Effect of different nitrogen‐forms and iron‐chelates on the development of stinging nettle

The development of stinging nettle (Urtica dioica L.) grown on culture solution containing with either ammonium or nitrate ions, or urea, was investigated under iron deficiency conditions, and with added FeEDTA or FeCto. Both seed‐cultured and vegetatively‐cultured stinging nettle plants produced normally developed green shoots when nitrate and 4 μM FeEDTA or FeCto were supplied. Stinging nettle plants were able to utilize Fe‐citrate, Fe‐ascorbate, and Fe‐malate effectively at the same concentration as well. When K3Fe(CN)6 was supplied, which is impermeable to the plasmalemma, and therefore is used to measure the reductive capacity of the roots, stinging nettle plants became chlorotic because the complex was stable at the pH of the culture solution. Urea did not induce chlorosis but inhibited growth. The plants died when ammonium was supplied as a sole N source. Applying bicarbonate and ammonium together prevented the plants from dying, but the plants became chlorotic. Total exclusion of iron from the culture solution resulted in iron‐deficiency stress reactions as has been described for other dicotyledonous plants (Strategy II).     

Lime chlorosis on photosynthesis and transpiration of iron‐inefficient soybeans

Abstract

Iron deficiency in PI54619–5–1 soybeans (Glycine max L.) decreased growth 37% and decreased the rate of photosynthesis by 33%, but had no influence on the rate of transpiration. In another experiment Fe deficiency resulted in a mild 18% decrease in the photosynthetic rate and a slight decrease in the transpiration rate. There were no differences in leaf resistances.     

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.     

Influences of ultra‐violet (UV)‐blue light radiation on the growth of cotton. II. Photosynthesis,leaf anatomy,and iron reduction

Cotton (Gossypium hirsutum L.) plants grown under low pressure sodium lamps (LPS) developed chlorosis which was similar in appearance to iron‐stress induced chlorosis, while plants under cool white fluorescent lamps (CWF) at the same level of photosynthetically active radiation (PAR) developed normally. These illumination sources differ in spectral irradiance; CWF lamps emit ultra violet (UV), whereas LPS lamps do not. Ultraviolet radiation is capable of reducing Fe³⁺ to Fe²⁺ through a chlorotic leaf which may be important in establishing an active iron fraction in the leaf. Root reduction of Fe³⁺ to Fe²⁺ was lacking in Fe‐stressed cotton under LPS light, but was present under CWF light. Net photosynthesis, photosynthetic electron transport, and leaf chlorophyll content were lower under LPS than CWF light in most of the growing media studies (soil or solutions with nitrate‐ or ammonium‐nitrogen supplied). Chloroplast ultrastructure and leaf thickness were also altered by LPS irradiance. Electron microscopic studies with plants grown in nutrient solutions for 4 weeks suggested that chioroplastic granal disorganization was more directly associated with diminished iron supplies than with light source. However, plants grown in soil for 6 weeks under LPS light had granal disorganization similar to that found in iron‐stressed plants. These studies suggest an important role for UV radiation in influencing the activity of iron in plants.     

Yield of iron‐sprayed and non‐sprayed strawberry cultivars grown on high ph calcareous soil

Abstract

Iron (Fe) deficiency chlorosis (FeDC) results in extensive reduction in yield of strawberry (Fragaria x ananassa Duch.) grown on high pH calcareous soils. Three cultivars differing in response to FeDC were grown on a high pH (8.2) calcareous soil (25.4% calcium carbonate equivalent in surface 20 cm) in the field (Choueifat, coastal area of Lebanon) to determine the effects of FeDC on fruit yield of cultivars sprayed with FeEDDHA [ferric ethylene‐diiminobis (2‐hydroxyphenyl) acetate]. The unsprayed plots were used as a control. No significant interaction (P<0.05) between cultivars x FeEDDHA spray treatment, and no significant differences (P<0.05) between one and two FeEDDHA spray(s)/week treatment was noted for visual FeDC, fruit number, and fruit yield. Sprayed cultivars once a week produced higher yields than unsprayed ones; overall increases were 33% (13% for ‘Motto’, 30% for ‘Chandler’, and 56% for ‘Douglas'). Even though only slight FeDC was noted on the ‘Motto’ cultivar receiving no Fe EDDHA spray, fruit yields were increased when sprayed with FeEDDHA. However, significant increases in yield for ‘Chandler’ and ‘Douglas’ cultivars with severe FeDC ratings were rioted when sprayed with FeEDDHA.     

Influence of air drying and soil gas‐phase carbon dioxide on DTPA‐extractable iron in calcareous soils

Abstract

The extraction of a field‐moist soil with DTPA will result in a level of extractable iron (Fe) lower than that of the air‐dried soil. Soil gas‐phase carbon dioxide (CO₂) levels may be considerably higher than ambient atmospheric levels, especially in wet soils in the field. This study was undertaken to determine whether gas‐phase CO₂ level influences the quantity of Fe extracted by DTPA. Three moist calcareous soils were incubated for 21 days, each at three different partial pressures of CO₂, after which the moist soils were extracted with DTPA. A sample of each soil was also air dried, and was subsequently extracted with DTPA. In each case, DTPA‐extractable Fe from the moist sample was lower than that from the air‐dried sample; however, DTPA‐extractable Fe increased with increasing CO₂ partial pressure of in the moist soils. DTPA‐extractable Fe concentration for a given soil following air drying was not significantly influenced by the CO₂ partial pressure during incubation of the originally field‐moist soil. DTPA‐extract pH of the moist soils followed the same trend as soil‐solution pH (i.e., as CO₂ concentration of the soil gas‐phase increased, soil solution pH and DTPA extract pH both decreased); however, the slope of the pH versus log P_CO2 curve was less pronounced in the DTPA extract due to the buffering capacity of the triethanolamine. From this study, it is concluded that elevated soil gas‐phase CO₂ partial pressure does not contribute to the lower level of DTPA‐extractable Fe observed when the extraction is performed on a field‐moist versus an air‐dried soil; increased CO₂ partial pressure actually resulted in a slight increase in concentration of DTPA‐extractable Fe obtained from a field‐moist soil.     

Chelation effects on the iron reduction and uptake by low‐iron stress tolerant and non‐tolerant citrus rootstocks

The relative rates of ferric‐iron (Fe³⁺) reduction and uptake by two citrus rootstocks were measured for a series of synthetic Fe³⁺ chelates and microbial siderophores. The rates of Fe³⁺ reduction by the citrus seedlings followed the order: FeHEDTA >> FeDPTA > FeCDTA. No reduction occurred for FeDFOB (ferrioxamine B) and FeTAF (ferric triacetylfusagen). Low rates of Fe³⁺ reduction occurred for Fe2RA3 (ferric rhodotorulic acid). The levels of ⁵⁵Fe taken up the citrus seedlings showed good correlations with the reduction rates. These results indicate the importance of Fe³⁺ reduction in the Fe uptake by citrus rootstocks. The immobility of a large percent of the ⁵⁵Fe taken up by the roots is attributed to the accumulation of Fe in the root apoplasts.     

Use of Minolta SPAD‐502 chlorophyll meter to quantify the effectiveness of mid‐summer trunk injection of iron on chlorotic pear trees

The severity of leaf chlorosis in iron (Fe)‐deficient fruit trees is often characterized using a semi‐quantitative visual rating index that is subject to evaluator bias. Analytical instruments are now available that provide a quantitative measure of leaf green color that could substitute for visual ratings. We injected limbs of mature chlorotic pear trees (Pyrus communis L. cv. Bartlett) with distilled water or a solution of 0.1% Fe (w/v) as FeSO₄‐7H₂O on 17 July 1995. Treatments were replicated eight‐fold. On 18 August 1995, a Minolta SPAD‐502 chlorophyll meter was used to measure the green color of 30 randomly sampled leaves located above the point of injection on each injected limb. Average leaf green color was higher in the Fe‐injected tree than in the water‐injected tree of each experimental block. Leaf green color (mean±SD) averaged 34.7±3.8 SPAD units for the Fe‐injected trees and 27.3±3.8 SPAD units for the water‐injected trees. The absolute increase in mean leaf color of 7.4 SPAD units was equivalent to a relative increase of 27%. Iron injection also induced more negative skewness and increased kurtosis in the frequency distribution curve for leaf SPAD meter readings. These results suggest that the SPAD meter can provide an unbiased quantitative measure of the severity of leaf chlorosis associated with Fe deficiency, and confirm that mid‐summer trunk injection of Fe can partially ameliorate Fe‐chlorosis symptoms.     

Nitric acid‐ and o‐phenanthroline‐extractable iron for diagnosis of iron chlorosis in citrus lemon trees

Abstract

Plant analysis for total iron (Fe) is frequency used for diagnosis of Fe‐deficiency chlorosis. However, chlorotic plants frequency contained similar or higher amount of total Fe than the healthy green plants. The objectives of this study were to (i) determine if Fe chlorosis in citrus lemon can be diagnosed by total or active Fe and can be related to the degree of chlorosis, and (ii) determine the optimum extraction time and ratio of extracting solution to plant sample for extracting the active Fe. Leaf samples of different degrees of Fe chlorosis were sampled from different citrus lemon trees from three different sites. Total Fe was extracted with nitric acid (HNO₃) and active Fe with o‐phenanthroline from lemon leaves. An extraction time of 20 and 45 hours and the ratios of the extractor to the sample of 5:l, 10:1, and 20:1 were investigated. The results indicated that an extraction time of 20 hours is enough for extracting the active Fe from citrus lemon leaves by o‐phenanthroline. The amount extracted by all ratios (5:1, 10:1, and 20:1) were detectable and at the same time similarly and consistency showed the differences in degrees of chlorosis in all plant samples. Total Fe content was always higher in moderately and severely chlorotic leaves compared to the green leaves and was not related to the degree of chlorosis. Therefore, total Fe cannot be used as a criteria to differentiate between the Fe‐deficient and non‐deficient plants. On the other hand, active Fe tended to decrease with the increase in the degree of chlorosis. The ratio of active to total Fe was calculated and was found to be closely correlated with the degree of chlorosis. This clearly illustrates the failure of plant analysis for total Fe and the effectiveness of active Fe and/or the ratio of active to total Fe for diagnosing Fe chlorosis.     

Monocot‐dicot variability in response to an iron oxide‐metallic iron source

Abstract

Iron from a mixture of Fe oxide and metallic Fe was more available to corn (Zea mays L.) than it was to soybeans when the plants wore grown in calcareous soil or in nutrient solution. All this Fe, however, was DTPA (diethylene triamine pentaacetic acid) extractable. In solution culture the Fe was available to the soybean (Glycine max L.) plants unless CaCO₃ was included in the nutrient solution.     

Differential response of groundnut genotypes to iron‐deficiency stress

Differential response of groundnut genotypes to iron‐deficiency stress was studied in soils containing high calcium carbonate. Genotypes differed significantly for some traits that appeared to be important in determining adaptation to low iron. The genotypes TCGS 273, TCGS 2, TCGS 37, and Kadiri 3 had higher total chlorophyll, total dry matter, and active iron (Fe²⁺) contents under iron‐deficiency stress conditions. Total chlorophyll followed by active iron were found to be sensitive parameters to Fe deficiency. Based on the visual deficiency symptoms (chlorosis score), the genotypes were classified into three groups. Efficient (no genotype was found efficient), moderately efficient (TCGS 273, TCGS 2, TCGS 3, and Kadiri 3), and inefficient (TCGS 1, TCGS 7, TCGS 11, TCGS 26, TCGS 28, TCGS 29, TCGS 30, TCGS 1518, TPT 1, TPT 2, ICGS 11, ICGS 44, Girnar, JL 24, ICGS(E) 21, and TMV 2).     

Nutrient‐solution techniques for evaluation of iron efficiency of soybean 1

Abstract

The iron (Fe) efficiency of soybean [Glycine max (L.) Merr.] genotypes generally has been evaluated in the field on calcareous soil. A nutrient‐solution system has been developed to permit evaluation of Fe efficiency throughout the year. The objectives of this study were to assess the effectiveness of nutrient‐solution tests for evaluating the Fe efficiency of soybean genotypes and to evaluate alternative nutrient‐solution techniques that could minimize the cost of labor and chemicals. Five bicarbonate (HCO₃ ^‐) concentrations and three solution‐change schedules were evaluated in a factorial arrangement. Eight soybean genotypes with a wide range of Fe efficiency were evaluated in each treatment and in replicated field tests on calcereous soil during 3 years. Rank correlation coefficients between mean chlorosis scores of genotypes in nutrient solution and field tests ranged from 0.81 to 0.91 for the three solution‐change schedules and from 0.85 to 0.89 for the five HCO₃ ^‐ concentrations. Replacing the solution every 4 d was not superior to replacing it only at each stage of plant development or not changing the solution throughout the test. A stepwise increase in HCO₃ ^‐ level at each stage of plant development was not superior to utilizing a constant level of HCO₃ ^‐ throughout the test. The most economical evaluation of the Fe efficiency of soybean genotypes in nutrient solution can be achieved with no change in the solution and one or more HCO₃ ^‐ levels that are held constant throughout the test.     

Effects of Dibutyl phthalate and phthalic acid on chlorosis recovery in iron‐deficiency stressed sorghum cultivars

The effects of DBP (Dibutyl phthalate) and PA (Phthalic acid) supplied to the nutrient medium of Fe‐deficiency stressed sorghum cultivars, CSH‐5, 2077‐A, and CS‐3541 were examined. It was found that both the chemicals (50 mg/1) caused recovery of the cultivars CSH‐5 and 2077‐A in 4 days of treatment. Furthermore, the growth of roots, especially the adventitious roots, was increased by the chemicals.     

Behavior of iron‐supplying materials in incubated calcareous soils 1

Two Fe chlorosis‐inducing calcareous soils were incubated for up to 5 months, at room temperature and field capacity, with Fe‐EDDHA, Fe‐DTPA, FeSO₄, an amino acid chelate “Fe‐Metalosate”;, an oxide “Micronized‐Iron”;, and a precipitated Fe‐S compound “Iron‐Sul”;. Other treatments included DTPA chelate alone, elemental S and H₂SO₄ at comparable rates. Both water‐soluble, and DTPA‐extractable Fe fractions were measured periodically from each sample. All water‐soluble sources decreased with time. Soluble Fe was highest after Fe‐EDDHA addition but was not detectable after “Fe‐Metalosate”; and FeSO₄. Acidification to neutralize CaCO₃ significantly increased DTPA‐extractable Fe, which remained high with increasing incubation time. “Micronized‐Iron”; and S had only a slight effect on DTPA‐ extractable Fe. Though Fe‐EDDHA is the most efficient Fe material, pelleted acidified Fe sources, i.e., “Iron‐Sul”;, may be more economical for some crops in the long term.     

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‐stress response of inoculated and non‐inoculated roots of an iron inefficient soybean cultivar in a split‐root system

The objective of this study was to establish whether the iron‐stress responses observed in T203 soybean (Fe‐inefficient) with active nodules are products of the nodules or of the entire root system. A split‐root system was used in which half the roots of each plant were inoculated and actively fixing nitrogen and the other half were not. Soybean cultivar T203 is normally Fe‐inefficient and does not exhibit the Fe‐stress responses, however an iron‐stress response did occur during active N₂ fixation in earlier studies. This implies that the active nodules influenced the plant's ability to respond to Fe‐deficiency stress. In this study, the Fe‐stress response (H⁺ and reductant release) observed in T203 soybean was limited to the inoculated side of the split‐root system. The severe Fe chlorosis which developed in these plants was overcome in a manner similar to Fe‐efficient cultivars undergoing normal Fe‐stress response and the T203 plants completely regreened. Exudation of H⁺ ions was similar in both the presence and absence of Fe, and was generally limited to inoculated roots. Reductant release was nearly nonexistent from the non‐inoculated roots and was greater for the Fe‐stressed (‐Fe) plants than for non‐stressed (+Fe) plants. Thus, the response observed, which alleviated Fe chlorosis, appeared to be associated with N₂ fixation of the active nodules.     

Influence of Loss‐on‐Ignition Temperature and Heating Time on Ash Content of Compost and Manure

Abstract

Loss‐on‐ignition (LOI) is a simple method for determining ash content, and by reciprocation, organic matter content of compost and manure. However, reported ignition temperatures and heating times for LOI measurements vary widely, and this brings into question the accuracy of one specific combination of ignition temperature and heating time over another. This study examined the effect of 42 temperature‐heating time combinations (six ignition temperatures from 400 to 650°C in 50°C increments by seven heating times of 1, 2, 8, 12, 16, 20, and 24‐h) on the ash content of a finished compost and a fresh manure. The experiment included the 550°C for 2‐h method recommended in Test Methods for Evaluation of Compost and Composting. The magnitude of the decrease in ash content due to increase in temperature was not consistent across all heating times. For example, after a 1‐h heating time for compost, ash content was 75.7% at 400°C and 67.5% at 650°C, compared to 69.6% at 400°C and 66.8% at 650°C after 24‐h. Irrespective of heating time, an ignition temperature of 400°C overestimated ash content for both compost and manure compared to the TMECC method. The TMECC method with its moderate temperature and short heating time requirement could reduce energy costs without affecting ash content results.     

Root responses of sterile‐grown onion plants to iron deficiency 1

Onion (Allium sativum) plants grown without iron (Fe) in sterile nutrient solutions readily developed chlorosis symptoms. Iron deficiency in the sterile‐grown plants stimulated the rates of root extracellular reduction of Fe³⁺, copper (Cu²⁺), manganese (Mn⁴⁺), and other artificial electron acceptors. While rapid reduction occurred with the synthetic chelate Fe³⁺HEDTA, no short‐term reduction occurred with the fungal siderophore Fe³⁺ferrioxamine B (FeFOB). In addition to the increased rate of extracellular electron transfer at the root surfaces, the Fe‐deficient plants showed greater rates of Fe uptake and translocation than the onion plants grown with Fe. The rates of uptake and translocation of Fe were sharply higher for the Fe‐deficient plants supplied with FeHEDTA than for similar plants supplied with FeFOB. Inhibition by BPDS of the Fe uptake by the Fe‐deficient onion plants further supported the importance of Fe³⁺ chelate reduction for the uptake of Fe into the roots. Rates of Fe uptake and translocation by Fe‐deficient onion plants supplied with ⁵⁵FeFOB were identical to the rates of uptake of ferrated [14C]‐FOD; a result that gives evidence of the uptake and translocation of the intact ferrated siderophore, presumably by a mechanism not involving prior extracellular Fe³⁺ reduction. Differences in the rates of transport of other micronutrients into the roots of the Fe‐deficient onion plants were evident by the significantly higher Zn and Mn levels in the shoots of the Fe‐deficient onion.     

Effect of sewage sludge application to amelio‐rate iron deficiency of grain sorghum

Abstract

Recent research has indicated that land application of municipal sewage sludge to calcareous soils can be used to ameliorate iron (Fe) deficiency of grain sorghum [Sorghum bicolor (L.) Monech]. A greenhouse study was conducted to determine the response of grain sorghum grown on three different soils to application of sewage sludge. Sludge applied at rates of 0, 7.5, 15.0, and 25.0 g/kg soil did not completely ameliorate grain sorghum Fe deficiency. When FeEDDHA was soil applied, sewage sludge application significantly increased plant growth due to increases in soil phosphorus (P) availability. Application of sewage sludge at rates greater than 7.5 g/kg reduced dry matter production of grain sorghum in the FeEDDHA amended Orelia SC soil, the soil with the lowest total neutralizing potential. The decreases yield was possibly due to toxic levels of soil and plant copper (Cu) and zinc (Zn), and increased soil salinity.     

Response to iron‐deficiency stress of pear and quince genotypes 1

Roots of iron (Fe)‐efficient dicots react to Fe‐deficiency stress by strongly enhancing the ferric (Fe³⁺)‐reductase system and by lowering the rhizo‐sphere pH. In this study, we tested whether such adaptation mechanisms characterize pear and quince genotypes known to have differential tolerance to calcareous and alkaline soils. Two trials were performed using micropagated plants of three quince rootstocks (BA29, CTS212, and MC), three Pyrus communis rootstocks (OHxF51 and two selections obtained at the Bologna University: A28 and B21) and of two pear cultivars (Abbé Fétel and Bartlett, own‐rooted). In the first trial, plants were grown in a nutrient solution with [Fe(+)] and without [Fe(‐)] Fe for 50 days. Their root Fe‐reducing capacity was determined colorimetrically using ferrozine and FeEDTA, and Fe uptake of Fe(+) plants was estimated. In the second trial, the rhizosphere pH of plants grown in an alkaline soil was measured by a micro‐electrode. With the only exception of pears OHxF51 and A28, whose Fe‐reduction rates were similar in Fe(+) and Fe(‐) plants, the Fe‐deficiency stress resulted in a significant decrease in Fe reduction. Among the Fe(‐) plants, the two pear cultivars, OHxF51 and A28, had a higher Fe‐reducing capacity than the quince rootstocks and the cv. Abb6 F. When plants were pre‐treated with Fe, reduction rate was highest in the P. communis rootstocks, intermediate in the own‐rooted cultivars, and lowest in the quinces. Root Fe‐reducing capacity of Fe(+) plants proved to be linearly and positively correlated with Fe uptake and root proton release. Rhizosphere pH was highest in quince MC, intermediate in the other two quinces and in the cv. Abbe F., and lowest in the pear rootstocks and in the cv. Bartlett. Our results indicate that roots of pear and quinces do not increase their ability to reduce the Fe under Fe‐deficiency stress. The genotypical differential tolerance to Fe chlorosis likely reflects differences in the standard reductase system and in the capacity of lowering the pH at the soil/root interface. The determination of the root Fe‐reducing capacity is a promising screening technique for selecting pear root‐stocks efficient in taking up Fe.