Stimulating effect of spermine on bulblet formation in bulb-scale segments of Lilium longiflorum

When bulb-scale segments of Lilium longiflorum were cultured on a medium containing auxin and cytokinin, the proportion of the expiants with newly-formed bulblets was significantly increased by the application of different polyamines. The most effective polyamine was spermine, where more than 90% of segments formed an average of 5 bulblets as compared to controls where less than 50% explants formed an average of 1.5 bulblets. Application of arginine one of the precursors putrescine biosynthesis, slightly promoted bulblet formation. The putrescine-stimulated bulblet formation was strongly inhibited by simultaneous addition of an inhibitor of the spermidine synthase, cyclohexylamine. The spermidine-promoted bulblet formation, however, could not be suppressed by this inhibitor. The promotive effect of spermidine on bulblet formation was reversed by an inhibitor of the spermine synthase, N-(3-aminopropyl)cyclohexylamine, but application of this inhibitor with spermine did not show any apparent effect on the bulblet formation. Endogenous level of spermine increased in common during bulblet formation that were stimulated by exogenous polyamines. Thus, spermine seemed to be the main stimulating chemical on bulblet formation in lily bulb-scale segments.Abbreviations APCHA N-(3-aminopropyl)cyclohexylamine - Arg arginine - BA benzyladenine - CHA cyclohexylamine - MS Murashige and Skoog's - NAA naphthaleneacetic acid - Orn ornithine - Put putrescine - Spd spermidine - Spm spermine     

High frequency of shoot multiplication and bulblet formation of garlic in liquid cultures

In vitro shoot proliferation and bulblet production of garlic (Allium sativum L.) was studied in liquid cultures. Shoots grown in vitro were used as explants and were cultured in MS medium supplemented with 2% (w/v) sucrose and 0.5 mg l^–1 2-iP. Three culture methods (semi-solid, liquid-immersion and raft) were compared for shoot proliferation. Explants in liquid (immersion) culture exhibited an increased multiplication rate and fresh weight of shoots after 3 weeks of culture as compared with the other treatments. Bulblet formation and growth were studied in liquid medium with different concentrations of sucrose (2–13%). MS medium containing 11% (w/v) sucrose was optimal for bulblet development and bulblets developed in this medium within 9 weeks in culture. The highest multiplication rate was (135 bulblets/explant) found when explants were cultured in bulbing medium (MS medium containing 0.1 mg l^–1 NAA+11% (w/v) sucrose) supplemented with 10 M JA. Growth retardants CCC, B-9, ABA also promoted induction and growth of bulblets. Darkness promoted the bulblet induction and growth compared to light conditions (16-h photoperiod of 50 mol m^–2 s^–1). The dormancy of bulblets was broken by cold treatment at 4 °C for 8 weeks.     

Effect of plant growth regulators,temperature and sucrose on shoot proliferation from the stem disc of Chinese jiaotou (<Emphasis Type="Italic">Allium chinense</Emphasis>) and in vitro bulblet formation

In vitro shoot proliferation from stem disc of Allium chinense, a vegetatively propagated plant, was investigated in this experiment. In the present study, shoots were formed directly on stem discs on a medium containing 1 mg/l N⁶-benzyladenine (BA) and 0.5 mg/lα-naphthaleneacetic acid (NAA). These shoots were further cultured on MS media supplemented with various levels of BA in combination with NAA, and new shoot clusters developed easily from the explants cultured despite considerable differences in the induction of shoot clusters with different levels of BA and NAA. The most productive combination of growth regulators proved to be 1.0 mg/l BA and 1.0 mg/l NAA, in which about 17 shoots were produced per cluster in 8 weeks culture. Most of the formed shoots were rooted 15 days after being cultured on MS media supplemented with 0.1–1.0 mg/l NAA. The survival rate of the plantlets under ex vitro conditions was 95% in pots filled with a peat: sand (2:1 v/v) mixture after two weeks. In vitro bulblet formation were strongly promoted by the high temperature of 30°C compared to that at 25, 20 and 15°C, and 12% (w/v) sucrose appeared to be optimal for bulblet development. Results from this study demonstrated that A. chinense could be in vitro propagated by using stem discs and in vitro bulblet formation could be achieved.     

The effect of methyl jasmonate and abscisic acid on differentiation of benzyladenine-induced bulblets inMuscari bulbs

Methyl jasmonate (JA-Me) at a concentration of 0.5% in lanolin paste totally inhibited bulblets formation induced by benzyladenine in intactMuscari bulbs. Lower concentrations of JA-Me delayed development and growth of bulblets induced by benzyladenine. It seems that methyl jasmonate acts as a powerful inhibitor of cell division induced by cytokinin in used test. In comparison with methyl jasmonate, abscisic acid did not show an inhibitory effect on bulblets formation induced by benzyladenine, even in a higher concentration.     

Light quality growth promotion of Spiraea nipponica: the influence of a low photon fluence rate and transfer time to a higher fluence rate

Combinations of different light quality and fluence exposure times were investigated for their effects on in vitro growth of the woody plant Spiraea nipponica. An interaction was demonstrated between different levels of benzyladenine (BA) used for in vitro propagation and the specific light regimes investigated. This relationship was affected by the length of exposure to either white or red/FR light and the time of transfer from one fluence rate to another. In all instances exposure to red/FR light resulted in more extensive growth than under white light. Thus explants cultured under 0.25 and 0.4 mg l^-1 of BA exhibited high shoot proliferation rates when transferred, after 4 weeks of low photon fluence red/FR light, to higher fluence white light for a further week. The proliferation rates obtained were higher than any white light treatment including that with the highest BA level of 0.5 mg l^-1. In addition, the combination of red/FR light exposure with a white light stage of higher fluence improved proliferation at lower exogenous BA levels.     

Bulblet Formation from Bulbscale Segments of Lilium Using Bioreactor System

In vitro bulblet formation was studied using solid, liquid and bioreactor culture (immersion and periodic immersion in liquid media using ebb and flood) in order to develop a cost effective method for the mass propagation of Lilium oriental hybrid ‘Casablanca’. Although the percent of bulblet formation was higher in solid culture, the increased growth rate and production of large number of bulblets in bioreactor makes it suitable for mass propagation. Four times per day and 15 min of medium supply was optimal for bulblet formation in ebb and flood bioreactor. Bulblet formation was also found to be effective in 16-h photoperiod. It was also observed that bulblet formation in the medium with 1.0 mg dm⁻³ BA and 0.3 mg dm⁻³ NAA was higher than in the medium without growth regulators, but formation of abnormal bulblets was higher in medium with BA and NAA. This revised version was published online in July 2006 with corrections to the Cover Date.     

Formation of onion bulblets in vitro and viability during medium-term storage

 The influences of light conditions, sucrose and ethylene on in vitro formation and storability of onion (Allium cepa L.) bulblets were studied in various accessions. Light, sucrose and ethylene influenced bulb formation. Storability was primarily enhanced by a high sucrose concentration (100 g/l) in the culture medium. The bulbing process was characterised by changes in bulbing ratio, leaf length, number of leaves and leaf development time. The viability of bulbs after 1 year of in vitro storage at low temperatures was determined by their growth reaction in subsequent subcultures, growth after transfer into the greenhouse and tetrazolium staining. Sufficient sprouting of bulblets previously stored at –1  °C demonstrated the possibility of storing them in a low-temperature, slow-growth culture. Received: 8 June 2000 / Revision received: 5 October 2000 / Accepted: 5 October 2000     

Phytochrome-mediated Carotenoid Biosynthesis and Its Influence by Plant Hormones

Lycopenc biosynthesis of parenchyma chromoplasts was studied in detached tomato fruits, Lycopersicum esculentum Mill, cv. Waltham Forcing, and found to be phytochrome mediated. A few minutes of red light during the day enhanced lycopene formation. Far-red irradiation did not enhance lyco-pene biosynthesis. Far-red following red nullified the promotive effect of red light. Lycopene content increased two-fold in the presence of abscisic acid. Ripening of tomatoes was inhibited when gibberellin, kinetin and ascorbic acid were applied to green tomatoes. Gibberellin (A₃) was more inhibitory to lycopene synthesis than kinetin.     

Similarity between Cytokinin and Blue Light Inhibition of Cucumber Hypocotyl Elongation

The cytokinin benzyladenine inhibited endogenous hypocotyl elongation in intact etiolated seedlings of cucumber (Cucumis sativus L.). In hypocotyl segments, the inhibitory effect of benzyladenine on growth was clearly detectable in the presence of indoleacetic acid. Fusicoccin-induced elongation was unaffected by the presence of cytokinin. The effect of cytokinin on elongation of the segments was determined by measuring changes in fresh weight, a linear function of extension growth. The effect of benzyladenine on hypocotyl growth was at least as large in segments prepared from red-light-grown seedlings as in those from seedlings grown in total darkness. A comparison was made between the inhibitory effects of cytokinin and blue light. The use of the calcium chelator ethyleneglycol-bis(β-aminoethyl ether)-N, N′-tetraacetic acid indicated that calcium ions are required for manifestation of benzyladenine-induced inhibition.     

Role of Ascorbic Acid in Bud Development

Ascorbic acid was found to increase bud development in Pisum sativum L. The interactions of ascorbic acid with indole-3-acetic acid, kinetin and gibberellic acid were studied. It was found that ascorbic acid promoted bud growth and overcame the inhibitory effect of auxin. When applied with gibberellin, bud growth was greatly enhanced. Ascorbic acid promoted bud development in red light only; it did not in far-red or dark.     

Stomatal Opening and Cell Enlargement in Response to Light and Phytohormone Treatments in Primary Leaves of Red-Light-Grown Seedlings of Phaseolus vulgaris L.

Cell enlargement in primary leaves of bean seedlings grown for10 days in dim red light in response to different light andphytohormone treatments was studied. On day 10, bean leaf discswere floated on 1% sucrose with, or without, phytohormones fordifferent periods (up to 24 h) under dim red light, or discswere floated in sucrose solution and irradiated with white orblue light. Cell enlargement was enhanced by continuous whiteand blue light and by benzyladenine, kinetin and gibberellicacid. When seedlings were grown for 8 days under dim red light afterwhich a 2-day dark period was interposed (for the accumulationof inactive phytochrome), cell enlargement was enhanced by a5-min irradiation with red light. This growth induction wasfar-red reversible. The conditions under which cell enlargement was promoted, alsoinduced the opening of the stomata. Red light induced a far-redreversible transient stomatal opening. Based on the kineticsof stomatal opening and cell enlargement we formulated the hypothesisthat cell enlargement in leaves in response to light and phytohormonesis mediated by the stomatal response to these factors. (Received September 30, 1983; Accepted February 27, 1984)     

The effect of light quality and gibberellic acid (GA3) on photosynthesis and respiration rates of pea seedlings

CO₂ exchange were measured on pea seedlings (Pisum sativum L. var. Bördi) cultivated from seeds imbibed either in water (C-plants) or in gibberellic acid (GA₃) at the concentration of 25 g/1 (GA-plants), and then grown under 17 W/m² blue light (B-plants) or 11 W/m² red light (R-plants).When measured under the same light conditions as during growth the net photosynthesis (APS) rate in B-plants was about twice higher than that in R-plants. Dark respiration (DR) rate was 70% higher in B- than in R-plants. Red light retarded the development of photosynthetic activity, but GA₃ suppressed this effect. The hormone enhanced net photosynthesis and dark respiration to the same extent.When measured under saturating white light net photosynthesis rate of C-plants was also two times higher in B-plants than in R-plants. Growth conditions had only a slight effect on the APS of GA-plants under white light. APS rates of GA-plants grown under red light were higher under white light than those of C-plants, but lower than those of plants grown under blue light.We assume that blue light induced formation of plants that were adapted to higher light intensity: red light had an opposite effect, whereas gibberellic acid induced formation of plants that were adapted to medium light intensity.     

Defined conditions for the initiation on growth of cotton callus in vitro I.Gossypium arboreum

Summary Defined in vitro conditions for callus initiation byGossypium arboreum L. were determined, and different tissues were evaluated as explant sources. Environmental conditions tested included light versus dark, and low light versus high light. Different nutrient media as well as carbohydrate sources were examined. Our data show that hypocotyl tissue was superior to cotyledon or leaf tissue as the explant source for callus proliferation; the Murashige-Skoog inorganic formulation with (in mg per 1) 100 myo-inositol, 0.4 thiamine·HCl, 2 indoleacetic acid (IAA), 1 kinetin, and 3% glucose solidified by agar was the best medium to initiate callus. Cultures with sucrose as a carbohydrate source browned rapidly. Callus proliferation was superior under high light (8000 to 9000 lux) conditions at 29±1°C. Various combinations of auxins and cytokinins were tested for their ability to improve callus proliferation and subsequent growth of subcultures. Although the MS medium containing IAA and kinetin was found superior for obtaining rapid proliferation of callus from hypocotyl explants, a second medium containing 2 mg per 1 naphthalenacetic acid (NAA) and 0.5 to 1 mg per 1 benzyladenine (BA) was found necessary for vigorous growth of subcultured callus. A MS medium with 5 to 10 mg per 1 {ie329-1} (2iP) and 1 mg per 1 NAA was also favorable for continued subculturing. Technical Article 12485 from the Texas Agricultural Experiment Station.     

Role of phytochrome in photoperiodic regulation of bulbing and growth in the long day plant Allium cepa

Plant elongation in Allium cepa L. cv. Dorata di Parma was stimulated by end-of-day far-red radiation, while the same treatment was ineffective with respect to bulbing response. It was concluded that the P_fr-dependent reactions which control bulbing are completed during the long daily light period (18 h). Day breaks of 3 h fluorescent white light, in the middle of the inductive photoperiod were inhibitory to bulbing. Repeated brief far-red irradiations could substitute for continuous far-red irradiations lasting 3 h in the middle of the photoperiod. Red light alone or applied immediately after each far-red irradiation inhibits bulb formation.     

Somatic embryogenesis and plant regeneration of <Emphasis Type="Italic">Lilium ledebourii</Emphasis> (Baker) Boiss., an endangered species

A somatic embryogenesis (SE) protocol was established for the regeneration of Lilium ledebourii (Baker) Boiss. whole plants using new vegetative bulblet microscales and transverse thin cell layers (tTCLs) of young bulblet roots as the explant sources. Bulblets were induced from bulb scale explants cultured for at least 3 months in the dark on Murashige and Skoog (MS) medium containing 3% sucrose, 0.8% agar, and different concentrations of α-naphthaleneacetic acid (NAA), 6-benzyladenine (BA), and thidiazuron. Embryo-like structures were obtained from tTCL explants of 3-month-old bulblets (excised from bulb scale explants) following culture on solid MS medium containing 3% sucrose and various concentrations of NAA and BA for 3 months in the dark. Both the explant source and the type of plant growth regulators affected the differentiation of somatic embryos. The highest percentage (65.55%) of embryogenesis was obtained from bulblet microscale tTCLs cultured on solid MS medium containing 0.54 μM NAA and 0.44 μM BA. Plants with normal shoots and roots were obtained following a 3-month culture of embryos on growth regulator-free MS medium at 25 ± 1°C under a 16/8-h light/dark photoperiod (light intensity 40 μmol m⁻² s⁻¹, cool-white fluorescent light). The plants were successfully acclimatized in the growth chamber.     

Effect of Auxins, Cytokinins, Gibberellins, Abscisic Acid and Ethephon on Regeneration and Growth of Bulblets on Excised Bulb Scale Segments of Hyacinth

The effect of various growth substances on regeneration and growth of bulblets on excised bulb scale segments of Hyacinthus orientalis L. cv. Pink Pearl was studied. Bulblet formation was promoted by the auxins IAA and IBA but was inhibited by NAA at high concentrations. IAA hardly affected bulblet weight, whereas IBA and NAA at high concentrations decreased it. Cytokinins had hardly any effect on bulblet regeneration and bulblet weight, Gibberellins inhibited both bulblet regeneration and bulblet weight; GA₄₊₇ acted much stronger than GA₃. ABA and ethephon decreased bulblet regeneration and bulblet growth.     

Auxin level and regeneration of Begonia leaves

Summary As previously found, both the level of ether-extractable auxin (presumably indole-3-acetic acid) and the root-forming ability of B.xcheimantha leaves are increased under long-day conditions by high temperature, whereas the capacity for adventitious bud formation is reduced. However, this relation is present under relatively high light intensity only. Under the low light intensities in late fall neither auxin level nor regeneration ability were significantly affected by temperature.Dark treatment of detached leaves for 2 to 16 days greatly counteracted the inhibitory effect of high temperature on bud formation and reduced both the auxin level and the root-forming ability of the leaves.The great seasonal changes in the regeneration ability of Begonia leaves seem to be the result of a complex interaction of temperature, day-length, and daily light energy on the level of endogenous auxin and other growth regulators.     

The effect of (2-chloroethyl)trimethylammonium chloride (CCC) and gibberellic acid on the growth and development of wheat cultivated under red or blue light

The effect of CCC and GA₃ on the growth and development of spring wheat (Triticum aestivum L.) cultivated under predominantly red (500–700 nm) or blue (400–500 nm) light was investigated. Red light enhanced the development of wheat during the exponential phase of growth. This effect presumably implicated the promotion of gibberellin synthesis under red light. The strong inhibitory action of CCC under red light (the inhibition was lower under blue light) might be interpreted in a similar way. The growth became more intensive under blue light after caring and was accompanied by increased susceptibility to giberellic acid treatment.     

Effects of Light Quality on the Interaction between Cucumber Mosaic Virus and Nicotiana tabacum

Light is an important environment factor controlling plant growth, development, and nutritional quality and is also one of the most important factors inducing plant defence. In this study, we assayed the potential effects of light quality on the interaction between Nicotiana tabacum and cucumber mosaic virus (CMV). Our results indicated that white light‐treated N. tabacum plants displayed obvious symptoms at early stage postinoculation, while the symptoms were significantly inhibited under red light and blue light. Western blotting and quantitative real‐time PCR (qRT‐PCR) analyses showed that blue light and red light can effectively delay the replication of CMV compared with white light. The activities of various reactive oxygen species (ROS)‐scavenging enzymes and reducing substances [reduced glutathione (GSH) and ascorbic acid (ASA)] were increased under blue light and red light. In addition, hormone measurements and qRT‐PCR analyses revealed that salicylic acid (SA)‐mediated signalling pathway plays positive role in the related regulation, and cytokinin (CTK) may also participate in them. Furthermore, we found that the formation of dark green islands (DGIs) was significantly suppressed in plants under red light and blue light at 30 days postinoculation (Dpi). However, the accumulation of virus in plants under different light conditions had no notable differences at later stage of postinoculation. Taken together, these results indicated that red light and blue light could effectively delay symptom expression and replication of CMV on N. tabacum at the relatively earlier stage postinoculation.     

Effects of auxins and cytokinins on formation of Catharanthus roseus G. Don multiple shoots

The effects of different combinations of plant growth regulators and light intensity on the formation of multiple shoots of Catharanthus roseus (L.) were studied. By composing three dimension surfaces and their topo views from experimental data, it was clear that Murashige-Shoog (MS) medium supplemented with 7.0 mg l^-1 BA and 1.0 mg l^-1 NAA strongly stimulated the formation of shoots, whereas medium supplemented with 2,4-d suppressed the formation of shoots or caused shoot dedifferentiated. Light intensities of 550–700 Lux were found to be beneficial to the formation of shoots when MS medium was supplemented with 2 mg l^-1 6-BA and 0–1.0mg l^-1 NAA.Abbreviations BA-6 benzyladenine - NAA -naphthalenacetic acid - 2,4-d 2,4-dichlorophenoxyacetic acid