Comparison of heavy metal phytoremediation in monoculture and intercropping systems of Phyllostachys praecox and Sedum plumbizincicola in polluted soil

A bamboo species (Phyllostachys praecox) and a Cd/Zn hyperaccumulator (Sedum plumbizincicola) were tested under different planting systems to compare their heavy metal phytoremediation ability. P. praecox (MP), S. plumbizincicola (MS) and P. praecox × S. plumbizincicola (IPS) plantations were established in Cu, Zn, and Cd-contaminated soil. Soil properties and heavy metal contents in plants were determined and compared after four years of plantation establishment. The rankings of available and total metal contents in soil layers were MP > MS > IPS (0–20 cm) and MP > IPS > MS (20–40 cm, except for Cu), respectively. The Cu and Zn contents in mature bamboo tissues were significantly lower, but the Cd contents in bamboo tissues (except for leaves) higher, in the IPS than in the MP. The bioconcentration and the translocation factors in most of bamboo tissues showed an increasing trend from the MP to the IPS. Heavy metal distribution in plants is greatly affected by the planting patterns. The tested intercropping system of two plant species showed higher biomass productivity, implying more heavy metals can be removed from the soil through the harvesting of plants. Therefore, the IPS leads to significant improvement of soil phytoremediation.     

Spatial variation of plant communities and shoot Cu concentrations of plant species at a timber treatment site

Plant species, spatial variability in plant diversity and vegetation cover were recorded at a French timber treatment site with Cu-contaminated soils (65–2600 mg/kg). Shoot biomass, shoot Cu concentration and accumulation were determined for each plant species found on 168 quadrats with increasing total Cu in soil and soil solution. A total of 91 species occurred on the site including four considered as invasive (Cyperus eragrostis, Phytolacca americana, Senecio inaequidens, and Sporobolus indicus). Species richness, Shannon index, vegetation cover and plant biomass decreased as soil Cu increased. At low soil Cu, members of the Poaceae were most frequent followed by Fabaceae, Rosaceae, and Asteraceae. At high soil Cu, Poaceae were again most frequent. Species known to form Cu-tolerant populations, i.e. Agrostis capillaris, A. stolonifera and Rumex acetosella were present. Shoot Cu concentration and accumulation were higher in plants growing in the most contaminated soils. At 2142 mg Cu/kg soil, shoot Cu accumulation peaked at 6 mg Cu/m² in A. capillaris, and its shoot Cu concentration (364 mg Cu/kg dry weight) exceeded the fodder Cu threshold for domestic livestock. In less Cu-contaminated soils some candidates were identified for sustainable phytoremediation with a potential financial return.     

A Study on Cadmium Phytoremediation Potential of Indian Mustard,Brassica juncea

The objective of this study was to investigate Cd phytoremediation ability of Indian mustard, Brassica juncea. The study was conducted with 25, 50, 100, 200 and 400 mg Kg^?1 CdCl₂ in laboratory for 21 days and Cd concentrations in the root, shoot and leaf tissues were estimated by atomic absorption spectroscopy. The plant showed high Cd tolerance of up to 400 mg Kg^?1 but there was a general trend of decline in the root and shoot length, tissue biomass, leaf chlorophyll and carotenoid contents. The tolerance index (TI) of plants were calculated taking both root and shoot lengths as variables. The maximum tolerance (TI _shoot = 87.4 % and TI _root = 89.6 %) to Cd toxicity was observed at 25 mg Kg^?1, which progressively decreased with increase in dose. The highest shoot (10791 μg g^?1 dry wt) and root (9602 μg g^?1 dry wt) Cd accumulation was achieved at 200 mg kg^?1 Cd treatment and the maximum leaf Cd accumulation was 10071.6 μg g^?1 dry wt achieved at 100 mg Kg^?1 Cd, after 21 days of treatment. The enrichment coefficient and root to shoot translocation factor were calculated, which, pointed towards the suitability of Indian mustard for removing Cd from soil.     

Study of liquid culture system for micropropagation of the medicinal plant Solanum nigrum L. and its effect on antioxidant property

Solanum nigrum Linn., known for hepatoprotective and antioxidant properties, is extensively harvested from the wild. Supply is far short of demand, necessitating requirement of efficient in vitro propagation protocols. Nodal explants from wild S. nigrum plants were cultured in vitro in MS medium supplemented with 3.0 mg L^?1 IAA, 0.5 mg L^?1 BAP and gelled with 0.8 % agar. After 30 days, shoots buds were transferred to liquid MS medium of same composition. Subsequent subculture was carried out every 6 days. Shoot doubling time in solid and liquid media was calculated. Total phenolics, proanthocyanidin and flavonoid contents, ABTS^.+ and hydrogen peroxide radical scavenging antioxidant capacity of wild and in vitro aqueous leaf extracts were estimated and compared. In MS agar, 18 shoot buds were produced per explant after 30 days of culture, with shoot doubling time of 7.11 days. In liquid media, 21 shoots per explant were produced in 6 days, with a 5-fold higher multiplication rate and shoot doubling time of 1.37 days. Leaves were morphologically similar to those of wild plants. Total phenolics, proanthocyanidin and flavonoid contents of in vitro leaf extracts was 5–10 times higher than that of wild plants while ABTS^.+ and H₂O₂ radical scavenging activity was similar in both extracts. Liquid media is better suited for in vitro propagation of S. nigrum since enhanced multiplication rate was observed with shorter subculture intervals. Moreover, plants retained normal morphology and antioxidant property.     

Effect of heavy metal pollution on mineral absorption in sunflower (Helianthus annuus L.) hybrids

The present study was conducted in a potted experiment to examine the effects of chromium pollution on absorption of mineral nutrients and some morpho-physiological attributes of two sunflower (Helianthus annuus L.) hybrids (FH-331 and FH-259) in the presence and absence of ethylene diamine tetra acetic acid (EDTA) used as a chelating agent. Four concentrations of chromium (Cr³⁺) i.e., 0, 20, 30 and 40 mg kg^?1 with and without 0.3 g kg^?1, EDTA as chelating agent were applied to 25-day-old sunflower plants. A gradually decreasing trend in absorption of all minerals and other parameters studied were observed. Different treatments of Cr³⁺ as well as Cr³⁺ and EDTA significantly reduced root and shoot fresh weight; however, root, shoot and achene Cr³⁺ contents of two sunflowers hybrids under higher chromium and EDTA stress varied significantly whereas movement of Cr³⁺ contents to leaves was non-significant. Absorption of Na⁺, K⁺, N₂ and P through roots and shoots significantly reduced with increasing concentration of Cr³⁺ treatments. In fact addition of EDTA to the medium further enhanced the toxicity of chromium.     

Modulation in growth,photosynthetic efficiency,activity of antioxidants and mineral ions by foliar application of glycinebetaine on pea (Pisum sativum L.) under salt stress

A pot experiment was carried out to explore the role of glycinebetaine (GB) as foliar spray foliar on two pea (Pisum sativum L.) varieties (Pea 09 and Meteor Fsd) under saline and non-saline conditions. Thirty-two-day-old plants were subjected to two levels 0 and 150 mM of NaCl stress. Salt treatment was applied in full strength Hoagland’s nutrient solution. Three levels 0, 5 and 10 mM of GB were applied as foliar treatment on 34-day-old pea plants. After 2 weeks of foliar treatment with GB data for various growth and physiochemical attributes were recorded. Rooting-medium applied salt (150 mM NaCl) stress decreased growth, photosynthesis, chlorophyll, chlorophyll fluorescence and soluble protein contents, while increasing the activities of enzymatic (POD and CAT) and non-enzymatic (ascorbic acid and total phenolics) antioxidant enzymes. Foliar application of GB decreased root and shoot Na⁺ under saline conditions, while increasing shoot dry matter, root length, root fresh weight, stomatal conductance (g _s), contents of seed ascorbic acid, leaf phenolics, and root and shoot Ca²⁺ contents. Of three GB (0, 5, 10 mM) levels, 10 mM proved to be more effective in mitigating the adverse effects of salinity stress. Overall, variety Pea 09 showed better performance in comparison to those of var. Meteor Fsd under both normal and salinity stress conditions. GB-induced modulation of seed ascorbic acid, leaf phenolics, g _s, and root Ca²⁺ values might have contributed to the increased plant biomass, reduction of oxidative stress, increased osmotic adjustment and better photosynthetic performance of pea plants under salt stress.     

Changes in photosynthesis, antioxidant enzymes and lipid peroxidation in soybean seedlings exposed to UV-B radiation and/or Cd

Aims

With a high growth rate and biomass production, bamboos are frequently used for industrial applications and recently have proven to be useful for wastewater treatment. Bamboos are considered as Si accumulators and there is increasing evidence that silicon may alleviate abiotic stresses such as metal toxicity. The aim of this study was to investigate the extent of metal concentrations and possible correlations with Si concentrations in plants.

Methods

This study presents, for the first time, reference values for silicon (Si), copper (Cu) and zinc (Zn) concentrations in stems and leaves of various bamboo species grown under the natural pedo-climatic conditions of the island of Réunion (Indian Ocean).

Results

A broad range of silicon concentrations, from 0 (inferior to detection limit) to 183 mg g^?1 dry matter (DM), were found in stems and leaves. Mean leaf Cu and Zn concentrations were low, i.e. 5.1 mg kg^?1 DM and 15.7 mg kg^?1 DM, respectively. Silicon, Cu and Zn concentrations increased over the following gradient: stem base?<?stem tip?<?leaves. Significant differences in Si, Cu and Zn contents (except Zn in the stem) were noted between bamboo species, particularly between monopodial and sympodial bamboo species, which differ in their rhizome morphology. Sympodial bamboos accumulated more Si and Cu than monopodial bamboos, in both stems and leaves, whereas sympodial bamboos accumulated less Zn in leaves than monopodial bamboos.

Conclusions

The findings of this study suggest that a genotypic character may be responsible for Si, Cu and Zn accumulation in bamboo.     

Enhancing Phytoremediation Potential of Pennisetum clandestinum Hochst in Cadmium-Contaminated Soil Using Smoke-Water and Smoke-Isolated Karrikinolide

The use of plant growth regulators (PGRs) and biostimulants to enhance phytoextraction is gaining popularity in phytoremediation technology. This study investigated the stimulatory effects of smoke-water (SW), a smoke-derived compound karrikinolide (KAR₁) and other known plant growth regulators (PGRs) [gibberellic acid (GA₃), kinetin (Kin) and indole-3-butyric acid (IBA)] to enhance the phytoextraction potential of Pennisetum clandestinum. Pennisetum clandestinum seedlings were grown for 10 weeks in vermiculite using Hoagland's nutrient solution and were treated with cadmium (Cd) (2, 5, and 10 mg L^?1) and SW, KAR₁ and PGRs. KAR₁ exhibited positive effects on shoot and root dry weight (140 and 137 mg respectively) at the highest concentration of Cd (10 mg L^?1) compared to all the other treatments. KAR₁ and SW treatments used in the present study significantly improved the phytoextraction potential of P. clandestinum (602 and 575 mg kg^?1 respectively) compared to the other tested PGRs. This is the first report on the use of SW and KAR₁ to enhance phytoremediation potential in P. clandestinum. Further studies are needed to elucidate the exact mechanisms of smoke constituents involved in phytoextraction potential of plant species.     

Phytoremediation of Wastewater with Limnocharis Flava,Thalia Geniculata and Typha Latifolia in Constructed Wetlands

Phytoremediation is thought to be the most sustainable wastewater treatment option for developing countries. However, its application is often limited by unavailability of suitable candidate species. In the present study, the potentials of Limnocharis flava, Thalia geniculata and Typha latifolia for remediation of heavy metal contaminated wastewater with a constructed wetland system were evaluated. The wetland consisted of three treatment lines each planted with sufficient and equal number of a species. Duplicate plant and water samples were collected bi-monthly and analyzed for Fe, Cu, Zn, Pb, and Hg using the atomic absorption spectrophotometer over a six month period. Bioaccumulation rates generally increased over time and varied among plants for these metals, with Fe (456–1549 mg kg¹ roots; 20–183 mg kg^?1 shoot) being the most sequestered and Pb (1.2–7.6 mg kg^?1 roots; 1.55–3.95 mg kg^?1 shoot) the least. Translocation factors differed among the species but generally remained stable over time. L. flava showed potential for hyperaccumulating Hg. Removal efficiencies varied for the studied metals (～ 20–77 %) and were generally related to metal uptake by the plants. These results demonstrate the suitability of the species for phytoremediation, and the usefulness of the technique as an option for improving irrigation water quality in Ghana.

Supplemental materials are available for this article. Go to the publisher's online edition of International Journal of Phytoremediation to view the supplemental file.     

Accumulation and tolerance characteristics of lead in <Emphasis Type="Italic">Althaea rosea</Emphasis> Cav. and <Emphasis Type="Italic">Malva crispa</Emphasis> L.

Two ornamental plants of Althaea rosea Cav. and Malva crispa L. were exposed to various concentrations of lead (Pb) (0, 50, 100, 200 and 500 mg·kg^?1) for 70 days to evaluate the accumulating potential and the tolerance characteristics. The results showed that both plant species grown normally under Pb stress, and A. rosea had a higher tolerance than M. crispa, while M. crispa had a higher ability in Pb accumulation than A. rosea. Besides, lower Pb concentration (50 mg·kg^?1) stimulated the shoot biomass in both plant species. Pb accumulation in plants was consistent with the increase of Pb levels, and the main accumulation sites were the roots and the older leaves. In addition, the photosynthetic pigments content and chlorophyll fluorescence parameters were influenced by Pb stress. In such case, both of the plants could improve the activities of antioxidant enzymes of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) and ascorbate peroxidase (APX), and the contents of the total soluble sugar and soluble protein, which reached the highest value at Pb 100 mg·kg^?1, as well as the accumulation of the total thiols (T-SH) and non-protein thiols (NP-SH) to adapt to Pb stress. Thus, it provides the theoretical basis and possibility for ornamental plants of A. rosea and M. crispa in phytoremediation of Pb contaminated areas.     

Effects of Reductants on Phytoextraction of Chromium (VI) by Ipomoea aquatica

Reductants are often used to reduce Cr(VI) in chemical treatments, yet the effects of the reductants on Cr(VI) phytoremediation are not fully understood. This study investigates the effects of different reductants on Cr(VI) phytoremediation by Ipomoea aquatica in simulated solution with 3 mg L^?1 of Cr(VI), pH₀ of 6, and an incubation time of 5 days. Results indicate that the applications of S₂O₃^2?, Fe⁰, and Fe²⁺ at low doses notably increased root Cr concentrations, which were obviously higher than that those in the control (Cr⁶⁺ alone). However, high reductant concentrations decreased bioaccumulation of Cr in the roots and shoots of the plant.

Statistical results indicate that Cr concentrations were significantly and negatively correlated with Fe concentrations in the roots and shoots of the plant (p < 0.05). This suggest that Fe accumulation inhibited Cr accumulation in the plant. A Cr(VI) concentration of 3 mg L^?1 caused short, brown lateral roots with tip necrosis, leaf chlorosis, and noticeable shoot wilting. The leaf necrosis and shoot wilting is caused by oxidative damage of lateral roots by Cr(VI) rather than by the reactive oxygen species generated by the oxidative stress. Addition of the reductants effectively reduced these plant injuries.     

Hyperaccumulator Oilcake Manure as an Alternative for Chelate-Induced Phytoremediation of Heavy Metals Contaminated Alluvial Soils

The ability of hyperaccumulator oilcake manure as compared to chelates was investigated by growing Calendula officinalis L for phytoremediation of cadmium and lead contaminated alluvial soil. The combinatorial treatment T₆ [2.5 g kg^?1oilcake manure + 5 mmol kg^?1 EDDS] caused maximum cadmium accumulation in root, shoot and flower up to 5.46, 4.74 and 1.37 mg kg^?1and lead accumulation up to 16.11, 13.44 and 3.17 mg kg^?1, respectively at Naini dump site, Allahabad (S₃). The treatment showed maximum remediation efficiency for Cd (RR = 0.676%) and Pb (RR = 0.202%) at Mumfordganj contaminated site (S₂). However, the above parameters were also observed at par with the treatment T₅ [2.5 g kg^?1oilcake manure +2 g kg^?1 humic acid]. Applied EDDS altered chlorophyll–a, chlorophyll–b, and carotene contents of plants while application of oilcake manure enhanced their contents in plant by 3.73–8.65%, 5.81–17.65%, and 7.04–17.19%, respectively. The authors conclude that Calendula officinalis L has potential to be safely grown in moderately Cd and Pb-contaminated soils and application of hyperaccumulator oilcake manure boosts the photosynthetic pigments of the plant, leading to enhanced clean-up of the cadmium and lead-contaminated soils. Hence, the hyperaccumulator oilcake manure should be preferred over chelates for sustainable phytoremediation through soil-plant rhizospheric process.     

Decontamination and functional reclamation of dredged brackish sediments

The continuous stream of sediments, dredged from harbors and waterways for keeping shipping traffic efficiency, is a considerable ongoing problem recognized worldwide. This problem gets worse as most of the sediments dredged from commercial ports and waterways turn out to be polluted by a wide range of organic and inorganic contaminants. In this study, phytoremediation was explored as a sustainable reclamation technology for turning slightly-polluted brackish dredged sediments into a matrix feasible for productive use. To test this possibility, a phytoremediation experimentation was carried out in containers of about 0.7 m³ each, filled with brackish dredged sediments contaminated by heavy metals and hydrocarbons. The sediments were pre-conditioned by adding an agronomic soil (30 % v/v) to improve their clayey granulometric composition, and by topping the mixture with high quality compost (4 kg m^?2) to favour the initial adaptation of the selected vegetal species. The following plant treatments were tested: (1) Paspalum vaginatum, (2) Phragmites australis, (3) Spartium junceum + P. vaginatum, (4) Nerium oleander + P. vaginatum, (5) Tamarix gallica + P. vaginatum, and (6) unplanted control. Eighteen months after the beginning of the experimentation, all the plant species were found in healthy condition and well developed. Throughout the whole experiment, the monitored biological parameters (total microbial population and dehydrogenase activity) were generally observed as constantly increasing in all the planted sediments more than in the control, pointing out an improvement of the chemico-physical conditions of both microorganisms and plants. The concentration decrease of organic and inorganic contaminants (>35 and 20 %, respectively) in the treatments with plants, particularly in the T. gallica + P. vaginatum, confirmed the importance of the root-microorganism interaction in activating the decontamination processes. Finally, the healthy state of the plants and the sediment characteristics, approaching those of an uncontaminated natural soil (technosoil), indicated the efficiency and success of this technology for brackish sediments reclamation.     

Effects of Surface-Modified Nano-Scale Carbon Black on Cu and Zn Fractionations in Contaminated Soil

Cu contamination soil (547 mg kg^–1) was mixed separately with the surface-modified nano-scale carbon black (MCB) and placed in the ratios (w/w) of 0, 1%, 3%, and 5% in pots, together with 0.33 g KH₂PO₄and 0.35 g urea/pot. Each pot contained 20 ryegrass seedlings (Lolium multiflorum). Greenhouse cultivation experiments were conducted to examine the effect of the MCB on Cu and Zn fractionations in soil, accumulation in shoot and growth of ryegrass. The results showed that the biomass of ryegrass shoot and root increased with the increasing of MCB adding amount (p < 0.05). The Cu and Zn accumulation in ryegrass shoot and the concentrations of DTPA extractable Cu and Zn in soil were significantly decreased with the increasing of MCB adding amount (p < 0.05). The metal contents of exchangeable and bound to carbonates (EC-Cu or EC-Zn) in the treatments with MCB were generally lower than those without MCB, and decreased with the increasing of MCB adding amount (p < 0.05). There was a positive linear correlation between the Cu and Zn accumulation in ryegrass shoot and the EC-Cu and EC-Zn in soil. The present results indicated the MCB could be applied for the remediation the soils polluted by Cu and Zn.     

Somatic embryogenesis and organogenesis in Dendrocalamus hamiltonii

In this study, mature zygotic embryos, plant growth regulators, and various media were tested with the aim of developing an efficient regeneration system for plantlets of the bamboo species Dendrocalamus hamiltonii. Callus formation was induced in explants cultured in Murashige and Skoog (MS) medium supplemented with 1.0–3.0 mg/l 2,4-dichlorophenoxyacetic acid. Optimal shoot differentiation and subsequent shoot growth were also obtained in MS medium supplemented with 2 mg/l benzyladenine, 1 mg/l kinetin, and 1 mg/l naphthaleneacetic acid. Root induction was enhanced by the addition of 5 mg/l indole-3-butyric acid to the culture medium. Histological analysis revealed that both somatic embryogenesis and organogenesis were induced during callus initiation, shoot differentiation, and the development of plantlets from the mature zygotic embryos. Our data provide a useful basis for developing culture protocols for the regeneration of bamboo plants.     

Phytoremediation of heavy metal contaminated soil potential by woody plants on Tonglushan ancient copper spoil heap in China

Fast-growing metal-accumulating woody plants are considered potential candidates for phytoremediation of metals. Tonglushan mining, one of the biggest Cu production bases in China, presents an important source of the pollution of environment. The sample was collected at Tonglushan ancient copper spoil heap. The aims were to measure the content of heavy metal in the soil and woody plants and to elucidate the phytoremediation potential of the plants. The result showed that soil Cu, Cd and Pb were the main contamination, the mean contents of which were 3166.73 mg/kg, 3.66 mg/kg and 137.06 mg/kg respectively, which belonged to severe contamination. Fourteen species from 14 genera of 13 families were collected and investigated; except for Ligutrum lucidum, the other 13 woody plants species were newly recorded in this area. In addition, to assess the ability of metal accumulation of these trees, we proposed accumulation index. Data suggested that Platanus × acerilolia, Broussonetia papyrifera, Ligutrum lucidum, Viburnum awabuki, Firmiana simplex, Robina pseudoacacia, Melia azedarach and Osmanthus fragrans exhibited high accumulated capacity and strong tolerance to heavy metals. Therefore, Platanus × acerilolia and Broussonetia papyrifera can be planted in Pb contaminated areas; Viburnum awabuki, Firmiana simplex, Robina pseudoacacia and Melia azedarach are the suitable trees for Cd contaminated areas; Viburnum awabuki, Melia azedarach, Ligutrum lucidum, Firmiana simplex, Osmanthus fragrans and Robina pseudoacacia are appropriate to Cu, Pb and Cd multi-metal contaminated areas.     

Copper tolerance in the cuprophyte Haumaniastrum katangense (S. Moore) P.A. Duvign. & Plancke

Cu tolerance and accumulation have been studied in Haumaniastrum katangense, a cuprophyte from Katanga (DR Congo), previously described as a copper hyperaccumulator. Nicotiana plumbaginifolia, a well-known non-tolerant and non-accumulator species, was used as a control. The germination rate of H. katangense was enhanced by copper and fungicide addition, suggesting that fungal pathogens, which restrain germination in normal conditions, are limiting. In hydroponic culture in the Hoagland medium, H. katangense did not grow well, in contrast to N. plumbaginifolia. Better growth was achieved by adding fungicide or higher copper concentrations. The maximal non-effective concentration (NEC) was 12 µM CuSO₄ for H. katangense grown in hydroponics, i.e. 24 times greater than Cu concentration in the Hoagland medium. By comparison, copper concentrations greater than 0.5 µM had a negative effect on the growth of N. plumbaginifolia. EC₅₀ (50% effective concentration) in hydroponics was 40 µM CuSO₄ for H. katangense and 6 µM CuSO₄ for N. plumbaginifolia. EC₁₀₀ (100% effective concentration) was 100 µM CuSO₄ for H. katangense and 15 µM CuSO₄ for N. plumbaginifolia. In soil, growth was also stimulated by Cu addition up to 300 mg kg^-1 CuSO₄. Surplus copper was also required for cultivating H. katangense in sterile conditions, suggesting that Cu excess may be necessary for needs other than pathogen defence. Cu accumulation in the shoot has been measured for N. plumbaginifolia and H. katangense at their respective NEC. Cu allocation in the two species showed a similar response to increasing Cu concentrations, i.e. root/shoot concentration ratio well above 1. In conclusion, H. katangense is highly tolerant to copper and has elevated copper requirement even in the absence of biotic interactions. Its accumulation pattern is typical of an excluder species.     

Micropropagation of the pistachio and its rootstocks by temporary immersion system

Although several studies have been reported on the micropropagation of the pistachio and its rootstocks, to date none of them had been efficient on the mass production of these plants in bioreactor systems. Thus, the micropropagation of juvenile pistachio shoot tips and nodal buds was investigated in a temporary immersion bioreactor system (RITA^®) and on a conventional semi-solid medium. Among the tested immersion conditions, immersion for 24 min every 16 h reduced vitrification and improved proliferation in the pistachio. Interactions were evident in immersion time and frequency in nodal segments. Nodal buds were better than shoot tips as the highest multiple shoot formation was recorded in MS medium containing 4 mg L^?1 BA and 0.1 mg L^?1 GA₃ in RITA^®. Although shoot tip necrosis (STN) was observed in shoots proliferated on semi-solid MS medium, such a symptom did not occur in shoots sprouted in the RITA^®. Additionally, these optimized conditions were applied to nodal buds of mature male pistachio ‘Atl?’ and Pistacia rootstocks (P. khinjuk Stocks and P. atlantica Desf.), and the micropropagation in the bioreactor system, in comparison to the semi-solid medium, was also improved. Furthermore, in vitro rooting of pistachio plantlets, despite the lower range (27.5 %), was also achieved in RITA^®. However, rooting was better on semi-solid medium for all tested species (ranged between 50 and 70 %). The results of this study showed that RITA^® could be used for the mass propagation of pistachio and its rootstocks, as well as for other woody plant species.     

Elevated CO2 improves root growth and cadmium accumulation in the hyperaccumulator Sedum alfredii

Aims

This study examined the effect of elevated CO₂ on plant growth, root morphology and Cd accumulation in S. alfredii, and assessed the possibility of using elevated CO₂ as fertilizer to enhance phytoremediation efficiency of Cd-contaminated soil by S. alfredii.

Methods

Both soil pot culture and hydroponic experiments were carried out to characterize plant biomass, root morphological parameters, and cadmium uptake in S. alfredii grown under ambient (350 μL L^?1) or elevated (800 μL L^?1) CO₂.

Results

Elevated CO₂ prompted the growth of S. alfredii, shoot and root biomass were increased by 24.6–36.7% and 35.0–52.1%, respectively, as compared with plants grown in ambient CO₂. After 10 days growth in medium containing 50 μM Cd under elevated CO₂, the development of lateral roots and root hairs were stimulated, additionally, root length, surface area, root volume and tip number were increased significantly, especially for the finest diameter roots. The total Cd uptake per pot was significantly greater under elevated CO₂ than under ambient CO₂. After 60 d growth, Cd phytoextraction efficiency was increased significantly in the elevated CO₂ treatment.

Conclusions

Results suggested that the use of elevated CO₂ may be a useful way to improve phytoremediation efficiency of Cd-contaminated soil by S. alfredii.     

Synergistic effects of drought and ascorbic acid on growth,mineral nutrients and oxidative defense system in canola (Brassica napus L.) plants

A study was conducted to find out the role of ascorbic acid (AsA) in modulating growth and different physio-biochemical attributes of canola plants under well-watered as well as water-deficit conditions. Drought stress imposed on 60 % field capacity significantly decreased the shoot and root fresh and dry weights, leaf chlorophyll contents, shoot and root P, root K⁺, and activity of CAT enzyme, while increased chlorophyll a/b contents, MDA, NPQ, leaf total phenolics, free proline and GB contents in both canola cultivars. Foliar-applied varying levels (50, 100 and 150 mg L^?1) of AsA enhanced shoot and root fresh and root dry weights, qN, NPQ, shoot and root P, AsA as well as the activity of POD enzyme particularly under drought stress conditions. Of both canola cultivars, cv. Dunkeld was higher in shoot fresh weights, ETR and F _v /F _m, MDA, proline and GB contents, and POD activity, however, cv. Cyclone in total phenolics and qN under well-watered and water-deficit conditions. Overall, the foliar-applied AsA had a positive effect, though not marked, on salt sensitive cv. Cyclone in terms of improved growth and other attributes, whereas exogenously applied AsA had a non-significant effect on relatively salt tolerant cv. Dunkeld.