Effects of Cadmium on Root Growth, Cell Division and Nucleoli in Root Tip Cells of Garlic

The effects of different concentrations (10⁻⁷ to 10⁻² M) of cadmium chloride on root growth, cell division and nucleoli in root tip cells of Allium sativum L. were investigated. At lower concentrations of Cd²⁺ (10⁻⁷ to 10⁻⁶ M), Cd²⁺ did not influence the root growth, even had a stimulation effects during a short treatment. The results showed that the rate of root growth per day at the treatment groups (10⁻⁴ to 10⁻² M Cd²⁺) decreased with increasing duration of the treatment and increasing Cd²⁺ concentration. Cd²⁺ induced c-mitosis, anaphase bridges, chromosome stickiness and on nucleoli, causing some particles of similar silver-stained material scattered in the nuclei and making the silver staining reaction at the periphery of the nucleolus weaker. This revised version was published online in July 2006 with corrections to the Cover Date.     

Attenuation of cadmium toxicity in mycorrhizal celery (<Emphasis Type="Italic">Apium graveolens</Emphasis> L.)

A pot-culture experiment was carried out to investigate the effect of arbuscular mycorrhizal (AM) fungus (Glomus macrocarpum Tul. and Tul.) on plant growth and Cd²⁺uptake by Apium graveolens L. in soil with different levels of Cd²⁺. Mycorrhizal (M) and non-mycorrhizal (NM) plants were grown in soil with 0, 5, 10, 40 and 80 Cd²⁺ mg kg⁻¹soil. The infectivity of the fungus was not affected by the presence of Cd²⁺ in the soil. M plants showed better growth and less Cd²⁺ toxicity symptoms. Cd²⁺ root : shoot ratio was higher in M plants than in NM plants. These differences were more evident at highest Cd²⁺ level (80 mg kg⁻¹ soil). Chlorophyll a and chlorophyll b concentrations were significantly higher in AM-inoculated celery leaves. The dilution effect due to increased biomass, immobilization of Cd²⁺ in root and enhanced P-uptake in M plants may be related to attenuation of Cd²⁺toxicity in celery.     

Cadmium-induced stress on the seed germination and seedling growth of <Emphasis Type="Italic">Brassica napus</Emphasis> L., and its alleviation through exogenous plant growth regulators

Because of its prolific growth, oilseed rape (Brassica napus L.) can be grown advantageously for phytoremediation of the lands contaminated by industrial wastes. Therefore, toxic effect of cadmium on the germination of oilseed rape, the capability of plants for cadmium phytoextraction, and the effect of exogenous application of plant growth regulators to mitigate phytotoxicity of cadmium were investigated. For the lab study of seedlings at early stage, seeds were grown on filter papers soaked in different solutions of Cd²⁺ (0, 10, 50, 100, 200 and 400 μM). In greenhouse study, seedlings were grown in soil for 8 weeks, transferred to hydroponic pots for another 6 weeks growth, and then treated with plant growth regulators and cadmium. Four plant growth regulators viz. jasmonic acid (12.5 μM), abscisic acid (10 μM), gibberellin (50 μM) and salicylic acid (50 μM); and three levels of Cd²⁺ (0, 50 and 100 μM) were applied. Data indicated that lower concentration of Cd²⁺ (10 μM) promoted the root growth, whereas the severe stresses (200 or 400 μM) had negative effect on the establishment of germinating seedlings. Plants treated with any of the tested plant growth regulators alleviated cadmium toxicity symptoms, which were reflected by more fresh weight, less malondialdehyde concentration in leaves and lower antioxidant enzyme activities. The application of abscisic acid to the plants cultivated in the medium containing 100 μM Cd²⁺ resulted in significantly lower plant internal cadmium accumulation. Huabing Meng and Shujin Hua contributed equally to this paper.     

Comparative study of effects of cadmium cations in free and chelated forms on activity of glutathione S-transferase, growth, and endocytosis in culture of the infusoriumTetrahymena pyriformis

Effects of cadmium cations in free (Cd²⁺) and chelated with EDTA (Cd²⁺-EDTA) forms were studied on growth, endocytosis, and activity of glutathione S-transferase (GT) in the free-living infusoriaTetrahymena pyriformis. It is shown that the cytotoxicity of Cd²⁺ in the free form at a concentration of 10 μM is much higher than of the Cd²⁺-EDTA complex at the equimolar concentration. Even at a low concentration (2 μM), Cd²⁺ produces an inhibition of the growth rate and endocytosis in theT. pyriformis culture, while the Cd²⁺-EDTA complex suppresses these functions insignificantly. Cd²⁺ in the free form at concentrations of 10 and 100 μM reduced activity of glutathione S-transferase by 39 and 61%. The chelated Cd²⁺-EDTA complex at these concentrations inhibited the GT activity by 5 and 55%, respectively.     

The role of sulphur in detoxication of cadmium in young sugar beet plants

In young sugar beet plants cadmium suppressed the activity of nitrate reductase, glutamine synthetase and glutamate dehydrogenase, whereas sulphur exhibited a protective role towards activity of these enzymes, except of glutamine synthetase. Protein synthesis was suppressed in the absence of S in nutrient medium; the lowest level was at 10^-3 M Cd²⁺. Chloroplast pigment contents were increased by S while Cd²⁺, even in the lowest concentration, (10⁻⁵ M) showed a repressive effect. The highest concentrations of Cd²⁺ (10−3 M) caused a decrease in dry mass, whereas S induced its increase. Nitrate content was increased in the presence of Cd²⁺ and decreased by increased concentration of S. Acknowledgement: The authors acknowledge financial support of the Ministry for Science and Technology of Serbia. The paper was presented at 9th Congress of the Federation of European Societies of Plant Physiology, Brno, Czech Republic, 3–8 July 1994.     

Melafen effect on ATP-dependent accumulation of calcium in plasma membrane vesicles from cells of potato tubers

Synthetic growth regulator melafen (10⁻⁵–10⁻¹⁰ M) was tested for aneffect on the Ca²⁺ accumulation in plasma membrane vesicles (PMVs) isolated from potato Solanum tuberosum L. tubers at forced rest and sprouting. Melafen proved to regulate the Ca²⁺ accumulation in PMVs by changing the activity of Ca²⁺, Mg²⁺-ATPase of the plasma membrane, while no effect was observed with respect to Ca²⁺ outflow from vesicles. The melafen effect on Ca²⁺, Mg²⁺-ATPase activity depended on the physiological condition of tubers and the melafen concentration.     

Cadmium and mineral nutrient accumulation in potato plantlets grown under cadmium stress in two different experimental culture conditions

In order to evaluate the effect of cadmium (Cd²⁺) toxicity on mineral nutrient accumulation in potato (Solanum tuberosum L.), two cultivars named Asterix and Macaca were cultivated both in vitro and in hydroponic experiments under increasing levels of Cd²⁺ (0, 100, 200, 300, 400 and 500 μM in vitro and 0, 50, 100, 150 and 200 μM in hydroponic culture). At 22 and 7 days of exposure to Cd²⁺, for the in vitro and hydroponic experiment, respectively, the plantlets were separated into roots and shoot, which were analyzed for biomass as well as Cd²⁺, and macro (Ca²⁺, K⁺ and Mg²⁺) and micronutrient (Cu²⁺, Fe²⁺, Mn²⁺ and Zn²⁺) contents. In the hydroponic experiment, there was no reduction in shoot and root dry weight for any Cd²⁺ level, regardless of the potato cultivar. In contrast, in the in vitro experiment, there was an increase in biomass at low Cd²⁺ levels, while higher Cd²⁺ levels caused a decrease. In general, Cd²⁺ decreased the macronutrient and micronutrient contents in the in vitro cultured plantlets in both roots and shoot of cultivars. In contrast, the macronutrient and micronutrient contents in the hydroponically grown plantlets were generally not affected by Cd²⁺. Our data suggest that the influence of Cd²⁺ on nutrient content in potato was related to the level of Cd²⁺ in the substrate, potato cultivar, plant organ, essential element, growth medium and exposure time.     

The toxicity of cadmium to barley plants as affected by complex formation with humic acid

An ‘alternating solution’ culture method was used to study the effects of chloride ions and humic acid (HA) on the uptake of cadmium by barley plants. The plants were transferred periodically between a nutrient solution and a test solution containing one of four levels of HA (0, 190, 569 or 1710 μg cm⁻³) and one of five levels of Cd (0, 0.5, 1.0, 2.5 or 5.0 μg cm⁻³) in either a 0.006M NaNO₃ or 0.006M NaCl medium. Harvest and analysis of shoots and roots was after nineteen days. The distribution of Cd in the test solutions between Cd²⁺, CdCl⁺ and HA-Cd was determined in a separate experiment by dialysis equilibrium. In the nitrate test solutions Cd uptake was clearly controlled by Cd²⁺ concentration and was therefore reduced by HA complex formation. In the absence of HA, chloride suppressed Cd uptake indicating that Cd²⁺ was the preferred species. However complex formation with Cl⁻ enhanced uptake when HA was present because of an increase in the concentration of inorganic Cd species relative to the nitrate system. The ratio root-Cd/shoot-Cd remained at about 10 across a wide range of shoot-Cd concentrations, from about 3 μg g⁻¹ (sub-toxic) up to 85 μg g⁻¹ (80% yield reduction). The ability of the barley plants to accumulate ‘non-toxic’ Cd in their roots was thus very limited. Humic acid also had no effect on Cd translocation within the plant and the root/shoot weight ratio did not vary with any treatment. At shoot-Cd concentrations in excess of 50 μg g⁻¹, K, Ca, Cu and Zn uptake was reduced, probably the result of root damage rather than a specific ion antagonism. The highest concentration of HA also lowered Fe and Zn uptake and there was a toxic effect with increasing HA concentration at Cd=0. However the lowest HA level, comparable with concentrations found in mineral soil solutions, only reduced yield (in the absence of Cd) by <5% while lowering Cd uptake across the range of Cd concentrations by 66%–25%.     

Lhcb2 gene expression analysis in two ecotypes of Sedum alfredii subjected to Zn/Cd treatments with functional analysis of SaLhcb2 isolated from a Zn/Cd hyperaccumulator

The Lhcb2 gene from hyperaccumulator Sedum alfredii was up-regulated more than three-fold while the non-hyperaccumulator accumulated one or two-fold higher amount of the mRNA than control plants under different concentrations of Cd²⁺ for 24 h. Lhcb2 expression was up-regulated more than five-fold in a non-hyperaccumulator S. alfredii when exposed to 2 μM Cd²⁺ or 50 μM Zn²⁺ for 8 d and the hyperaccumulator had over two-fold more mRNA abundance than the control plants. Over-expression of SaLhcb2 increased the shoot biomass by 14–41% and the root biomass by 21–57% without Cd²⁺ treatment. Four transgenic tobacco lines (L5, L7, L10 and L11) possessed higher shoot biomass than WT plants with Cd²⁺. Four transgenic lines (L7, L8, L10 and L11) accumulated 6–35% higher Cd²⁺ amounts in shoots than the wild type plants.     

The role of GA,IAA and BAP in the regulation of <Emphasis Type="Italic">in vitro</Emphasis> shoot growth and microtuberization in potato

The effect of auxin, GA and BAP on potato shoot growth and tuberization was investigated under in vitro condition. The shoot length of potato explants increased with the increasing of concentrations (0.5 – 10 mg dm⁻³) of IAA treatment especially with the addition of GA₃ (0.5 mg dm⁻³), but was inhibited by BAP (5 mg dm⁻³). The root number and root fresh weight of potato explants increased with the increasing of IAA levels either in the presence of GA₃ (treatment IAA+GA) or not (IAA alone). However, no root was observed in the treatment IAA+BAP, instead there were brown swollen calli formed around the basal cut surface of the explants. The addition of GA₃ remarkably increased the fresh weight and diameter of calli. Microtubers were formed in the treatments of IAA+BAP and IAA + GA + BAP but not observed in the treatments of IAA alone or IAA + GA. IAA of higher concentrations (2.5 – 10 mg dm⁻³) was helpful to form sessile tubers. With the increasing of IAA levels, the fresh weight and diameter of microtubers increased progressively. At 10 mg/L IAA, the fresh weight and diameter of microtubers in the treatment of IAA + GA + BAP were 409.6 % and 184.4 % of that in the treatment of IAA + BAP respectively, indicating the interaction effect of GA and IAA in potato microtuberization.     

Different characteristics of roots in the cadmium-tolerance and Cd-binding complex formation between mono- and dicotyledonous plants

Effects of Cd²⁺ on growth and Cd-binding complex formation in roots were examined with various seedlings of mono- and dicotyledonous plants. Maize, oat, barley and rice exhibited the greater tolerance to Cd²⁺ (100 μM) than did azuki bean, cucumber, lettuce, pea, radish, sesame and tomato (10–30 μM). Azuki bean was the most sensitive to Cd²⁺ (<10 μM). Under these Cd-treatments, cereal roots accumulated Cd²⁺ in the cytoplasmic fractions and transported Cd²⁺ into the same fractions of shoot tissues, to larger extents than did dicotyledonous roots. Cereal roots synthesized a Cd-binding complex containing phytochelatins in the cytoplasmic fractions, depending upon Cd²⁺ concentrations applied (30–100 μM). Such a complex was not detected from the same fractions of dicotyledonous roots treated with Cd²⁺. These results suggest that the Cd-binding complex formation has an important role in the tolerance of cereal roots against Cd²⁺.     

Effect of flow rate on heavy metal accumulation by rotating biological contactor (RBC) biofilms

Immobilized biofilms are effective in heavy metal removal. The current studies investigated the use of rotating biological contactor (RBC) biofilms in treatment of a wastewater containing cadmium, copper and zinc, each at a concentration of 100 mg L⁻¹. In particular, the influence of hydraulic retention time (HRT) on metal accumulation was studied. Longer HRTs (>12 h) were associated with greater metal removal than short HRTs, particularly with regard to cadmium and zinc. The system was also shown to operate successfully over an extended period of time, at an HRT of 24 h, with removal efficiencies of approximately 34%, 85% and 57% for Cd²⁺, Cu²⁺ and Zn²⁺ respectively after 5–8 weeks contact. Journal of Industrial Microbiology & Biotechnology (2000) 24, 244–250. Received 28 July 1999/ Accepted in revised form 21 December 1999     

Cd-induced growth reduction in the halophyte <Emphasis Type="Italic">Sesuvium portulacastrum</Emphasis> is significantly improved by NaCl

The effects of Cd²⁺ and NaCl, applied together or separately, on growth and uptake of Cd²⁺ were determined for the halophyte Sesuvium portulacastrum L. Seedlings were cultivated in the presence of 50 or 100 μmol L⁻¹ Cd²⁺ alone or combined with 100 or 400 mmol L⁻¹ NaCl. Data showed that alone, Cd²⁺ induced chlorosis, necrosis, and inhibited growth. Addition of NaCl to Cd²⁺-containing medium restored growth and alleviated the toxicity, however. NaCl also enhanced the amounts of Cd²⁺ accumulated in the shoots. All Cd²⁺ treatment reduced K⁺ and Ca²⁺ uptake and transport to the shoots. Accumulation of Na⁺ in the shoots was not affected by Cd²⁺, however. Thus S. portulacastrum maintained its halophytic characteristics in the presence of Cd²⁺. We suggest this halophyte could be used for phytoextraction of Cd²⁺ from salt-contaminated sites.     

<Emphasis Type="Italic">Tolypothrix tenuis</Emphasis> stress response to nickel

Summary Metal ions are both essential and potentially toxic. The aim of this work was to demonstrate that diazotrophic cyanobacterium Tolypothrix tenuis N° 54 can tolerate toxic concentrations of Ni²⁺ in order to use the biomass in biofilters or as biofertilizer. For this purpose, growth, pigment and protein contents and catalase activity of T. tenuis growing in increasing concentrations of Ni²⁺ ranging from 10⁻¹⁰ to 10⁻⁴ M were assesed. The strain did not grow at Ni²⁺ concentration of 10⁻⁴ M, but at lower concentrations there were no significant differences with the control; it was tolerant at 10⁻¹⁰ and 10⁻⁸ M. Nickel concentration of 10⁻⁶ M is toxic for this cyanobacterial strain, because dry weight decreased by 30%; allophycocyanin and phycoerythrin decreased by 92% and 98%, respectively and protein content increased by 42%. Chlorophyll a concentration was more than double the control value in 10⁻¹⁰ and 10⁻⁸ M, but in 10⁻⁶ M it decreased by 19%. Catalase (E.C. 1.11.1.6) activity doubled the control value in the lowest nickel concentration whereas in 10⁻⁸ M there was no significant difference with the control and in 10⁻⁶, it decreased by 78%. The living biomass of this strain could be used as a step in the bioremediation process in waters contaminated with concentrations of nickel lower than 10⁻⁶ M and eventually as a biofertilizer.     

Growth-Regulating Activity of Three 4-Hydroxycoumarin Derivatives on Inoculated Soybean Plants

Three 4-hydroxycoumarin derivatives (ethyl 2-[(4-hydroxy-2-oxo-2H-chromen-3-yl)(4-hydroxyphenyl)methyl]-3-oxobutanoate (SS-14), ethyl 2-[(4-hydroxy-2-oxo-2H-chromen-3-yl)(3-nitrophenyl)methyl]-3-oxobutanoate (SS-21), and 2-[(3,4,5-trimethoxyphenyl)(4-hydroxy-2-oxo-2H-chromen-3-yl)methyl]-3-oxobutanoate (T-2)] were tested for growth-regulating activity on nitrogen-fixing soybean plants in different concentrations: 10⁻⁵, 10⁻⁴, and 10⁻³ M. They revealed growth-regulating activity in a concentration-dependent manner. The most powerful suppression effect of T-2 on shoot and root fresh and dry biomass accumulation, length of roots, and height of plants was found. Shoot fresh biomass was suppressed in an equal extent at 10⁻³ M of the three compounds but the order of inhibition regarding the three applied concentrations was T2 > SS-14 ≈ SS-21. The compound SS-14 inhibited nodule number and nodule biomass mainly at the highest applied concentration, 10⁻³ M. The highest inhibition of nitrogenase activity was established at the three applied concentrations of the compound SS-14.     

Cadmium Induced Ultrastructural Changes in Shoot Apical Meristem of Elodea Canadensis Rich.

The ultrastructure of cells of ground meristem in the peripheral zone of shoot apical meristem in Elodea canadensis Rich. was studied after treatment with cadmium in concentrations 0.5, 1, 2, 3, 5, and 6 g(Cd²⁺) m⁻³. After 5 d treatment, changes in the structural organisation of the plastid apparatus were found, namely in proplastid, amyloplast, and amoeboid stages of plastid development. This revised version was published online in June 2006 with corrections to the Cover Date.     

Cadmium and zinc influx characteristics by intact corn (Zea mays L.) seedlings

Summary Cadmium and zinc uptake parameters were determined for intact corn (Zea mays L.) seedlings grown for 15 and 22 in nutrient solutions containing levels of Cd and Zn that were similar to those found in soil solutions. Uptake of both elements was assumed to follow Michaelis-Menten kinetics. Calculations were based on the concentrations of free ionic Cd (Cd²⁺) and Zn (Zn²⁺) rather than the total solution concentration. Rates of Zn uptake were measured by determining depletion of Zn for periods of up to 30 h from solutions containing initial concentrations of 1.5 and 10μmol Zn 1⁻¹. Depletion curves suggested that Zn uptake characteristics were similar at both levels of Zn in solution. The Imax for Zn uptake decreased from 550 to 400 pmol m⁻² root surface s⁻¹ between 16 and 22 d of growth while Km decreased from 2.2 to 1.5 μmol Zn²⁺ 1⁻¹. Cadmium uptake parameters were measured by controlling Cd²⁺ activities in nutrient solution betwen 6.3 to 164 nmol l⁻¹ by continuous circulation of nutrient solution through a mixed-resin system. Imax for Cd uptake was 400 pmol m⁻² root surface s⁻¹ at 15 and 22 d of growth. The magnitude of Km increased from 30 to 100 nmol Cd²⁺ 1⁻¹ during this time period. The Km value suggests that corn is efficient for Cd uptake. The results of these uptake studies are consistent with the observed uptake of Zn and Cd by corn seedlings in soils.     

The combined effect of Cd2+ and ACh on action potentials of Nitellopsis obtusa cells

Interrelations between the action of acetylcholine (ACh) and cadmium ions (Cd²⁺) on bioelectrogenesis of Nitellopsis obtusa cells were investigated. We analyzed repetitively triggered action potentials (AP), their reproducibility, shape and dynamics of membrane potential after AP induction. ACh significantly increased membrane permeability only at high concentrations (1 mM and 5 mM). Repolarisation level of action potential after the first stimulus was much more positive in all cells treated with ACh as compared to the control. Differences of membrane potentials between points just before the first and the second stimuli were 23.4±.0 mV (control); 40.4±5.9 mV (1 mM ACh solution) and 57.7 ± 8.5 mV (5 mM ACh solution). Cd²⁺ at 20 μM concentration was examined as a possible inhibitor of acetylcholinesterase (AChE) in vivo. We found that cadmium strengthens depolarizing effect of acetylcholine after the first stimulus. The highest velocity of AP repolarization was reduced after ACh application and Cd²⁺strengthened this effect. There were no differences in dynamics of membrane potential after repetitively triggered action potentials in ACh or ACh and Cd²⁺ solutions. This shows that cadmium in small concentration acts as inhibitor of acetylcholinesterase.     

Exposure time-dependent cadmium toxicity to <Emphasis Type="Italic">Moina macrocopa</Emphasis> (Cladocera): a life table demographic study

In this work, we quantified the life table demographic responses of Moina macrocopa daily exposed to three concentrations, 0, 0.08, 0.16, and 0.32 mg l⁻¹ of CdCl₂ for 3, 6, 12, and 24 h. These cadmium levels represented 10–50% of the median lethal concentration known for M. macrocopa. In general, increase in CdCl₂ concentration and increase in the exposure time had a negative impact on the both survivorship and reproduction variables of M. macrocopa. The survivorship curves showed drastic mortality of M. macrocopa exposed for 24 h per day at all three concentrations used. The survival of animals was distinctly lower than in controls for the 3-h exposure at 0.08 mg l⁻¹ of CdCl₂. The cladocerans ceased to reproduce when exposed to 0.32 mg l⁻¹ CdCl₂ for 6 h or longer. Depending on the heavy metal concentration and the duration of exposure, the average lifespan, net reproductive rate, generation time, and the rate of population increase varied from 3 to 10 days, 1 to 30 offspring female⁻¹, 4 to 8 days, and −0.20 to +0.59 day⁻¹, respectively. Even the lowest CdCl₂ concentration for an exposure time of 3 h had an adverse effect on M. macrocopa, which suggested the importance of including pulsed exposure times in ecotoxicological evaluations.     

Effect of jasmonic acid on in vitro explant growth and microtuberization in potato

The shoot fresh mass, root length and root numbers of two potato (Solanum tuberosum L.) cultivars Favorita and Helanwuhua were increased significantly by the application of 0.2 – 2 mg dm⁻³ jasmonic acid (JA) in the Murashige and Skoog medium. However, the growth of potato explants was inhibited by JA at high concentrations (20 – 50 mg dm⁻³). Chlorophyll content in explant leaves decreased with an increase in the concentration of JA. In leaves treated with 0.2 mg dm⁻³ JA acid peroxidase activity increased, while in the leaves treated with more than 2 mg dm⁻³ JA peroxidase activity decreased. Under the dark, the microtuber numbers, fresh mass and percentage of big microtubers of two potato cultivars were not promoted by the application of 0.2 – 50 mg dm⁻³ JA.