Non-Reversibility of Gibberellin-Induced Inhibition of Regeneration in Begonia Leaves

With applied to the petioles of detached Begonia x cheimantha leaves before planting, Gibberellic acid (GA₃) inhibited the formation of adventitious buds and roots ill an apparently irreversible manner. Bud formation was entirely suppressed by 10^?6M and higher concentrations and a significant inhibition was still present at 10^?9M the lowest concentration tested. Root formation was not affected by GA₃ below 10^?7M and was possible even at 10^?4 M GA₃. Petiole elongation was stimulated by GA₃ with an optimum at 10^?5M. GA₃ also blocked the action of 6-benzyiamino-purine (BAP) and 1-naphthaleneacetic acid (NAA), compounds which are potent stimulators of bud and root formation, respectively. When applied simultaneously with GA₃ they were, at their optimal concentrations, devoid of any effect in counteracting or reversing the gibberellin-induced inhibitions. Abscisic acid and the growth retardants CCC and Phosfon also were unable to restore bud and root formation. In leaves initially treated with water or 10^?5M BAP, endogenous bud and root formation as well as BAP-induced bud formation were entirety suppressed when 10^?5M GA₃ was applied 8 days after the initial treatments. Even when delayed for 14 days GA₃ treatment inhibited BAP-induced bud formation, while treatment after 21 days bad little effect on bud and root formation. Development of pre-existing, visible bud primordia was not inhibited by GA₃. BAP and NAA competitively inhibited the action of GA₃ in petiole extension growth. The results are discussed in relation to results obtained in other plant systems. It is suggested that GA₃ acts by blocking of the organized cell divisions initiating the formation of bud and root primordia.     

Higher Production of Forskolin in Genetically Transformed Cultures of Coleus forskohlii Briq Induced by Growth Regulators

Increased forskolin yield was obtained in transformed root, rhizogenic calli and cell suspension cultures of Coleus forskohlii when treated alone with various concentrations of auxins (IAA, IBA, NAA, 2,4-0), auxin conjugates ( IAA-ala, IAA-gly, IAA-phe, IAA-asp), cytokinins (Kn, BAP) and gibberellic acid (GA₃). An 8.9-fold stimulation in forskolin production was achieved in transformed rhizogenic line GCO-RCH-10 in presence of 1.0 mg I^-1 GA₃, 6-fold in cell suspension line GSO-5/7-k in presence of 2 mg I^-1 BAP and 4.3-fold in root line RC-ST -2/16 in presence of 0.5 mg I^-1 GA₃ at the end of a culture period of 4 weeks. Growth and morphology was found to be influenced by the growth regulators studied. A seven fold increase in biomass was obtained in rhizogenic line GCO-RCH-10 with 0.5 mg I^-1 GA₃ In root line RC-ST-2/16, different concentrations of IAA, IAA conjugates and GA3 stimulated growth while cytokinins inhibited growth of roots. The shoot culture line ST -2/51/d, showed prolific growth in the presence of all cytokinins but no forskolin was detected in the shoot cultures treated with any of these hormones.     

Gibberellic acid improves water deficit tolerance in maize plants

The combination effects of water stress and gibberellic acid (GA₃) on physiological attributes and nutritional status of maize (Zea mays L. cv., DK 647 F1) were studied in a pot experiment. Maize plants were grown in the control (well watered WW) and water stress subjected to treated both water stress and two concentrations of gibberellic acid (GA₃ 25 mg L⁻¹, 50 mg L⁻¹). WS was imposed by maintaining the moisture level equivalent to 50 % pot capacity whereas the WW pots were maintained at full pot capacity. Water stress reduced the total dry weight, chlorophyll concentration, and leaf relative water content (RWC), but it increased proline accumulation and electrolyte leakage in maize plants and appears to affect shoots more than roots. Both concentrations of GA₃ (25 and 50 mg L⁻¹) largely enhanced the above physiological parameters to levels similar to control. WS reduced leaf Ca²⁺ and K⁺ concentrations, but exogenous application of GA₃ increased those nutrient levels similar or close to control. Exogenous application of GA₃ improved the water stress tolerance in maize plants by maintaining membrane permeability, enhancing chlorophyll concentration, leaf relative water content (LRWC) and some macro-nutrient concentrations in leaves.     

Effect of Gibberellic Acid, (2-Chloroethyl) Phosphonic Acid, Actinomycin-D and Cycloheximide on the Activity and Leaching of Some Hydrolases in Pollen Suspension Cultures of Crotalaria juncea

Gibberellic acid (GA₃) 20 mg 1^?1 and (2-chloroethyl) phosphonic acid (Ethephon) 10 mg 1^?1 enhanced pollen tube length in Crotalaria juncea L. GA₃ markedly increased the activity of amylase, acid phosphatase and β-glucosidase and enhanced leaching of amylase and acid phosphatase enzymes. The rise in the activity level and leaching of amylase and acid phosphatase after Ethephon treatment was comparatively less than that of GA₃ and the response to Ethephon was restricted to the 45 and 90 min period of culturing. Ethephon did not affect the activity/leaching of β-glucosidase significantly. Actinomycin-D (Act.D) 25 mg l^?1 and Cycloheximide (CH) 10 mg 1^?1 reduced the tube growth as well as activity of these enzymes suggesting their de novo synthesis during pollen tube growth.     

Effects of growth retardants on bulbil production by Narcissus twin-scales

Narcissus twin-scale propagules, cut from various positions in the parent bulb, were incubated with gibberellic acid (GA₃) or growth retardants. Bulbil production was inhibited in all cases by GA₃ at 10–100 mg/litre. Chlormequat chloride, chlorphonium chloride and paclobutrazol also inhibited bulbil production; in the case of paclobutrazol, outer twin-scales were more sensitive to lower concentrations of the retardant than inner ones. Ancymidol enhanced bulbil production (in numbers by up to 15%) in the outermost twin-scales, and had no stimulatory effect on the inner twin-scales. Treatments affected bulbil numbers and bulbil lengths about equally.     

Gibberellic acid bioassay based on the inhibition of anthocyanin production in tomato seedlings

A simple bioassay of gibberellic acid (GA₃) based on the GA₃-induced reduction of anthocyanin contents in young seedlings of tomato is described and compared with the amaranthin reduction test. It was found that GA₃-induced reduction of anthocyanin in tomato seedlings was linear from 10⁻⁵ to 10 mg 1⁻¹ GA₃ whereas the reduction of amaranthin inAn aranthus caudatus seedlings was linear from 10⁻³ to 10 mg 1⁻¹ GA₃. From these results, it is concluded that the anthocyanin reduction test for GA₃ is more sensitive at lower concentrations of GA₃ than the amaranthin reduction test.     

Efficient Evergreen Plant Regeneration of <i>Cinnamomum japonicum</i> Sieb. through <i>in vitro</i> Organogenesis

Cinnamomum japonicum Sieb. is an excellent roadside tree and medicinal tree species with considerable ornamental and economic value. In this study, we successfully developed a large-scale micropropagation protocol for C. japonicum for the first time. Sterilized shoots were excised and used as explants for shoot induction on several basal media, supplemented with different concentrations of plant growth regulators (PGRs), such as Thidiazuron (TDZ), N⁶ -Benzyladenine (6-benzylaminopurine) (BA), α-naphthaleneacetic acid (NAA) and Gibberellic acid (GA₃). After comparison, the most efficient medium for shoot regeneration was 1/2 Murashige and Skoog (MS) medium containing 0.5 mg L^–1 BA, 0.05 mg L^–1 NAA and 0.2 mg L^–1 GA₃, which resulted in an average number of induced shoots per explant and shoot length of 5.2 and 1.62 cm at 28 d, respectively. Then, elongated adventitious shoots were transferred to induce roots. 86.7% of shoots was able to root on 1/2 MS medium supplemented with 0.5 mg L^–1 NAA and 0.1 mg L^–1 BA. The earliest rooting time observed was after 21 d and the average root length was up to 3.3 cm after 28 d. Our study shows that C. japonicum can be successfully regenerated through de novo organogenesis, which lays a foundation for future transformation research on this tree.     

不同培养条件对勺叶茅膏菜试管苗矶松素含量的影响

为探讨培养条件对勺叶茅膏菜(Drosera spatulata)试管苗矶松素积累的影响,采用高效液相色谱(HPLC)法测定矶松素含量,对不同器官和不同培养条件下的勺叶茅膏菜试管苗矶松素含量变化进行研究。结果表明,勺叶茅膏菜试管苗根的矶松素含量显著高于叶片;光质和有机物含量对勺叶茅膏菜试管苗矶松素含量的影响不显著,但对试管苗的生长具有显著影响,最佳培养光质为白光,其次为红光和蓝光,最后为绿光;适当降低培养基中有机物含量可促进勺叶茅膏菜试管苗的生长发育;植物生长调节剂对矶松素积累的影响效应依次为6-BANAAKTGA3,而对试管苗生长的影响效应依次为6-BAGA3NAAKT。因此,勺叶茅膏菜试管苗的最佳培养条件为:以1/2MS为基本培养基,添加0~0.2 mg L–1 6-BA、0.2 mg L–1 NAA、0.5 mg L–1KT和0.1 mg L–1 GA3,于白光下培养。     

Activity of Various Growth Substances in the Avena First Internode Test

The elongation growth of the Avena first internode segments was studied in the presence of one or several of the following growth substances: indoleacetic acid (IAA), 6-fur-furylamino purine (FAP, kinetin), 6-benzylamino purine (BAP), gibberellin A₃ (GA₃) and A₄₊₇ (GA₄₊₇), and abscisic acid (ABA). The cytokinins at concentrations of 10^?7 to 10^?6M stimulated growth with 4 to 6 per cent but this effect was not statistically significant. Concentrations higher than 5 × 10^?6M inhibited growth. FAP and BAP (from 10^?8M to 10^?6M) had no significant interaction with any other growth substance used. The two-factor interactions of IAA × ABA, IAA × GA₃, and GA₃× ABA, as well as the three-factor interaction IAA × ABA × GA₃ were significant. However, the IAA × ABA interaction was significant only when high concentration (10^?6M) of ABA was used. The growth inhibition produced by 10^?7 and 10^?6M ABA was overcome by about equimolar concentrations of IAA. The stimulation of growth by GA₃ and GA₄₊₇ (10^?9 to 10^?7M) was prevented by simultaneous application of ABA, and it was reduced significantly by application of IAA (10^?7 to 10^?8M). GA3 at 10^?8M combined with different concentrations of IAA gave slightly higher elongation than IAA alone but the observed values were significantly lower than expected assuming independent additive action.     

Enhanced Phytoremediation of Cadmium-Contaminated Soil by Parthenium hysterophorus Plant: Effect of Gibberellic Acid (GA3) and Synthetic Chelator,Alone and in Combinations

The roles of gibberellic acid (GA₃) and ethylenediaminetetraacetic acid (EDTA) in phytoremediation of cadmium (Cd)-contaminated soil by Parthenium hysterophorus plant was investigated. GA₃ (10^?9, 10^?7, and 10^?5M) was applied as a foliar spray. EDTA was added to soil in a single dose (160 mg/kg soil) and split doses (40 mg/kg soil, four split doses). GA₃ and EDTA were used separately and in various combinations. P. hysterophorus was selected due to its fast growth and unpalatable nature to herbivores to reduce the entrance of metal into the food chain. The Cd phytoextraction potential of the P. hysterophorus plant was evaluated for the first time. Cd significantly reduced plant growth and dry biomass (DBM). GA₃ alone increased the plant growth and biomass in Cd-contaminated soil, whereas EDTA reduced it. GA₃ in combination with EDTA significantly increased the growth and biomass. The highest significant DBM was found in treatment T3 (10^?5M GA₃). All treatments of GA₃ or EDTA significantly enhanced the plant Cd uptake and accumulation compared with control (C1). The highest significant root and stem Cd concentrations were found in the combination treatment T11 (GA₃ 10^?5M + EDTA split doses), whereas in leaves it was found in the EDTA treatments. Cd concentration in plant parts increased in the order of stem < leaves < roots. The combination treatment T9 (GA₃ 10^?7M + EDTA split doses) showed the significantly highest total Cd accumulation (8 times greater than control C1, i.e., only Cd used). The GA₃ treatments accumulated more than 50% of the total Cd in the roots, whereas the EDTA treatments showed more than 50% in the leaves. Root dry biomass showed a positive and significant correlation with Cd accumulation. GA₃ is environment friendly as compared with EDTA. Therefore, further investigation of GA₃ is recommended for phytoremediation research for the remediation of metal-contaminated soil.     

Effects of gibberellic acid on hairy root cultures of Artemisia annua: Growth and artemisinin production

Summary Artemisinin (AN), a potent antimalarial drug that has been used for centuries as a folk remedy in China, is an effective treatment against quinine-resistant strains of Plasmodium. It can be produced through the in vitro culture of genetically transformed (hairy) roots. The effect of gibberellic acid (GA₃) on the growth and secondary metabolite production of hairy roots of Artemisia annua was investigated. Six different concentrations of GA₃ were tested in shaker flasks to determine the optimum concentration. GA₃ levels of 0.01–0.001 mg/l (28.9–2.89 μM) provided the most significant increase in biomass, and 0.01 mg/l (28.9 μM) produced the highest amount of AN. Investigation of growth kinetics showed that the use of GA₃ at 0.01 mg/l (28.9 μM) increased the growth rate of hairy roots of A. annua by 24.9%. Thus, the cultures treated with GA₃ reached stationary phase faster than control cultures.     

Effects of gibberellin GA7 on kinetics of growth and tropane alkaloid accumulation in hairy roots of Brugmansia candida

Summary Brugmansia candida, an indigenous South American plant, produces the tropane alkaloids scopolamine and hyoscyamine, which are widely employed in medicine as anticholinergic agents. In this research, hairy roots of Brugmansia candida, obtained through infection with Agrobacterium rhizogenes LBA 9402, were employed to produce these tropane alkaloids in vitro. The effects of different concentrations of GA₇ on kinetics of growth and alkaloid accumulation on two different hairy root clones of B. candida were analyzed, and the influence of GA₇ on the number of new branches and rates of elongation was also studied. On clone 7A, GA₇ at concentrations of 10⁻⁴, 10⁻¹, and 1 mg/l increased the exponential growth rate. Levels of 10⁻¹ and 10⁻⁴ mg/l GA₇ elevated the scopolamine/hyoscyamine (S/H) ratios in the early phases of growth, but the sum of scopolamine plus hyoscyamine per flask (S + H) decreased during that period. When 1 mg/l GA₇ was used, the highest S/H ratios were observed in late exponential/early stationary phases, but the highest S + H totals were obtained in mid-exponential phase. GA₇ at levels of 10⁻¹ and, especially, 1 mg/l exerted a positive effect on formation, emergence, and rate of elongation of lateral roots (clone 7A). On clone 7B, levels of 10⁻¹ and 1 mg/l GA₇ did not alter significantly the exponential growth rate. GA₇ in concentrations of 10⁻¹ mg/l induced increases in both S/H ratio and S + H totals in late phases of growth.     

Efficient plant regeneration from protoplasts of Arachis paraguariensis Chod. et Hassl. using a nurse culture method

Factors influencing in vitro growth rates of soybean embryos were investigated using embryos isolated in the cotyledon stage. The influence of these factors on final plant recovery from the embryos cultured was tested. Sucrose and glucose could serve as carbon sources with final plant yields being higher with sucrose than with glucose. A culture medium containing only KNO₃ (25 mM) as the nitrogen source supported embryo growth. Adding glutamine (10 mM) to the medium containing KNO₃ increased final plant recovery to 25%. Of several vitamin supplements tested a combination of pyridoxine-HCl, nicotinic acid and pantothenic acid (0.5; 1.0; 0.5 mg l^-1) provided the best growth and plant yield. Of the plant growth regulators tested IAA, BAP and GA₃ stimulated embryo growth and plant development when added to the medium at a low concentration (0.1 M). The optimal temperature for in vitro growth of cotyledon stage embryos was 27°C. Temperatures above 30°C caused growth retardation and reduced plant yield. A protocol for culturing soybean cotyledon stage embryos under conditions ensuring high plant recovery is proposed.Abbreviations IBA indole-3-butyric acid - GA₃ gibberellic acid - IAA indole-3-acetic acid - NAA -naphthaleneacetic acid - BAP 6-benzylaminopurine - 2,4-D 2,4-dichlorophenoxyacetic acid     

Effect of relative hormone concentration on auxin-gibberellin interaction in correlative inhibition of axillary buds

Summary Indole-3-acetic acid (IAA) applied to the fully elongated second internode of decapitated Phaseolus multiflorus plants always inhibited axillary bud elongation at concentrations down to 100 g/g lanolin, whereas gibberellic acid (GA₃) enhanced bud elongation at concentrations down to 1000 g/g lanolin. Lower concentrations than these of either IAA or GA₃ were without significant effect. All possible combinations of IAA and GA₃ within the concentration range 10¹ to 10⁵ g/g lanolin were antagonistic; IAA tending to inhibit, and GA₃ promote, axillary bud elongation growth. Treatment of an elongating internode with the hormones resulted in an increase in inhibition of bud growth by IAA in the presence of GA₃.     

In vitro propagation of Populus x wilsocarpa — a hybrid of ornamental value

Populus x wilsocarpa, a hybrid of important ornamental value, cannot be seed-propagated, nor grafted, since a compatible rootstock has not been identified. A micropropagation protocol consisting of a series of steps was therefore developed to facilitate the commercial production of this species. The technique involved the transfer of swelling buds to a growth initiation medium with the following composition: N6 macronutrients, MS micronutrients and vitamins supplemented with 0.5 mg l^-1 BAP. The best buds were from dormant twigs, stored at 0–2°C and then forced to burst prior to culture initiation. Shoot multiplication was on a basal WPM medium including 0.1 mg l^-1 BAP and 0.001 mg l^-1 NAA. Shoot elongation and rooting was also on a basal WPM medium supplemented with 1.0 mg l^-1 GA₃ followed by a transfer to a peat-perlite mix in the greenhouse.Abbreviations ABA abscisic acid - BAP benzylaminopurine - GA₃ gibberellic acid (GA₃) - MS Murashige and Skoog [17] - NAA naphthaleneacetic acid - N6 medium [Chu et al., 7] - WPM woody plant medium [16]     

Factors affecting gibberellic acid production by Fusarium moniliforme in solid-state cultivation on starch

The production of gibberellic acid (GA₃) by Fusarium moniliforme M-7121 in solid-state culture was evaluated in flask cultures as well as in 3-I horizontal rotary reactors. The highest production rate of GA₃ was with 80% (w/v) maize flour mixed with wheat bran. The optimum initial moisture content was inversely dependent on the ambient relative humidity. The initial water activity range for optimal growth and GA₃ accumulation was about 0.98 to 0.99, which is unusually high for a filamentous fungus. A low O₂ concentration resulted in a much decreased GA₃ yield and the appearance of a yellow to reddish pigmentation in the mycelium. The lag phase was short and rapid growth continued for up to 2 days in the rotary reactor, with a maximum specific growth rate of 0.12 h^–1. The maximum rate of GA₃ production occurred during the subsequent 3 to 10 days of incubation and the final GA₃ concentration reached was 18.7 mg to 19.3 mg/g dry culture. The point of maximum GA₃ accumulation after 10 to 12 days of incubation was usually marked by a sharp increase in pH.The authors are with the Department of Microbiology and Biochemistry, University of the Orange Free State, P.O. Box 339, 9300 Bioemfontein, Republic of South Africa     

The effect of plant growth regulators on growth, morphology and condensed tannin accumulation in transformed root cultures of Lotus corniculatus

This study concerns the effects of four different classes of plant growth regulators on root morphology, patterns of growth and condensed tannin accumulation in transgenic root cultures of Lotus corniculatus L. (Bird's-foot trefoil). Growth of transformed roots in 2,4-dichlorophenoxyacetic acid (2,4-D) resulted in decreased tannin levels relative to controls at concentrations of 10^-6 M and above, while gibberellic acid (GA₃) inhibited tannin accumulation at concentrations of 10^-7 M and above. Benzyladenine (BA) had little effect at low concentrations (10^-7 M and below) but resulted in an increase in tannin levels at 10^-6 M. Abscisic acid had little effect on levels of condensed tannins at any of the concentrations used. Experiments involving growth regulator addition and medium transfer demonstrated that 2,4-D inhibition of tannin accumulation could be reversed by GA₃ and BA, while GA₃ downregulation could only be reversed by the addition of 2,4-D. Although 2,4-D inhibited tannin accumulation, addition of 2,4-D to root cultures grown for 14 or 28 days in the absence of plant growth regulators stimulated both growth and tannin biosynthesis. Characteristic alterations in root morphologies accompanied growth regulator-mediated modulation of tannin biosynthesis. Growth in 2,4-D resulted in partially de-differentiated root cultures while growth in GA₃ produced roots with an elongated phenotype. Restoration of tannin biosynthesis in 2,4-D-treated roots was accompanied by root re-differentiation and the production of new lateral roots.Abbreviations ABA abscisic acid - BA benzyladenine - 2,4-d 2,4-dichlorophenoxyacetic acid - GA₃ gibberellic acid 3 - FW fresh weight     

In vitro establishment and multiplication of Nymphaea hybrid ‘James Brydon’

Rhizome tips were the most suitable explants for in vitro plant regeneration and multiplication of Nymphaea hybrid James Brydon on Murashige and Skoog medium containing different concentrations and combinations of indole-3-acetic acid, 1-naphthaleneacetic acid (NAA), 2,4-dichlorophenoxyacetic acid, 6-benzyladenine (BA), kinetin, 2-isopentenyladenine (2iP) and gibberellic acid (GA₃). A combination of 2iP, BA, and NAA strongly favored induction of shoot buds and shoot proliferation. Pretreatment of shoot cultures at 8°C for 30 days or with 14.4 or 28.9 M GA₃ for 15 days did not improve shoot multiplication. A 16-h photoperiod with photosynthetic photon flux of 30 mol m^-2 s^-1 was found to be the optimum light condition for shoot growth and multiplication. Multiple shoots produced well developed root systems within 4 weeks after transfer to a plant growth regulator-free medium containing activated charcoal.Abbreviations BA 6-benzyladenine - 2,4-d 2,4-dichlorophenoxyacetic acid - GA₃ gibberellic acid - IAA indole-3-acetic acid - 2iP 2-isopentenyladenine - MS Murashige and Skoog medium - NAA 1-naphthaleneacetic acid     

Responsiveness of Amaranthus retroflexus seeds to ethephon, 1-aminocyclopropane 1-carboxylic acid and gibberellic acid in relation to temperature and dormancy

Dormant Amaranthus retroflexus seeds do not germinate in the dark at temperatures below 35°C. Fully dormant seeds germinate only at 35–40°C whereas non-dormant ones germinate within a wider range of temperatures (15 to 40°C). Germination of non-dormant seeds requires at least 10% oxygen, but the sensitivity of seeds to oxygen deprivation increases with increasing depth of dormancy. 10^–6 to 10^–4 M ethephon, 10^–3 M 1-aminocyclopropane 1-carboxylic acid (ACC) and 10^–3 M gibberellic acid (GA₃) break this dormancy. In the presence of 10^–3 M GA₃ dormant seeds are able to germinate in the same range of temperatures as non-dormant seeds. The stimulatory effect of GA₃ is less dependent on temperature than that of ethephon, while ACC stimulates germination only at relatively high temperatures (25–30°C). The results obtained are discussed in relation to the possible involvement of endogenous ethylene in the regulation of germination of A. retroflexus seeds.Abbreviations ACC 1-aminocyclopropane 1-carboxylic acid - GA₃ gibberellic acid - SD standard deviation     

Regulation of Growth in Avena (Oat) Stem Segments by Gibberellic Acid and Abscisic Acid

The purpose of this study was to analyze the nature of the interaction between gibberellic acid (GA₃) and abscisic acid (ABA) in the regulation of growth in excised Avena (oat) stem segments. Growth, compared to sucrose controls, was inhibited by ABA in the range of 10^?4 to 10^?6M. GA₃-promoted growth was also inhibited by ABA in the same concentration range. A Lineweaver-Burk analysis of the interaction between GA₃ and ABA indicated that ABA acts in a non-competitive fashion with GA₃. This same result was obtained previously with GA₃-indoleacetic acid (IAA) and GA₃-kinetin interactions with Avena stem sections. Our results indicate that ABA can inhibit GA₃-promoted growth within physiological concentrations, and that it is probably acting at a different physiological site from that for GA₃.