Seed priming to optimize germination in Arthrocnemum Moq.

BACKGROUND: Seed germination and seedling growth constitute the first stage of a plant's life cycle for crop establishment. Arthrocnemum Moq. is a halophyte of the subfamily Salicornioideae (Amaranthaceae), which could be recognized in the foreseeable future as an emerging candidate in applied biosaline agricultural programs, mainly due to the large biomass it represents in coastal and inland saltmarshes, in addition to its interesting nutritional and pharmacological properties. However, to ensure their subsequent use as a crop, it is necessary to optimize their germination through appropriate seed priming treatments. The main goal of this work was to seek the optimization of Arthrocnemum germination process using different pretreatments: exposure to sodium chloride (100 to 1200 mM) in the dark and its subsequent transferred to distilled water separately and together with the combination of pH (5, 7, 9), salinity (0, 100, 200 mM NaCl), and iron conditions (0, 200, 400 µM FeSO4). The experiments were tested on six samples of two different species: A. meridionale (from Tunisia) and A. macrostachyum (from Spain). RESULTS: Salinity priming of seeds for 15 days in darkness improved germination percentages by almost 25% at 600 mM NaCl, in both Tunisian and Spanish species. However, keeping seeds at different salt concentrations for 30 days produced higher improvement percentages at lower concentrations in A. meridionale (100-200 mM NaCl), while in A. macrostachyum the highest improvement percentages were obtained at 600 mM NaCl (percentage improvement of 47%). When the dark time period is reduced to 5 days at higher salt concentrations, the greater germination percentages were reached in all the samples at the concentration of 800 mM NaCl, increasing the improvement of germination between 17 and 50%. Finally, the conditions of pH = 7, pretreatment in darkness at 800 mM NaCl and 400 µM or iron, turned out to be an effective medium for seed germination. CONCLUSIONS: Therefore, before using Arthrocnemum seeds in applied biotechnological programs, a seed priming treatment based on prior exposure to high salt concentrations (600-1000 mM NaCl) is recommended in order to maximize germination percentages.

Timing for a sustainable fertilisation of Glycine max by using HBED/Fe3+ and EDDHA/Fe3+ chelates.

BACKGROUND: Efficient use of Fe chelates is crucial to avoid environmental risks and reduce economic losses. HBED/Fe3+ has been recently approved by the European Union for soil fertilisation, but studies delving into the best timing for its application are necessary. In this work, a batch incubation experiment and two biological experiments were developed to determine the optimal physiological stage for a sustainable application of HBED/Fe3+ in soil fertilisation compared with EDDHA/Fe3+ fertilisers using 57 Fe. RESULTS: HBED/Fe3+ demonstrated a high durability in soils and soil materials, maintaining more than 80% of Fe chelated after 70 days, and its application at an early physiological stage resulted in a high Fe accumulation in soybean and soil after 36 days. In contrast, the stability of EDDHA/Fe3+ decreased because of the retention of its lowest stable isomers. The best timing for chelates application was confirmed in a 52 day experiment. The application of HBED/Fe3+ at the early stage increased the Fe translocation to fruits; while o,o-EDDHA/Fe3+ accumulated more Fe in fruits when added at the fructification stage. CONCLUSION: The high HBED/Fe3+ stability in calcareous soil requires a differentiate application timing, and its addition at early physiological stages leads into the most efficient fertilisation. © 2016 Society of Chemical Industry.

Can silicon partially alleviate micronutrient deficiency in plants? A review.

Silicon protects plants against various biotic and abiotic stresses, including metal toxicity. Under a high metal concentration, Si can externally decrease metal availability to the plant by its precipitation in the growth media, and Si also affects the metal distribution inside the plant, diminishing the damage. Could Si also protect plants against metal deficiency stress? Recently, the physiological role of Si in relation to micronutrients deficiency symptoms has been assessed in several plant species in hydroponics. In cucumber, Si supply mitigated the symptoms of Fe deficiency, but this effect was not clear under Zn- or Mn-deficiency conditions. The main factor controlling this beneficial effect seems to be the Si contribution to the formation of metal deposits in the root and/or leaves apoplast and its role in their following remobilization when required. The enhancement of the content of long-distance transport molecules (such as citrate) due to Si addition should also contribute to the metal transport from root to shoot, which will diminish deficiency symptoms.

Silicon (Si) mitigates the negative effects of iron deficiency in common bean (Phaseolus vulgaris L.) by improving photosystem activities and nutritional status.

Silicon (Si) is the second most abundant element in the Earth's crust after oxygen. Its beneficial impact on crop development and yield, particularly under stressful conditions such as iron (Fe) deficiency, has been well documented. Fe deficiency is a critical constraint that limits crop production globally. The objective of this study was to investigate the effects of silicon (Na2SiO3) on common bean (Phaseolus vulgaris L. 'Coco Rose' variety) under iron-deficient conditions. The common bean plants were subjected to six treatments, which included three sufficient iron treatments (50 µM Fe) each paired with three varying silicon concentrations (0, 0.25, and 0.5 mM Si), and three iron-deficient treatments (0.1 µM Fe) each associated with the same silicon concentrations (0, 0.25, and 0.5 mM Si). The results indicate that iron deficiency had a negative impact on almost all the measured parameters. However, under silicon treatments, especially with 0.5 mM Si, the depressive effects of iron deficiency were significantly mitigated. The addition of 0.5 mM Si alleviated leaf chlorosis and improved biomass production, nutritional status, photosynthetic pigment content, photosynthetic gas exchange, and photosystem (PSI and PSII) activities. Interestingly, a greater beneficial effect of silicon was observed on PSII compared to PSI. This was accompanied by a significant augmentation in leaf iron concentration by 42%. Therefore, by enhancing the photosystem activities and nutritional status, among other mechanisms, silicon is capable of mitigating the adverse effects of iron-deficient conditions, making it a successful and effective solution to cope with this nutritional stress.

Priming With Silicon: A Review of a Promising Tool to Improve Micronutrient Deficiency Symptoms.

Priming consists of a short pretreatment or preconditioning of seeds or seedlings with different types of primers (biological, chemical, or physical), which activates various mechanisms that improve plant vigor. In addition, stress responses are also upregulated with priming, obtaining plant phenotypes more tolerant to stress. As priming is thought to create a memory in plants, it is impairing a better resilience against stress situations. In today's world and due to climatic change, almost all plants encounter stresses with different severity. Lots of these stresses are relevant to biotic phenomena, but lots of them are also relevant to abiotic ones. In both these two conditions, silicon application has strong and positive effects when used as a priming agent. Several Si seed priming experiments have been performed to cope with several abiotic stresses (drought, salinity, alkaline stress), and Si primers have been used in non-stress situations to increase seed or seedlings vigor, but few has been done in the field of plant recovery with Si after a stress situation, although promising results have been referenced in the scarce literature. This review pointed out that Si could be successfully used in seed priming under optimal conditions (increased seed vigor), to cope with several stresses and also to recover plants from stressful situations more rapidly, and open a promising research topic to investigate, as priming is not an expensive technique and is easy to introduce by growers.

Comparative study of the chemical composition and antifungal activity of commercial brown seaweed extracts.

Introduction: A sustainable agriculture and the great increase in consumers of organic products in the last years make the use of natural products one of the main challenges of modern agriculture. This is the reason that the use of products based on seaweed extracts has increased exponentially, specifically brown seaweeds, including Ascophyllum nodosum and Ecklonia maxima. Methods: In this study, the chemical composition of 20 commercial seaweed extract products used as biostimulants and their antifungal activity against two common postharvest pathogens (Botrytis cinerea and Penicillium digitatum) from fruits were evaluated. Data were processed using chemometric techniques based on linear and non-linear models. Results and discussion: The results showed that the algae species and the percentage of seaweed had a significant effect on the final composition of the products. In addition, great disparity was observed between formulations with similar labeling and antifungal effect of most of the analyzed products against some of the tested pathogens. These findings indicate the need for further research.

Fluorescent enzymatic assay for direct total polyphenol determination in food-related samples.

A direct and simple fluorescent assay for the total polyphenol determination based on the bioconjugate formed between the laccase enzyme (TvL from Trametes versicolor) and carbon nanodots (CD) is developed. One of the most used reactions for the determination of phenols is based on the enzymatic reaction of their oxidation to quinones. In this work, CD has been biofunctionalized with TvL (TvL-CD) and employed as a fluorescent label to follow the enzymatic reaction. The bioconjugate was formed and characterized by spectroscopy and microscopy. The optimal TvL-CD ratio was established. The reaction between the bioconjugate and a phenolic compound such as gallic acid (GA) was followed by monitoring the fluorescence bioconjugate decrease due to the quenching effect of the quinones generated in the enzymatic reaction. These studies confirm that bioconjugation does not inhibit the enzymatic activity and the fluorescence decrease during the enzymatic reaction is mainly due to an electron transfer processes. Based on these results, a new method for the quantitative determination of polyphenols measured as GA concentration is developed. The detection and quantification limit was found to be 7.4 and 25 µM, respectively. Subsequently, the method has been applied to the direct determination of GA in wine, juice, and rice leaf extracts.

Influence of irradiation time and solution concentration on the photochemical degradation of EDDHA/Fe3+: effect of its photodecomposition products on soybean growth.

BACKGROUND: Ethylenediamine-N, N'-bis(2-hydroxyphenylacetic acid (EDDHA) is one of the most efficient iron-chelating agents employed to relieve iron chlorosis in plants. It has been well known for decades that this compound is photosensitive, but in spite of this fact its degradation pathways are virtually unknown. The aim of this work was to evaluate how the length of sunlight exposure and the concentration of irradiated EDDHA/Fe(3+) solutions influence the photostability of the chelate at constant pH. Moreover, the possible toxic effect of the chelate photodegradation products, elsewhere proposed, on soybean growth has been tested. RESULTS: The photodecomposition of the chelate increased as the time of sunlight exposure increased, and resulted in a partial decomposition of the organic ligand. Moreover, EDDHA/Fe(3+) photodecomposition was highly correlated with the concentration of solution exposed. Plants did not present differences in recovery from chlorosis among treatments with and without decomposition products. CONCLUSIONS: EDDHA/Fe(3+) undergoes photodegradation, like other aminopolycarboxylic acids, being more degraded as solution concentration decreases and exposure time increases. The photodecomposition products salicylic acid, salicylaldehide and Salicylaldehyde ethylenediamine diimine tested did not have negative effects on soybean growth, at least in the short-term hydroponic experimental design tested.

Use of the stable isotope (57) Fe to track the efficacy of the foliar application of lignosulfonate/Fe(3+) complexes to correct Fe deficiencies in cucumber plants.

BACKGROUND: During the last decade, environmental concerns regarding the use of recalcitrant synthetic chelates to overcome iron chlorosis has increased and new ligands such as lignosulfonates (LS) have been evaluated. However, the efficacy of these products is variable. In this work a hardwood (eucalyptus) and softwood (spruce) LS were compared to try to relate their physico-chemical characteristics and their efficacy. Also two more products derived from the eucalyptus lignosulfonate were tested. RESULTS: All the LS tested presented a good ability to complex Fe, but only the spruce LS was capable to maintain significant amounts of soluble Fe above pH 8. According to the FTIR data, structural changes related to the Fe source (Fe(2+) or Fe(3+) ) used to form the complex occurred in the LS molecule and might influence their efficacy. Cucumber (Cucumis sativus L. cv Ashley) chlorotic plants were used to test lignosulfonate efficacy when applied through foliar sprays in comparison with FeSO(4) and EDTA/(57) Fe(3+) . The (57) Fe content of plants sprayed with LS was very low in respect to the EDTA treatment, but this was not reflected in the biomass and re-greening rates. Eucalyptus LS modifications improve its efficacy for iron chlorosis recovery to levels similar to those found for the spruce LS. Two applications of the LS are recommended. CONCLUSIONS: Lignosulfonates did not require surfactants for their application; they did not burn the leaves, and had a stimulating effect on the vegetative growth of the plants. So these by-products could be a good alternative when applied through foliar sprays for cucumber plants.

Rice responses to silicon addition at different Fe status and growth pH. Evaluation of ploidy changes.

It has been described in rice that Si only plays a physical barrier that does not allow Fe to enter cell apoplast, causing Fe deficiency responses even under Fe sufficiency growth conditions. Most of the conclusions were attained at acidic pH, but rice is also grown at calcareous conditions, which especially induce Fe deficiency in the plants. In this study, we assay the effect of Si in rice suffering both Fe deficiency and sufficiency in hydroponics at two pHs (5.5 and 7.5). Plant biometric parameters, ROS concentration, enzymatic activities, and total phenolic compounds, as well as ploidy levels, have been determined. In general, both pHs promoted similar rice responses under Fe sufficiency and deficiency status, but at pH 7.5, stress was favored. Flow cytometry studies revealed that Fe deficiency increased the percentage of cells in higher ploidy levels. Moreover, under this Fe status, Si addition enhanced this effect. This increase contributed to maintaining chloroplast structure which may have preserved antioxidant activities, and fortified cell walls, diminishing Fe uptake. The first is considered a beneficial effect as plants presented acceptable SPAD values, well chloroplast structure, and qualitatively high fluorescence observed by confocal microscopy, even under Fe deficiency. But contributes to intensify the Fe shortage, by decreasing apoplast Fe pools. In summary, Si addition to rice plants may not only behave as an apoplastic barrier but may also protect plant chloroplast and alter the plant endoreplication cycle, giving a memory effect to cope with present and future stresses.

Beneficial Effect of Root or Foliar Silicon Applied to Cucumber Plants under Different Zinc Nutritional Statuses.

Zinc (Zn) is an essential micronutrient involved in a large variety of physiological processes, and its deficiency causes mainly growth and development disturbances, as well as oxidative stress, which results in the overproduction and accumulation of reactive oxygen species (ROS). A possible environmentally friendly solution is the application of silicon (Si), an element that has shown beneficial effects under abiotic and biotic stresses on many crops. Si could be applied through the roots or leaves. The aim of this work is to study the effect of Si applied to the root or shoot in cucumber plants under different Zn statuses (sufficiency, deficiency, and re-fertilization). Cucumber plants were grown in hydroponics, with 1.5 mM Si applied at the nutrient solution or sprayed on the leaves. During the different Zn statuses, SPAD index, fresh weight, ROS, and Si, Zn, P, Cu and B mineral concentration were determined. The results suggested that Si application had no effect during sufficiency and deficiency periods, however, during re-fertilization foliar application of Si, it showed faster improvement in SPAD index, better increment of fresh weight, and a decrease in ROS quantity, probably due to a memory effect promoted by Si previous application during the growing period. In summary, Si application to cucumber plants could be used to prepare plants to cope with a future stress situation, such as Zn deficiency, due to its prompt recovery after overcoming the stress period.

Iron supply to soybean plants through the foliar application of IDHA/Fe3+: effect of plant nutritional status and adjuvants.

BACKGROUND: Synthetic Fe chelates are commonly used to overcome Fe deficiencies in crops, but most of them are scarcely biodegradable. Iminodisuccinic acid (IDHA) is a biodegradable chelating agent that is currently being evaluated as an alternative to EDTA. In this work, the efficacy of the foliar application of IDHA/Fe(3+) to soybean chlorotic plants under controlled conditions was studied, testing the influence of the adjuvant used and of the plant nutritional status. RESULTS: When IDHA/Fe(3+) was applied to soybean plants with severe Fe chlorosis and the foliar sprays were the sole source of Fe, this chelate behaved similarly to the EDTA/Fe(3+) and the recovery of the plants was slight in both cases. The same chelates were tested when foliar sprays were an additional source of Fe for mildly chlorotic plants, which were also being supplied with low concentrations of Fe applied to the nutrient solution. Then, plant recovery was appreciable in all cases, and the IDHA/Fe(3+) was as effective as EDTA/Fe(3+). Among the adjuvants studied, a urea-based product was the only one that did not damage the leaf surface and that could improve the efficiency of IDHA/Fe(3+) up tp the level of EDTA/Fe(3+). CONCLUSIONS: Thus, it was concluded the foliar application of IDHA/Fe(3+) can be an environmentally friendly alternative to the non-biodegradable chelate EDTA/Fe(3+) when the appropriate adjuvant is used.

Silicon beneficial effects on yield, fruit quality and shelf-life of strawberries grown in different culture substrates under different iron status.

The silicon application either as foliar or to the radicular system of strawberry plants was investigated. Fortuna strawberry plants were grown in two different substrates (coconut fibre and organic substrate) under optimal (20 µM) or low (5 µM) iron (Fe) conditions. During the study, crop parameters including leaf area, SPAD and fruit yield were measured. At harvest, fruit quality and post-harvest shelf-life were evaluated. Results indicated that "Fortuna" strawberries plants had a poor development in coconut fibre and excellent growth and yield in the organic substrate. In the coconut fibre substrate, no differences in foliar area, fruit diameter, colour, pH and shelf-life were observed related to the Si addition under deficient Fe conditions, but an increased in weight and the firmness of the fruits, as well as in fructose content was shown. However, when 20 µM Fe were supplied, the root application of Si significantly increases: protein, mineral and sugar content, as well as fruit shelf-life by an average of 1.5 days. Likewise, the radicular silicon application to the organic substrate considerably improved yield, fruit diameter, fruit weight, glucose and fructose fruit content and the fruit shelf-life without causing distinguishable chemical or physicochemical changes. In summary, Si application to Fortuna strawberries through the roots could be a good solution to increase fruit quality and yield and to increase benefits from the agronomical point of view. Further studies in other strawberry varieties and dose rates will allow knowing with better precision how the radicular application of silicon contributes to yield and fruit shelf-life.

Root Silicon Addition Induces Fe Deficiency in Cucumber Plants, but Facilitates Their Recovery After Fe Resupply. A Comparison With Si Foliar Sprays.

Silicon has not been cataloged as an essential element for higher plants. However, it has shown beneficial effects on many crops, especially under abiotic and biotic stresses. Silicon fertilization was evaluated for the first time on plants exposed to fluctuations in an Fe regime (Fe sufficiency followed by Fe deficiency and, in turn, by Fe resupply). Root and foliar Si applications were compared using cucumber plants that were hydroponically grown in a growth chamber under different Fe nutritional statuses and Si applied either to the roots or to the shoots. The SPAD index, Fe, and Mn concentration, ROS, total phenolic compounds, MDA concentration, phytohormone balance, and cell cycle were determined. The results obtained showed that the addition of Si to the roots induced an Fe shortage in plants grown under optimal or deficient Fe nutritional conditions, but this was not observed when Si was applied to the leaves. Plant recovery following Fe resupply was more effective in the Si-treated plants than in the untreated plants. A relationship between the ROS concentration, hormonal balance, and cell cycle under different Fe regimes and in the presence or absence of Si was also studied. The contribution of Si to this signaling pathway appears to be related more to the induction of Fe deficiency, than to any direct biochemical or metabolic processes. However, these roles could not be completely ruled out because several hormone differences could only be explained by the addition of Si.

Assessing metal-lignosulfonates as fertilizers using gel filtration chromatography and high-performance size exclusion chromatography.

Lignosulfonates (LSs) are by-products from the paper industry used as biodegradable fertilizers. However, metal-LS ability to provide micronutrients to crops is related to the stability of the complex and the amount of metal complexed. This work evaluated these parameters using ultraviolet-visible (UV-Vis), Fourier-transform infrared (FTIR), and 13C-nuclear magnetic resonance (NMR), along with gel filtration chromatography (GFC) and high-performance size exclusion chromatography (HPSEC), for different spruce, eucalyptus, and pine LSs. GFC and HPSEC pointed out that the amount and type of complexed metal in the LS depends on the molecular weight, pH, and sulphite pulping processes. Both techniques indicated that the low molecular weight LS enriched with phenolic groups has the highest Fe(III) complexing capacity. Also, Fe(III)/LS showed the formation of high molecular weight compounds, whereas Zn(II)/LS and Mn(II)/LS complexes did not form aggregates. Metal-LS fractionation provided considerable information to identify LSs with potential fertilizer capacity and to assess the effectiveness of their complexes.

Isotope pattern deconvolution as a tool to study iron metabolism in plants.

Isotope pattern deconvolution is a mathematical technique for isolating distinct isotope signatures from mixtures of natural abundance and enriched tracers. In iron metabolism studies measurement of all four isotopes of the element by high-resolution multicollector or collision cell ICP-MS allows the determination of the tracer/tracee ratio with simultaneous internal mass bias correction and lower uncertainties. This technique was applied here for the first time to study iron uptake by cucumber plants using 57Fe-enriched iron chelates of the o,o and o,p isomers of ethylenediaminedi(o-hydroxyphenylacetic) acid (EDDHA) and ethylenediamine tetraacetic acid (EDTA). Samples of root, stem, leaves, and xylem sap, after exposure of the cucumber plants to the mentioned 57Fe chelates, were collected, dried, and digested using nitric acid. The isotopic composition of iron in the samples was measured by ICP-MS using a high-resolution multicollector instrument. Mass bias correction was computed using both a natural abundance iron standard and by internal correction using isotope pattern deconvolution. It was observed that, for plants with low 57Fe enrichment, isotope pattern deconvolution provided lower tracer/tracee ratio uncertainties than the traditional method applying external mass bias correction. The total amount of the element in the plants was determined by isotope dilution analysis, using a collision cell quadrupole ICP-MS instrument, after addition of 57Fe or natural abundance Fe in a known amount which depended on the isotopic composition of the sample.

Silicon induced Fe deficiency affects Fe, Mn, Cu and Zn distribution in rice (Oryza sativa L.) growth in calcareous conditions.

A protective effect by silicon in the amelioration of iron chlorosis has recently been proved for Strategy 1 species, at acidic pH. However in calcareous conditions, the Si effect on Fe acquisition and distribution is still unknown. In this work, the effect of Si on Fe, Mn, Cu and Zn distribution was studied in rice (Strategy 2 species) under Fe sufficiency and deficiency. Plants (+Si or-Si) were grown initially with Fe, and then Fe was removed from the nutrient solution. The plants were then analysed using a combined approach including LA-ICP-MS images for each element of interest, the analysis of the Fe and Si concentration at different cell layers of root and leaf cross sections by SEM-EDX, and determining the apoplastic Fe, total micronutrient concentration and oxidative stress indexes. A different Si effect was observed depending on plant Fe status. Under Fe sufficiency, Si supply increased Fe root plaque formation, decreasing Fe concentration inside the root and increasing the oxidative stress in the plants. Therefore, Fe acquisition strategies were activated, and Fe translocation rate to the aerial parts was increased, even under an optimal Fe supply. Under Fe deficiency, +Si plants absorbed Fe from the plaque more rapidly than -Si plants, due to the previous activation of Fe deficiency strategies during the growing period (+Fe + Si). Higher Fe plaque formation due to Si supply during the growing period reduced Fe uptake and could activate Fe deficiency strategies in rice, making it more efficient against Fe chlorosis alterations. Silicon influenced Mn and Cu distribution in root.

Response of soybean plants to the application of synthetic and biodegradable Fe chelates and Fe complexes.

The growing concern over the environmental risk of synthetic chelate application promotes the search for alternatives in Fe fertilization, such as biodegradable chelating agents and natural complexing agents. In this work, plant responses to the application of several Fe treatments (chelates and complexes) was analyzed to study their potential use in Fe fertilization under calcareous conditions. Thus, the root ferric chelate reductase (FCR) activity of soybean (Glycine max cv. Klaxon) plants was determined, and the effectiveness of the Fe chelates and complexes assessed in a pot experiment, by SPAD and fluorescence induction measurements, and the determination of Fe distribution in plant and soil. Additionally, 57Fe Mössbauer spectroscopy was conducted to identify the Fe forms present in the soybean roots. The highest FCR activity was observed for the chelates EDDS/Fe3+ and IDHA/Fe3+; while no activity was observed when using complexes as Fe substrates. In contrast to the FCR data, the pot experiment confirmed that the o,oEDDHA/Fe3+ is the most effective treatment, and the complexes LS/Fe3+ and GA/Fe3+ are able to alleviate Fe chlorosis, also indicated by SPAD data and the maximal quantum efficiency of photosystem II reaction centers as vitality parameters, and the enhanced plant uptake of Fe from natural sources.

Structure and fertilizer properties of byproducts formed in the synthesis of EDDHA.

The synthesis of commercial EDDHA produces o,o-EDDHA as the main reaction product, together with a mixture of regioisomers (o,p-EDDHA and p,p-EDDHA) and other unknown byproducts also able to complex Fe3+. These compounds have been obtained by direct synthesis, and their structures have been determined by ESI-MS analysis as oligomeric EDDHA-like products, formed by polysubstitution in the phenolic rings. Short-term experiments show that the iron complexes of samples enriched in these oligomeric byproducts have adequate stability in solution, but a significant amount of them is lost after interaction with soils and soil materials. Mildly chlorotic cucumber plants are able to reduce iron better from o,p-EDDHA/Fe3+ than from the iron complexes of the oligomeric byproducts. In hydroponics, the chlorotic soybean susceptible plants have a lower potential for Fe absorption from these byproducts than from o,o-EDDHA/Fe3+ and from o,p-EDDHA/Fe3+. In the studied conditions, the iron chelates of EDDHA byproducts do not have the long-lasting effect shown by o,o-EDDHA/Fe3+ and present a less efficient fast-action effect than the o,p-EDDHA/Fe3+.

EDTA Shuttle Effect vs. Lignosulfonate Direct Effect Providing Zn to Navy Bean Plants (Phaseolus vulgaris L 'Negro Polo') in a Calcareous Soil.

Zn-Lignosulfonates (LS) fertilizers are used as an eco-friendly alternative to chelate formulations. The mechanisms of Zn release in the rhizosphere by both types of products are compared. The ability to provide Zn to Phaseolus vulgaris L of non-modified and chemically modified ZnLS and ZnEDTA is compared in a hydroponic assay. Stable isotope 67Zn was used to study Zn source (fertilizer, ZnFer, or native, ZnNat) uptake and distribution in plants in two soil pot experiments. ZnEDTA was the best treatment to provide both ZnFer and ZnNat to navy bean plants. A shuttle effect mechanism and an isotopic exchange may occur. ZnLS from eucalyptus (ZnLSE) provides more Zn to the plant than LS from spruce. Chemical modifications of ZnLSE does not improve its efficiency. A double dose of ZnLSE provides similar ZnFer in leaves and similar soluble ZnFer content in soil than ZnEDTA. A model for the Zn fertilizers behavior in the soil and plant system is presented, showing the shuttle effect for the synthetic chelate and the direct delivery in the rhizosphere for the ZnLS complex.