High frequency embryogenic callus induction and plant regeneration from mature caryposis of big bluestem and little bluestem

Big bluestem (Andropogon gerardii Vitman) and little bluestem [Schizachyrium scoparium (Michaux) Nash.] are native to the North America and are important forage grasses and ornamental grasses. Both grasses are proposed as ideal biomass producers for cellulosic ethanol production. To apply genetic transformation, which is an important tool for incorporating desirable agronomic traits into plants to both species, however requires an efficient and reproducible regeneration protocol. We used mature caryopses from big and little bluestem as explants and tested the effect of various combinations of 2, 4-dichlorophenoxyacetic acid (2, 4-D) (1, 2, 3, 4 or 5 mg l⁻¹) and kinetin (KT) (0, 0.1 or 0.2 mg l⁻¹) on embryogenic callus induction with LS as the basal medium. The highest percentage of embryogenic calli induction occurred on medium containing 2, 4-D alone at 2 mg l⁻¹ for ‘Bison’ and on medium containing 4 mg l⁻¹ 2, 4-D alone for ‘Bonilla’ big bluestem. For little bluestem, the highest percentage of embryogenic callus induction occurred on medium containing 3 mg l⁻¹ 2, 4-D plus 0.1 mg l⁻¹ kinetin, suggesting that addition of KT is beneficial. Shoot regeneration took place on LS basal medium without any plant growth regulator for both species, although the addition of KT increased both regeneration frequency and the number of shoots produced per callus. Rooting of shoots reaching about 2 cm long occurred readily with or without α-naphthaleneacetic acid (NAA). Rooted plantlets were all successfully established in the soil.     

Effect of 4-chloro-2-methylphenoxyacetic acid and 2,4-dimethylphenol on human erythrocytes

The effects of exposure of human erythrocytes to different concentrations of 4-chloro-2-methylphenoxyacetic acid (MCPA) and its metabolite—2,4-dimethylphenol (2,4-DMP) were studied. The investigations concerned mainly the content of glutathione (GSH and GSSG), glutathione peroxidase (GSH-Px), glutathione transferase (GST), and the level of adenine energy charge (AEC). Reactive oxygen species (ROS) such as hydroxyl radical, superoxide anion, hydrogen peroxide, and nitric oxide are produced during normal processes in the cell. Under normal conditions, antioxidant systems of the cell minimize damage caused by ROS. When ROS generation increases to an extent that it overcomes the cellular antioxidant systems, the result is oxidative stress. We observed that MCPA and 2,4-DMP decreased the level of GSH in erythrocytes in comparison with control. MCPA did not affect glutathione peroxidase and glutathione transferase activity, while 2,4-DMP increased their activity. 2,4-DMP decreased the level of ATP and increased the content of ADP and AMP, leading to the fall of the level of AEC. MCPA and 2,4-DMP transform hemoglobin into methemoglobin, thus preventing oxygen transport. Comparison of the toxicity of MCPA and 2,4-DMP revealed that the most prominent changes occurred in human erythrocytes incubated with 2,4-DMP.     

Nanostructured liquid crystalline particle assisted delivery of 2,4-dichlorophenoxyacetic acid to weeds,crops and model plants

Routine agricultural practices are heavily dependent on the use of surfactants, many of which are toxic to humans and detrimental to the environment. In proof of concept work we have previously shown the potential of nanostructured liquid crystalline particles (NLCP) to safely interact with plant leaf cuticular surfaces with minimal impact on epicuticular waxes. Here we demonstrate the use of NLCP to effectively deliver the auxin herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) to plant leaves in laboratory and field studies. In the laboratory, the physiological stress responses of lupin, Lupinus angustifolius (L.) (Fabaceae) towards NLCP spray applications were shown to be much reduced in comparison with application of two common surfactants. Phytotoxicity assays of 2,4-D loaded NLCP were used to validate the herbicidal effects on Arabidopsis thaliana (L.) Heynth. (Brassicaceae) and established a similarity with that of surfactant assisted 2,4-D delivery when tested at a concentration of 0.1%. Field trials were conducted to test the efficacy of NLCP-assisted delivery of 2,4-D in comparison with commercial surfactants for the control of the invasive weed wild radish, Raphanus raphanistrum (L.) (Brassicaceae), in wheat, Triticum aestivum (L.) (Poaceae) crop fields. Compared against Estercide 800, a commercially available 2,4-D formulation, NLCP assisted delivery of 2,4-D was effective at low concentrations of 0.03% and 0.06%. The crop yield remained similar for all the tested concentrations and formulations of 2,4-D loaded NLCP and Estercide 800. This is the first report to directly show that, as an alternative to conventional methods, NLCP can be used under both laboratory and field conditions to successfully delivery an agrochemical.     

Ethoxylated rapeseed oil derivatives as novel adjuvants for herbicides

Ethoxylates of rapeseed oil and of methylated rapeseed oil were synthesized and tested as adjuvants for 2,4-D and phenmedipham. Provided they had less than 6 units of ethylene oxide (EO), 1.0 to 10 g litre(-1) ethoxylates in water induced droplet spreading on barley leaves. In an acetone-based medium all derivatives strongly promoted the foliar uptake of 2,4-D, with no clear influence of the ethoxylation degree. In the same medium there was a negative influence of ethoxylate chain length on the foliar uptake of phenmedipham. In a water-based medium, phenmedipham applied with rapeseed oil emulsified with ethoxylated (20 EO) rapeseed oil displayed uptake rates close to a commercial preparation. The same was true for phenmedipham applied with ethoxylated (2 EO) methylated rapeseed oil. In bioassays, phenmedipham prepared with methylated rapeseed oil emulsified with ethoxylated (20 EO) rapeseed oil was as efficacious on barley as a commercial formulation. The same was true for phenmedipham prepared with ethoxylated (2 EO) methylated rapeseed oil. However, neither rapeseed oil nor methylated rapeseed oil emulsified with ethoxylated (2 EO) methylated rapeseed oil conferred good efficacy to phenmedipham. Hence, ethoxylated rapeseed oil derivatives are promising adjuvants or formulants for herbicides.     

High frequency plantlet regeneration from callus and artificial seed production of rock plant Pogonatherum paniceum (Lam.) Hack. (Poaceae)

Pogonatherum paniceum (Lam.) Hack. is a rock plant with good potential for vegetative recovery on naked lands. A high frequency in vitro regeneration system was developed for P. paniceum. Calli were induced from explants of mature seeds, seedlings, young leaves, and stem segments on Murashige and Skoog (MS) medium supplemented with 1.0 mg L⁻¹ 2,4-dichlorophenoxyacetic acid (2,4-D), 2.0 mg L⁻¹ α-naphthalene acetic acid (NAA) and 0.2 mg L⁻¹ 6-benzylaminopurine (BAP). High induction rates (59.57%) and regeneration rates (100%) were obtained from mature seed explants; calli were sub-cultured for over 2 years and still retained a high regenerative capacity. One seed explant resulted in 69,997 plants in 1 year. Shoot buds derived from calli were used for encapsulation in liquid MS medium containing 3% sucrose and two different alginate matrices (3% sodium alginate (w/v) + MS medium containing 3% sucrose and 3% sodium alginate + 1% activated carbon (w/v) + MS medium containing 3% sucrose) with a 20-min exposure to 2% CaCl₂ and 0.3% bavistin (w/v). The capsule with 3.0% sodium alginate (w/v) and 1% activated carbon (w/v) showed a higher conversion rate (61.58%) and stronger plantlets under non-aseptic conditions. These systems are useful for the rapid clonal propagation and dissemination of artificial seed material of P. paniceum for eco-recovery.     

Genomic analysis of antifungal metabolite production by <Emphasis Type="Italic">Pseudomonas fluorescens</Emphasis> Pf-5

The complete genomic sequences of several Pseudomonas spp. that inhabit the rhizosphere are now available, providing a new opportunity to advance knowledge of plant growth-promoting rhizobacteria (PGPR) through genomics. Among these is the biological control bacterium Pseudomonas fluorescens Pf-5. Nearly 6% of the 7.07 Mb genome of Pf-5 is devoted to the biosynthesis of secondary metabolites, including antibiotics toxic to soilborne fungi and Oomycetes that infect plant roots, and two siderophores involved in iron acquisition. Three orphan gene clusters, for which the encoded natural product was unknown, also were identified in the genome of Pf-5. The product synthesized from one of the orphan gene clusters was identified recently using a new ‘genomisotopic approach’, which employs a combination of genomic sequence analysis and isotope guided fractionation. Application of the genomisotopic approach to one orphan gene cluster in Pf-5 resulted in the discovery of orfamide A, founder of a new group of bioactive cyclic lipopeptides with a putative role in biological control of plant disease.     

Condensation reactions of phenolic resins III: self-condensations of 2,4-dihydroxymethylphenol and 2,4,6-trihydroxymethylphenol (1)

This study reexamined the kinetics of the condensation reactions of hydroxymethylphenols with the purpose of elucidating the reaction mechanisms. This report discusses experimental results on the self-condensations of 2,4-dihydroxymethylphenols (2,4-DHMP) and 2,4,6-trihydroxymethylphenol (THMP), focusing on the order of reaction. The relations between the initial rates of reaction and the initial concentrations of reactants were investigated. Results quite different from those of previous reports were obtained. The order of reaction of the selfcondensation of 2,4-DHMP was found to be 1.1, which did not change with the alkali/2,4-DHMP molar ratio. The order of reaction of the self-condensation of THMP was found to vary with both the concentration of THMP and the alkali/THMP molar ratio. In the region of THMP concentrations above 1.5mol/l, the order of reaction was confirmed to be 2.0, which did not change with the alkali/THMP molar ratio. In the region of THMP concentrations below 1.0mol/l, the order of reaction varied with the alkali/THMP molar ratio, showing fractional numbers of 1.2–1.6. These results indicate that unimolecular reaction(s) and bimolecular reaction(s) take place simultaneously as the ratedetermining step in the condensation reactions of 2,4-DHMP and THMP and that the reaction mechanism changes with the species of reactant and, in some cases, with the reaction conditions.Part of this study was presented at the Wood Adhesives 2000 symposium, South Lake Tahoe, Nevada, USA, June 2000     

Chemical cotton stalk destruction for maintenance of host-free periods for the control of overwintering boll weevil in tropical and subtropical climates

In the Lower Rio Grande Valley (LRGV) of Texas, cotton regrows and produces fruit from undestroyed stalks throughout the winter, and in spring weevils from such locations become a serious threat. The success of the boll weevil eradication program, which was reintroduced in the LRGV in 2005, will be dependent on thorough stalk destruction following harvest. However, adverse weather conditions and conservation tillage often impede immediate and complete stalk destruction using typical tool implements, and alternative stalk control methods are needed. This study provides an examination of the efficacy for cotton stalk destruction of different herbicides (thifensulfuron-methyl + tribenuron-methyl, dicamba-diolamine, 2,4-D-dimethylammonium, flumioxazin, 2,4-DB-dimethylammonium and carfentrazone-ethyl) and their rates, spray volumes and application timings on shredded or standing cotton stalks after stripper or picker harvest. None of the tested herbicides, except 2,4-D-dimethylammonium, stopped post-harvest cotton regrowth and fruiting. 2,4-D-dimethylammonium sprayed once (0 or 7 days) after cotton was harvested at 1 lb AE acre(-1) (1.12 kg ha(-1)), in a spray volume of 10 gal water acre(-1) (93.5 L ha(-1)) with 5 mL L(-1) surfactant, was highly effective in stalk destruction (72-90%). The best results were achieved when the herbicide was applied immediately after the cotton was shredded, followed by standing stripper-harvested and standing picker-harvested cotton. 2,4-D-dimethylammonium applied twice, 0 and 14 (or 21) days after cotton harvest, was 100% effective in killing stalks, regardless of whether they were shredded or standing, or whether harvest was by stripper or picker. These findings showed that 2,4-D-dimethylammonium cotton stalk destruction eliminated food and reproductive opportunities for managing overwintering boll weevils [Anthonomus grandis grandis Boheman (Coleoptera: Curculionidae)].     

A study of goldfish oocyte meiosisin vitro: effects of 2,4-dinitrophenol and adenosine-5-triphosphate

Germinal vesicle migration (GVM) and/or dissolution (GVD) were measured in goldfish oocytes, treated with 17α, 20β dihydroxyprogesterone (DHP) and other compounds considered to effect the cytoskeleton and oxidative phosphorylation,in vitro. Administration of DHP reinitiated meiotic maturation, increasing GVM and GVD in goldfish oocytes. Addition of 2,4-dinitrophenol (DNP) to the incubation medium significantly inhibited DHP-induced GVM and GVD. The DNP effect was found to be partially reversible after 24 h and could be reversed fully after a further delay of approximately 24h. Treatment of goldfish oocytes with demecolcine (DE; a colchicine derivative also known as colcemid) induces GVM to the micropyle without effecting GVD; while Cytochalasin-B which inhibits microfilament polymerization impairs both GVM and GVD. Administration of DNP, significantly inhibited DE-induced GVM, suggesting that GVM as well as GVD are dependent upon the process of oxidative phosphorylation. Addition of adenosine-5′ -triphosphate (ATP) at low concentrations (0.01–0.1 mM) did not effect DHP-induced or DNP-inhibited GVD in goldfish oocytes. The present results are consistent with the idea that migration of the oocyte nucleus during meiosis reinitiation has an energy requirement and involves participation by the cytoskeleton.     

高效液相色谱法测定电子烟烟液中8种挥发性羰基化合物

[目的]建立同时测定电子烟烟液中甲醛、乙醛、丙酮、丙烯醛、丙醛、巴豆醛、2-丁酮和丁醛8种挥发性羰基化合物含量的高效液相色谱法。[方法]电子烟烟液经2,4-二硝基苯肼溶液衍生后,衍生物直接用HPLC测定。选用DIONEX Acclaim Explosive E2色谱柱(250 mm×4.6 mm,5μm),以乙腈和水为流动相进行梯度洗脱,通过紫外检测器检测烟液中羰基化合物。[结果]8种羰基化合物的DNPH衍生物在一定浓度范围内与峰面积线性关系良好,相关系数均达到0.999以上,3个加标水平的平均回收率在96.4%~101.1%,相对标准偏差(RSD)小于3.26%,检出限(LOD)为0.009~0.035 mg/L。[结论]该方法前处理简单,灵敏度高,精密度及准确度好,适用于电子烟烟液中羰基化合物的检测。