Hoagland Nutrient Research Articles

Selenite antagonizes the phytotoxicity of Cd in the cattail Typha angustifolia.

The Phytotoxicity of and mechanism underlying selenite-mediated tolerance to Cd stress in Typha angustifolia were studied hydroponically with respect to metal uptake and translocation, photosynthesis-related parameters, contents of proline and O2•-, products of lipid peroxidation, cell viability, enzymatic and non-enzymatic antioxidants, glyoxalases and phytochelatins. T. angustifolia were exposed to 25, 50 and 100μM of Cd alone and in conjunction with 5mgL-1 of selenite in full-strength Hoagland's nutrient solution for 30 days. Results showed that Cd contents in T. angustifolia leaves and roots increased in a dose-dependent manner and were higher in roots, but those of BAC, BCF and TF changed in a contrary pattern. Addition of selenite to Cd-containing treatments further reduced Cd levels in T. angustifolia leaves and roots, as well as BAC, BCF and TF. A diphasic effect was found in T. angustifolia for the contents of total chlorophyll, GSH, PC and GSSG, as well as activities of CAT, POD, SOD and GR, in response to Cd stress alone and in conjunction with selenite supplementation, but the same effect was not observed for Pn, Cond, Tr, Ci, Fv/Fm and ϕPSII. In contrast, exogenous selenite supplementation enhanced the contents of total chlorophyll and the non-enzymatic antioxidants, as well as activities of enzymatic antioxidants, while the values of photosynthetic fluorescence parameters were rescued. Selenite addition decreased Cd-induced cell death. Proline contents and Gly I activities in T. angustifolia leaves kept increasing in a dose-dependent manner of Cd concentrations in the growth media and selenite addition further enhanced both parameters. Addition of selenite could quench Cd-mediated generation of MDA, O2•- and MG in T. angustifolia leaves and reduce Cd-induced Gly II activity. A U-shaped GSH/GSSG ratio in T. angustifolia leaves suggests a possible trade-off between PC synthesis and GR activity since both share the same substrate GSH. Therefore, confined BAC, BCF and TF were a mechanism that confers T. angustifolia tolerance to Cd stress, and that exogenous selenite supplementation could depress Cd-induced stress in T. angustifolia by rescuing the photosynthetic fluorescence, enhancing non-enzymatic and enzymatic antioxidants that scavenge O2•- and MG, and potentiating PC synthesis that chelates Cd.

Effect of salinity on physiological, biochemical and photostabilizing attributes of two genotypes of quinoa (Chenopodium quinoa Willd.) exposed to arsenic stress

Soil salinity and arsenic (As) contamination are serious environmental problems. To investigate the effects of salinity on As uptake and physiological and biochemical attributes of quinoa (Chenopodiumquinoa Willd.), a hydroponic experiment was performed. One-month old healthy plants of two quinoa genotypes; Vikinga and A7 were transplanted in plastic tubs containing half strength Hoagland's nutrient solution. Plants were exposed to different levels of As (0, 150 and 300 μM), salinity (0, 150 and 300 mM) and their combinations (150 μM As + 300 mM NaCl; 300 μM As + 300 mM NaCl) for five weeks. Results revealed that combined application of salinity and As caused more pronounced reduction in growth, chlorophyll contents and caused more oxidative damage in both quinoa genotypes. Under combined application of salinity and As, Na+ concentration was increased whereas As content was decreased in plant tissues. Quinoa genotype A7 was more tolerant than Vikinga against salinity, As and their combination perhaps because of less uptake of toxic ions and higher activities of antioxidant enzymes (SOD, CAT, POD). Bioconcentration factor (BCF), translocation factor (TF) and tolerance index (TI) indicated that genotype A7 can be successfully employed for phytostabilization of As contaminated saline soils.

Veronica becabonga L. as a hyperaccumulatorplant for cadmium

Heavy metal pollution of water is a major environmental problem facing the modem world.The major objective of this research was to evaluate the potential of water-speedwell plant,Veronica becabonga L. to uptake and accumulate heavy metal cadmium under greenhouseconditions, Veronica becabonga L., were cultured in 3% Hoagland's nutrient medium, whichwas supplemented with 0, 25, 50,100, 200, 300 mg/I of Cd(NO3)2 4H2O over one weektreatment period. Plants were harvested at the end of this period and heavy metals from theentire shoot tissue was extracted using the closed Teflon vessel method and metal content inthe extract was estimated using a Flame atomic absorption spectrophotometry. The resultsshowed that the uptake and accumulation of Cd in V becabonga L. showed significantincrease when metal concentration was increased. The highest amount of Cd accumulationwas detected at 100mg/I Cd(NO3)24H2O in the culture solution that was 20660.3 mg/kg DWof shoots. The linear pattern of uptake suggest the involvement of both active and passivetransport mechanisms for Cd uptake, Finally, since the high concentrations cadmiumaccumulation in shoots of plants has far exceeded 0.01% DW V becabonga L. is ahyperaccumulator plant for this metal and has potential for phytoremediation of watercontaminated with cadmium,

24-epibrassinolide pre-treatment alleviates the salt-induced deleterious effects in medicinal pumpkin (Cucurbita pepo) by enhancement of GABA content and enzymatic antioxidants

It is known that epibrassinolide (EBL) plays an important role in the variety of plant developmental processes and adaptation to various environmental stresses. Salt stress is one of the most important environmental problems which limit crop growth and productivity. Here, the effects of EBL pretreatment on amelioration of the adverse effects of salinity were investigated in pumpkin, especially at the establishment stage. For this purpose, uniform-sized seedlings were transplanted to plastic containers containing one-half-strength Hoagland's nutrient solution. EBL was added at 0.1 and 0.01 μM to the hydroponic medium for 5 days before stress. The plants were treated with 40 and 80 mM NaCl for inducing salinity stress. Salt stress reduced the plant growth, calcium and potassium content in leaves and roots, and these detrimental effects were alleviated when plants were pretreated with EBL. Salinity stress caused a significant increase in lipid peroxidation, sodium, and γ-amino butyric acid (GABA) content. EBL pretreatment ameliorated these effects by reducing lipid peroxidation, sodium content and increasing GABA content. The increase in activities of guaiacol peroxidase, catalase, ascorbate peroxidase, and superoxide dismutase was observed under salinity stress. Application of exogenous EBL pretreatment further increased antioxidant enzymes activities. The present work emphasizes the protective role of EBL in the regulation of antioxidant enzymes and GABA accumulation and its possible link in amelioration of stress in plants. This is the first report dealing with EBL effect on GABA content under salt stress.

Phytotoxicity and degradation of antibiotic ofloxacin in duckweed (Spirodela polyrhiza) system

The phytotoxicity and degradation of ofloxacin (OFX) in duckweed Spirodela polyrhiza based system was estimated in this study. For that, OFX was added in an environmentally relevant range (0.01–1.0 mg L−1) in medium (Hoagland nutrient) and toxicity biomarkers, i.e. changes in plant biomass, relative growth rate (RGR), photopigment (Chl-a, Chl-b and carotenoids), protein content, antioxidative enzymes (catalase, CAT; superoxide dismutase, SOD; and ascorbate peroxidases, APX) in fronds were estimated. The batch-scale setups (250 ml) was prepared in triplicate for each concentration of OFX and reared in growth chambers (Algae Tron AG 230) for 7 d. Results suggested that the high concentrations of OFX caused a reduction in biomass (4.8–41.3%), relative root growth (RGR), protein (4.16–11.28%) and photopigment contents. The fronds in OFX spiked setups showed an increased level of antioxidative enzymes: CAT (0.230–0.338 mmolH2O2 mg−1 protein), APX (0.043–0.074 mmolascorbate mg−1 protein), and SOD (0.267–0.317 U mg−1 protein) than control. At the end (7 d), the residual OFX content in the medium was also estimated, and results suggested a significant (p < 0.05) reduction (93.73–98.36%) in OFX content than control setup (54.76–75.53%) at the end of the experimentation. The trend of residual OFX suggested phytodegradation as a significant mechanism of antibiotic degradation other than hydrolysis and photodegradation processes. This study indicates that duckweed can be an effective bio-tool for the removal of environmental relevant concentration of the antibiotics from the wastewater.

Interplaying roles of silicon and proline effectively improve salt and cadmium stress tolerance in Phaseolus vulgaris plant

The interplaying defensive roles of silicon (Si) and proline (Pro) in improving growth and yield attributes, physio-biochemical attributes, and antioxidant defense systems in common bean plant grown under saline (NaCl) and/or cadmium (Cd2+) stress were assessed. Seed were sown in plastic pots filled with sand-free ions as a growing medium that watered with a ½-strength Hoagland's nutrient solution. Twenty five days after planting, pots were split into 4 plots; control (no stress), 150 mM NaCl (salt stress), 1.5 mM Cd2+ in CdCl2 (Cd2+ stress), and 100 mM NaCl + 1.0 mM Cd2+ (salt + Cd2+ stress). Four treatments; foliar spray with distilled water, 6 mM Si (in K2SiO3.nH2O) solution, 6 mM Pro solution, and a combination of Si and Pro were allotted under each of the 4 plots. The experimental layout was a completely randomized design with 15 replicates. Compared to control, NaCl or Cd2+ stress significantly (P ≤ 0.05) reduced plant growth and yield attributes, leaf contents of chlorophylls, carotenoids, N, P, and K+, K+/Na+ ratio, RWC, MSI, Pn and Tr, while elevated significantly leaf EL, leaf contents of proline, soluble sugar, glutathione, MDA, Na+, and root, leaf and pod contents of Cd2+. The activities of antioxidant enzymes were also raised. The combined stress (NaCl + Cd2+) was more influential. Addition of Si and/or Pro for common bean plants under NaCl and/or Cd2+ stress significantly enhanced all investigated attributes of physiology, morphology, and biochemistry, and further increased the activities of antioxidant enzymes. Supplementation of Si + Pro was the best treatment having more positive influential, especially reducing the Cd2+ content in Phaseolus vulgaris pods to the limits (0.27 mg kg−1) for legumes. Therefore, this combined treatment is recommended to use for alleviating environmental stress effects, especially salinity and Cd2+ for common bean production.

Kuraklık Stresinin Bazı Domates GenotiplerindeAntioksidatif Enzim ve Besin Elementi Değişimleri Üzerine Etkileri

Along with global warming, serious&#x0D; reductions occurred in water resources. The drought stress resulting from&#x0D; global warming has greatly affected production. As well as reducing yield and&#x0D; quality in production, drought also reduces farmer's income. One of the&#x0D; measures to be taken in order to minimize the damage caused by the effect of&#x0D; drought stress is to determine the tolerance of the genotypes to drought.&#x0D; Accordingly, three hybrids varieties, three standards varieties and three&#x0D; landraces of tomatoes were used in the present study. Tomato seeds were sown in&#x0D; a 2 liters-pot that contains 1:1 mixture of peat + perlite. After the true&#x0D; leaves emerged, the seedlings were irrigated with the Hoagland nutrient&#x0D; solution. While irrigation was carried on the control plants until the end of&#x0D; the application, irrigation was completely terminated during the seedling&#x0D; period in the plants that are exposed to drought. 12 days after the irrigation&#x0D; cut in tomato genotypes, the changes in the level of catalase (CAT), superoxide&#x0D; dismutase (SOD), ascorbate peroxidase (APX), potassium (K), calcium (Ca) and magnesium were examined. It was observed that there were significant&#x0D; differences in these parameters examined for the determination of tomato&#x0D; genotypes that are tolerant and sensitive to drought stress.

Silicon induced mitigation of TCA cycle and GABA synthesis in arsenic stressed wheat (Triticum aestivum L.) seedlings

The metalloid arsenic (As) is considered to be biologically non-essential and major environmental concern to all organisms. The aim of our study was to evaluate whether silicon (Si) has ameliorative effects on growth, respiratory cycle and Gamma-Aminobutyric acid (GABA) synthesis in wheat (Triticum aestivum L. cv PBW 343) seedlings under arsenic stress. The experiments were performed in a completely randomized design with three repeats and two replicates for each treatment. The seedlings were subjected to different doses of arsenate As (V) (25, 50 and 100 μM) with or without silicate (5 mM) in modified Hoagland's nutrient media for 21 days. Arsenate stress decreased seedling growth, activities of respiratory cycle enzymes particularly dehydrogenases while enhanced the levels of oxidative stress markers, Krebs cycle intermediates and GABA including activities of enzymes associated with GABA synthesis. Arsenate treatment disturbed the phosphate contents and impaired the respiratory process. Irrespective of arsenate concentrations, silicate administration substantially modulated the toxic effects of the metalloid in the test cultivar. Thus, silicon supplementation may emerge as a beneficial strategy to reduce potential health risks and might help to mitigate arsenic- induced stress in wheat seedlings.

Herbivory-induced overcompensation and resource-dependent production of extrafloral nectaries in Luffa cylindrica (Cucurbitaceae)

Extrafloral nectaries (EFNs) are nectar secretory structures involved in the indirect defense of plants. In the sponge gourd (Luffa cylindrica), EFNs commonly occur on the lower surface of leaf blades and stipules and remain functional until leaf senescence. To test the hypothesis that the development of EFNs is influenced by herbivore damage and resource availability, we grew Luffa cylindrica under different concentrations of Hoagland's nutrient solution (nutrient-poor conditions: 10%, 50%; and control condition: 100%) and two herbivory treatments (damaged and undamaged leaves). We collected ten leaves from treated plants to quantify leaf area and EFN density. Overall, leaf area increased and EFN decreased in damaged plants, but this significantly depended on nutritional status. In undamaged plants, EFN density tended to remain constant, whereas foliar area increased with nutrient input. Under herbivory, foliar area increased at 10% but decreased at 50 and 100% of nutrients in relation to undamaged plants, whereas EFN density tended to increase with nutrient availability to exceed undamaged plants under control concentrations. Plants under nutrient-poor conditions subjected to herbivory exhibited an increased foliar area, characterizing a compensatory mechanism. Our results suggest that herbivore-induced indirect defense is a damage- and resource-dependent response in Luffa cylindrica. These findings contribute to understanding the factors that modulate indirect defenses and plant-herbivore-environment interactions.

Effects of cesium accumulation on chlorophyll content and fluorescence of Brassica juncea L.

The aim of our study was to investigate the toxicological mechanism of cesium on Indian mustard (Brassica juncea L.). The impact of cesium toxicity to plants was evaluated using phytophysiology and genetic methods. In this study, Brassica juncea was grown on Cs-contaminated Hoagland's nutrient solution, and chlorophyll content, chlorophyll fluorescence, and Cs bioaccumulation were measured. Transcriptome data was used to perform an in-depth analysis of the molecular mechanisms underlying the effects of Cs accumulation. The results showed that Cs accumulated up to 3586.70 mg kg−1 in B. juncea treated with 100 mg L−1 Cs. The chlorophyll content and several chlorophyll fluorescence parameters (Fv/F0, Fv/Fm, ΦPS II, qP, and NPQ) significantly decreased under Cs exposure. The starting process of PSII was also inhibited under higher Cs conditions. These results indicate that excessive Cs can damage PS II in leaves, decreasing photochemical activity and the energy conversion rate. Further analysis revealed that Cs interfered with the expression of chloroplastic metabolic genes (25 up and 36 down) and inhibited the expression of PsaB, psbC, PetF, LHCA1, and LHCB5. The results indicate that stable Cs leads to abnormal expression of genes related to photosynthesis pathway, blocking the electron transport process from plastoquinone-QA to plastoquinone-QB, resulting in abnormal photosynthesis, which leads to abnormal growth of B. juncea.

The mechanism of hydrogen sulfide mitigation of iron deficiency-induced chlorosis in strawberry (Fragaria × ananassa) plants.

A study was carried out to assess the mitigation mechanism of exogenously applied sodium hydrosulfide (NaHS) as a donor of H2S on strawberry seedlings under iron deficiency. The ameliorative effects of NaHS on oxidative damage, ion hemostasis and uptake, and availability of Fe were investigated by spraying solution of 0.2mM NaHS or 0.2mM NaHS plus 0.2mM hypotaurine (HT), a scavenger of H2S to plant leaves. Iron deficiency was created using 0.1mM FeSO4 instead of 0.1mM EDTA-Fe in Hoagland's nutrient solution. After a 28-day treatment, strawberry plants exhibited leaf interveinal chlorosis under Fe deficiency, but these apparent symptoms of iron deficiency were overcome by foliar application of NaHS. Exogenously applied NaHS enhanced chlorophyll contents and available iron and Fe accumulation in young leaves, but application of H2S scavenger hypotaurine with NaHS did not change those parameters under Fe deficiency. This clearly shows that NaHS improved iron availability in the strawberry plants. Furthermore, exogenously applied NaHS increased endogenous H2S and iron levels in the roots and leaves. Moreover, NaHS enhanced the levels of zinc (Zn2+), calcium (Ca2+), and magnesium (Mg2+) in both leaves and roots of the strawberry plants grown at Fe deficiency, except for Zn in roots which decreased significantly. This also suggests that NaHS maintains the levels of inorganic ions restricted by Fe deficiency. Fe deficiency increased electrolyte leakage (EL) and the levels of malondialdehyde (MDA) and hydrogen peroxide (H2O2) in plant leaves. Exogenous NaHS reduced the accumulation of H2O2, MDA, and EL and upregulated the activities of key antioxidant enzymes. Overall, NaHS improved Fe uptake and activation by improving endogenous H2S, maintained balance of mineral nutrients and activities of the antioxidant enzymes, and reduced the generation of MDA and H2O2 as well as electrolyte leakage caused by Fe deficiency. So NaHS proved to be effective in ameliorating iron chlorosis caused by iron deficiency.

Manganese tolerance in Verbascum olympicum Boiss. affecting elemental uptake and distribution: changes in nicotinic acid levels under stress conditions

A multielemental determination methodology in conjunction with an organic acid analysis that were supplemented with other stress parameters and an ultrastructural analysis used herein to study Verbascum olympicum Boiss. (Scrophulariaceae) under Mn stress. Uptake and accumulation characteristics of B, Cu, Fe, Mn, Mo, and Zn were evaluated in 8-week-old seedlings grown in Hoagland's nutrient solution and exposed to 5 (CK), 50, and 200μM MnSO4 for 7days. Hydrogen peroxide levels were determined to evaluate oxidative stress, and changes in compatible substance levels (total phenolic contents, glutathione and glutathione disulfide levels) were determined to assess antioxidant defense mechanisms. The distribution of manganese on the root surface was characterized by scanning electron microscopy images and energy-dispersive X-ray spectroscopy analysis. The levels of nicotinic acid, which is involved in nicotinamide adenine dinucleotide biosynthesis, were determined in roots and leaves to assess tolerance mechanisms. V. olympicum exhibited the ability to cope with oxidative stress originating from excessive Mn, while increased Mn concentrations were observed in both roots and leaves. The translocation factor of B was the most affected among other studied elements under the experimental conditions. Total nicotinic acid levels exhibited a trend of reduction in the roots and leaves, which could be attributed to the appropriate metabolic progress associated with oxidative stress based on the nicotinamide adenine dinucleotide cycle that may reach glutathione in response to manganese stress during plant growth.

Mitigation of arsenic toxicity and accumulation in hydroponically grown rice seedlings by co-inoculation with arsenite-oxidizing and cadmium-tolerant bacteria

Arsenic (As) contamination of rice grain is a serious problem worldwide. The objective of this study was to mitigate As toxicity and accumulation in hydroponically grown KDML105 rice seedlings using bacteria isolated from heavy metal-contaminated soils. Seven strains (KKU2500-1, −2, −3, −9, −12, −16 and −22) of 24 cadmium (Cd)-tolerant bacteria produced high levels of inorganic sulfide and thiol-rich compounds in As-supplemented media. The strains were allowed to colonize rice seedlings growing in arsenite [As(III)]- or arsenate [As(V)]-supplemented Hoagland's nutrient solutions. Colonization by strains KKU2500-3 and −12 led to increases in plant growth parameters and similarly reduced As translocation into shoots [translocation factor (TF) = 0.05] in the As(V)-supplemented solution. Strains KKU2500-1 and − 12 also greatly reduced As translocation into shoots (TF = 0.16–0.20) in As(III)-supplemented solution. KKU2500-3 and − 12 co-colonized onto seedlings with the As(III)-oxidizing isolates 4.25, 4.27, 4.40 and 4.44, and the strain combinations KKU2500-12/4.25, KKU2500-3/4.25, KKU2500-3/4.27 and KKU2500-3/4.44 resulted in higher growth parameters for plants grown in As [As(III)+As(V)]-supplemented solution than other combinations. Moreover, the combinations KKU2500-3/4.25 and KKU2500-3/4.44 greatly reduced As translocation (TF = 0.15 and 0.12, respectively), and this decreased As accumulation in shoots was significantly correlated with increased sulfide stimulation in roots and nutrient solution. These results indicate that these co-inoculated bacteria can mitigate As toxicity, translocation and accumulation in KDML105 seedlings and thus demonstrate synergistic activity in rice plants, and this effect can be further developed in field trials.

Response of foliar-applied nutrient solution with and without soil-applied fertilizers on growth and yield of mung bean

ABSTRACTHoagland's nutrient solution of 0, 25, 50, or 75% strength with or without soil-applied nitrogen, phosphorus, and potassium (NPK) fertilizers were sprayed at 7, 14, and 21 days after emergence on two cultivars (AZRI-2006 and NIAB-2011) of mung bean (Vigna radiata (L.) Wilczek). Hoagland's nutrient solution of 75% strength with soil-applied NPK fertilizers markedly increased the growth and yield of mung bean cultivars if applied at 21 days after crop emergence. However, 75% strength Hoagland's nutrient solution without soil-applied NPK fertilizers was comparable to 0, 25, and 50% strengths without NPK fertilizers. Foliar application of 75% strength of Hoagland's nutrient solution with soil-applied NPK fertilizers might enhance the yield of mung bean in low fertile areas. Performance of NIAB-2011 was superior to the other cultivar. It is concluded that Hoagland's nutrient solution of 75% strength can be sprayed at 21 days after emergence to get better yield of mung bean.

Differential Calcium responsiveness in terms of Plant's Growth and accumulation of Nutrient-Anti nutrient in two Finger Millet Genotypes differing in grain Calcium content using a designed Circulatory Hydroponics system

Finger millet (Eleusine coracana) commonly known as ragi is model crop of choice for variety of reasons. These include its high nutraceutical value, excellent storage qualities and most important low input crop. In this study, circulatory hydroponic system was designed and optimized to assess the nutrient responsiveness under the influence of exogenous calcium (Ca) application in finger millet. Impact of different concentrations of exogenous Ca in the form of calcium nitrate on plant's growth and nutrient-antinutrient changes were determined in grains of two contrasting genotypes GP-1 (low Ca) and GP-45 (high Ca) of finger millet. The plants were supplied regularly with different levels of Ca in Hoagland's nutrient medium. Up to 10 mM of exogenous supplied Ca concentration, the threshold potential in terms of Ca accumulation as well as different plant's growth parameters of GP-45 (high Ca) genotype was higher than GP-1 (low Ca); while at 20 mM of Ca concentration, the decline in Ca accumulation and plant's growth was observed in both the genotypes. The highest Ca accumulation was recorded in GP-45 genotype at 10 mM of Ca concentration. Interestingly, with increasing concentration of exogenous Ca, a higher oxalic acid content in grains was observed in GP-1 while higher content of tartaric acid were observed in GP-45 genotype having high grain Ca. These results revealed that Ca interacts with oxalic acid and other organic acids like tartaric acid which is genotype dependent. Hence, the interaction of Ca with antinutrient(s) might be under control of both genetic and epigenetic factor(s).

Melatonin and resveratrol reverse the toxic effect of high boron (B) and modulate biochemical parameters in pepper plants (Capsicum annuum L.)

The objectives of this research were to test a possible involvement of melatonin (MEL) and resveratrol (RES) in restoring growth and to control boron (B) toxicity in peppers. The plants were subjected to four different nutrient solution treatments as following: 1) half-strength Hoagland's nutrient solution (Control), 2) half-strength Hoagland's nutrient solution+100 μM B (100 μMB), 3) half-strength Hoagland's nutrient solution+100 μM boron+100 μMresveratrol (100 μMRES), and 4) half-strength Hoagland's nutrient solution+100 μM B+1 μMmelatonin (1 μM MEL). Pepper plants subjected to B excess (100 μM) for 68 days (d) exhibited visible B toxicity symptoms, reduced rate of photosynthesis (Pn) and reduced dry weight (DW), while their leaf and fruit had the greatest increase of B concentration. The reduction of photosynthesis was restored, the reduction of DW was prevented, while the B leaf and fruit accumulation was moderated with the application of both 100 μMresveratrol (RES) and 1 μMmelatonin (MEL). Moreover, plants exposed to MEL and/or RES displayed no visible B toxicity symptoms. The present study revealed a novel role of MEL and/or RES in the adaptation of pepper plants to B excess based on plant growth, physiological and biochemical criteria.

Removal of boron from wastewater: Evaluation of seven poplar clones for B accumulation and tolerance

Boron (B) contamination of wastewater is a serious environmental and health problem, which has proved difficult to remediate. One potential approach is phytoremediation, i.e., the use of plants to extract B into the shoot systems, which can then be harvested and removed. The purpose of this study was to investigate the ability of seven hybrid poplar clones to accumulate and tolerate B at different levels of B and salinity. The clones were grown in quarter strength Hoagland's nutrient solution and exposed to four B treatments: 0.25, 25, 75 and 125 mg B L−1 in factorial combination with three salinity treatments: 0, 0.5 and 5 g L−1. Measurements were made of biomass (dry weight) and B concentrations (analyzed by inductively coupled plasma-optical emission spectroscopy) of plant tissues. The results showed that, with increasing level of B supply, the B concentrations in the shoot tissue of the poplar clones increased, while shoot biomass decreased. Comparison of the seven different poplar clones revealed that the clone designated 195–529 exhibited the greatest ability for B accumulation and tolerance. Generally, the 0.5 g L−1 level of salinity was beneficial for poplar growth and B removal, while the high salinity level of 5 g L−1 significantly inhibited poplar growth and B translocation from roots to shoots. Based on the results obtained with this hydroponic system, the clone 195–529 (P. trichocarpa × P. deltoides) is likely to be the most useful for the removal of B from B contaminated wastewater.

Accumulation capacity of ions in cabbage (Brassica oleracea L.) supplied with sea water

Cabbage seedlings were grown hydroponically to study the effects of different concentrations of seawater on the seedling growth, ion content under one-fourth strength Hoagland's nutrient solution in the greenhouse. The biomass of various organs of cabbage seedlings as well as the whole plants was significantly higher in the treatments with 1 g and 2 g sea salt/L than the no-salt control, but the treatments with 4, 5 or 6 g sea salt/L caused a decrease in growth. Root/shoot ratio remained at the level of control regardless of the sea salt treatment. Na+ and Cl- concentration in different parts of cabbage seedlings increased significantly, whereas K+ and Ca2+ concentration generally increased at low concentrations of sea salt and then decreased with increasing seawater concentration. Sodium and K+ concentrations were significantly higher in the stems than roots and leaves regardless of the sea salt treatment. The sea salt treatment increased Mg2+ concentration in stems and leaves of cabbage seedlings. An increase in Na+ and Cl- concentration in roots, stems and leaves of cabbage seedlings was the main contributor to declining ratios of K+/Na+, Ca2+/Na+ and Mg2+/Na+. The obtained data suggest that cabbage seedlings have strong ability to sustain seawater stress by the regulation of transport and distribution of ions.

Morpho-physiological response of Populus alba to erythromycin: A timeline of the health status of the plant

Populus alba Villafranca clone was chosen for a proof of concept study to determine the potential uptake and accumulation of antibiotics by trees. Plants were grown hydroponically and irrigated with a recirculating Hoagland's nutrient solution (control) and Hoagland's nutrient solution fortified with erythromycin at 0.01, 0.1 and 1mgL−1. After 3 and 28days of treatment, poplar plants were separated into roots, stem, and leaves. Plants showed good health all over the period of treatment, and no differences in poplar growth for all the concentrations of erythromycin tested were observed. Quantification of erythromycin was performed using liquid chromatography electrospray ionization tandem mass spectrometry (LC-MS/MS) in positive ion mode using multiple reaction ion monitoring. Erythromycin was detected in all organs analyzed. Roots showed an erythromycin concentration tenfold higher than leaves. The photochemical efficiency of photosystem II did not show a dose-dependant trend. From the quenching analysis of chlorophyll fluorescence, low nonphotochemical quenching (NPQ) and high photochemical quenching (qP) for the first week of erythromycin exposure was observed, depending on leaves position along the stem. Results suggest a short term adaptation of the photosynthetic apparatus of Populus alba in response to environmental realistic erythromycin concentrations.

The memory of iron stress in strawberry plants

To provide information towards optimization of strategies to treat Fe deficiency, experiments were conducted to study the responses of Fe-deficient plants to the resupply of Fe. Strawberry (Fragaria × ananassa Duch.) was used as model plant. Bare-root transplants of strawberry (cv. ‘Diamante’) were grown for 42 days in Hoagland's nutrient solutions without Fe (Fe0) and containing 10 μM of Fe as Fe-EDDHA (control, Fe10). For plants under Fe0 the total chlorophyll concentration of young leaves decreased progressively on time, showing the typical symptoms of iron chlorosis. After 35 days the Fe concentration was 6% of that observed for plants growing under Fe10. Half of plants growing under Fe0 were then Fe-resupplied by adding 10 μM of Fe to the Fe0 nutrient solution (FeR). Full Chlorophyll recovery of young leaves took place within 12 days. Root ferric chelate-reductase activity (FCR) and succinic and citric acid concentrations increased in FeR plants. Fe partition revealed that FeR plants expressively accumulated this nutrient in the crown and flowers. This observation can be due to a passive deactivation mechanism of the FCR activity, associated with continuous synthesis of succinic and citric acids at root level, and consequent greater uptake of Fe.