Bacterial blight pathogen concentration in cotton seeds; its role in seed quality parameters of fuzzy and acid delinted seeds

Abstract

The adverse effects of increasing concentration of Xanthomonas axonopodis pv. malvacearum on cotton seed quality parameters, seedling dry weight and on defense-related enzyme, Phenylalanine Ammonia Lyase (PAL) were studied. Different concentrations of pathogen (1×10² to 1×10⁸ CFU/ml) were treated on both fuzzy and acid delinted seeds and subjected to the standard blotter method to study the effect of the pathogen on seed quality parameters. The seedling symptom test following the roll towel method, the modified germination test to study the blight incidence and the field emergence test were carried out to discover the field planting value and disease incidence under laboratory and field conditions. From these experiments, it was found that the decrease in the seed quality parameters like seed germination, seedling vigour, and the dry weight of seedlings when X. axonopodis pv. malvacearum concentration was increased. Whereas the bacterial blight incidence increased with an increase in pathogen concentration, in both greenhouse and field conditions. Phenylalanine ammonia lyase activity was found to increase along with the pathogen concentrations, but total phenol content decreased as pathogen concentration increased. The effect of X. axonopodis pv. malvacearum load on seed quality parameters, PAL enzyme activity of fuzzy and acid delinted cotton seeds are discussed in the present study.     

Eucalyptus urograndis and Pinus taeda enhance removal of chlorobenzene and benzene in sand culture: A greenhouse study

Contamination of soils and groundwater by chlorobenzene and benzene is a common problem at industrial sites worldwide. Since chemical remediation techniques are rarely completely effective, remnants of these contaminants often persist at levels that can still influence ecosystem health. We evaluated the potential of Pinus taeda and Eucalyptus urograndis to accelerate the removal of these compounds from sand/water systems using a completely randomized block greenhouse experiment with a no-plant control. At 2-day intervals, we added a solution containing both chlorobenzene and benzene with the same concentration of 50 mg L^?1 (25 mg pot^?1), and we monitored leachate concentrations daily. The planted treatments showed greater decrease of contaminants over time. In the absence of plants, the contaminant mass decreased 50–60% during each 2-day cycle; whereas, in the planted treatments the contaminant mass decreased 91–98%. At the end of the experiment the plant roots, leaves, and the sand-substrate each contained less than 1 mg kg^?1 of contaminants, which is ～1% of the total contaminant mass added. In addition, we observed no tree mortality even at concentrations exceeding the aqueous solubility limit of both compounds. Our results suggest both trees are good candidates for remediating chlorobenzene and benzene in soils and groundwater.     

Effect of hot water and ultra violet radiation on the incidence of seedborne fungi of okra

Seed samples of okra (Abelmoschus esculentus (L.) Moench) variety Arka anamika were subjected to hot water treatment at 42, 52 and 62°C for a period of 30 min and UV light treatment for 10, 20, 30 min at 28 ± 2°C. Their efficacy was tested against some seedborne fungal species. Among them, seeds under hot water treatment at 52°C for 30 min and UV light at 20 min were found to be more effective in the improvement of crop, both in greenhouse and field conditions. Ultimately, there was increase in the total number of leaves, fruits, length of the fruit, girth and biomass of the plants. Apart from these the total number of seeds per fruit, 1000 seed weight and ascorbic acid content were also found to be enhanced. These treatments also reduced the incidence of mycoflora in the seeds and thereby enhanced the seed germination percentage and vigour index of the seedlings.     

Enhancing of Phytoremediation Efficiency Using Indole-3-Acetic Acid (IAA)

In this study, a pot experiment using Solanum nigrum L. grown in cadmium-contaminated soil was conducted in a greenhouse. Indole-3-acetic acid (IAA) was applied at three different concentrations (1 mg L^?1, 10 mg L^?1, and 100 mg L^?1) to examine the effects on phytoremediation efficiency. According to the experimental results, IAA increased the shoot biomass of S. nigrum significantly, by 124% at the highest concentration used, and increased the Cd concentration in the shoot of S. nigrum by 16%. The Cd extraction amount from a single plant was increased by up to 158%, demonstrating potential practical application for remediation practice.     

Controlling grey and blue mould diseases of apple fruits using acetic acid vapours

Abstract

The effect of acetic acid vapours at three application times on grey and blue moulds on the incidence of apple fruits was studied. Acetic acid vapour at 6 µl/l caused complete inhibition of linear growth and spore germination of Botrytis cinerea and Penicillium sp. The most effective concentration was AA at 4 µl/l, which reduced spore germination and linear growth by more than 82.4 and 68.3% of both fungi respectively compared with un-fumigated fungi. On other trials the diameter of the inhibited growth zone of both fungi gradually increased as AA concentrations increased. The highest increase in inhibition zone diameter was obtained with AA at 12 µl/l followed by AA at 8 µl/l, meanwhile AA at 4 µl/l had a moderate effect. Apple fruits were divided into three groups, the first was fumigated at 24 h before inoculation, the second at zero time the and third at 24 h after inoculation and storage for 30 days. Results indicate that the higher reduction of grey and blue mould incidence was obtained with AA at 12 µl/l of three application times which reduced the disease incidence by more than 81.0, 81.0 and 73.5% before, at zero time and after inoculation, respectively. Acetic acid at 8 µl/l reduced the incidence of both diseases more than 52.0% with all application times. As for application times the most effective times were 24 before and at the zero time of inoculation which reduced both diseases more than 81.0 and 75.5 with AA vapours at 12 and 8 µl/l, respectively. Meanwhile treated apple fruits after inoculation was less effective. The same trend between disease incidence and percentage of rotted tissue parts was observed. It could be suggested that acetic acid vapours might be safely used commercially for controlling post-harvest disease of apple fruits during storage.     

STRESS MODIFICATION OF ALLELOPATHY OF HELIANTHUS ANNUUS L. DEBRIS ON SEED GERMINATION

Helianthus annuus L. variety “Russian Mammoth” was grown in pots, in both the greenhouse and the field, under density treatments of 1, 3, 6 or 12 plants per pot and nutrient treatments of full-strength, ½, ¼, ⅛ or 1/16 strength Hoagland's solution. The plants responded in typical fashion to both nutrient and density stress. Within each nutrient treatment, as the density of planting increased, biomass per pot first increased and then leveled off while biomass per plant decreased. Within each density treatment, as the nutrient level decreased, biomass per pot and per plant decreased. Therefore, both nutrient and density treatments imposed a stress (measured as a reduction in biomass) on individual H. annuus plants. Total phenolic compounds from the Helianthus annuus tissue, expressed as chlorogenic acid equivalents and determined by the PVP method, increased with increasing nutrient stress (i.e., lower nutrient availability); however, increasing density stress failed to significantly modify total phenolic compounds. The maximum total phenolic level determined for field-grown plants (69.70 mg g^-1 tissue) was approximately 58% greater than that found for greenhouse-grown plants (44.16 mg g^-1 tissue). When coarsely ground H. annuus plant material from the stress studies was added to soil, there was a significant depressive effect on germination of Amaranthus retroflexus seeds. In these germination was more closely correlated with total phenolic compounds (chlorogenic acid equivalents) added to the soil by the debris than with any other variable measured. Correlations were best for phenolic values of 200 μg g^-1 soil or greater. Chlorogenic acid (an abundant phenolic acid present in H. annuus) did not inhibit A. retroflexus seed germination when added to soil in pure form. The addition of a nutrient solution to soil containing H. annuus debris reduced subsequent inhibition of A. retroflexus seed germination.     

Changes in western wheatgrass foliage quality following defoliation: consequences for a graminivorous grasshopper

We determined the effects of defoliation by a graminivorous grasshopper on the foliage quality of the C3 plant, western wheatgrass (Pascopyrum smithii [Rydb] A. Love). Additionally, we determined the effects of this defoliation upon the subsequent feeding of the graminivorous grasshopper Phoetaliotes nebrascensis Thomas (Orthoptera: Acrididae). In field and greenhouse studies, graminivorous grasshopper herbivory altered the quality of remaining western wheatgrass foliage. In the greenhouse, severe (50% foliage removal) grasshopper grazing (638 grasshoppers/m² for 72h) resulted in decreased foliar nitrogen (–12%), carbohydrate (–11%) and water (–2.5%) concentrations, and increased phenolic concentrations (+43%). These changes were associated with decreased adult female grasshopper mass gain, consumption rate, approximate digestibility, and food conversion efficiencies. In the field, moderate (14% foliage removal) grasshopper grazing (20 grasshoppers/m² for 20 days) led to a 10% reduction in foliar nitrogen concentrations. Foliage quality changes in the field were not associated with any reductions in grasshopper mass gain, consumption rates, food digestibility, or conversion efficiencies. The results presented here are consistent with the hypothesis that defoliation leads to a reallocation of carbon and nitrogen compounds within the plant such that foliage quality for P. nebrascensis is reduced.     

Efficacy of Boric Acid,Monopotassium Phosphate and Sodium Metabisulfite on the Control of Apple Scab

In vitro experiments indicated that boric acid, monopotassium phosphate, sodium metabisulfite and synthetic fungicide fluopyram + tebuconazole were effective in inhibiting conidia germination and germ‐tube elongation of Venturia inaequalis. Monopotassium phosphate even at the highest concentration used in the study reduced conidia germination and germ‐tube elongation of V. inaequalis by 22.1% and 28.8%, respectively; however, the difference between two compounds at lower concentrations except 0.05% (for conidia germination) and 0.1% (for germ‐tube elongation) of boric acid was statistically significant (P ≤ 0.05). Complete inhibition was achieved by 0.01% sodium metabisulfite, 0.035% fluopyram + tebuconazole and 0.2% boric acid. Two orchard trials were conducted on the highly susceptible cv. Mutsu to apple scab to ascertain the efficacy of 0.2% boric acid, 0.5% monopotassium phosphate, 0.5% sodium metabisulfite and 0.035% fluopyram + tebuconazole for the control of apple scab. In both 2013 and 2014, except for the applications of monopotassium phosphate and sodium metabisulfite, the applications of boric acid and fluopyram + tebuconazole to trees at 10‐day intervals significantly reduced disease incidence and severity on leaves and fruit compared to the water‐treated control. In both years, the efficacy of boric acid and fluopyram + tebuconazole treatments was similar in reducing both disease incidence and severity on leaves and fruit in all monthly assessments from July to September. All treatments were neither phytotoxic to leaves and fruit nor did they adversely affect quality parameters of harvested fruit. These results show that boric acid treatment may be applied as an alternative chemical for the control of apple scab.     

南美天胡荽及其根际土壤水浸提液化感成分分析

为探讨南美天胡荽对其他植物种子萌发的影响以及筛选影响其他植物的主要化合物,该文采用种子萌发试验、气相色谱-质谱联用以及液相色谱-质谱联用的方法,分析了南美天胡荽不同溶剂浸提液对种子萌发的影响、南美天胡荽植株及其根际土壤浸提液成分。结果表明:(1)南美天胡荽不同溶剂浸提物均具有一定程度的抑制种子萌发作用。(2)气相色谱-质谱分析下,南美天胡荽植株水浸提液中共分离鉴定了35种化合物,其中,邻苯二甲酸二丁酯(15.2%)、10,15-十八烷二元酸(8.58%)、2,4-二叔丁基苯酚(6.81%)相对含量最高; 根际土壤水浸提液中共分离鉴定了17种化合物,其中,油酸酰胺(26.47%)、正二十七烷(9.63%)、十六酸乙酯(4.83%)相对含量最高。(3)液相色谱-质谱分析下,南美天胡荽植株水浸提液共分离鉴定了109种化合物,ESI⁺模式下,L-苯丙氨酸(3 483.99 ng·mg^-1)、木犀草素(2 306.64 ng·mg^-1)含量最多,ESI^-模式下,右旋奎宁酸(21 827.71 ng·mg^-1)、绿原酸(12 589.25 ng·mg^-1)含量最多; 根际土壤水浸提液中共分离鉴定了93种化合物,ESI⁺模式下,丁酸(7 660.53 ng·mg^-1)、棕榈酰胺(3 200.36 ng·mg^-1)含量最多,ESI^-模式下,正二十八酸(18 605.35 ng·mg^-1)、蔗糖(12 183.23 ng·mg^-1)含量最多。(4)南美天胡荽的潜在化感物质主要为脂肪酸类、酰胺类、酯类、芳香酸类化合物,而土壤中直接起化感作用的物质可能为丁酸、正二十八酸、羟基乙酸、油酸酰胺、棕榈酰胺、十六酸乙酯、苯甲酸,其中脂肪酸类化合物输入可能来源于南美天胡荽、土壤微生物和土壤动物,酰胺类、酯类、芳香类化合物则更可能来源于南美天胡荽植株。     

Foliar application of l-phenylalanine and ferulic acids to pea plants: induced phenylalanine ammonia lyase activity and resistance against Erysiphe pisi

Phenylalanine ammonia lyase (PAL) activity was measured using HPLC in pea leaves following exogenous application of l-phenylalanine and ferulic acid. Treatment with different concentrations (50, 100 and 150 ppm) of l-phenylalanine caused increased activity of PAL in comparison to the control. In pea leaves treated with 50 ppm l-phenylalanine, maximum PAL activity was observed after 72 h of treatment. Application of ferulic acid first reduced PAL activity at lower concentration (50 ppm) but increased at higher concentrations of the compound (100 and 150 ppm) in pea leaves as compared to the control. Maximum PAL activity was 0.19 nM cinnamic acid/min/g fresh wt. after 24 h at 50 ppm and then increased with time. Treatment with both the compounds significantly reduced conidial germination of Erysiphe pisi on pea leaves. They were equally effective at 100 and 150 ppm in reducing conidial germination. The conidial germination on l-phenylalanine-treated leaves was 26% after 24 h and that on ferulic acid-treated leaves was 34% as compared to the control (46%). Foliar application of different concentrations of l-phenylalanine increased the level of ferulic acid in the leaves of pea plants. Maximum accumulation of ferulic acid (79.3 and 83.5 μg/g fresh wt.) was observed following the application of l-phenylalanine after 24 h and 48 h, respectively. At 50 ppm, ferulic acid accumulation in pea leaves was 35.6 and 39.4 μg/g fresh wt. and 74.3 and 86.5 μg/g fresh wt. at 100 ppm.     

Exogenous application of rutin and gallic acid regulate antioxidants and alleviate reactive oxygen generation in <Emphasis Type="Italic">Oryza sativa</Emphasis> L.

The effect of rutin and gallic acid on growth, phytochemical and defense gene activation of rice (Oryza sativa L.) was investigated. The seeds of rice were primed with different concentrations of rutin and gallic acid (10–60 µg mL^?1) to explicate the effect on germination on water agar plates. Further, to study the effect of most effective concentrations of gallic acid (60 µg mL^?1) and rutin (50 µg mL^?1), greenhouse pot experiment was set up to determine the changes in growth, antioxidant and defense parameters. The results revealed more pronounced effect of gallic acid on total chlorophyll and carotenoids as well as on total flavonoid content and free radical scavenging activities. Gene expression analysis of OsWRKY71, PAL, CHS and LOX genes involved in strengthening the plant defense further validated the results obtained from the biochemical analysis. Microscopic analysis also confirmed reduction in total reactive oxygen species, free radicals like H₂O₂ and O₂ ^? by exogenous application of gallic acid and rutin. The data obtained thus suggest that both gallic acid and rutin can affect the growth and physiology of rice plants and therefore can be used to develop effective plant growth promoters and as substitute of biofertilizers for maximizing their use in field conditions.     

In vitro antifungal activity and mode of action of selected polyphenolic antioxidants on Botrytis cinerea

Six selected antioxidants (catechin, quercetin-3-galactoside, cyanidin-3-glucoside, pelargonidin-3-glucoside, ellagic and gallic acids) were evaluated in vitro for their antifungal activities and mode of action on Botrytis cinerea Pers., one of the most important pathogens of strawberries. Inhibitory effects were found for all the tested antioxidants, but varied at different fungal developmental stages. Catechin and quercetin-3-galactoside showed linear inhibitory effects on germ tube elongation, with the highest suppression ratios of 54.8% and 58.8% respectively. No significant effect was found on spore germination between treatments and control. Gallic acid showed very strong and linear inhibition on spore germination (r = ?0.95), but the effect diminished after spore germination. Cyanidin-3-glucoside and pelargonidin-3-glucoside provided effective control on the fungi as concentrations increased. The arresting effect of ellagic acid on development of B. cinerea was quadratic. Ellagic acid inhibited germ tube elongation and mycelial growth at its highest and lowest concentrations, while no effects were observed at its medium concentration used in this study.     

Exogenous application of L-phenylalanine and ferulic acid enhance phenylalanine ammonia lyase activity and accumulation of phenolic acids in pea (Pisum sativum) to offer protection against Erysiphe pisi

Phenylalanine ammonia lyase (PAL) activity was measured using HPLC in pea leaves following exogenous application of L-phenylalanine and ferulic acid. Treatment with different concentrations (50, 100, 150 ppm) of L-phenylalanine caused increased activity of PAL activity in comparison to control. In pea leaves treated with 50 ppm L-phenylalanine, maximum PAL activity was observed after 72 h of treatment. Application of ferulic acid first reduced PAL activity at lower concentration (50 ppm) but it further increased at higher concentrations of the compound (100 and 150 ppm) in pea leaves compared to control. Minimum PAL activity was 0.19 nM cinnamic acid/min/g fresh wt after 24 h at 50 ppm and then increased with time. Treatment with both compounds significantly increased the accumulation of phenolic acids and salicylic acid and reduced conidial germination of Erysiphe pisi on pea leaves. They were equally effective at 100 and 150 ppm in reducing conidial germination. Conidial germination on L-phenylalanine-treated leaves was 26% after 24 h and that on ferulic acid treated leaves 34% compared to control (46%). Foliar application of different concentrations of L-phenylalanine increased the level of ferulic acid in the leaves of pea plants. Maximum enzyme activity in terms of the accumulation of cinnamic acid (79.3 and 83.5 μg/g fresh wt) was observed following the application of L-phenylalanine after 24 and 48 h respectively. At 50 ppm, cinnamic acid accumulation in pea leaves was 35.6 and 39.4 μg/g fresh wt and 74.3 and 86.5 μg/g fresh wt at 100 ppm.     

Tree fine root Ca/Al molar ratio – Indicator of Al and acidity stress

Many Aloe species are exploited as natural products. Generally, the leaves are unsustainably picked from wild plants to meet the market demand. Basic scientific information on seed biology and the ways of increasing levels of secondary metabolites in seedlings is still lacking for Aloe species. This study investigated seed germination requirements and evaluated levels of secondary metabolites in seedlings of Aloe arborescens, an important species in traditional medicine. The highest percentage germination (78%) and the fastest germination rate (GR) (10% d^? 1) with a mean germination time (MGT) of 9 days were achieved at 20°C under a 16-h photoperiod. At 25°C, maximum percentage germination (67%) (P < 0.05), higher GR (13% d^? 1) and shorter MGT (6 days) were obtained under constant light. These results indicate that temperature and light play a significant role in germination of A. arborescens seeds. Increasing osmotic pressure on seeds decreased percentage germination, whereas buffering the solution to a range of pH values (4–10) did not significantly affect germination. Smoke–water (1:500 v/v), smoke-isolated karrikinolide (10^? 8 and 10^? 9 M) and potassium nitrate (10^? 3 and 10^? 4 M) significantly promoted germination compared with the control at 25°C (supra-optimal temperature) under a 16-h photoperiod. These treatments were also effective in increasing secondary metabolite levels (flavonoids and phenolics) in A. arborescens seedlings.     

Exploiting medicinal plants and phylloplane microflora for the management of grapevine downy mildew

Abstract

Grapevine downy mildew is the most devastating disease throughout the world causing huge monetary losses. Twenty medicinal plant extracts and six phylloplane microfloras were evaluated for their efficacy against sporangial germination of grapevine downy mildew pathogen Plasmopara viticola in vitro. The results revealed that the Neem Seed Kernel Extract (NSKE) at 5% significantly inhibited the sporangial germination (75.36%) of P. viticola. Among the phylloplane microflora Pseudomonas fluorescens was highly effective in reducing the sporangial germination (64.26%). Post inoculation spraying of NSKE (5%) and P. fluorescens (0.2%) effectively inhibited the disease development in the greenhouse. Three sprays with NSKE (5%) and phylloplane P. fluorescens (0.2%): first spray after initial appearance of disease and the second and third at 10 day intervals were found to be promising in reducing disease incidence in the field.     

Isolation of antifouling compounds from the marine bacterium, <Emphasis Type="Italic">Shewanella oneidensis</Emphasis> SCH0402

Two compounds, 2-hydroxymyristic acid (HMA) and cis-9-oleic acid (COA), were isolated from a chloroform extract of the marine bacterium, Shewanella oneidensis SCH0402. In a spectrophotometer-based chemotaxis assay, HMA completely eliminated the optical density (OD) of Alteromonas marina SCH0401 and Bacillus atrophaeus SCH0408, motile, fouling bacteria, at 100 and 1000 μg ml⁻¹, respectively. COA similarly decreased the OD of A. marina and B. atrophaeus by 100% at 1000 μg ml⁻¹. The commercially available, highly toxic anti-fouling compound, tributyltin oxide (TBTO) never reduced the OD of the target bacteria by 100% even at higher concentration. Instead, all the test bacterial cells were killed at higher than 1000 μg ml⁻¹ of concentration. Both HMA and COA inhibited germination of Ulva pertusa spores completely at 10 and 100 μg ml⁻¹, respectively, while TBTO inhibited germination at 0.01 μg ml⁻¹. However, in field assays, both HMA and COA showed anti-fouling activities as potent as TBTO against a wide range of fouling organisms, including micro- and macro-algae, barnacles, and mussels. The average fouling coverage on the surface of the control panel was 93 ± 6% after 1.5 years but no fouling was observed on the surface of the test panel onto which each compound was applied separately. Thus, bacterial repellent compounds can be used as substitutes for potent toxic anti-fouling compounds, resulting in higher standards of environmental safety without loss of anti-fouling performance.     

Improved somatic embryogenesis in wheat by partial simulation of the in-ovulo oxygen,growth-regulator and desiccation environments

The effects of O₂, growth-regulators and desiccation on callus growth and somatic embryo (embryoid) development were investigated in cultures of immature embryos of two lines of Triticum aestivum L. Callus and embryoid formation were induced on media that contained N⁶-furfurylamin-opurine (kinetin) and either 2,4-dichlorophenoxyacetic acid or 3,6-dichloro-o-anisic acid, either with or without abscisic acid (ABA). Cultures containing differentiated embryoids were then exposed to high concentrations of both ABA and indole-3-acetic acid, after which samples were desiccated to approx. 10% tissue moisture. Incubating cultures in 3.2 mmol·l^-1 O₂ (approx. 9%, low-O₂) increased embryoid formation sixfold in one wheat line and nearly threefold in another. In the former line low-O₂ caused the formation of mostly embryogenic callus. Low-O₂ also decreased precocious germination of immature embryos, decreased callus growth, and improved development and viability of the resultant embryoids. Including 1.9 mol·l^-1 ABA in the callus-induction medium reduced germination of immature embryos and reduced the incidence of embryoids with visible abnormalities. Despite the improved morphology, significantly fewer of the embryoids produced on ABA-containing medium germinated. Desiccation significantly enhanced germination of these embryoids as well as those produced on ABA-free medium.Abbreviations ABA abscisic acid - DPA days post-anthesis - dicamba 3,6-dichloro-o-anisic acid - 2,4-D 2,4-dichlorophen-oxyacetic acid - FW fresh weight - IAA indole-3-acetic acid - Kin kinetin (N⁶-furfurylaminopurine) - MS Murashige and Skoog (1962) medium Contribution of the Utah Agricultural Experiment Station, Utah State University, Logan, UT, Journal Paper No. 3565     

Activities of Antioxidant Systems During Germination of Chenopodium rubrum Seeds

The activities of superoxide-dismutase (SOD), catalase (CAT) and peroxidase (POD), and concentrations of glutathione and ascorbate have been studied during the first stages of germination in Chenopodium rubrum L. seeds. The highest CAT and SOD activity was found prior to radicle protrusion, while POD activity was maximal at the time of radicle protrusion and seedling development, new POD isozymes simultaneously appearing. The concentrations of total, reduced and oxidized glutathione showed similar changes during germination, the highest values being detected at the time of radicle protrusion. Ascorbic acid was present in the seeds in a detectable concentration only at the time preceding radicle protrusion, while its oxidized form dehydroascorbic acid was detected during the whole germination period studied. Gibberellic acid (GA₃, 160 M) had no effect on germination percentage, but in presence of GA₃, SOD and CAT activity notably increased prior to radicle protrusion, and oxidized glutathione concentration decreased in further germination.     

Interactions of ancymidol with sucrose and α-naphthaleneacetic acid in promoting asparagus (Asparagus officinalis L.) somatic embryogenesis

Interactions of varying ancymidol concentrations with those of α-naphthaleneacetic acid (NAA) or sucrose in embryo induction medium were related to the production and development of asparagus (Asparagus officinalis L.) somatic embryos, and to the ability of these embryos to germinate. A significant sucrose×ancymidol interaction was observed only for the production of bipolar embryos; 4% sucrose with 0.75 mg l^–1 ancymidol gave the best result, 78 g^–1 callus. The frequency of globular embryos decreased as sucrose or ancymidol concentrations increased. Sucrose concentration affected embryo germination; 3% and 4% sucrose were optimal with approximately 60% and 40% of bipolar and globular embryos germinating, respectively. Significant ancymidol×NAA interactions were observed for the production of bipolar and globular embryos and their germination. Varying ancymidol concentrations affected embryo production and germination in combination with 0.1 mg l^–1 NAA, but not with 1.0 mg l^–1 NAA. The treatment combination of 0.1 mg l^–1 NAA with 0.75 mg l^–1 ancymidol produced the most bipolar embryos, 64 g^–1 callus, and the greatest percentages of bipolar and globular embryos germinated, 63% and 42%, respectively. Received: 19 August 1996 / Revision received: 24 April 1997 / Accepted: 22 May 1997     

Effects of citric acid and the siderophore desferrioxamine B (DFO-B) on the mobility of germanium and rare earth elements in soil and uptake in Phalaris arundinacea

Effects of citric acid and desferrioxamine B (DFO-B) on the availability of Ge and selected rare earth elements (REEs) (La, Nd, Gd, Er) to Phalaris arundinacea were investigated. A soil dissolution experiment was conducted to elucidate the effect of citric acid and DFO-B at different concentrations (1 and 10 mmol L^?1 citric acid) on the release of Ge and REEs from soil. In a greenhouse, plants of P. arundinacea were cultivated on soil and on sand cultures to investigate the effects of citric acid and DFO-B on the uptake of Ge and REEs by the plants. Addition of 10 mmol L^?1 citric acid significantly enhanced desorption of Ge and REEs from soil and uptake into soil-grown plants. Applying DFO-B enhanced the dissolution and the uptake of REEs, while no effect on Ge was observed. In sand cultures, the presence of citric acid and DFO-B significantly decreased the uptake of Ge and REEs, indicating a discrimination of the formed complexes during uptake. This study clearly indicates that citric acid and the microbial siderophore DFO-B may enhance phytoextraction of Ge and REEs due to the formation of soluble complexes that increase the migration of elements in the rhizosphere.