Uptake of different species of iodine by water spinach and its effect to growth

Iodine biofortification of Swiss chard (Beta vulgaris ssp. vulgaris var. cicla) and its wild ancestor sea beet (Beta vulgaris ssp. maritima) grown hydroponically as baby leaves: effects on leaf production and quality

BACKGROUND

About 35-45% of the global population is affected by iodine deficiency. Iodine intake can be increased through the consumption of biofortified vegetables. Given the increasing interest in wild edible species of new leafy vegetables due to their high nutritional content, this study aimed to evaluate the suitability of Swiss chard (Beta vulgaris ssp. vulgaris var. cicla) and its wild ancestor sea beet (Beta vulgaris ssp. maritima) to be fortified with iodine. Plants were cultivated hydroponically in a nutrient solution enriched with four different concentrations of iodine (0, 0.5, 1.0, and 1.5 mg L-1 ), and the production and quality of baby leaves were determined.

RESULTS

Sea beet accumulated more iodine than Swiss chard. In both subspecies, increasing the iodine concentration in the nutrient solution improved leaf quality as a result of greater antioxidant capacity - the ferric reducing ability of plasma (FRAP) index increased by 17% and 28%, at 0.5 and 1.5 mg L-1 iodine, respectively - the content of flavonoids (+31 and + 26%, at 1 and 1.5 mg L-1 of iodine, respectively), and the lower content of nitrate (-38% at 1.5 mg L-1 of iodine) and oxalate (-36% at 0.5 mg L-1 of iodine). In sea beet, however, iodine levels in the nutrient solution higher than 0.5 mg L-1 reduced crop yield significantly.

CONCLUSIONS

Both subspecies were found to be suitable for producing iodine-enriched baby leaves. The optimal iodine levels in the nutrient solution were 1.0 in Swiss chard and 0.5 mg L-1 in sea beet, as crop yield was not affected at these concentrations and leaves contained enough iodine to satisfy an adequate daily intake with a serving of 100 g. © 2023 Society of Chemical Industry.

Iodine-Biofortified Microgreens as High Nutraceutical Value Component of Space Mission Crew Diets and Candidate for Extraterrestrial Cultivation

The success of Space missions and the efficacy of colonizing extraterrestrial environments depends on ensuring adequate nutrition for astronauts and autonomy from terrestrial resources. A balanced diet incorporating premium quality fresh foods, such as microgreens, is essential to the mental and physical well-being of mission crews. To improve the nutritional intake of astronaut meals, two levels of potassium iodide (KI; 4 µM and 8 µM) and an untreated control were assessed for iodine (I) biofortification, and overall nutraceutical profile of four microgreens: tatsoi (Brassica rapa L. subsp. narinosa), coriander (Coriandrum sativum L.), green basil, and purple basil (Ocimum basilicum L.). A dose-dependent increase in I was observed at 8 µM for all species, reaching concentrations of 200.73, 118.17, 93.97, and 82.70 mg kg^-1 of dry weight, in tatsoi, coriander, purple basil, and green basil, respectively. Across species, I biofortification slightly reduced fresh yield (-7.98%) while increasing the antioxidant activity (ABTS, FRAP, and DPPH). LC-MS/MS Q extractive orbitrap analysis detected 10 phenolic acids and 23 flavonoids among microgreen species. The total concentration of phenolic acids increased (+28.5%) in purple basil at 8 µM KI, while total flavonoids in coriander increased by 23.22% and 34.46% in response to 4 and 8 µM KI, respectively. Both doses of KI increased the concentration of total polyphenols in all species by an average of 17.45%, compared to the control.

A review of iodine in plants with biofortification: Uptake, accumulation, transportation, function, and toxicity

Iodine deficiency can cause thyroid disease, a serious health problem that has been affecting humans since several years. The biofortification of plants with iodine is an effective strategy for regulating iodine content in humans. In addition, radioiodine released into the atmosphere may contaminate terrestrial ecosystem along with dry or wet deposition and its accumulation in plants may cause exposure risks to humans via food chain. Recent progress in understanding the mechanisms related to iodine uptake, elementary speciation, dynamic transportation, nutritional role, and toxicity in plants is reviewed here. First, we introduced the iodine cycle in a marine-atmosphere-land system. The content and speciation of iodine in plants under natural conditions and biofortification backgrounds were also analyzed. We then discussed the mechanisms of iodine uptake and efflux by plants. The promotion or inhibition effects of iodine on plant growth were also investigated. Finally, the participation of radioiodine in plant growth and its safety risks along the food chain were evaluated. Furthermore, future challenges and opportunities for understanding the participation of iodine in plants have been outlined.

Iodine supplementation through its biofortification in Brassica species depending on the type of soil

Iodine is an essential microelement for humans and its deficiency leads to iodine deficiency disorder (IDD) which is a common problem faced by people in hilly areas. Biofortification of iodine is an option to overcome the IDD problem. Herein, we investigated the iodine uptake and accumulation in the edible portion of vegetables such as Brassica napus (BNP) and Brassica pekinensis (BPK) which were grown on two different soils such as sandy soil (SS) and silty loam soil (SLS) with different concentrations of iodine application (used in sodium iodide form) such as 0 ppm, 50 ppm, and 100 ppm. The concentration of iodine was determined by the oxidation of iodide, and nutrients were examined by double acid digestion. Different concentrations of iodine were noticed in silty loam and sandy soils, roots, and shoots of BNP and BPK, while the concentration follows the order: soils > roots > shoots. Iodine concentrations in the roots of BNP and BPK ranged from 46 to 223.7 μg/g which shows a strong correlation with other soil nutrients. Moreover, a large amount of iodine was lost due to the leaching. It is concluded that the biofortification of iodine increases its concentration in Brassica species. This work provides a reference for the iodine biofortification in plant species which will be helpful to control IDD.

Synthesis of Organic Iodine Compounds in Sweetcorn under the Influence of Exogenous Foliar Application of Iodine and Vanadium

A human’s diet should be diverse and rich in vitamins, macro- and microelements essential for the proper functioning of the human body. Globally, a high percentage of the human population suffers from malnutrition, deficiencies of nutrients and vitamins also known as the problem of hidden hunger. This problem it is not only common in poor countries, but also occurs in developed countries. Iodine is a nutrient crucial for the proper functioning of the human and animal body. For plants, it is referred to as a beneficial element or even a microelement. The design of the biofortification experiment was determined on the basis of the interaction of iodine and vanadium (synergistic interaction in marine algae), where vanadium-dependent iodoperoxidase catalyzes apoplastic oxidation of iodine, resulting in high efficiency of iodine uptake and accumulation in brown algae (Laminaria digitate). Three independent experiments (Exp.) were carried out with the foliar application of vanadium (V) and iodine (I) compounds. The main differences between the experiments with the adapted proper corn biofortification method were the different application stage between the individual experiments, the application intervals and the dose of the iodine–vanadium compound. In each experiment, the accumulation of iodine and vanadium in the grain was several times lower than in the leaves. The combination iodine and vanadium significantly increased the accumulation of iodine in the grain in the case of applying V with inorganic iodine compounds, and a decrease in the accumulation of I after applying V with organic iodine compound —especially in Exp. No. 3. In grain, the highest content of I−, IO3− was in combination with the application of 2-iodobenzoic acid (products of its metabolism). In most of the tested combinations, vanadium stimulated the accumulation/synthesis of exogenous/endogenous 5-iodosalicylic acid (5ISA) and 2-iodobenzoic acid (2IBeA), respectively, and decreased the content of 2,3,5-triiodobenzoic acid (2,3,5-triIBeA) in leaves and grains. The tested compounds I and V and the combinations of their application had a diversified effect on the vitamin C content in the grains. Vanadium in the lower dose of 0.1 µM significantly increased the sugar content in the grain.

Efficacious bioremediation of heavy metals and radionuclides from wastewater employing aquatic macro- and microphytes

Cytotoxic, mutagenic, and carcinogenic contaminants, such as heavy metals and radionuclides, have become an alarming environmental concern globally, especially for developed and developing nations. Moreover, inefficient prevalent wastewater treatment technologies combined with increased industrial activity and modernization has led to increase in the concentration of toxic metals and radioactive components in the natural water bodies. However, for the improvement of ecosystem of rivers, lakes, and other water sources different physicochemical methods such as membrane filtration, reverse osmosis, activated carbon adsorption, electrocoagulation, and other electrochemical treatment are employed, which are uneconomical and insufficient for the complete abatement of these emerging pollutants. Therefore, the application of bioremediation employing aquatic macrophytes and microphytes have gained considerable importance owing to the benefits of cost-effectiveness, eco-friendly, and higher energy efficiency. Thus, the present review aims to enlighten the readers on the potential application of algae, cyanobacteria, plant, and other aquatic micro- and macrophytes for the elimination of carcinogenic metals and radioactive isotopes from wastewater. Additionally, the use of transgenic plants, genetically modified species, algal-bacterial symbiosis for the enhancement of removal efficiency of mutagenic contaminants are also highlighted. Furthermore, species selection based on robustness, mechanism of different pathways for heavy metal and radionuclide detoxification are elucidated in this review article.

Anti- and pro-oxidant potential of lettuce (Lactuca sativa L.) biofortified with iodine by KIO3, 5-iodo- and 3,5-diiodosalicylic acid in human gastrointestinal cancer cell lines

Vegetables are particularly rich sources of micronutrients and phytochemicals such as polyphenols and vitamins. These plant-derived bioactive compounds provide antitumor and antioxidant properties due to their capacity to interact with reactive oxygen species (ROS). The objective of this study was to determine the effect of iodine biofortification (potassium iodate/KIO₃/, 5-iodosalicylic acid/5-ISA/, and 3,5-diiodosalicylic acid/3,5-diISA/) on the antioxidant activity of lettuce (Lactuca sativa L. capitata) cv. ‘Melodion’. In this work, HPLC analysis was used to identify polyphenolic compounds while the antioxidant activity of iodine-enriched vegetables was determined by using DPPH, ABTS and FRAP methods. The content of the water-soluble vitamins was analyzed by using the LC-MS/MS technique. The impact of extracts from iodine-biofortified lettuce on production of reactive oxygen species (ROS) in gastrointestinal cancer cells was also evaluated. The results from this research indicate that application of iodine compounds improves the antioxidant potential of lettuce by increasing the concentration of some vitamins, antioxidant enzymes and polyphenolic compounds in the enriched plants. Moreover, the study has shown that iodine-biofortified lettuce induces production of ROS in cancer cells, resulting in an anticancer effect by the induction of programmed cancer cell death.

Vegetables are particularly rich sources of micronutrients and phytochemicals such as polyphenols and vitamins.

New Aspects of Uptake and Metabolism of Non-organic and Organic Iodine Compounds-The Role of Vanadium and Plant-Derived Thyroid Hormone Analogs in Lettuce

The process of uptake and translocation of non-organic iodine (I) ions, I^- and IO₃ ^-, has been relatively well-described in literature. The situation is different for low-molecular-weight organic aromatic I compounds, as data on their uptake or metabolic pathway is only fragmentary. The aim of this study was to determine the process of uptake, transport, and metabolism of I applied to lettuce plants by fertigation as KIO₃, KIO₃ + salicylic acid (KIO₃+SA), and iodosalicylates, 5-iodosalicylic acid (5-ISA) and 3,5-diiodosalicylic acid (3,5-diISA), depending on whether additional fertilization with vanadium (V) was used. Each I compound was applied at a dose of 10 μM, SA at a dose of 10 μM, and V at a dose of 0.1 μM. Three independent 2-year-long experiments were carried out with lettuce; two with pot systems using a peat substrate and mineral soil and one with hydroponic lettuce. The effectiveness of I uptake and translocation from the roots to leaves was as follows: 5-ISA > 3,5-diISA > KIO₃. Iodosalicylates, 5-ISA and 3,5-diISA, were naturally synthesized in plants, similarly to other organic iodine metabolites, i.e., iodotyrosine, as well as plant-derived thyroid hormone analogs (PDTHA), triiodothyronine (T3) and thyroxine (T4). T3 and T4 were synthesized in roots with the participation of endogenous and exogenous 5-ISA and 3,5-diISA and then transported to leaves. The level of plant enrichment in I was safe for consumers. Several genes were shown to perform physiological functions, i.e., per64-like, samdmt, msams5, and cipk6.

Evidences for a Nutritional Role of Iodine in Plants

Little is known about the role of iodine in plant physiology. We evaluated the impact of low concentrations of iodine on the phenotype, transcriptome and proteome of Arabidopsis thaliana. Our experiments showed that removal of iodine from the nutrition solution compromises plant growth, and restoring it in micromolar concentrations is beneficial for biomass accumulation and leads to early flowering. In addition, iodine treatments specifically regulate the expression of several genes, mostly involved in the plant defence response, suggesting that iodine may protect against both biotic and abiotic stress. Finally, we demonstrated iodine organification in proteins. Our bioinformatic analysis of proteomic data revealed that iodinated proteins identified in the shoots are mainly associated with the chloroplast and are functionally involved in photosynthetic processes, whereas those in the roots mostly belong and/or are related to the action of various peroxidases. These results suggest the functional involvement of iodine in plant nutrition.

Biofortification of Potato and Carrot With Iodine by Applying Different Soils and Irrigation With Iodine-Containing Water

Accumulation of iodine by potato (Solanum tuberosum L.) and carrot (Daucus carota L. var. sativus) plants cultivated on different soils (sand, sandy silt, and silt) using irrigation water containing iodine at concentrations of 0.1 and 0.5 mg/L was investigated. In the edible organs of potato and carrot control plants grown on sand, sandy silt, and silt soils, the iodine concentrations were 0.15, 0.17, and 0.20 mg/kg (potato) and 0.012, 0.012, and 0.013 mg/kg (carrot); after the treatment by applying 0.5 mg/L iodine dosage, the iodine concentrations were 0.21, 0.19, 0.27 mg/kg (potato) and 3.5, 3.7, 3.0 mg/kg (carrot), respectively. Although the iodine treatment had no significant effect on the biomass production of these plants, in potato tubers, it resulted in higher Fe and lower Mg and P concentrations, whereas no similar trend was observable in carrot roots. The accumulation of Mn, Cu, Zn, and B in the edible part of both plants was not influenced by the iodine treatment. The soil properties did not have a significant impact on biomass production under the same environmental conditions. The concentration and the distribution of iodine in both plants were slightly modified by the growing medium; however, the photosynthetic efficiency and the chlorophyll content index of potato plants cultivated in silt soil increased significantly. Potato plant was not suitable for biofortification with iodine, while considering the iodine concentration and the moisture content of carrot roots, it can be calculated that consuming 100 g fresh carrot would cover about 38% of the daily iodine intake requirement for an average adult person.

Iodine distribution and cycling in a beech (Fagus sylvatica) temperate forest

Radioiodine is of health concerns in case of nuclear events. Possible pathways and rates of flow are essential information for risk assessment. Forest ecosystems could influence the global cycle of long-lived radioiodine isotope (¹²⁹I) with transfer processes similar to stable isotope (¹²⁷I). Understanding iodine cycling in forest involves study of the ecosystem as a whole. In this context, we determined the ¹²⁷I contents and distribution in soil, tree compartments and atmospheric inputs during a three years in situ monitoring of a temperate beech forest stand. The iodine cycle was first characterized in terms of stocks by measuring its concentrations in: tree, litterfall, humus, soil, rainfall, throughfall, stemflow and soil solutions. Main annual fluxes (requirement, uptake and internal transfers) and forest input-output budget were also estimated using conceptual model calculations. Our findings show that: (i) soil is the main I reservoir accounting for about 99.9% of ecosystem total stock; (ii) iodine uptake by tree represents a minor fraction of the available pool in soil (<0.2%); (iii) iodine allocation between tree compartments involves low immobilization in wood and restricted location in the roots; (iv) translocation of excess iodine towards senescing foliage appears as an elimination process for trees, and (v) litterfall is a major pathway in the I biological cycling. In our soil conditions, the input - output budget shows that the ecosystem behaves as a potential source of I for groundwater.

Organic iodine supply affects tomato plants differently than inorganic iodine

Iodine is a beneficial element for humans but very lowly represented in our diet. Iodine-enriched vegetables could boost the iodine content in the food chain. Despite being a beneficial element for plants, little is known about the effect of different iodine forms on plant growth. This work analyses the effect of uptake of mineral (KI) and organoiodine (5-iodosalicylic acid, 5-ISA; 3,5-diiodosalicylic acid, 3,5-di-ISA; 2-iodobenzoic acid, 2-IBeA; 4-iodobenzoic acid, 4-IBeA) compounds on tomato plants at an early stage of vegetative growth. As many organoiodine compounds are derived from salicylic (SA) and benzoic acids (BeA), treatments with I, SA and BeA in various treatments were realized and the influence of tested compounds on plant growth was analyzed. Iodine content was measured, as well as expression of key genes involved in I and SA metabolism. Organoiodine compounds accumulated mainly in roots whereas iodine accumulated in the upper parts when given as KI. The shoot system had 5, 12 and 25 times higher iodine content after KI treatment than after 4-IBeA, 5-ISA and 2-IBeA, or 3,5-diISA treatments, respectively. A toxic effect on plants was observed only for 3,5-diISA and 4-IBeA. The expression levels of a gene related to iodine metabolism (HMT, halide ion methylotransferase), a gene responsible for SA methylation in leaves (SAMT) and a gene related to SA catabolism (S3H, salicylic acid 3-hydroxylase) were modified differently depending on the iodine source. Overall, our data point out to a difference in plant uptake, transport of iodine in tomato plants based on the form of iodine compound.

Potential of higher plants, algae, and cyanobacteria for remediation of radioactively contaminated waters

The potential of photosynthetic organisms to remediate radioactively contaminated water was evaluated for scenarios related to nuclear installations and included the following radionuclides: ¹³⁷Cs, ¹³⁴Cs, ¹³⁶Cs, ⁹⁰Sr, ¹³¹I, ²³⁹Pu, ²⁴¹Am, ¹³²Te/¹³²I, ⁵⁸Co, ⁶⁰Co, ⁵¹Cr, ^110mAg, ⁵⁴Mn, ¹²⁴Sb, ⁵⁹Fe, ⁶⁵Zn, ⁹⁵Zr, and ⁹⁵Nb. An extensive literature review was undertaken leading to the creation of a database including more than 20,000 entries from over 100 references in which terrestrial and aquatic plants, macro- and microalgae, cyanobacteria and biosorbents derived from these organisms were used to clean water from these specific radionuclides or their stable isotopes. In a first phase, the remediation potential of the organisms and biosorbents was evaluated for the individual elements based on parameters such as plant uptake, removal percentage, and bioconcentration factor, and for two radionuclide mixtures based on the ability of the organisms/biosorbents to work under mixture conditions. As the experimental and environmental conditions will influence the performance of the organisms and biosorbents, a literature-based evaluation of the most influencing or restricting parameters was made and water pH, competing ions, and the chemical modification of biosorbents showed to be of major importance. Finally, the most promising organisms and biosorbents were identified using a specifically developed selection procedure taking into account their performance and robustness. Ranking was done based on clear criteria with a distinct weight and scoring scheme. As such, 20 organisms/biosorbents were identified that showed high potential to clean waters contaminated with (mixtures of) radionuclides related to nuclear installations and which can be used for further experimental investigations.

Preliminary Evidences of Biofortification with Iodine of "Carota di Polignano", An Italian Carrot Landrace

The "Carota di Polignano" (Polignano Carrot - PC, Daucus carota L.) is a multi-colored landrace, cultivated in the Southern Italy, whose colors range from yellow to purple. Iodine is an essential micronutrient for humans, since it is a key component of thyroid hormones, which regulate the growth and development of the human body. The main source for iodine assumption is represented by diet, but its concentration in the vegetables is usually limited with respect to human needs. To this purpose, two experimental trials (in open field and in greenhouse with a soil-less system) were carried out to enrich PC with iodine. Three levels of iodine (control treatment, C - 0 mg·L^-1; low, L - 50 mg·L^-1; and high, H - 500 mg·L^-1), distributed with foliar spray fertilizations (in both open field and greenhouse) or with nutrient solution (in greenhouse, at the level of 50 mg·L^-1) in the form of KIO₃ were compared. In open field, the H treatment showed a biofortification that was double and triple respect to L and C treatments, respectively, without influencing color and biometric parameters, such as the fresh and dry weight of roots and DM percentage. In greenhouse, the biofortification done with foliar spray fertilization followed the same trend of open field, while the biofortification by means of nutrient solution was more effective but reached very high levels that had toxic effects on the plants and could be too high for human nutrition. However, the concentrations of iodine into biofortified carrots in open field can allow to satisfy the recommended daily allowance (RDA) by consuming 100 and 200 g of fresh product for the treatment H and L, respectively. Regarding the greenhouse biofortification, the RDA would be satisfied by consuming 200 g of fresh carrots (with the high level of foliar fertilization).

Iodide and iodate effects on the growth and fruit quality of strawberry

BACKGROUND

Iodine deficiency is an environmental health problem affecting one-third of the global population. An iodine biofortification hydroponic experiment was conducted to explore the iodide and iodate uptake characteristics of strawberry plants, to measure the dosage effects of iodine on plant growth and to evaluate the influence of I^- or IO₃^- application on fruit quality.

RESULTS

After biofortification, the iodine contents of the fresh strawberry fruits were 600-4000 µg kg^-1 , covering the WHO dietary iodine allowance of 150 µg · day^-1 for adults. The iodine uptake of the strawberry plants increased with increasing I^- or IO₃^- concentration of the culture solution. At the same iodine concentration, the iodate uptakes of various plant organs under I^- treatments were apparently more than those under IO₃^- treatments. Low-level exogenous iodine (I^- ≤ 0.25 mg L^-1 or IO₃^- ≤ 0.50 mg L^-1 ) not only promoted plant growth and increased biomass per plant, but also improved fruit quality by enhancing the vitamin C and soluble sugar contents of the strawberry fruits. Nevertheless, excessive exogenous iodine inhibited plant growth and reduced biomass per plant. IO₃^- uptake apparently increased the total acidity and nitrate content of the fruits, reducing the quality of the strawberry fruits. Conversely, I^- uptake obviously decreased the total acidity and nitrate content of the strawberry fruits, improving the fruit quality.

CONCLUSION

The strawberry can be used as a target crop for iodine biofortification. Furthermore, applying an appropriate dose of KI can improve the fruit quality of the strawberry plants. © 2016 Society of Chemical Industry.

Use of Iodine to Biofortify and Promote Growth and Stress Tolerance in Crops

Iodine is not considered essential for land plants; however, in some aquatic plants, iodine plays a critical role in antioxidant metabolism. In humans, iodine is essential for the metabolism of the thyroid and for the development of cognitive abilities, and it is associated with lower risks of developing certain types of cancer. Therefore, great efforts are made to ensure the proper intake of iodine to the population, for example, the iodization of table salt. In the same way, as an alternative, the use of different iodine fertilization techniques to biofortify crops is considered an adequate iodine supply method. Hence, biofortification with iodine is an active area of research, with highly relevant results. The agricultural application of iodine to enhance growth, environmental adaptation, and stress tolerance in plants has not been well explored, although it may lead to the increased use of this element in agricultural practice and thus contribute to the biofortification of crops. This review systematically presents the results published on the application of iodine in agriculture, considering different environmental conditions and farming systems in various species and varying concentrations of the element, its chemical forms, and its application method. Some studies report beneficial effects of iodine, including better growth, and changes in the tolerance to stress and antioxidant capacity, while other studies report that the applications of iodine cause no response or even have adverse effects. We suggested different assumptions that attempt to explain these conflicting results, considering the possible interaction of iodine with other trace elements, as well as the different physicochemical and biogeochemical conditions that give rise to the distinct availability and the volatilization of the element.

An innovative approach for iodine supplementation using iodine-rich phytogenic food

Iodine, as one of the essential trace elements for human body, is very important for the proper function of thyroid gland. In some regions, people are still suffering from iodine deficiency disorder (IDD). How to provide an effective and cost-efficient iodine supplementation has been a public health issue for many countries. In this review, a novel iodine supplementation approach is introduced. Different from traditional iodine salt supplement, this approach innovatively uses cultivated iodine-rich phytogenic food as the supplement. These foods are cultivated using alga-based organic iodine fertilizer. The feasibility, mechanics of iodine absorption of plants from soil and the bioavailability of iodine-rich phytogenic food are further discussed.