous soil properties. Thirty‐five grapevines (V. vinífera L. cv. Pedro Ximenez grafted on V. berlandieri×V. rupestris 110 Ritcher) showing different degree of Fe chlorosis were selected from 13 vineyards. The leaf chlorophyll concentration (estimated by the SPAD value measured with a Minolta meter) was positively correlated with the contents in different soil Fe forms but not with alkalinity‐related soil properties (pH, calcium carbonate equivalent, and active lime). The acid NH₄ oxalate‐extractable Fe (Fe_o) was the most useful simple variable to predict the occurrence of Fe chlorosis. A Fe_o/active lime ratio of 25×10^–4 was found to be useful to class soils into two groups according to the probability of inducing Fe chlorosis.     

Effect of chromium VI on mineral element composition of bush beans

Bush beans (Phaseolus vulgaris L. cv Contender) were grown on perlite with nutrient solution and 0, 1, 2.5 and 5 ppm levels of Na₂CrO₄ Significant decrease of top growth and chlorosis in trifoliated leaves were observed for 2.5 and 5 ppm Cr, with Cr concentrations (μg/g) in tops:≥ 12.1, in roots:≥ 509.9. Cr decreased K, Na, Mg and Fe concentrations, and increased P and Mn concentrations in roots. In tops decreased N, K, Na and Fe concentrations and increased Mn and Ca concentrations were observed, Translocation of P, Zn, Cu and Fe was inhibited; Ca and Mn translocation was generally enhanced. P/Fe ratio was increased up to 60% in chlorotic plants, indicating a shift from Fe²⁺ to Fe³⁺.     

Chromium III‐iron interaction in iron sufficient and iron deficient bean plants. II. Ultrastructural aspects

The influence of a growth stimulating low Cr III concentration (1.0 μM) on chloroplast ultrastructure, the Fe, Cr, and Mn content of chloroplast extracts, o‐phenantroline extractable leaf Fe, and catalase activity was studied in both Fe‐sufficient and Fe‐deficient bush bean (Phaseolus vulgaris L.) plants. Chromium supply hardly affected the chloroplast ultrastructure of Fe‐sufficient plants but significantly improved chloroplast ultrastructure in Fe‐deficient leaves. Generally, Cr supply did not significantly influence chloroplast Fe‐content, but increased the Fe/Mn ratio in Fe‐deficient chloroplasts. In leaves from Fe‐deficient plants, o‐phenantroline extractable Fe was significantly increased, while catalase activity was not significantly influenced by Cr supply. The possible mechanisms of the beneficial effects of Cr III in Fe‐deficient plants are discussed.     

CHLOROSIS IN WILD PLANTS: IS IT A SIGN OF IRON DEFICIENCY?

ABSTRACT

Chlorosis in crops grown on calcareous soil is mainly due to iron (Fe) deficiency and can be alleviated by leaf application of soluble Fe²⁺ or diluted acids. Whether chlorosis in indigenous plants forced to grow on a calcareous soil is also caused by Fe deficiency has, however, not been demonstrated. Veronica officinalis, a widespread calcifuge plant in Central and Northern Europe, was cultivated in two experiments on acid and calcareous soils. As phosphorus (P) deficiency is one of the major causes of the inability of many calcifuges to grow on calcareous soil we added phosphate to half of the soils. Leaves in pots with the unfertilized and the P-fertilized soil, respectively, were either sprayed with FeSO₄ solution or left unsprayed. Total Fe, P, and manganese (Mn) in leaves and roots and N remaining in the soil after the experiment were determined. In a second experiment, no P was added. Leaves were either sprayed with FeSO₄ or with H₂SO₄ of the same pH as the FeSO₄ solution. Degree of chlorosis and Fe content in leaves were determined. Calcareous soil grown plants suffered from chlorosis, which was even more pronounced in the soils supplied with P. Newly produced leaves were green with Fe spray but leaves that were chlorotic before the onset of spraying did not totally recover. H₂SO₄ spray even increased chlorosis. This demonstrated that chlorosis was due to Fe deficiency. As total leaf Fe was similar on acid and calcareous soil, it was a physiological Fe deficiency, caused by leaf tissue immobilization in a form that was not metabolically “active”. Iron in the leaves was also extracted by 1,10-phenanthroline, an Fe chelator. In both experiments, significant differences between leaves from acid and calcareous soil were found in 1,10-phenanthroline extractable Fe but not in total leaf Fe, when calculated on a dry weight basis. Differences in 1,10-phenanthroline extractable Fe were more pronounced when calculated per unit dry weight than calculated per leaf area, whereas the opposite condition was valid for total leaf Fe.     

Iron fertilizers applied to calcareous soil on the growth of peanut in a pot experiment

A greenhouse pot experiment was conducted with peanuts (Arachis hypogaea L., Fabceae) to evaluate iron compound fertilizers for improving within-plant iron content and correcting chlorosis caused by iron deficiency. Peanuts were planted in containers with calcareous soil fertilized with three different granular iron nitrogen, phosphorus and potassium (NPK) fertilizers (ferrous sulphate (FeSO₄)–NPK, Fe–ethylendiamine di (o-hydroxyphenylacetic) (EDDHA)–NPK and Fe–citrate–NPK). Iron nutrition, plant biomass, seed yield and quality of peanuts were significantly affected by the application of Fe–citrate–NPK and Fe–EDDHA–NPK to the soil. Iron concentrations in tissues were significantly greater for plants grown with Fe–citrate–NPK and Fe–EDDHA–NPK. The active iron concentration in the youngest leaves of peanuts was linearly related to the leaf chlorophyll (via soil and plant analyzer development measurements) recorded 50 and 80 days after planting. However, no significant differences between Fe–citrate–NPK and Fe–EDDHA–NPK were observed. Despite the large amount of total iron bound and dry matter, FeSO₄–NPK was less effective than Fe–citrate–NPK and Fe–EDDHA–NPK to improve iron uptake. The results showed that application of Fe–citrate–NPK was as effective as application of Fe–EDDHA–NPK in remediating leaf iron chlorosis in peanut pot-grown in calcareous soil. The study suggested that Fe–citrate–NPK should be considered as a potential tool for correcting peanut iron deficiency in calcareous soil.     

Iron deficiency and zinc toxicity in soybean grown in nutrient solution with different levels of sulfur

A typical symptom of iron (Fe) deficiency in plants is yellowing or chlorosis of leaves. Heavy metal toxicity, including that of zinc (Zn), is often also expressed by chlorosis and may be called Fe chlorosis. Iron deficiency and Zn toxicity were evaluated in soybean (Glycine max [L.] Merr.) at two levels each of Zn (0.8 and 40 μM), Fe (0 and 20 μM), and sulfur (S) (0.02 and 20 mM). Reduction in dry matter yield and leaf chlorosis were observed in plants grown under the high level of Zn (toxic level), as well as in the absence of Fe. Zinc toxicity, lack of Fe, and the combination of these conditions reduced dry matter yield to the same extent when compared to the yield of the control plants. The symptoms of Zn toxicity were chlorosis in the trifoliate leaves and a lack of change in the orientation of unifoliate leaves when exposed to light. The main symptoms of Fe deficiency were chlorosis in the whole shoot and brown spots and flaccid areas in the leaves. The latter symptom did not appear in plants grown with Fe but under Zn toxicity. It seems that Fe deficiency is a major factor impairing the growth of plants exposed to high levels of Zn. Under Zn toxicity, Fe and Zn translocation from roots to shoots increased as the S supply to the plants was increased.     

EVALUATION OF DIFFERENT IRON SOURCES FOR IRON CHLOROSIS RECOVERY IN LOW-CHILL PEACH CULTIVARS

An experiment was conducted with iron chlorosis affected low-chill peach cultivars such as ‘Shaharanpur Prabhat’, ‘Shan-e-Punjab’, and ‘Pratap’ to examine the recovery upon foliar application of three iron sources namely iron (Fe)-sulfate, Fe-citrate and Fe ethylenediaminetetraacetic acid (EDTA). All the iron sources significantly increased the SPAD meter value, physiologically active (Fe²⁺) iron and total iron content of the leaves over control. However, highest values were noted with foliar spray of 1.0% Fe-sulfate. The low-chill peach cultivar ‘Saharanpur Prabhat’ responded best with iron resupply treatment. Significant correlations (at P ≤ 0.01) were obtained between SPAD meter readings with both physiologically active iron (Fe²⁺) and total iron content of leaves in all peach cultivars. Among the sources, the correlations between SPAD meter readings, physiologically active iron (Fe²⁺) and total iron contents were significant at P ≤ 0.01 for only Fe-sulfate and Fe-citrate. The regression analysis showed that the SPAD meter reading accounted 78.2 to 88.0% variation in physiologically active iron (Fe²⁺) and 65.0 to 73.7% variation in the total iron content in the low-chill peach cultivars. The SPAD readings could be used for management of iron chlorosis in peach orchard.     

Activities of Iron‐Containing Enzymes in Leaves of Two Tomato Genotypes Differing in Their Resistance to Fe Chlorosis

Abstract

Two tomato (Lycopersicon esculentum Mill., cvs. Pakmor and Target) genotypes differing in resistance to iron (Fe) deficiency were grown in nutrient solution under controlled environmental conditions over 50 days to study the relationships between severity of leaf chlorosis, total concentration of Fe, and activities of Fe‐containing enzymes in leaves. The activities of Fe‐containing enzymes ascorbate peroxidase, catalase, and guaiacol peroxidase, and additionaly the activity of glutathione reductase, an enzyme that does not contain Fe, were measured. Plants were supplied with 2 × 10^?7 M (Fe deficient) and 10^?4 M (Fe sufficient) FeEDTA, respectively. Leaf chlorosis appeared more rapidly and severely in Target (Fe deficiency senstive genotype) than Pakmor (Fe deficiency resistant genotype). On day 50, Pakmor had 2‐fold more chlorophyll than Target under Fe deficiency, while at adequate supply of Fe the two genotypes were very similar in chlorophyll concentration. Despite distinct differences in development of leaf chlorosis and chlorophyll concentrations, Pakmor and Target were very similar in concentrations of total Fe under Fe deficiency. In contrast to Fe concentration, activities of Fe‐containing enzymes were closely related to the severity of leaf chlorosis. The Fe‐containing enzymes studied, especially catalase, showed a close relationship with the concentration of chlorophyll and thus differential sensitivity of tomato genotypes to Fe deficiency. Glutathione reductase did not show relationship between Fe deficiency chlorosis and enzyme activity. The results confirm that measurement of Fe‐containing enzymes in leaves is more reliable than the total concentration of Fe for characterization of Fe nutritional status of plants and for assessing genotypical differences in resistance to Fe deficiency. It appears that Fe deficiency‐resistant genotype contains more physiologically available Fe in tissues than the genotype with high sensitivity to Fe deficiency.     

Mechanisms of exogenous nitric oxide and 24-epibrassinolide alleviating chlorosis of peanut plants under iron deficiency

Iron(Fe) is a crucial transition metal for all living organisms including plants; however, Fe deficiency frequently occurs in plant because only a small portion of Fe is bioavailable in soil in recent years. To cope with Fe deficiency, plants have evolved a wide range of adaptive responses from changes in morphology to altered physiology. To understand the role of nitric oxide(NO) and 24-epibrassinolide(EBR) in alleviating chlorosis induced by Fe deficiency in peanut(Arachis hypogaea L.) plants, we determined the concentration of chlorophylls, the activation, uptake, and translocation of Fe, the activities of key enzymes, such as ferric-chelate reductase(FCR),proton-translocating adenosine triphosphatase(H~+-ATPase), and antioxidant enzymes, and the accumulation of reactive oxygen species(ROS) and malondialdehyde(MDA) of peanut plants under Fe sufficiency(100 μmol L~(-1)ethylenediaminetetraacetic acid(EDTA)-Fe) and Fe deficiency(0 μmol L~(-1)EDTA-Fe). We also investigated the production of NO in peanut plants subjected to Fe deficiency with foliar application of sodium nitroprusside(SNP), a donor of NO, and/or EBR. The results showed that Fe deficiency resulted in severe chlorosis and oxidative stress, significantly decreased the concentration of chlorophylls and active Fe, and significantly increased NO production. Foliar application of NO and/or EBR increased the activity of antioxidant enzymes, superoxide dismutase,peroxidase, and catalase, and decreased the ROS and MDA concentrations, thus enhancing the resistance of plants to oxidative stress.Application of NO also significantly increased Fe translocation from the roots to the shoots and enhanced the transfer of Fe from the cell wall fraction to the cell organelle and soluble fractions. Consequently, the concentrations of available Fe and chlorophylls in the leaves were elevated. Furthermore, the activities of H~+-ATPase and FCR were enhanced in the Fe-deficient plants. Simultaneously,there was a significant increase in NO production, especially in the plants that received NO, regardless of Fe supply. These suggest that NO or EBR, and, especially, their combination are effective in alleviating plant chlorosis induced by Fe deficiency.     

The paramount influence of nitrate in increasing apoplastic pH of young sunflower leaves to induce Fe deficiency chlorosis,and the re-greening effect brought about by acidic foliar sprays

The main objective of the present work was to clarify the causal relationship between leaf apoplastic pH increase and Fe chlorosis under alkaline growth conditions. It has been shown that nitrate supply in contrast to ammonium supply induced a pH increase in the apoplast of young green leaves of Helianthus annuus which was followed within 12 hours by leaf yellowing. Hence nitrate nutrition is the primary cause of a high leaf apoplastic pH which induces Fe deficiency chlorosis and not the impaired provision of ATP for plasmalemma H⁺ pumps in yellow leaves. Supply of bicarbonate in physiological concentrations had virtually no influence on leaf apoplastic pH. Spraying leaves with diluted acids (citric acid, sulphuric acid) resulted in a decrease of apoplastic pH followed by leaf re-greening. Interestingly, the Fe concentrations remained the same in the yellow control leaves and in the sprayed green leaves. From this it follows that Fe efficiency in leaves is mainly related to the Fe distribution between apoplast and symplast. It was demonstrated that Fe chlorosis induced by nitrate nutrition begins from the base of the youngest leaves, presumably from growing interveinal microsites showing high nitrate uptake rates. Leaf yellowing spread gradually from the leaf base to the tip and after seven days of nitrate supply the leaf was almost completely yellow (98%). Leaf yellowing was measured by means of a video imaging technique. Leaf apoplastic pH recordings were conducted after loading the fluorescent dye FITC-Dextran (4000 D) into the leaf apoplast of intact plants thus simulating in vivo conditions. It was also shown using the new loading technique that the fluorescent dye did not penetrate the leaf symplast.     

Arsenic–iron interaction: Effect of additional iron on arsenic-induced chlorosis in barley grown in water culture

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.     

Predicting the incidence of iron chlorosis in calcareous soils of southern Spain

Abstract

Iron chlorosis is a serious crop production problem in many calcareous soils of Southern Spain. The objective of this study was to determine which indigenous soil properties (i.e., those which are essentially permanent) were related to Fe chlorosis. Experiments, using two chickpea (Cicer ariethinum L.) cultivars and a sunflower (Helianthus annuuus L.) cultivar, were carried out in a growth chamber with 25 calcareous soils representing widespread Xerofluvents, Xerorthents, Xerochrepts, Haploxeralfs, Rodoxeralfs, Chromoxererts, and Pelloxererts of Southern Spain. The average chlorophyll contents for the three cultivars were significantly correlated with several properties of the carbonate and Fe oxide phases, such as calcium carbonate equivalent (r = 0.69***), “active lime”; (r = 0.58**), acid NH₄‐oxalate extractable Fe (r = 0.68***), Tiron‐extractable Fe (r = 0.61**), and DTPA‐extractable Fe (r = 0.55**). The present and other studies indicate that the soil property most consistently related to Fe chlorosis is acid NH₄‐oxalate extractable Fe (Feo). The Feo critical level separating soils with a high probability from those with a low probability of responding to Fe fertilization was 0.63 g/kg soil, a value similar to those found in other studies. This further supports the use of Feo as a key property to predicting the appearance of Fe chlorosis.