Effect of thidiazuron on vegetative tissue-derived somatic embryogenesis and flowering of bamboo Bambusa edulis

Current research on somatic embryogenesis of bamboo uses reproductive tissue as explants. However, it was hard to obtain the explant. Shoots of a local accession (3–4 m high) were used for multiple shoot production. In order to obtain embryogenic callus, nodal and internodal tissues from in vitro plantlets were placed on Murashige and Skoog (MS) medium supplemented with 9.2 M kinetin (KN), 13.6 M 2,4-dichlorophenoxyacetic acid (2,4-D), 0.1% (v/v) coconut milk, and 6% (w/v) sucrose. We studied the effects of sucrose and thidiazuron (TDZ) on callus proliferation. Optimal additives to the MS medium for embryogenic callus proliferation were 0.046 M TDZ, 13.6 M 2,4-D and 3% (w/v) sucrose. TDZ also promoted the germination of bamboo somatic embryos. The germination rate of the somatic embryos exceeded 80% on MS-based medium supplemented with 0.455M TDZ. Naphthaleneacetic acid (NAA) reduced germination. Well-developed plantlets were successfully transferred to soil. There was no albino mutant in subsequent culture. In vitro regenerants and potted plants flowered, but no seeds were produced.     

Plant regeneration through shoot formation from callus of Areca catechu L.

In order to establish and optimize an in vitro micropropagation protocol of Venus fly trap (Dionaea muscipula Ellis), a carnivorous plant, the effects of medium type, MS medium concentration, pH, and cytokinin and auxin types on shoot proliferation and root formation were investigated using 3-month-old shoots. The shoot proliferation was most effective in 2.3 M kinetin-supplemented 1/3MS medium at pH 5.5. The best conditions for rooting were 1/3MS medium supplemented with 0.5 M IBA. All subcultured shoots produced extensive root systems after 5–6 weeks culture. When plantlets after rooting were planted in plastic pots filled with 1:1 peat moss and sand, the survival rate of plantlets was almost 100%, exhibiting normal development. With subculture every 8 weeks, hundreds of the plants were propagated from a single plant within a year.     

Uremic Retention Solute Indoxyl Sulfate Level Is Associated with Prolonged QTc Interval in Early CKD Patients

Total mortality and sudden cardiac death is highly prevalent in patients with chronic kidney disease (CKD). In CKD patients, the protein-bound uremic retention solute indoxyl sulfate (IS) is independently associated with cardiovascular disease. However, the underlying mechanisms of this association have yet to be elucidated. The relationship between IS and cardiac electrocardiographic parameters was investigated in a prospective observational study among early CKD patients. IS arrhythmogenic effect was evaluated by in vitro cardiomyocyte electrophysiological study and mathematical computer simulation. In a cohort of 100 early CKD patients, patients with corrected QT (QTc) prolongation had higher IS levels. Furthermore, serum IS level was independently associated with prolonged QTc interval. In vitro, the delay rectifier potassium current (IK) was found to be significantly decreased after the treatment of IS in a dose-dependent manner. The modulation of IS to the IK was through the regulation of the major potassium ion channel protein Kv 2.1 phosphorylation. In a computer simulation, the decrease of IK by IS could prolong the action potential duration (APD) and induce early afterdepolarization, which is known to be a trigger mechanism of lethal ventricular arrhythmias. In conclusion, serum IS level is independently associated with the prolonged QTc interval in early CKD patients. IS down-regulated I_K channel protein phosphorylation and the I_K current activity that in turn increased the cardiomyocyte APD and QTc interval in vitro and in the computer ORd model. These findings suggest that IS may play a role in the development of arrhythmogenesis in CKD patients.     

TIBA affects the induction of direct somatic embryogenesis from leaf explants of Oncidium

To study the effect of auxin on direct somatic embryogenesis from leaf cultures ofOncidium `Gower Ramsey', 1-cm-long explants have been cultured in vitro testing IAA, 2,4-, quercetin, TIBA and PCIB. On a modified MS medium devoid of plant growth regulators, leaf cells of three regions (leaf tips, adaxial sides and cut ends) formed somatic embryos. After 8 weeks in culture, the frequencies of embryo-forming explants were 55, 52.5 and 30 % on leaf tips, adaxial sides and cut ends, respectively, and the numbers of embryos per dish was 89.3. Except for TIBA, other growth regulators (IAA, 2,4-, quercetin, PCIB) and their combinations tested, all retarded direct embryo formation. In the presence of 0.1 and 0.5 μM TIBA, leaf tip, adaxial sides and cuts end of explants gave almost the same embryogenic response as the control. However, 10 and 27.5 % of explants were induced to form embryos from abaxial sides, and these explants did not form embryos on cut ends. In addition, after 8?weeks in culture, TIBA at 0.5?μM highly promoted the mean numbers of embryos per dish to 134.2.     

Cytokinins promotion of flowering in Cymbidium ensifolium var. misericors in vitro

Callus-derived rhizomes of Cymbidium ensifolium var. misericors produced flowers precociously on a defined basal medium (1/2MS) containing of NAA with thidiazuron (TDZ), N⁶-(2-isopentenyl) adenine (2iP) or N⁶-benzyladenine (BA) within 100 d of culturing. Among eight cytokinins tested, TDZ at 3.3–10 µM or 2iP at 10–33 µM combined with 1.5 µM NAA were the most effective combinations for achieving flower induction in vitro. These undersized flowers were physically normal and bloomed for two weeks in vitro.     

Micropropagation of Cymbidium ensifolium var. Misericors through callus-derived rhizomes

Summary The effects were studied of light intensity, culture method and cytokinins on plant formation from callus-derived rhizomes of Cymbidium ensifolium var. misericors. The results demonstrated that one piece of rhizome produced seven shoot buds in 45 d when cultured in 1/2 MS basal liquid medium supplemented with 0.17 μM N⁶-(2-isopentenyl) adenine, 0.17 μM thidiazuron, 33 μM 6-aminopurine adenine and 1.5 μM naphthaleneacetic acid under 10 μmol m⁻² s⁻¹ artificial light and agitated at 60 rpm on a rotary shaker. These shoot-cm plantlets in 5 mo. when transferred to the same Gelrite-gel basal medium supplemented with 50 g l⁻¹ banana pulp. Plantlets were acclimated and grew well when potted in the greenhouse.     

Long-term effect of weak nitrogen limitation on polyhydroxyalkanoates production of propionate-fed activated sludge operated at long sludge retention time

A sequencing batch reactor (SBR) submitted to aerobic dynamic feeding condition was fed with weakly nitrogen-limited substrate (COD/N ratio of 60?mg/mg, propionate as the sole carbon source), and operated at 15?days sludge retention time (SRT). Then, the nitrogen-limited sludges at different cultivating periods (45th, 120th, 195th and 240th days) were harvested to conduct aerobic batch experiments of PHAs production under various nitrogen concentrations. Experimental results indicated that PHAs accumulating behavior of the propionate-fed sludge declined significantly after long-term cultivation, implying that weak nitrogen limitation and long SRT operation cannot achieve a stable PHAs producing performance of the sludge. Supplementing enough nitrogen was consequently a requisite to guarantee the stability of the propionate-fed PHAs accumulating culture. Besides, the sludge with higher PHAs content in SBR did not ensure a better PHAs producing capability in the batch PHAs production phase. Batch experiments also indicated that the propionate-fed sludge with 0.7?N?mmol/L exhibited a better PHAs producing capability than with other nitrogen concentrations.     

Shoot development and plant regeneration from protocorm-like bodies of <Emphasis Type="Italic">Zygopetalum mackayi</Emphasis>

Stem nodal segments of a sympodial orchid, Zygopetalum mackayi, were used as explants to induce protocorm-like body (PLB) formation on a hormone-free 1/2 Murashige and Skoog (1962) modified medium (1/2MS-0) or 1/2MS supplemented with 0.045–4.54 μM 1-phenyl-3-(1,2,3-thiadiazol-5-yl)-urea [TDZ] in light. After 1 mo of culture, pale to dark green, compact and irregular nodulars of PLBs formed from the explants. For PLB induction, TDZ had no significant effect on the percentage of PLB formation but promoted mean numbers of PLBs per responding explant at 0.045–4.54 μM. For plant conversion, PLBs were transferred onto the same basal medium devoid of TDZ. After 2–3 mo of culture, these PLBs successfully formed shoots and then roots with normal morphology. For PLB proliferation, TDZ has no significant effects on the fresh weight of PLB aggregates, but there is significantly retarded shoot development at 0.45–4.54 μM after 1 mo of culture. When transferring these PLB aggregates onto hormone-free medium for plant conversion, PLBs derived from TDZ-containing medium showed a decrease of shoot length (0.86–2.08 cm in shoot length) compared to those derived from 1/2MS-0 (2.74 cm in shoot length) after 1 mo of culture. Gibberellin A₃ [GA₃] at 0.29–8.66 μM significantly retarded PLB proliferation, but at 0.03 and 0.29 μM resulted in longer shoot length than the control treatment. Histological studies reveal that shoot development originated from the outer region of PLB aggregates. The young shoots initially connected to each other at their basal tissues with the parental PLBs. Plants were successfully obtained from PLBs and then gradually became more loosely connected with each other as well as with the parental aggregates. Several dozen plants were acclimatized in the greenhouse and showed normal morphology.     

Contents Volume 76 2004

Volume Contents

Contents Volume 76 2004