Physiological and Biochemical Mechanisms Preventing Cd Toxicity in the New Hyperaccumulator <Emphasis Type="Italic">Abelmoschus manihot</Emphasis>

Abelmoschus manihot, an ornamental plant, was examined for phytoremediation purposes in accordance with the ability to accumulate cadmium and physiological mechanisms of cadmium tolerance. A net photosynthetic rate (A _N) glasshouse experiment for 60 days was conducted to investigate the influence of different cadmium amounts (0–100 mg kg^?1) on the growth, biomass, photosynthetic performance, reactive oxygen species (ROS) production, antioxidative enzyme activities, Cd uptake and accumulation of A. manihot. Exposure to cadmium enhanced plant growth even at 100 mg kg^?1, without showing symptoms of visible damage. The cadmium concentration of shoots (stems or leaves) and roots was more than the critical value of 100 mg kg^?1 and reached 126.17, 185.26 and 210.24 mg kg^?1, respectively. BCF values of A. manihot plants exceeded the reference value 1.0 for all the Cd treatments, and TF values were greater than 1 at 15–60 mg kg^?1 Cd treatment. The results also showed that cadmium concentrations of 60 mg kg^?1 or less induced a significant enhancement in plant net photosynthetic rate (A _N), stomatal conductance (G _s), transpiration rate (T _r), photosynthetic pigments and F _v/F _m. These parameters were slightly decreased at the higher concentration (100 mg kg^?1). The ROS production (O₂ ^?, H₂O₂) and antioxidative response including SOD, CAT and POD were significantly enhanced by increasing cadmium. These results suggest that A. manihot can be considered as a Cd-hyperaccumulator and the hormetic effects may be taken into consideration in remediation of Cd contamination soil.     

Increased nitrogen deposition alleviated the adverse effects of drought stress on <Emphasis Type="Italic">Quercus variabilis</Emphasis> and <Emphasis Type="Italic">Quercus mongolica</Emphasis> seedlings

The plasticity response of Quercus variabilis and Quercus mongolica seedlings to combined nitrogen (N) deposition and drought stress was evaluated, and their performance in natural niche overlaps was predicted. Seedlings in a greenhouse were exposed to four N deposition levels (0, 4, 8, and 20 g N m^?2 year^?1) and two water levels (80 and 50 % field-water capacity). Plant traits associated with growth, biomass production, leaf physiology, and morphology were determined. Results showed that drought stress inhibited seedling performance, altered leaf morphology, and decreased fluorescence parameters in both species. By contrast increased N supply had beneficial effects on the nutritional status and activity of the PSII complex. The two species showed similar responses to drought stress. Contrary to the effects in Q. mongolica, N deposition promoted leaf N concentration, PSII activity, leaf chlorophyll contents, and final growth of Q. variabilis under well-watered conditions. Thus, Q. variabilis was more sensitive to N deposition than Q. mongolica. However, excessive N supply (20 g N m^?2 year^?1) did not exert any positive effects on the two species. Among the observed plasticity of the plant traits, plant growth was the most plastic, and leaf morphology was the least plastic. Therefore, drought stress played a primary role at the whole-plant level, but N supply significantly alleviated the adverse effects of drought stress on plant physiology. A critical N deposition load around 20 g N m^?2 year^?1 may exist for oak seedlings, which may more adversely affect Q. variabilis than Q. mongolica.     

<Emphasis Type="Italic">Terminalia arjuna</Emphasis> bark extract alleviates nickel toxicity by suppressing its uptake and modulating antioxidative defence in rice seedlings

Terminalia arjuna (Ta) bark contains various natural antioxidants and has been used to protect animal cells against oxidative stress. In the present study, we have examined alleviating effects of Ta bark aqueous extract against Ni toxicity in rice (Oryza sativa L.). When rice seedlings were raised for 8 days in hydroponics in Yoshida nutrient medium containing 200 μM NiSO₄, a decline in height, reduced biomass, increased Ni uptake, loss of root plasma membrane integrity, increase in the level of O₂˙^?, H₂O₂ and ˙OH, increased lipid peroxidation, decline in photosynthetic pigments, increase in the level of antioxidative enzymes superoxide dismutase, catalase and glutathione peroxidase and alterations in their isoenzyme profile patterns were observed. Transmission electron microscopy (TEM) showed damage to chloroplasts marked by disorganised enlarged starch granules and disrupted thylakoids under Ni toxicity. Exogenously adding Ta bark extract (3.2 mg ml^?1) to the growth medium considerably alleviated Ni toxicity in the seedlings by reducing Ni uptake, suppressing generation of reactive oxygen species, reducing lipid peroxidation, restoring level of photosynthesis pigments and ultrastructure of chloroplasts, and restoring levels of antioxidative enzymes. Results suggest that Ta bark extract considerably alleviates Ni toxicity in rice seedlings by preventing Ni uptake and reducing oxidative stress in the seedlings.     

Iron homeostasis in tropical <Emphasis Type="Italic">indica</Emphasis> rice (<Emphasis Type="Italic">Oryza sativa</Emphasis> L.) cultivars having contrasting grain iron concentration

Iron homeostasis was studied in two tropical indica rice cultivars viz. Sharbati (high Fe) and Lalat (low Fe) having contrasting grain Fe concentration. Plants were hydroponically grown with 5 concentrations of Fe (0.05, 2, 5, 15, 50 mg L^?1) till maturity. The effect of incremental Fe treatment on the plant was followed by analyzing accumulation of ferritin protein, activities of aconitase enzyme, enzymes of anti-oxidative defense and accumulation of hydrogen peroxide and ascorbic acid. Plant growth was adversely affected beyond 15 mg L^?1 of Fe supplementation and effects of Fe stress (both deficiency and excess) were more apparent on the high Fe containing cultivar Sharbati than the low Fe containing Lalat. Level of ferritin protein and aconitase activity increased up to 5 mg L^?1 of Fe concentration. Lalat continued to synthesize ferritin protein at much higher Fe level than Sharbati and the cultivar also had higher activities of peroxidase, superoxide dismutase and glutathione reductase. It was concluded that the tolerance of Lalat to Fe stress was because of its higher intrinsic ability to scavenge free radicals of oxidative stress for possessing higher activity of antioxidative enzymes. This, together with its capacity to sequester the excess Fe in ferritin protein over a wider range of Fe concentrations made it more tolerant to Fe stress.     

Silicon Alleviates Cadmium Toxicity in Two Cypress Varieties by Strengthening the Exodermis Tissues and Stimulating Phenolic Exudation of Roots

The aim of this work was to investigate the effect of silicon (Si) on phenolic exudation of plant roots and cadmium (Cd) bioavailability in rhizospheres. For this purpose, pot experiments with two cypress varieties, Juniperus chinensis and Platycladus orientalis, each subjected to 100 mg kg^?1 Cd and/or 400 mg kg^?1 Si for 220 days, were conducted using a rhizobag technique. The results showed that P. orientalis accumulated a higher amount of Cd, hence caused higher growth inhibition on the leaves compared with J. chinensis. Si alleviated the growth inhibition induced by Cd toxicity on both varieties, but the mechanisms involved were species specific. For J. chinensis, Si did not affect the root exudation but enhanced the Cd retention of the roots by strengthening the exodermis tissues, restraining Cd translocation from the roots to the shoots. For P. orientalis, Si exposure significantly elevated the phenolic exudation (for example, ferulic acid, catechin, and gallic acid) of the roots, which caused greater Cd mobility in the rhizosphere and enhancement of Cd accumulation in the shoots compared with Cd treatment alone. These results suggest that Cd-chelating with the Si-induced phenolics in the rhizosphere is involved in the Cd detoxification in P. orientalis.     

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.     

Effect of over-expression of <Emphasis Type="Italic">Linum usitatissimum</Emphasis> PINORESINOL LARICIRESINOL REDUCTASE (<Emphasis Type="Italic">LuPLR</Emphasis>) gene in transgenic <Emphasis Type="Italic">Phyllanthus amarus</Emphasis>

Shoot tip explants of Phyllanthus amarus were cocultivated with Agrobacterium tumefaciens strain LBA 4404 carrying plasmid pCAMBIA 2301 harbouring genes coding for betaglucuronidase (gus), kanamycin (kan), and neomycin phosphotransferase II (nptII) along with a gene coding for Linum usitatissimum PINORESINOL LARICIRESINOL REDUCTASE (Lu-PLR). Transformed shoot tip explants were maintained in a Murashige and Skoog (MS) medium containing TDZ 1.54 mg l^?1, kan 50 mg l^?1 and cephotaxime 62.5 mg l^?1. The optimum medium for regeneration of multiple shoots was MS supplemented with TDZ 1.54 mg l^?1, kan 50 mg l^?1. Efficient and effective rooting of plantlets was achieved by culturing the in vitro regenerated shoots on liquid ½ MS medium containing 0.7 mg l^?1 indole 3-butyric acid (IBA) and 5 mg l^?1 kan. Rooted plants were acclimatized in the mixtures of vermiculite and soil. The transformation of kan-resistant plantlets regenerated from shoot-tip explants was confirmed by GUS and polymerase chain reaction (PCR) analysis. Southern blot and reverse transcribed PCR (RT-PCR) analysis confirmed successful integration and expression of Lu-PLR gene. Quantitative analysis of phyllanthin performed on transgenic and wild plants using high-performance liquid chromatography (HPLC) revealed that transgenic lines contained higher phyllanthin content (0.3–0.81% w/w) than wild plants (0.09% w/w). The highest yield of phyllanthin was detected in transgenic lines was up to 1.16, 1.22 and 1.23 folds higher than that of wild plant. This report highlights the transgenic approach to enhance the contents of phyllanthin and hypophyllanthin.     

Alterations in photosynthetic pigments,protein, and carbohydrate metabolism in a wild plant <Emphasis Type="Italic">Coronopus didymus</Emphasis> L. (Brassicaceae) under lead stress

Coronopus didymus has been emerged as a promising wild, unpalatable plant species to alleviate lead (Pb) from the contaminated soils. This work investigated the hypothesis regarding various metabolic adaptations of C. didymus under lead (Pb) stress. In pot experiments, we assessed the effect of Pb at varied concentrations (500–2900 mg kg^?1) on growth, photosynthetic pigments, alteration of macromolecular (protein and carbohydrate) content, and activities of enzymes like protease, α-and β-amylase, peroxidase (POX), and polyphenol oxidase (PPO) in C. didymus for 6 weeks. Results revealed that Pb exposure enhanced the growth, protein, and carbohydrate level, but decreased the leaf pigment concentration and activities of hydrolytic enzymes. The activities of POX and PPO in roots increased progressively by ~337 and 675%, respectively, over the control, at 2900 mg kg^?1 Pb treatment. Likewise, contemporaneous findings were noticed in shoots of C. didymus, strongly indicating its inherent potential to cope Pb-induced stress. Furthermore, the altered plant biochemical status and upregulated metabolic activities of POX and PPO indulged in polyphenol peroxidation elucidate their role in allocating protection and conferring resistance against Pb instigated stress. The current work suggests that stress induced by Pb in C. didymus stimulated the POX and PPO activities which impart a decisive role in detoxification of peaked Pb levels, perhaps, by forming physical barrier or lignifications.     

Phycoremediation potential,physiological, and biochemical response of <Emphasis Type="Italic">Amphora subtropica</Emphasis> and <Emphasis Type="Italic">Dunaliella</Emphasis> sp. to nickel pollution

Metal pollution can produce many biological effects on aquatic environments. The marine diatom Amphora subtropica and the green alga Dunaliella sp. possess a high metal absorption capacity. Nickel (Ni) removal by living cells of A. subtropica and Dunaliella sp. was tested in cultures exposed to different Ni concentrations (100, 200, 300, and 500 mg L^?1). The amount of Ni removed by the microalgae increased with the time of exposure and the initial Ni concentration in the medium. The metal, which was mainly removed by bioadsorption to Dunaliella sp. cell surfaces (93.63% of total Ni (for 500 mg Ni L^?1) and by bioaccumulation (80.82% of total Ni (for 300 mg Ni L^?1) into Amphora subtropica cells, also inhibited growth. Exposure to Ni drastically reduced the carbohydrate and protein concentrations and increased total lipids from 6.3 to 43.1 pg cell^?1, phenolics 0.092 to 0.257 mg GAE g^?1 (Fw), and carotenoid content, from 0.08 to 0.59 mg g^?1 (Fw), in A. subtropica. In Dunaliella sp., total lipids increased from 26.1 to 65.3 pg cell^?1, phenolics from 0.084 to 0.289 mg GAE g^?1 (Fw), and carotenoid content from 0.41 to 0.97 mg g^?1 (Fw). These compounds had an important role in protecting the algae against ROS generated by Ni. In order to cope with Ni stress shown by the increase of TBARS level, enzymatic (SOD, CAT, and GPx) ROS scavenging mechanisms were induced.     

Over-expression of tobacco <Emphasis Type="Italic">UBC1</Emphasis> encoding a ubiquitin-conjugating enzyme increases cadmium tolerance by activating the 20S/26S proteasome and by decreasing Cd accumulation and oxidative stress in tobacco (<Emphasis Type="Italic">Nicotiana tabacum</Emphasis>)

Ubiquitin (Ub)-conjugating enzyme (UBC, E2) receives Ub from Ub-activating enzyme (E1) and transfers it to target proteins, thereby playing a key role in Ub/26S proteasome-dependent proteolysis. UBC has been reported to be involved in tolerating abiotic stress in plants, including drought, salt, osmotic and water stresses. To isolate the genes involved in Cd tolerance, we transformed WT (wild-type) yeast Y800 with a tobacco cDNA expression library and isolated a tobacco cDNA, NtUBC1 (Ub-conjugating enzyme), that enhances cadmium tolerance. When NtUBC1 was over-expressed in tobacco, cadmium tolerance was enhanced, but the Cd level was decreased. Interestingly, 20S proteasome activity was increased and ubiquitinated protein levels were diminished in response to cadmium in NtUBC1 tobacco. By contrast, proteasome activity was decreased and ubiquitinated protein levels were slightly enhanced by Cd treatment in control tobacco, which is sensitive to Cd. Moreover, the oxidative stress level was induced to a lesser extent by Cd in NtUBC1 tobacco compared with control plants, which is ascribed to the higher activity of antioxidant enzymes in NtUBC1 tobacco. In addition, NtUBC1 tobacco displayed a reduced accumulation of Cd compared with the control, likely due to the higher expression of CAX3 (Ca²⁺/H⁺ exchanger) and the lower expression of IRT1 (iron-responsive transporter 1) and HMA-A and -B (heavy metal ATPase). In contrast, atubc1 and atubc1atubc2 Arabidopsis exhibited lower Cd tolerance and proteasome activity than WT. In conclusion, NtUBC1 expression promotes cadmium tolerance likely by removing cadmium-damaged proteins via Ub/26S proteasome-dependent proteolysis or the Ub-independent 20S proteasome and by diminishing oxidative stress through the activation of antioxidant enzymes and decreasing Cd accumulation due to higher CAX3 and lower IRT1 and HMA-A/B expression in response to 50 µM Cd challenge for 3 weeks.     

CAT and MDH improve the germination and alleviate the oxidative stress of cryopreserved <Emphasis Type="Italic">Paeonia</Emphasis> and <Emphasis Type="Italic">Magnolia</Emphasis> pollen

Researches have reported that reactive oxygen species (ROS)-induced oxidative stress plays an important role in cell cryodamage during cryopreservation. In the current study, pollen from Magnolia denudata and Paeonia lactiflora ‘Zi Feng Chao Yang’ was cryopreserved and incubated with exogenous catalase (CAT) and malate dehydrogenase (MDH) immediately after thawing. The effect of CAT and MDH on the germination of cryopreserved pollen was measured. Based on that, the ROS level, lipid peroxidation and antioxidants activities in fresh pollen, cryopreserved pollen added with or without CAT or MDH were determined to investigate their relationship with oxidative stress. Pollen from Magnolia and Paeonia showed a significant loss of germination, but marked increase of ROS and malondialdehyde (MDA) production after cryostorage. Antioxidant profiles in them were also enhanced. CAT and MDH addition increased the post-LN pollen germination of Magnolia and Paeonia significantly. Their germination rate achieved the highest with 100 IU ml^?1 MDH and 400 IU ml^?1 CAT application, respectively. Compared to their untreated controls, ROS and MDA accumulation reduced significantly in cryopreserved Magnolia pollen treated with 100 IU ml^?1 MDH, while superoxide dismutase (SOD) activity improved markedly. In the case of Paeonia, significantly lower level of ROS and MDA, but higher activity of CAT and SOD were observed in cryopreserved pollen treated with 400 IU ml^?1 CAT. In conclusion, pollen deterioration after cryopreservation is associated with ROS-induced oxidative stress. Exogenous CAT and MDH can reduce the oxidative damage through the activity stimulation of antioxidant enzymes, and play a protective role in the pollen during cryopreservation.     

Cadmium induced oxalic acid secretion and its role in metal uptake and detoxification mechanisms in <Emphasis Type="Italic">Phanerochaete chrysosporium</Emphasis>

This study examines the role of oxalic acid in the uptake of Cd and participation in detoxification process in Phanerochaete chrysosporium. Cd-induced oxalic acid secretion was observed with growth inhibition and enzyme inactivation (LiP and MnP) of P. chrysosporium. The peak value of oxalic acid concentration was 16.6 mM at initial Cd concentration of 100 mg L^?1. During the short-term uptake experiments, the uptake of Cd was enhanced and accelerated in the presence of oxalic acid and resulted in alleviated growth and enzyme inhibition ratios. The formation of a metal-oxalate complex therefore may provide a detoxification mechanism via effect on metal bioavailability, whereby many fungi can survive and grow in environments containing high concentrations of toxic metals. The present findings will advance the understanding of fungal resistance to metal stress, which could show promise for a more useful application of microbial technology in the treatment of metal-polluted waste.     

Efficacy of plants extracts from the Cerrado against adult female of <Emphasis Type="Italic">Dermacentor nitens</Emphasis> (Acari: Ixodidae)

Dermacentor nitens tick is commonly found in the equine auditory canal, where it causes economic losses due to its direct damage, causing blood spoliation, stress, transmission of pathogens, and predisposition to myasis and secondary bacterial infection in its hosts. In this study we evaluated the effect of ethanolic extracts of Cerrado plants on biological parameters of engorged females of D. nitens. Ethanolic extracts were prepared from the leaves of Schinopsis brasiliensis, Piptadenia viridiflora, Ximenia americana, and Serjania lethalis at 25–150 mg mL^?1. Groups of 10 engorged adult females were treated with these extracts and compared with a control containing distilled water and another control with organophosphate, using five replicates for each group. Compared with the control with water, S. lethalis and X. americana extracts at 100 and 150 mg mL^?1 significantly inhibited the posture ability. Differently, extracts of S. brasiliensis and P. viridiflora were the most effective in inhibiting larval hatching. Extracts of X. americana and P. viridiflora showed effective inhibition of reproductive parameters of the tick, presenting dose-dependent effect with IC₉₀ 78.86 and 78.94 mg mL^?1, respectively. Theses effective extracts contained low condensed tannin levels and their HPLC chromatograms revealed the presence of flavonoids. The efficacies of P. viridiflora and X. americana extracts were higher than 90% indicating that these extracts are promising as alternative agents for D. nitens control.     

Interactive effects of soil salinity and boron on growth,mineral composition and CO<Subscript>2</Subscript> assimilation of pistachio seedlings

Pistachio is a tree of the arid and semi-arid regions where salinity and boron (B) toxicity can be major environmental stresses. In this study, individual and combined effects of different concentrations of NaCl (0, 800, 1600, 2400 and 3200 mg kg^?1 soil) and B (0, 2.5, 5.0, 10.0 and 20.0 mg kg^?1 soil) were studied on growth, gas-exchange and mineral composition of pistachio seedlings for a duration of 120 days. Excess amounts of salinity (> 1600 mg NaCl kg^?1 soil) and B (20.0 mg kg^?1 soil) significantly reduced the plant growth and CO₂ assimilation, which was associated with accumulation of Na, Cl and B in leaves. There was also a decline in cell membrane stability index (MSI). Reduced stomatal conductance (g _s) was the primary cause of inhibition of photosynthesis rate (P _N) under mild to moderate salinity. However, under severe salt stress and B toxicity, non-stomatal effects contributed to the inhibition of CO₂ assimilation in addition to the decline in g _s value. Application of 5.0–10.0 mg B kg^?1 soil significantly improved the plant growth and P _N and also recovered the MSI as countermeasures against salt stress. These observations were related to the role of B in cell membrane structure and functioning which reduced the concentration of toxic ions in the leaves. However, cell membrane damages and chlorophyll loss in plants affected by salt were observed to be exacerbated when excess amounts of B were present. In conclusion, the results revealed that optimizing the B nutrition can improve the performance of pistachio seedlings under salt stress, and NaCl also showed a mitigating effect on B toxicity if its concentration in the soil is kept under the plant salt tolerance threshold.     

Shrub Expansion of <Emphasis Type="Italic">Alnus viridis</Emphasis> Drives Former Montane Grassland into Nitrogen Saturation

The N₂-fixing shrub Alnus viridis is currently encroaching on montane grasslands in the Alps as a result of reduced land management and complete abandonment. Alnus introduces large amounts of nitrogen (N) into these formerly N-poor grasslands and restricts the succession to montane forests. We studied pools and fluxes of N and the associated C pools in pastures (controls) and adjacent Alnus shrublands at two elevations (1650 versus 1950 m a.s.l.) in three valleys in the Swiss central Alps. The total N and C pools stored in 50-year-old Alnus shrubland did not exceed those in adjacent pastures with a total of approximately 610 g N m^?2 in phytomass plus soil (down to 30 cm) at both elevations. In Alnus stands, reduced soil N pools balanced the gain in phytomass N pools, a likely result of a faster turnover of soil N. The soil solution under Alnus was continuously enriched with nitrate, with a total N leaching of 0.79 g N m^?2 season^?1 (June–October) under 50-year-old stands at both elevations and the highest flux of 1.76 g N m^?2 season^?1 in 25-year-old shrubland at low elevation, clearly indicating an excess of available N in Alnus shrubland. In contrast, N leaching across all pastures was close to zero (0.08 g N m^?2) throughout the season. At the catchment scale, streamlet water showed increased nitrate concentrations with typical flushing peaks in spring and autumn, provided more than one fifth of the catchment area was covered by Alnus shrubs. We conclude that the expansion of Alnus rapidly converts centuries-old, N-poor grassland into N saturated shrubland, irrespective of elevation, and it reduces the C storage potential of the landscape because the Alnus dominance constrains re-establishment of a natural montane forest.     

Micropropagation, <Emphasis Type="Italic">in vitro</Emphasis> flowering,and tuberization in <Emphasis Type="Italic">Brachystelma glabrum</Emphasis> Hook.f., an endemic species

Brachystelma glabrum Hook.f. is an endemic plant species of Eastern Ghats, India. In this study, efficient protocols for in vitro micropropagation, flowering, and tuberization of this plant were developed. Sterilized shoot tip and nodal explants were cultured on Murashige and Skoog (MS) medium supplemented with different plant growth regulators (PGRs) and additives for shoot induction and multiplication. Both shoot tip and nodal explants showed the best response (90 and 100%, respectively) on MS medium supplemented with thidiazuron (TDZ) at 1.0 mg L^?1. The microshoots multiplied best on MS + TDZ (1.0 mg L^?1) in combination with α-naphthaleneacetic acid (NAA) at 0.5 mg L^?1 and coconut water (CW) at 25%. The highest number of in vitro flowers (4.0 flowers per microshoot) was observed on MS medium supplemented with a combination of N6-benzyladenine (BA) and indole-3-butyric acid (IBA), each at 1.5 mg L^?1. In vitro-derived shoots produced aerial tubers on MS + TDZ (2.0 mg L^?1) + IBA (0.5 mg L^?1) and basal tubers on MS + TDZ at 2.0 mg L^?1. In vitro shoots were best rooted on half-strength (½) MS + NAA at 0.5 mg L^?1. The rooted plantlets were successfully acclimatized in pots with 70% survival after a hardening period of 1 mo. This protocol provides an effective method for the conservation of this endemic plant species.     

Integrated control of tobacco black shank by combined use of riboflavin and <Emphasis Type="Italic">Bacillus subtilis</Emphasis> strain Tpb55

We investigated the effect of riboflavin on the biocontrol activity of Bacillus subtilis Tpb55 against Phytophthora nicotianae (Pn), which causes tobacco black shank. Riboflavin (0.2 mg ml^?1) significantly improved the biocontrol activity of Tpb55 (2.0 × 10⁸ cfu ml^?1). Riboflavin (0.02–0.5 mg ml^?1) alone could not significantly inhibit Pn growth. However, it enhanced the B. subtilis population, both in vitro and in tobacco roots and significantly increased the activity of defense enzymes, peroxidase, catalase, superoxide dismutase, and β-1,3-glucanase, in the roots of B. subtilis-treated tobacco seedlings. Our results indicate that riboflavin can stimulate the growth of B. subtilis Tpb55 and induce resistance to Pn in tobacco plants. These findings should boost the prospects for practical application of B. subtilis Tpb55 as a biocontrol agent against black shank of tobacco.     

Potential Outdoor Cultivation of Green Microalgae Based on Response to Changing Temperatures and by Combining with Air Temperature Occurrence

In this study, our working hypothesis was to examine whether temperature alters biomass and metabolite production by microalgae according to strain. We also addressed whether it is possible to choose a strain suitable for growing in each season of a given region. A factorial experiment revealed a significant interaction between chlorophylls a and b (Chl a and Chl b), carotenoid/Chl (a?+?b) ratio, biomass and total lipid productivity of six green microalgae (four Chlorella spp., Chlorella sorokiniana and Neochloris oleoabundans) after 15 days at four temperatures. At 39/35 °C, two Chlorella sp. strains (IPR7115 and IPR7117) showed higher total carotenoids/Chl (a?+?b) (0.578 and 0.830), respectively. N. oleoabundans had the highest Chl a (8210 μg L^?1) and Chl b (1909 μg L^?1) at 19/15 °C and highest maximum dry biomass (2900 mg L^?1), specific growth rate (0.538 day^?1) and total lipids (1003 mg L^?1) at 15/8 °C. We applied a method to infer the growth of these six green microalgae in outdoor ponds, as based on their response to changing temperatures and by combining with historical data on day/night air temperature occurrence for a given region. We conclude that the use of regionalized maps based on air temperature is a good strategy for predicting microalgal cultivation in outdoor ponds based on their features and tolerance to changing temperature.     

Endoplasmic reticulum stress and calcium imbalance are involved in cadmium-induced lipid aberrancy in <Emphasis Type="Italic">Saccharomyces cerevisiae</Emphasis>

The endoplasmic reticulum is the key organelle which controls protein folding, lipid biogenesis, and calcium (Ca²⁺) homeostasis. Cd exposure in Saccharomyces cerevisiae activated the unfolded protein response and was confirmed by the increased Kar2p expression. Cd exposure in wild-type (WT) cells increased PC levels and the PC biosynthetic genes. Deletion of the two phospholipid methyltransferases CHO2 and OPI3 modulated PC, TAG levels and the lipid droplets with cadmium exposure. Interestingly, we noticed an increase in the calcium levels upon Cd exposure in the mutant cells. This study concluded that Cd interrupted calcium homeostasis-induced lipid dysregulation leading to ER stress.     

Effects of a combined use of macronutrients nitrate,ammonium, and phosphate on cadmium absorption by <Emphasis Type="Italic">Egeria densa</Emphasis> Planch. and its phytoremediation applicability

Phosphorus and nitrogen fertilizers represent a source of cadmium (Cd) which may be leached into aquatic systems. Macrophytes accumulate contaminants, and Egeria densa has been shown to grow in aquatic environments polluted with trace elements. In this study, Cd accumulation by E. densa exposed to two Cd treatments (3 and 5 mg L^?1) was evaluated under increasing nutrient levels (NP as N–NO₃ ^?, N–NH₄ ⁺, and P–PO₄ ^3?, in concentrations 5-, 10- and 100-fold higher (NP₅, NP₁₀ and NP₁₀₀) than in the sampling site) to simulate different levels of eutrophication. Bioaccumulation factors and Cd recovery were calculated and effects on plants were evaluated based on chloroplastidic pigment concentrations (chlorophylls a and b, and carotenoids). We conclude that Cd accumulation by Egeria densa is positively influenced by increasing availability of N and P at the level of around NP₁₀ and probably at a broader concentration range not defined in this study. A further increase in N and P, however, does not generate a significant increase in Cd accumulation. Chloroplastidic pigment concentrations were not linearly correlated with Cd accumulation and the NP₁₀ experiment produced less damage to macrophyte when compared to NP₅ and NP₁₀₀ experiments. Under controlled conditions, it was possible to satisfactorily model Cd bioaccumulation over time, in order to provide essential data for E. densa use in phytoremediation processes. The Cd residence in the macrophyte tissue is increased in eutrophic environments, which puts at risk the whole food chain of the aquatic ecosystem, mainly the primary consumers.