A dynamic river model for biodegradability studies

The objective of this publication is to present a new dynamic aerobic biodegradation test method simulating a river. A laboratory cascade test system and standardized batch shake flask tests were used for biodegradation studies with the non-volatile and non-sorbing model compounds 2,4-dinitrophenol, naphthalene-1-sulphonic acid and sulphanilic acid. To be closer to the often very low concentrations of substances in the environment the concentrations of the compounds used were standard test concentrations and lower. ¹⁴C labelled compounds were measured at 50 μg/l, capillary electrophoresis at 5000 μg/l and the removal of dissolved organic carbon at 50000 μg/l. The test results obtained confirmed the known ultimate biodegradability of the test compounds and showed that biodegradation degrees, rates and degradation durations depended on the test systems, the concentrations of test compounds and the inocula. The river model is a suitable simulation test for natural dynamic surface waters which can be used to perform biodegradability studies at low test concentrations if adequate analytical tools, preferably radioactive-labelled substances, are available.     

Factors influencing shoot regeneration from cotyledonary explants ofCucumis melo

Cotyledonary explants of 4-day-oldCucumis melo cv. Hale's Best Jumbo in vitro seedlings showed maximum initiation of shoot buds when cultured onto a revised Murashige & Skoog medium supplemented with 5 M indole-3-acetic acid and 5 M benzylaminopurine and cultured at 25–29°C under low light intensity (5–30 mol m^-2 s^-1). Subculture of the shoot buds onto the same medium without auxin and supplemented with 3 M benzylaminopurine caused the development of shoots from 30% of the buds. The presence of abscisic acid significantly increased the number of explants producing shoot buds. Bud initiation was affected by genotype, seedling age, light intensity, and temperature. Addition of gibberellic acid, thidiazuron or silver nitrate to regeneration medium did not improve either bud initiation or shoot regeneration.     

Phenylacetic acid-induced somatic embryogenesis in cultured hypocotyl explants of geranium (Pelargonium x hortorum Bailey)

Summary The effect of a non-indole compound, phenylacetic acid (PAA), on the induction of somatic embryogenesis in tissue cultures of geranium (Pelargonium x hortorum Bailey cv. Scarlet Orbit Improved) was investigated. Hypocotyl explants derived from young, dark-grown seedlings were cultured on Murashige and Skoog (1962) medium (MS) supplemented with PAA or IAA (0.01–120 M) alone or in combination with BAP (8 M). Somatic embryogenesis was induced by both PAA and IAA at 0.01–20 M with 8 M BAP, however, the optima differed considerably for the two compounds. Maximal activity of IAA for somatic embryogenesis was found at 0.1–2.5 M, whereas PAA gave best results at 10 and 20 M under identical culture conditions. Higher concentrations (30–120 M) of IAA or PAA in the medium induced callusing in the explants, but the callus was neither embryogenic nor morphogenic.Abbreviations BAP N⁶-benzylaminopurine - IAA indole-3-acetic acid - MS Murashige and Skoog (1962) - PAA phenylacetic acid     

Characterization of Melittin Effects in Synaptosomes

The effects of melittin at increasing concentrations on: [³H]GABA release from mouse brain synaptosomes; on the radioactivity released from [³H]arachidonic acid labeled synaptosomal membranes; on synaptosomes ultrastructure and on the leakage of the cytoplasmic marker, lactate-dehydrogenase (LDH) was investigated. Melittin 0.3, 1, 3, 7, and 10 M progressively increases [³H]GABA release, but the efficacy of melittin is decreased when the amount of tissue exposed to a constant concentration of the toxin increases. The release of [³H]GABA induced by melittin below 3 M is Ca²⁺ dependent, but not that induced by the higher concentrations. The Ca²⁺ dependent fraction of the [³H]GABA released by 0.3 M melittin is selectively inhibited by 10 M quinacrine and 1 M nordihydroguaiaretic acid (NDGA) and facilitated by 3 M indomethacin, whereas the Ca²⁺ independent fraction of the [³H]GABA released by melittin is not. In the presence of Ca²⁺, melittin 0.3, 1 and 10 M progressively increases [³H]arachidonic acid release over control release, but the effectiveness of melittin is also decreased as the amount of tissue increases. No apparent changes in synaptosomes ultrastructure are observed in 0.3 M treated synaptosomes, but a noticeable disorganization is produced in 10 M melittin-treated synaptosomes, independently on the presence of external Ca²⁺. LDH activity only increases over control activity in the supernatant solutions of 10 M melittin treated synaptosomes, also in a Ca²⁺ independent manner. Our interpretation of these results is that the Ca²⁺-dependent, pharmacologic sensitive component of melittin-induced release of [³H]GABA, unmasked when 0.3 M melittin was used, involves the activation of a Ca²⁺-dependent type of membrane PLA₂. The Ca²⁺-independent release of [³H]GABA is in contrast, highly probable to be due to the membrane perturbation produced by complex melittin/lipid interactions.     

Phosphorylation of the Ca2+ pump intermediate in intact red cells,isolated membranes and inside-out vesicles

Summary Ca²⁺-entry into intact red cells containing [³²P]-ATP increases the phosphorylation of the 150 000 dalton polypeptide of the membrane. This phosphorylation occurs even in Mg²⁺-depleted red cells. Extracellular lanthanum applied during ATP-depletion further increases the Ca ²⁺ -induced phosphorylation.In fragmented membranes or resealed insideout vesicles (IOVs) membrane bound Mg²⁺ is sufficient to catalyze the phosphorylation of spectrin 2 and Band 3 polypeptides with low concentrations (< 1 M) of [³²P]-ATP. In Ca-EDTA buffers one single polypeptide is phosphorylated which is located in the 150 000 molecular weight region. K_mCa for phosphorylation is much lower (0.2 m) than for active Ca²⁺ transport (40 M) in IOVs. Lanthanum induced phosphorylation (up to 250 m La_free) is significantly greater than Ca²⁺-induced phosphorylation. Hg²⁺ inhibits both Ca²⁺ and La³⁺ induced phosphorylation. Ca²⁺-induced labelling can be rapidly chased by unlabelled ATP +Mg²⁺, but not with EGTA+Mg²⁺. Dephosphorylation in Ca ²⁺ phosphorylated membranes and IOVs is significantly inhibited by La ³⁺. It can be concluded that the mechanism of La and H g2+ inhibition of the Ca ²⁺ pump is different in intact cells and isolated membranes or IOVs.Abbreviations EDTA ethylenediamine tetraacetate - EGTA ethyleneglycol-bis(2-aminoethylether)-N-N-tetraacetate - IOV inside-out vesicle - SDS sodium dodecylsulfate - TCA trichloroacetic acid     

Effect of iron on growth and toxin production byClostridium botulinum type A

The kinetics of growth and toxin production by the Hall strain ofClostridium botulinum type A was examined in the presence of various concentrations of iron (0.1 to 10.1 g/ml, 1.8 to 182 M) in a chemically defined medium. At concentrations below 0.5 g/ml, iron insufficiency limited the growth of the organism. The maximum amount of toxin produced varied by only twofold (6×10⁵ to 1.2×10⁶ mouse median lethal doses/ml per A₅₄₀ unit) over the 100-fold range of iron concentrations used. High concentrations of iron did not reduce the elaboration of botulinum toxin, in contrast with its marked inhibitory effects on the production of many bacterial toxins. Iron is unlikely to be a regulatory effector for the formation of botulinum toxin by the Hall strain of type A.     

Biodegradation of naphthalenesulphonic acid-containing sewages in a two-stage treatment plant

The production of naphthol the coupling compound in the syntheses of azo-dyes occurs a naphthalenesulphonic acid-containing wastewater. The aerobic biodegradation of a complex mixture of naphthalenemono- and -disulphonic acids with high amounts of inorganic salts was examined in a two-stage plant with specially adapted and immobilized microorganisms fixed on broken sand particles. The plant consists of two airlift-loop reactors. An interposed settling tank separates the two different bacterial communities in the stages. In the first stage the sequential metabolization of naphthalene-2- and-1-sulphonic acid was achieved by strain Pseudomonas testosteroni A3 at residence times down to 1.5 h. The total degradation of remaining naphthalene-1-sulphonic acid and the degradation of recalcitrant naphthalenedisulphonic acids was obtained by a defined mixed culture in the second unit. Because of the more recalcitrant character of the remaining components in the second stage examinations with Na₂SO₄-loaded and salt-free wastewater were carried out at mean residence times between 50 and 6.3 h. With salt-loaded sewage an overall degradation of approximately 71% was achieved. The main component in the effluent was non-biodegradable naphthalene-1.5-disulphonic acid. Investigations with salt-free wastewater have shown an increasing overall degradation up to 84%. Thus, in the presence of inorganic salts a considerable inhibition of the biological degradation of the recalcitrant substances in the second unit was found.List of Symbols 1NS naphthalene-1-sulphonic acid - 2NS naphthalene-2-sulphonic acid - 1.5NDS naphthalene-1.5-disulphonic acid - 1.6NDS naphthalene-1.6-disulphonic acid - 2.6NDS naphthalene-2.6-disulphonic acid - 2.7NDS naphthalene-2.7-disulphonic acid - 6A2NS 6-amino-naphthalene-2-sulphonic acid - D 1/h dilution rate - K _s mg/l Monod coefficient - m _s mg_s/(h g_BM) maintenance coefficient - NDS naphthalenedisulphonic acids - NS naphthalenemonosulphonic acids - NSS total naphthalenesulphonic acids - Pr mg/(h l) substrate degradation rate - Pr substrate degradation rate in dimensionless form - S mg/l substrate concentration - S _E mg/l substrate input concentration - u _g cm/s superviciai gas velocity - X _f g/l free biomass concentration - X _i g/l immobilized biomass concentration - Y _X/s g_BM/g_s] substrate yield coefficient - X_i/ (K_s Y_X/S) immobilized biomass concentration in dimensionless form - 1/h specific growth rate - _max 1/h maximum specific growth rate     

Effect of a non-ionic surfactant added to the soil surface on the biodegradation of aromatic hydrocarbons within the soil

A study was conducted to determine whether a non-ionic surfactant (Novel II 1412-56) added to the surface of Lima silt loam would enhance the biodegradation of phenanthrene and biphenyl present within the soil. Water containing the surfactant at concentrations of 10 and 100 g/ml was pumped through the soil. At 10 g/ml, Novel II 1412-56 markedly enhanced the rate and extent of phenathrene mineralization and the extent but not the initial rate of biphenyl mineralization. The stimulation was less if the water added to the soil surface contained 100 g surfactant/ml. Addition of the surfactant at the two concentrations did not result in leaching of either phenanthrene or biphenyl, but products of the degradation were found in the soil leachate with or without the surfactant. We suggest that surfactants at low concentrations may be useful for in-situ bioremediation of sites contaminated with hydrophobic pollutants without causing movement of the parent compounds to ground-waters.     

Al-induced inhibition of root elongation in corn,Zea mays L. is overcome by Si addition

The effect of silicic acid on Al-induced inhibition of root elongation was investigated in corn roots (Zea mays L. cv. golden cross bantam) in 100 t M CaCl2 solution at pH 4.3. Twenty t M Al inhibited root elongation (20 h) about 70%, however, inhibition was alleviated by addition of silicic acid. The alleviative effect increased with higher silicic acid concentrations. The concentration of Al3+, the toxic species, in solution was decreased to about 15, 10, and 5 t M, respectively, from the initial concentration of 20 t M by addition of silicic acid at 500, 1000, and 2000 t M Si. Under the same concentration of Al3+, Al-induced inhibition of root elongation showed the same extent regardless of the addition of silicic acid or not by comparing 5 t M Al treatment with 20 t M Al + 2000 t M Si treatment, and 10 t M Al treatment with 20 t M Al +1000 t M Si treatment. Viability of cells on the root tip surface was decreased by Al addition. Cell viability was not improved by addition of silicic acid under the same concentration of Al3+. All these facts suggest that the alleviative effect of silicic acid on Al toxicity resulted from decreasing toxic Al3+ concentration by forming Al-Si complexes rather than from other physiological effects of silicic acid in corn roots.     

Micropropagation of Santolina canescens Lagasca and in vitro volatiles production by shoot explants

Shoot-tips of Santolina canescens, an aromatic species producing a novel diacetylene derivative, were in vitromultiplied on Murashige-Skoog basal medium (MS) containing different concentrations of 6-benzyladenine (BA) and kinetin (KIN). Rooting phase was performed on media supplemented with different auxins: 3-indoleacetic acid (IAA), 3-indolebutyric acid (IBA) and 1-naphthaleneacetic acid (NAA). The best axillary-bud proliferation was recorded on MS medium containing 1.33 M BA plus 0.32 M NAA. Plantlets rooted easily on the different tested media, but more abundant and stronger roots occurred on media containing 2.68 M NAA. The composition of oil obtained through the cultured explants was analyzed by headspace gas chromatography (HS-GC), and santolindiacetylene (SDA) in vitro production was tested. In order to stimulate the production of this product, different concentrations of linoleic acid were supplemented to the media. The best santolindiacetylene production was obtained when the rooting media was supplemented with 0.36 M linoleic acid.     

Molecular Properties of Purified Human Uncoupling Protein 2 Refolded from Bacterial Inclusion Bodies

One way to study low-abundance mammalian mitochondrial carriers is by ectopically expressing them as bacterial inclusion bodies. Problems encountered with this approach include protein refolding, homogeneity, and stability. In this study, we investigated protein refolding and homogeneity properties of inclusion body human uncoupling protein 2 (UCP2). N-methylanthraniloyl-tagged ATP (Mant-ATP) experiments indicated two independent inclusion body UCP2 binding sites with dissociation constants (K _d) of 0.3–0.5 and 23–92 M. Dimethylanthranilate, the fluorescent tag without nucleotide, bound with a K _d of greater than 100 M, suggesting that the low affinity site reflected binding of the tag. By direct titration, UCP2 bound [8-¹⁴C] ATP and [8-¹⁴C] ADP with K _ds of 4–5 and 16–18 M, respectively. Mg²⁺ (2 mM) reduced the apparent ATP affinity to 53 M, an effect entirely explained by chelation of ATP; with Mg²⁺, K _d using calculated free ATP was 3 M. A combination of gel filtration, Cu²⁺-phenanthroline cross-linking, and ultracentrifugation indicated that 75–80% of UCP2 was in a monodisperse, 197 kDa form while the remainder was aggregated. We conclude that (a) Mant-tagged nucleotides are useful fluorescent probes with isolated UCP2 when used with dimethylanthranilate controls; (b) UCP2 binds Mg²⁺-free nucleotides: the K _d for ATP is about 3–5 M and for Mant-ATP it is about 10 times lower; and (c) in C₁₂E₉ detergent, the monodisperse protein may be in dimeric form.     

Adventitious shoot regeneration from in vitro-cultured leaves of Rubus genotypes

Regeneration of adventitious shoots from leaves of several in vitro-cultured Rubus genotypes was affected by media components and incubation conditions. Leaves cultured at 20°C with a photosynthetic photon flux (PPF) of 40 mol m^-2 s^-1 had a higher regeneration frequency and more shoots per regenerating leaf than ones cultured at 25°C with a PPF of either 40 or 80 mol m^-2 s^-1. Thidiazuron (TDZ) was significantly more effective than benzyladenine. Medium containing 1 M TDZ had the highest percentage regeneration for leaves of Autumn Bliss, Canby, Summit and Sentry red raspberries, whereas leaves of MD-ETCE-1 blackberry hybrid responded more to 10 M TDZ. Higher regeneration frequencies were obtained with 0.5 M indolebutyric acid (IBA) than with 1 M, but no significant difference was observed between 0.5 M and no IBA in other experiments. More shoots per regenerating leaf formed on Murashige and Skoog (MS) and N6 media, than on half-strength MS, Anderson, or Woody Plant media for all genotypes tested. The youngest two expanding leaves near the shoot apex were the most regenerative and yielded the highest number of shoots per regenerating leaf.Abbreviations AND Anderson (1980) - BA benzyladenine - IBA indolebutyric acid - MS Murashige & Skoog (1962) - N6 Chu et al. (1975) - NAA naphthaleneacetic acid - PPF photosynthetic photon flux - TDZ thidiazuron (N-phenyl-N'-1, 2, 3-thiadiazol-5-ylurea) - WPM Woody Plant Medium [Lloyd & McCown (1980)]     

Antioxidant Properties of New Chalcogenides Against Lipid Peroxidation in Rat Brain

Ebselen (2-phenyl- 1,2-benzisoselenazole-3 (2H)-one) is a seleno-organic compound with antioxidant properties, and anti-inflammatory actions. Recently, ebselen improved the outcome of acute ischemic stroke in humans. In the present study, the potential antioxidant capacity of organochalcogenide compounds diphenyl diselenide (PhSe)₂, diphenyl ditelluride (PhTe)₂, diphenyl disulfide (PhS)₂, p-Cl-diphenyl diselenide (pCl-PhSe)₂, bis-[S-4-isopropyl 2-phenyl oxazoline] diselenide (AA-Se)₂, bis-[S-4-isopropyl 2-phenyl oxazoline] ditelluride (AA-Te)₂ and bis-[S-4-isopropyl 2-phenyl oxazoline] disulfide (AA-S)₂ was compared with that of ebselen (a classical antioxidant). Spontaneous and quinolinic acid (QA)- (2 mM) and sodium nitroprusside (SNP)- (5 M)-induced thiobarbituric reactive species (TBARS) production by rat brain homogenates was determined colorimetrically. TBARS formation was reduced by ebselen, (PhSe)₂, (PhTe)₂, (AA-Se)₂, (AA-S)₂ and (pCl- PhSe)₂ to basal rates. The concentrations of these compounds needed to inhibit TBARS formation by 50% (lC₅₀) are 1.71 M, 3.73 M, 1.63 M, 9.85 M, > 33.3 M, 23.2 M and 4.83 M, respectively for QA. For TBARS production induced by SNP the lC₅₀ was 2.02 M, 12.5 M, 2.80 M, > 33.3 M, 24.5 M and 7.55 M, respectively. The compounds (AA-Te)₂ and (PhS)₂ have no antioxidant activity and pro-oxidant activity, respectively. These results suggest that (AA-Se)₂ and (AA-S)₂ can be considered as potential pharmaceutical antioxidant agents.     

Anions modify the response of guard-cell anion channels to auxin

The anion channel in the guard-cell plasma membrane of Vicia faba, GCAC1, possesses recognition sites for the plant growth hormone auxin at the extracellular mouth of the channel (Marten et al. 1991, Nature 353:759-762). Using the patch-clamp technique we could demonstrate that auxins induced a shift of the voltage dependence of the anion channel to hyperpolarized potentials; the shift was attenuated during an increase in the extracellular chloride concentration, indicating that chloride shields the hormone-binding site. The auxin-induced shift was concentration-dependent, characterized by a Michaelis-Menten type of behaviour with a half saturation constant (K _m) of about 10 M naphthalene-1-acetic acid (1-NAA) in the presence of 2 mM Cl^– and 12 M in 80 mM Cl^–. In the presence of malate, another gating modulator of GCAC1, auxins were less effective, indicating that both ligands compete for common sites. Inactive auxins with respect to stomatal opening or stimulation of the plasma membrane H⁺-ATPase, such as 2-NAA, modulated the activation threshold and kinetics of GCAC1 similar to the active form 1-NAA. At a concentration of 100 M 2-NAA the peak-current potential shifted by about 30 mV more negative.Abbreviations GCAC1 guard cell anion channel 1 - 1-NAA naphthalene-1-acetic acid - 2-NAA naphthalene-2-acetic acid - TEA tetraethylammonium     

Clonal propagation of Virginia Pine (Pinus virginiana Mill.) by organogenesis

Clonal propagation of Virginia Pine (Pinus virginiana Mill.) was achieved by organogenesis on cotyledon explants. The influence of several cytokinins and abscisic acid on adventitious shoot production from cotyledon explants was investigated. Benzyladenine was more effective in shoot induction than three other cytokinins tested. Benzyladenine (22.2 M) in combination with naphthaleneacetic acid(0.05 M) in a Gresshoff and Doy (1972) medium was found to increase shoot bud production. Abscisic acid (7.6 M) in combination with benzyladenine and naphthaleneacetic acid enhanced shoot formation by an additional 65%. Root initiation was achieved with 0.5 strength Gresshoff and Doy media amended with naphthaleneacetic acid (1.3 M), indole-3-butyric acid (1.2 M) and benzyladenine (0.4 M). Over 2400 plantlets from 2 families survived and were transferred to a greenhouse in preparation for field planting. After ten months, the maximum number of surviving plantlets/seed explant from these two sources was 57 for family ALPV-38 and 41 for family ALPV-78, respectively.Abbreviations ABA Abscisic acid - BA N⁶-Benzyladenine - GD Gresshoff and Doy (1972) nutrient media - IBA Indole-3-butyric acid - KN Kinetin - NAA -Naphthaleneacetic acid - 2iP 2-isopentenyl adenine - ZN Zeatin     

Enhancement of shoot regeneration from cotyledon explants of Brassica rapa ssp oleifera through pretreatment with auxin and cytokinin and use of ethylene inhibitors

The presence of benzyladenine or naphthaleneacetic acid in seed germination medium markedly enhanced subsequent shoot regeneration from the base of the excised cotyledon explants of Brassica rapa cv. Horizon. Cotyledon explants from younger seedlings (3 or 4-day old) produced more shoots than those from older seedlings. Addition of the ethylene inhibitor aminoethoxyvinylglycine (1.0 M) to the regeneration medium improved shoot regeneration three fold.Abbreviations AVG aminoethoxyvinylglycine - BA benzyladenine - MGBG methylglyoxal-bisguanylhydrazone - MSBN ms (murashige & skoog 1962) medium supplemented with 4.4 m BA & 5.4 m NAA, 2% sucrose - NAA naphthaleneacetic acid     

Localization of 3H-dihydrotestosterone in the pituitary gland of the rhesus monkey

Summary The uptake and retention of radiolabelled dihydrotestosterone by the pituitary gland was examined in the rhesus monkey. Two animals were given an intravenous injection of 1.0g/kg ³H-dihydrotestosterone (DHT) alone while one monkey received both the labelled androgen and 100g/kg of unlabelled steroid. One and a half hours later, they were sacrificed. The pituitary glands were removed and processed for autoradiography and immunocytochemistry. Autoradiographic localization of DHT was discernible in the partes nervosa, intermedia and distalis, albeit the highest concentration of radiolabelled cells was noted in the pars distalis. Immunocytochemical staining with antibodies to rat PRL, human TSH and ovine LH revealed a population of steroid-concentrating cells that contained TSH and a second group that contained LH. None of the cells that reacted with the anti-PRL serum were radiolabelled.     

Influence of phenolic acids on phosphorus mobilisation in acidic and calcareous soils

Phenolic acids and phenols are abundant in soils. However, little information is available on the role of these compounds in mobilisation of soil phosphorus (P). The present study examined the effects of three phenolics on P mobilisation in comparison with citric acid in three soils differing in chemical properties. The soils were incubated with organic compounds at concentrations of 0 to 100 mol g^–1 soil for 30 min. While the addition of phenolic acid anions and phenol decreased soil pH, citrate either increased or did not affect soil pH depending on the soil type. All the organic compounds increased the amounts of easily-mobilised P fractions in the order of catechol citric acid proto-catechuic acid caffeic acid for the acid soils and citric acid > catechol = proto-catechuic acid > caffeic acid for the calcareous soil. Phosphorus mobilisation did not correspond to the amounts of Ca, Fe or Al ions released from the soils. These results suggest that organic acids and phenols altered the P fractions from stable, sparingly-soluble forms to easily dissolvable forms, and that chelation or precipitation of cations with organic ligands occur before biodegradation of the ligands.     

Influence of plant growth regulators,basal media and carbohydrate levels on the in vitro development of Pinus ponderosa (Dougl. ex Law.) cotyledon explants

Applications of in vitro screening techniques for Pinus ponderosa resistance to Peridermium harknessii could be beneficial in a tree breeding program. Plant growth regulators, basal media formula and carbohydrate levels were examined to determine the various effects each would have on excised cotyledon growth and development. Proliferating green callus was initiated from cotyledon explants on SH basal medium containing 4.4 M BA:5.4 M NAA and 1% sucrose. Subsequent subculturing onto LS medium supplemented with 44.0 M BA: 5.4 M NAA and 2% sucrose improved callus maintenance. The highest frequency of caulogenesis from cotyledon explants occurred on a modified GD medium containing 44.0 M BA: 0.054 M NAA and 4% glucose. The influence of nitrogen source, osmoticum and medium salt concentrations are discussed relative to callus initiation and caulogenesis.Abbreviations BA 6-benzyladenine - NAA -naphthaleneacetic acid - IAA indole-3-acetic acid - IBA indole-3-butyric acid - 2,4-D 2,4-dichlorophenoxyacetic acid - CD Campbell & Durzan - GD Gresshoff & Doy - LP Le Poivre - LS Linsmaier & Skoog - MC McCown - SH Schenk & Hildebrandt     

In vitro regeneration of silktree (Albizzia julibrissin) from excised roots

Root segments (1 cm long) were excised from 15–20 day old seedlings of silktree (Albizzia julibrissin) grown on B5 medium. About 50% of the control (no growth regulators added) root explants formed shoot buds within 15 days after placement on the culture medium. After 30 days, there were about 4 shoots per control explant. Addition of low levels of various auxins (0.5 M) did not influence the formation of shoot buds from the explants. Higher concentrations (5M), however, decreased shoot regeneration. Kinetin and 2iP did not influence shoot regeneration at the concentrations tested (1 & 10 M). Addition of benzyladenine, Zeatin, or thidiazuron to the culture medium increased both the percentage of explants that formed shoots and the number of shoots per explant. Thidiazuron was highly effective in stimulating shoot formation at low concentrations (<1 M). At 0.05 M thidiazuron, 95% of the explants produced shoots and about 10 shoots were formed per explant. Compared to TDZ, higher concentrations (10 M) of benzyladenine and Zeatin were required to enhance shoot formation. Upon excision and transfer to B5 medium, regenerated shoots developed into normal rooted plantlets.Abbreviations BA Benzyladenine - IAA Indoleacetic acid - IBA Indolebutyric acid - NAA Naphthaleneacetic acid - TDZ Thidiazuron - 2ip Isopentenyladenine