Shoot Zn Research Articles

Effect of copper and zinc on growth characteristics, concentration of some mineral elements and translocation capacities of elements into infusion and decoction of dragon’s head (Lallemantia iberica F. & C.M) under greenhouse conditions

In order to investigate the effect of different levels of Copper (Cu) and Zinc (Zn) on morphological traits of dragon’s head, concentration of Cu, Zn, Fe, Mn, P and K in root and shoot and concentration of Cu and Zn in infusion and decoction, a greenhouse experiment was conducted as factorial based on complete randomized design with three replications. Treatments consisted of three levels of Cu (0, 5 and 25 mg CuSO4/kg soil), three levels of Zn (0, 10 and 50 mg ZnSO4/kg soil) and their interactions. Results showed that Cu and Zn had significant effect on dry weight of root, chlorophyll (SPAD), leaf area, concetration of K and P in roots and shoots and concetration of Fe and Mn in the roots. Also, their intraction had significant effect on dry weight of shoots, plant height and concentration of Cu and Zn in roots, shoots, infusion and decoction and concentarion of Fe and Mn in shoots. The highest dry weight of shoots (3.97 g/pot) and plant height (58.02 cm) was obsevred in combined treatment of Cu5Zn10 and their minimum values (2.1 g/pot and 36.18 cm, respectively) in treatment Cu25Zn50. Application Cu25Zn50 produced maximum value of concentration of Cu, Zn, Fe and Mn in roots (58.85, 338.06, 3766.91 and 135.97 mg/kg, respectively). Maximum values of concentration of Cu in shoots, infusion and decoction (28.38, 1.49 and 4.55 mg/kg, respectively) were obtained in Cu25Zn10. In general, the results of this study showed that a negative interaction occurred between Cu, Zn, Fe and Mn when higher Cu and Zn concentrations were applied. High translocation capacity of Cu and Zn in infusion and decoction was proved in this study. So, due to the lack of required standards for these elements in medicinal plants, if this plant is grown in soils contaminated with Cu and Zn, it should be used with caution in infusion and decoction.

Enhanced Heavy Metal Tolerance and Accumulation by Transgenic Sugar Beets Expressing Streptococcus thermophilus StGCS-GS in the Presence of Cd, Zn and Cu Alone or in Combination.

Phytoremediation is a promising means of ameliorating heavy metal pollution through the use of transgenic plants as artificial hyperaccumulators. A novel Streptococcus thermophilus γ-glutamylcysteine synthetase-glutathione synthetase (StGCS-GS) that synthesizes glutathione (GSH) with limited feedback inhibition was overexpressed in sugar beet (Beta vulgaris L.), yielding three transgenic lines (s2, s4 and s5) with enhanced tolerance to different concentrations of cadmium, zinc and copper, as indicated by their increased biomass, root length and relative growth compared with wild-type plants. Transgenic sugar beets accumulated more Cd, Zn and Cu ions in shoots than wild-type, as well as higher GSH and phytochelatin (PC) levels under different heavy metal stresses. This enhanced heavy metal tolerance and increased accumulation were likely due to the increased expression of StGCS-GS and consequent overproduction of both GSH and PC. Furthermore, when multiple heavy metal ions were present at the same time, transgenic sugar beets overexpressing StGCS-GS resisted two or three of the metal combinations (50 μM Cd-Zn, Cd-Cu, Zn-Cu and Cd-Zn-Cu), with greater absorption in shoots. Additionally, there was no obvious competition between metals. Overall, the results demonstrate the explicit role of StGCS-GS in enhancing Cd, Zn and Cu tolerance and accumulation in transgenic sugar beet, which may represent a highly promising new tool for phytoremediation.

Mineral composition of ‘Selva’ strawberry as affected by time of application of nitric oxide under saline conditions

The objective of present study was to evaluate the impact of time of application of nitric oxide (NO) on mineral composition of strawberry ‘Selva’ plants under saline conditions. Well-rooted daughter plants were planted in 3L plastic pots filled with 1:1 (v/v) ratio of peat moss and perlite and grown under the greenhouse conditions (21 ± 2/17 ± 2°C and RH = 60 ± 5% under natural sunlight). After full establishment of plants they were divided into 10 groups: control, plants sprayed with distilled water and exposed to 40 mM NaCl salinity stress, plants sprayed with 50 or 75 μM NO solutions under non-stress conditions, and plants sprayed with 50 or 75 μM NO solutions at three different application times, one week before, at the beginning, and one week after initiation of 40 mM NaCl salt stress. Results indicated that concentrations of macro-nutrients, Fe and Zn in shoots and roots were decreased due to salinity stress. The NO application, regardless of time of application and level, mitigated the deleterious effect of salinity on minerals uptake. Time aspect of NO application was important as plants received 75 μM NO solution, one week before initiation of salt stress had higher shoot N, K, and Ca concentration, productivity and leaf relative water content as compared with those received NO solution at the same concentration, one week after exposure to salt stress. Higher K/Na ratio of shoot was also observed in plants treated with 75 μM NO solution one week before start of salinity compared with salt-stressed, non-NO-treated plants. It seemed that time of NO application could change the strategy of plant against stress.

Salicylic Acid–Induced Salinity Redressal in Hydroponically Grown Strawberry

The present study was conducted to evaluate shoot and root mineral composition of salt-stressed Selva strawberry under application timing of salicylic acid (SA). Treatments included plants sprayed with 0.5 or 1 mM SA, plants exposed to 40 mM sodium chloride (NaCl), and plants sprayed with 0.5 or 1 mM SA 1 week before, simultaneously, or after initiation of 40 mM salinity. Results indicated that under saline conditions, sodium (Na) and chloride (Cl) contents increased along with decrease in nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), iron (Fe), and zinc (Zn) in shoot and root of plants. In plants treated with SA at 1 mM concentration, 1 week before salinity application, root Mg and shoot Ca were greater in comparison to salt-stressed plants treated with the same SA concentration 1 week after their exposure to salt stress. Thus, earlier SA application appears to be a better strategy for optimized protection against deleterious influence of salinity.

Bioavailability of Zn in ZnO nanoparticle-spiked soil and the implications to maize plants

Little is known about the relationships between Zn bioavailability in ZnO nanoparticle (NP)-spiked soil and the implications to crops. The present pot culture experiment studied Zn bioavailability in soil spiked with different doses of ZnO NPs, using the diethylenetriaminepentaacetic acid (DTPA) extraction method, as well as the toxicity and Zn accumulation in maize plants. Results showed that ZnO NPs exerted dose-dependent effects on maize growth and nutrition, photosynthetic pigments, and root activity (dehydrogenase), ranging from stimulatory (100–200 mg/kg) through to neutral (400 mg/kg) and toxic effect (800–3200 mg/kg). Both Zn concentration in shoots and roots correlated positively (P < 0.01) with ZnO NPs dose and soil DTPA-extractable Zn concentration. The BCF of Zn in shoots and roots ranged from 1.02 to 3.83 when ZnO NPs were added. In most cases, the toxic effects on plants elicited by ZnO NPs were overall similar to those caused by bulk ZnO and soluble Zn (ZnSO4) at the same doses, irrespective of some significant differences suggesting a higher toxicity of ZnO NPs. Oxidative stress in plants via superoxide free radical production was induced by ZnO NPs at 800 mg/kg and above, and was more severe than the same doses of bulk ZnO and ZnSO4. Although significantly lower compared to bulk ZnO and ZnSO4, at least 16 % of the Zn from ZnO NPs was converted into DTPA-extractable (bioavailable) forms. The dissolved Zn2+ from ZnO NPs may make a dominant contribution to their phytotoxicity. Although low amounts of ZnO NPs exhibited some beneficial effects, the accumulation of Zn from ZnO NPs into maize tissues could pose potential health risks for both plants and human.

Mutual Effects of Boron and Zinc on Peanut (Arachis hypogaea L.) Growth and Mineral Nutrition

The mutual effects of boron (B) and zinc (Zn) on growth, total chlorophyll (Chl), membrane permeability (MP), and nutrient content were investigated in peanut (Arachis hypogaea L.). The soil was treated with five levels of B (0, 4, 8, 16, 32 mg kg−1) and three levels of Zn (0, 10, 20 mg kg−1). Plant growth was progressively depressed with increasing of B. However, Zn addition had an inhibitory effect on B toxicity and decreased growth reduction caused by excess B. In Zn-untreated plants, B and Zn contents were enhanced by increasing of B; moreover, both Zn and B addition enhanced Zn content. The Chl content decreased and MP increased, resulting from B toxicity; however, Zn addition partially ameliorated the adverse effects of B toxicity on Chl and MP. Increasing B enhanced phosphorus (P), potassium (K), calcium (Ca), iron (Fe), Zn, copper (Cu), and sodium (Na) contents in peanut shoots.

Enhanced Phytoextraction of Heavy Metals from Contaminated Soil by Plant Co-cropping Associated with PGPR

In this study, 1-year greenhouse pot experiments were conducted to investigate the effect of Phyllobacterium myrsinacearum strain RC6b on the growth and phytoextraction efficiency of heavy metals by a Zn/Cd hyperaccumulator (Sedum alfredii) and alfalfa (Medicago sativa L.) in a co-cropping system. The treated soil sample was collected from a land reclamation site of Pb/Zn mine tailings in Hanzhong City, Shaanxi Province, China. Results showed that, with the inoculation of RC6b, shoot biomass yields of plants were significantly increased by 15.9–20.2 % and 17.2–19.9 % for alfalfa and S. alfredii, respectively, compared to the non-inoculated plants. Biomass yield of alfalfa was higher than that of S. alfredii. RC6b inoculation increased metal concentrations by 18.6–31.2 % (Pb), 23.8–37.5 % (Cd), and 26.4–38.3 % (Zn) in S. alfredii shoots, and by 13.8–24.7 % (Pb), 15.8–26.6 % (Cd), and 24.8–35.6 % (Zn) in alfalfa shoots, respectively. After six consecutive harvests of shoots, RC6b inoculation increased the phytoextraction efficiencies of Pb, Cd, and Zn by shoots of the co-planting system by 16.9, 46.3, and 60.9 %, respectively. Nevertheless, phytoextraction of Cu was not improved by RC6b inoculation. In the co-planting/inoculation system, the percentage removals of metals from soil by the plant shoots were 6.09, 30.97, 11.10, and 1.68 % for Pb, Cd, Zn, and Cu, respectively, after six harvests of shoots. Inoculation with RC6b significantly increased the soil microbial activity and the carbon utilization ability of the soil microbial community.

Impact of long-term cadmium exposure on mineral content of Solanum lycopersicum plants: Consequences on fruit production

In young tomato plants, modifications in mineral composition by short-term cadmium (Cd) treatments have been extensively examined. However, long-term Cd treatments have been fewly investigated, and little information about Cd-stress in fruiting plants is available. In the present work, we examined the changes in mineral nutrients of roots, stems, leaves, flowers, seeds and fruit pericarp of tomato plants submitted to a long-term Cd stress. After a 90-day culture period in hydroponic contaminated environment (0, 20 and 100μM CdCl2), fruit production was affected by increasing external Cd levels, with the absence of fruit set at 100μM Cd. Meanwhile, Cd altered the plant mineral contents with an element- and organ-dependent response. At 20μM, Cd triggered a significant increase in Ca content in roots, mature leaves, flowers and developing fruits. However, at 100μM Cd, Ca content was reduced in shoots, and enhanced in roots. Cd stress reduced Zn and Cu contents in shoots and increased them in roots. High Cd level led to a significant decrease in K and Mg content in all plant organs. Furthermore, Fe concentration was reduced in roots, stems and leaves but increased in flowers, seeds and red ripe fruits. Our results suggest that tomato plants acclimatize during long-term exposure to 20μM Cd, while 100μM Cd results in drastic nutritional perturbations leading to fruit set abortion.

The combination of compost addition and arbuscular mycorrhizal inoculation produced positive and synergistic effects on the phytomanagement of a semiarid mine tailing

A field experiment was carried out to assess the effectiveness of combining mycorrhizal inoculation with a native AM fungus (Glomus sp.) and the addition of an urban organic waste compost (OWC) applied at two rates (0.5 and 2.0% (w:w)), with regard to promoting the establishment of Anthyllis cytisoides L. seedlings in a heavy metal polluted mine tailing, as well as stimulating soil microbial functions. The results showed that the combined use of the highest dose of OWC and AM inoculation significantly increased shoot biomass – by 64% – compared to the control value. However, the separate use of each treatment had no effect on the shoot biomass of this shrub species. At the 2% rate, OWC enhanced root colonisation by the introduced fungus as well as soil nutrient content and soil dehydrogenase and ß-glucosidase activities. The combined treatment increased the uptake of Zn and Mn in shoots, although only Zn reached excessive or potentially toxic levels. This study demonstrates that the combination of organic amendment and an AM fungus is a suitable tool for the phytomanagement of degraded mine tailings, although its effectiveness is dependent on the dose of the amendment.

How important is the mycorrhizal pathway for plant Zn uptake?

Formation of arbuscular mycorrhizas can enhance plant uptake of immobile nutrients such as zinc (Zn) and phosphorus (P). Enhancement of Zn uptake by arbuscular mycorrhizal (AM) fungi on Zn-deficient soils has been studied previously, however, the quantity of Zn that is contributed by the AM pathway of uptake to the plant has not previously been reported for soil of any Zn status. We grew a mycorrhiza-defective mutant tomato (Solanum lycopersicum L.) genotype (rmc) and its mycorrhizal wild-type progenitor (76R) in pots containing a hyphal compartment (HC) accessible only by the external hyphae of AM fungi, and containing the radioisotope 65Zn. This was repeated at three soil Zn concentrations, ranging from low to high. We estimated the amount of Zn delivered via both the AM and direct (root) pathways. Up to 24 % of Zn in the shoots of the AM plants was delivered via the AM pathway at the lowest soil Zn treatment. This decreased significantly, to 8 %, as soil Zn concentration increased. No 65Zn was detected in the tissues of the non-mycorrhizal genotype. The relative contribution to shoot Zn by the AM pathway of uptake was highest when soil Zn was low, and decreased with increasing soil Zn concentration.

Corn Silage (Zea mays L.) Response to Zinc Foliar Spray Concentration When Grown on Sandy Soil

The objective of this study is to identify an adequate zinc (Zn) foliar spray concentration which corrects Zn deficiency without disrupting other plant mineral contents, enhances plant growth, and thereby corn silage yield when grown on sandy soil. A field experiment was conducted using five Zn foliar spray concentrations (w/v): 0.03%, 0.07%, 0.10%, 0.14% and 0.18%. Zn sulfate (ZnSO 4 . 7H 2 O) was used as a source of Zn. Zn foliar application was realized at two growth stages (6-7 and 9-10 leaf stages). A treatment without Zn foliar spray was maintained as control. The results showed a quadratic response of corn silage towards Zn foliar spray concentrations, in which 0.09% was the optimum value for overcoming Zn deficiency. Such level increased shoot Zn concentration at harvest from 15 mg kg -1 to 21.8 mg kg -1 , didn’t decrease plant mineral content below critical levels, enhanced plant growth and raised silage yield by 49.4% compared to control. On the other hand, Zn foliar spray concentration up to 0.10% induced visible leaf damage, growth inhibition and a decrease of 26% in silage yield compared to Zn foliar applications at 0.09%.

Effects of EDDS and plant-growth-promoting bacteria on plant uptake of trace metals and PCBs from e-waste–contaminated soil

The present study investigated the effects of the biodegradable chelant S,S-ethylenediaminedisuccinic acid (EDDS) and the plant-growth-promoting bacterium DGS6 on pollutant uptake by corn from e-waste–contaminated soils. The highest concentration and total uptake of Cu and Zn in corn shoots were observed in the presence of EDDS and DGS6+EDDS, respectively. The ΣPCB concentrations in shoots ranged from 0.53 to 0.72ngg−1, and the highest PCB concentration was observed in the presence of EDDS. This could be ascribed to the enhanced dissolved organic carbon, increased dissolution and efficient translocation of PCBs from roots to shoots, as well as potential root damage due to increased soluble metal levels in soil solution. In contrast, the highest total uptake of PCBs in shoots was observed in the presence of DGS6, likely due to enhanced shoot biomass and high levels of air deposition.

How do glycine and histidine in nutrient solution affect zinc uptake and root-to-shoot translocation by wheat and triticale?

Understanding how complexes with amino acids in soil solution affect plant zinc (Zn) uptake may aid in optimising plant Zn nutrition. We investigated the influence of histidine and glycine in nutrient solution on apoplastic and symplastic uptake and root-to-shoot translocation of Zn in a triticale (×Triticosecale cv. Elinor) and a bread wheat cultivar (Triticum aestivum cv. Back Cross Rushan). Six-week-old seedlings of the two cultivars were transferred to a nutrient solution containing 20 µm Zn, to which 50 µm histidine, 50 µm glycine or no amino acids were added. Control plants were transplanted to nutrient solution with no Zn or amino acids. Higher concentrations of Zn were found in root and shoots of wheat and triticale plants supplied with Zn than in the control plants without Zn supply. Among the treatments with Zn supply, histidine enhanced, whereas glycine reduced, symplastic root Zn concentration in bread wheat. Both amino acids decreased the symplastic root Zn concentration but had no effect on apoplastic Zn in triticale. Both amino acid treatments also reduced Zn concentrations in the xylem sap of the two plant species compared with the treatment with Zn addition only. In bread wheat, the effect was stronger for glycine than for histidine; in triticale, it was the same for both amino acids. The concentration of Zn in xylem sap was always greater in wheat than in triticale. Addition of histidine to the nutrient solution increased the total amount of shoot Zn in triticale but not in bread wheat, compared with the treatment with Zn addition only, whereas glycine had no significant effect on total shoot Zn in either of the plant species. The results show that histidine, but not glycine, can enhance Zn uptake and translocation into the aboveground parts of triticale. We suggest that this ability of histidine was due to the formation of strong complexes with Zn.

Effects of Arbuscular Mycorrhizal Fungi on Metals Uptake, Physiological and Biochemical Response of &amp;lt;i&amp;gt;Medicago Sativa&amp;lt;/i&amp;gt; L. with Increasing Zn and Cd Concentrations in Soil

The effect of mycorrhizal symbiosis on metal accumulation and plant tolerance are not commonly studied in medicinal plants under metal stress. The objective of this study was to assess the impact of mycorrhiza on alfalfa plants with the increase of Zn and Cd toxicity. The experiment was conducted under controlled laboratory conditions. Zinc (Zn) and cadmium (Cd) uptake, some biochemical and physiological parameters were studied in eight-week-old alfalfa plants in response to inoculation or not with arbuscular mycorrhizal fungi (AMF) and with the increase of Zn (0, 100, 300, 900 mg·kg-1) and Cd concentrations (0, 100, 300, 600 mg·kg-1) in soil. The results showed that mycorrhizal (M) plants exhibited tolerance to Zn and Cd up to 300 mg·kg-1 in comparison to non-mycorrhizal (NM) plants which exhibited a significant growth reduction at the same soil Zn and Cd level. M inoculation reduced the Zn and Cd accumulation in shoot and showed higher Zn and Cd contents in roots which showed a different Zn and Cd distribution in AMF associated or non-associated plants. Mycorrhizal plants increased phosphorus (P) contents at all Zn and Cd concentrations except the highest (600 and 900 mg·kg-1) leading significant alterations in biochemical contents such as proline, antioxidant enzymes in leaves and also in nutrients (N, P, K, Cu, Ni, Fe, Mn). Zn and cadmium toxicity cause to increase the proline content in shoot of NM plants, however, proline contents are lower in M plants. Results confirmed that AMF protected alfalfa plants against Zn and Cd toxicity. Mycorrhizal colonization was able to form an efficient symbiosis with alfalfa plants in moderately contaminated Zn and Cd soils (300 mg·kg-1) and play an important role in food quality and safety.

Metal accumulation by Arabidopsis halleri subsp. gemmifera at a limestone mining site

Arabidopsis halleri subsp. gemmifera, a close wild relative of A. thaliana in eastern Asia, is an important model species of Brassicaceae used to study cadmium (Cd) and zinc (Zn) tolerance and hyperaccumulation in plants. To investigate the effects of soil factors on metal accumulation in this plant, we collected plants and rhizosphere soil samples from a limestone mining site on Mount Ibuki, and compared them with those collected from non-calcareous soil in Japan. Irrespective of the sampling site, all the plants efficiently accumulated Cd in shoot tissues. The plants growing on non-calcareous soil also accumulated Zn in shoot tissues, but shoot Zn concentration in plants growing on calcareous soils was below the level required for hyperaccumulators. The pH of calcareous soil samples was between 7.68 and 8.21. Total Zn contents were similar in calcareous and non-calcareous soils, but the amounts of Zn extractable by 0.1 M HCl were lower in calcareous than in non-calcareous soil. These results indicate that the properties of calcareous soil affect metal accumulation in plants.

Effect of Soil Water Stress and Nickel Application on Micronutrient Status of Canola Grown on Two Calcareous Soils

Recently, application of sewage sludge/effluents to soils as an alternative source of organic matter in arid/semiarid regions and as a practical approach to remove its sanitary adverse effects in urban and industrial regions is gaining increased attention. This may lead to high levels of nickel (Ni) in soil and plants. On the other hand, in these regions water shortage is a major constraint of plant productivity. To determine the combined effects of Ni and water stress on the nutritional status of canola, we studied the effect of five Ni levels (0, 0.05, 0.1, 0.5 and 1 mg Ni kg–1 soil as Ni(NO3)2) and two levels of water status (field capacity, FC, and 0.6 FC) on the contents of iron (Fe), manganese (Mn), zinc (Zn) and copper (Cu) in canola (Brassica napus L.) on two loamy and sandy clay calcareous soils in greenhouse conditions. Shoot/root dry matter yield (SDMY/ RDMY), their Fe, Zn and Mn content decreased under 0.6 FC conditions; whereas, their concentrations increased. Shoot /root Cu concentration /content decreased in water-stressed plants. Application of > 0.05 mg Ni kg–1 to loamy soil increased SDMY, however Ni did not affect SDMY positively or even decreased it in sandy clay soil. Application of 0.01~0.5 mg Ni increased RDMY in loamy soil under FC conditions; whereas, higher levels of Ni decreased it. Nickel decreased RDMY in sandy clay soil, whereas did not affect micronutrient concentrations in the root. The concentration and content of Mn in the shoot followed different patterns in response to applied Ni. Although the highest level of applied Ni increased shoot Zn content. Application of 0.05 and 1 mg Ni decreased the Cu concentration in the shoot on loamy and sandy clay soils, respectively. However, Ni did not affect the Cu content of shoot. Nickel had different impacts on the content of each micronutrient and was not effective in mitigating the adverse effects of drought stress.

Revegetation of abandoned sulphur Flotation Waste in Keçiborlu, Isparta/Turkey: heavy metals concentrations of growing media and Agropyron elongatum grass.

The main objectives of the study are to evaluate the effectiveness of using amendment materials (calcareous soil and farmyard manure) and to grow Agropyron elongatum (tall wheat grass) for the revegetation of sulphur flotation waste in tailing ponds. Calcareous soil (CS) at 10, 20, 30, 40% and farmyard manure (FYM) at 4, 8% were applied to the flotation waste (FW). pH, electrical conductivity (EC), DTPA-extractable Fe, Zn, Mn, Cu, Ni, Cr, Pd, Cd, Co concentrations of growing media, also, total Fe, Zn, Mn, Cu, Ni, Cr, Pd, Cd, Co concentrations of plants were analysed together with the dry weight yield of the plant which were determined at end of the experiment. The results have shown that pH, shoot Zn, Mn, Cu and Pb concentrations increased by CS-alone but this increment tended to decrease by FYM. The EC, DTPA-extractable Fe, Zn, Mn, Ni, Cr, Co and shoot Fe, Ni, Cr, Co concentrations were decreased by CS-alone, but this decline tended to increase by FYM. There was no change in DTPA-extractable Pb and Cd concentrations between CS and CS with FYM. The dry weight of the plant shoots increased CS with FYM more than CS-alone. The plant grew well and had high cover in CS with FYM treatments compared to CS-alone. However this work indicates that A. elongatum can be used to revegetate sulphur flotation waste, further studies with different plant species are needed in order to obtain better plant cover in revegetation efforts.

Effects of lead and nitric oxide on photosynthesis, antioxidative ability, and mineral element content of perennial ryegrass

Hydroponics experiments were conducted to study the effects of sodium nitroprusside (SNP, a donor of NO) on lead toxicity in ryegrass (Lolium perenne L.) seedlings. When the ryegrass seedlings were grown in a nutrient solution containing 500 μM Pb2+ for two weeks, the plant biomass as well as net photosynthetic rate, transpiration rate, chlorophyll and carotenoid content of leaves decreased. The Pb stress also induced the production of superoxide anion (O2 ·−) and hydrogen peroxide (H2O2), leading to malondialdehyde (MDA) accumulation. Furthermore, the activities of superoxide dismutase (SOD), peroxidase (POD), and ascorbate peroxidase (APX) decreased in the Pb-treated seedlings, but the catalase (CAT) activity increased. Additionally, the content of Cu in shoots and the content of K, Mg, Fe, and Zn in both shoots and roots decreased, but the content of Ca in shoots and roots increased under the Pb stress. Moreover, Pb accumulated mostly in roots, whereas a small quantity was translocated to shoots. However, the addition of 50, 100, and 200 μM SNP into the solution containing Pb increased the chlorophyll content and net photosynthetic rate, reduced Pb-induced oxidative damages, improved antioxidant enzyme activities, and inhibited translocation of Pb from roots to shoots. In particular, 100 μM SNP had the best effect on promoting growth of the ryegrass seedlings under the Pb toxicity. However, the application of 400 μM SNP had no obvious alleviating effect on Pb toxicity in the ryegrass seedlings.

Erratum to: Predicting zinc bioavailability to wheat improves by integrating pH dependent nonlinear root surface adsorption

Aim Our aim was to improve the prediction of Zn bioavailability to wheat grown on low-Zn soils. The classical approach that directly relates Zn in a certain soil extract to Zn uptake has been shown to be inadequate in many cases. We tested a stepwise approach where the steps of the uptake process are characterized with, respectively, Zn solid-solution distribution, adsorption of Zn to root surface, Zn uptake into root and Zn translocation to shoot. Methods Two pot experiments were done with wheat grown on nine low-Zn soils varying widely in pH, clay and organic matter content. Soluble Zn concentrations in two soil extracts (DTPA and CaCl2) were measured. Free Zn ion concentrations in CaCl2 soil extracts were determined with the Donnan Membrane Technique. These Zn concentrations were then related to plant Zn uptake following both the direct and the stepwise approach. Results In the direct approach, Zn in the DTPA extract was a better predictor for shoot Zn uptake than Zn in the CaCl2 extract. In the stepwise approach, the relationship between Zn in CaCl2 extracts and the root surface adsorbed Zn was pH-dependent and nonlinear. Root surface adsorbed Zn was linearly related to root Zn uptake, and the latter was linearly related to the shoot Zn uptake. The stepwise approach improved the Zn uptake prediction compared to the direct approach and was also validated for different wheat cultivars. Conclusions The adsorption of Zn on the root surface is pH dependent and nonlinear with respect to the soil Zn concentration, and a useful proxy for bioavailable Zn over a wide range of soils.

Towards Practical Cadmium Phytoextraction with Noccaea Caerulescens

A series of field trials were conducted to investigate the potential of Noccaea caerulescens F.K. Mey [syn. Thlaspi caerulescens J &C Presl. (see Koch and Al-Shehbaz 2004)] populations (genotypes) derived from southern France to phytoextract localized Cd/Zn contamination in Thailand. Soil treatments included pH variation and fertilization level and application of fungicide. N. caerulescens populations were transplanted to the field plots three months after germination and harvested in May, prior to the onset of seasonal rains. During this period growth was rapid with shoot biomass ranging from 0.93–2.2 g plant–1 (280–650 kg ha–1) DW. Shoot Cd and Zn concentrations for the four populations evaluated ranged from 460–600 and 2600–2900 mg kg–1 DW respectively. Cadmium and Zn Translocation Factors (shoot/root) for the populations tested ranged from 0.91–1.0 and 1.7–2.1 and Bioaccumulation Factors ranged from 12–15 and 1.2–1.3. We conclude that optimizing the use of fungicidal sprays, acidic soil pH, planting density and increasing the effective cropping period will increase rates of Cd and Zn removal enough to facilitate practical Cd phytoextraction from rice paddy soils in Thailand.