Effects of Ethylenediaminetetraacetic Acid, Auxin and Gibberellic Acid on Phytochrome Controlled Nyctinasty in Albizzia julibrissin

Nyctinastic closure of Albizzia julibrissin pinnules is inhibited by 5 × 10^?2M ethylenediaminetetraacetic acid. At least two hours of incubation are required for maximum inhibition and destruction of the phytochrome effect. Concentrations of 10^?3 to 10^?5M naphthaleneacetic acid reduced the nyctinastic closure of pinnules but not the phytochrome response. Similar results were obtained with indoleacetic acid and gibberellic acid. No appreciable differences in pinnule movements could be attributed to pH. Chelation or the inhibition of ion transport resulting in, or caused by, changes in membrane permeability are suggested as possible mechanisms involved in these effects.     

Phytochrome-controlled Nyctinasty in Albizzia julibrissin: III. Interactions between an Endogenous Rhythm and Phytochrome in Control of Potassium Flux and Leaflet Movement

Prolonged irradiation during appropriate parts of the diurnal cycle promotes the opening of Albizzia julibrissin leaflets. Leaflets also open without illumination, but such opening starts later and is slower and less complete. Opening in the dark is accompanied by lower potassium efflux from dorsal pulvinule motor cells but equal or greater potassium movement into ventral motor cells than occurs during opening in the light. Far red-absorbing phytochrome inhibits opening in the dark, indicating that its action is similar during endogenously controlled opening and nyctinastic closure; i.e., a high far redabsorbing phytochrome level is associated with low potassium content in ventral motor cells, high potassium content in dorsal motor cells, and a small angle between leaflets.     

Phytochrome control of rapid nyctinastic movements and membrane permeability in Albizzia julibrissin

Summary The rapid nyctinastic movements of Albizzia julibrissin pinnules are under the control of phytochrome. When given prior to a dark period, red light facilitates and far-red light inhibits pinnule closure in the dark. These light effects are mutually photoreversible. The opening reaction of the pinnules following a dark period is mediated mainly by blue light. The nyctinastic closure response is accompanied by an increased rate of electrolyte efflux from the cut pinna base. This observation, coupled with the fact that the rapid nyctinastic movement is not affected by actinomycin D, supports the view that phytochrome control of the sleep movement is not mediated through effects on RNA metabolism, but rather through changes in membrane permeability.     

Phytochrome-controlled Nyctinasty in Albizzia julibrissin: IV. Auxin Effects on Leaflet Movement and K Flux

Indole-3-acetic acid, α-naphthylacetic acid, and 2,4-dichlorophenoxyacetic acid (0.001 to 1.0 mm) inhibit the nyctinastic closure of excised Albizzia leaflet pairs; antiauxins and auxin analogs are ineffective, and the auxin effects seem not to be mediated by ethylene. Indoleacetic acid (0.001 to 0.1 mm) also promotes rhythmic opening in the dark, but is ineffective during that phase of rhythmic closure (“leaky phase”) which is insensitive to azide. At these concentrations, all of the indoleacetic acid effects are reversible upon transfer of the tissue to water and are linked to alteration of potassium flux in pulvinule motor cells.     

Phytochrome Effects in the Nyctinastic Leaf Movements of Albizzia julibrissin and Some Other Legumes

Participation of phytochrome is evident in the nyctinastic response of leaves of Albizzia julibrissin (silk-tree), Albizzia lophantha, Leucaena glauca, Poinciana gilliesi and Calliandra inequilatera; closure of excised pairs of pinnules upon darkening is rapid following red illumination and slow following far-red. Under good conditions the difference is obvious within 10 minutes. These observations confirm a report by Fondeville, Borthwick, and Hendricks on the sensitive plant, Mimosa pudica, but indicate that the effect bears no necessary relationship to the anomalous sensitivity of Mimosa. In A. julibrissin, phytochrome control is marked in experiments conducted early in the daily 12-hour light period and appears absent, or nearly so, toward the end of the light period, perhaps due to interaction with an endogenous circadian rhythm. Effects of leaf maturity and of the position of a pinnule-pair within a leaf are also evident.

These results are not easily reconciled with hypotheses of phytochrome action through gene activation and nucleic acid synthesis, but are consistent with hypotheses based on permeability changes and membrane properties. The magnitude and reproducibility of the response in A. julibrissin suggest its use as a laboratory exercise; this and related systems should prove valuable for eventual identification of the mechanism of phytochrome action.

     

Effect of EGTA on Nyctinastic Closure Mediated by Phytochrome in Albizzia lophantha

The role of extracellular calcium on nyctinastic closure ofAlbizzia lophantha leaflets has been studied by testing theeffect of ethyleneglycol-bis-(ß-aminoethylether)-N,N,N',N'-tetraaceticacid (EGTA) and its reversibility by calcium. EGTA (1 and 5mM) causes an inhibition of nyctinastic closure and at a concentrationof 1 mM EGTA it decreases the difference between the effectof red light (R) and far-red light (FR) irradiation on leafletclosure. A simultaneous or subsequent supply of CaCl₂ (5 or10 mM) reverses EGTA (5 mM) inhibition on closure as well ascausing an additional promotion of closure. We suggest that external calcium could play a dual role in nyctinasticclosure. Phytochrome control of leaflet closure probably needsexternal Ca²⁺ and, in addition, Ca²⁺ could regulate the closuremechanism by controlling ionic fluxes through the plasma membranein pulvinular motor cells. (Received June 9, 1989; Accepted November 27, 1989)     

Rhythmic Leaflet Movement in Albizzia julibrissin: Effect of Electrolytes and Temperature Alteration

The rhythmic movement of darkened Albizzia leaflets is accompanied by K⁺ flux in pulvinule motor cells whose turgor changes control opening and closing. The azide-sensitive open phase is promoted by an increase in temperature from 16 to 33C (Q₁₀ = 3), implying active transport of K⁺ ions during this period. The azide-insensitive closed phase is less temperature-sensitive and has a Q₁₀ less than 1, implying diffusion or some other physical process as the predominant pathway of K⁺ flux at this time. Thus rhythmic leaflet movement is probably due to oscillation in active K⁺ transport or membrane permeability or both. External electrolytes (0. 1 n) alter leaflet angle during the open, but not the closed, phase of the rhythm. All chlorides except NH₄⁺ promote opening, with divalent more effective than monovalent ions. Some anions promote and others inhibit opening; activity is not correlated with charge. It is likely that electrolytes alter leaflet movement by altering K⁺ flux, accomplishing this by interacting with key macromolecules in motor cell membranes.     

Tyrosine Phosphorylation Regulates the Activity of Phytochrome Photoreceptors

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Effect of gibberellin biosynthesis inhibitors on shoot regeneration from hypocotyl explants of Albizzia julibrissin

Summary Hypocotyl explants of Albizzia julibrissin were placed on Gamborg's B5 medium supplemented with various levels of paclobutrazol, uniconazole, prohexadione calcium, or GA₃. Callus formation was evident within one week after placement of the explants on the culture media. Green nodule-like structures protruded from the distal end of the explants within 10 days and developed into shoots within a month. These shoots readily formed adventitious roots when placed on fresh culture medium. All three of the gibberellin biosynthesis inhibitors increased shoot formation compared to the control. The number of shoots per explants was increased 107, 79, and 168% by 0.3–0.4 μM paclobutrazol, uniconazole, and prohexadione calcium, respectively. In contrast to the gibberellin biosynthesis inhibitors, GA₃ decreased shoot formation. These results indicate that modification of gibberellin status can have a strong impact on the number of shoots formed.     

Effects of light flashes on the dark closure of Albizzia julibrissin pinnules

An electronic flash unit is used to deliver, at the beginning of a 10 min dark period and within a few ms, large doses of light to Albizzia julibrissin pinnules, to ascertain their effects on the rate of pinnule closing. In a series of alternating light flashes at 710 and 550 nm, the first 710 nm light flash significantly retards closing. A following light flash at 550 nm negates the far-red induced delay. The second 710 nm light flash delays closing less effectively than the first when given within 4 s after the green flash, but is just as effective when given after 30 s. The delay brought about by the second 710 nm light flash is again abolished by a light flash at 550 nm. A light flash at 660 nm has no effect on pinnule closing by itself and is also ineffective in reversing the far-red induced delay. A series of ten 710 nm light flashes becomes most effective in delaying closure when there is a dark interval of one min between flashes. The closing delay induced by a 710 nm light flash escapes reversal by a 550 nm light flash when the dark interval between the two flashes exceeds 2–3 min. A 750 nm light flash has no retarding effect on pinnule closing, but it becomes effective when preceded by a 660 nm or 550 nm light flash. The results obtained are suggested to be due to light absorbed by phytochrome and an unknown photoreceptor with green, far-red photoreversal property.     

Interaction of phytohormones and far-red irradiation on the nyctinastic closing of Albizzia julibrissin pinnules

In order for far-red radiation at 760 nm to delay dark closing of Albizzia julibrissin pinnules, red light must be given simultaneously with or just prior to it. Studies have been made to determine whether a phytohormone can replace this red light requirement. Abscisic acid, gibberellin, kinetin, and indole-3-acetic acid have been found to replace the red light. Indole-3-carboxylic acid and a cytokinin antagonist are ineffective. In this hormone and far-red interaction, all hormones are effective at μ M or lower concentrations. The hormones show no interaction with red light at 660 nm. Simultaneous irradiation at 550 nm negates the effect of hormone and far-red interaction in delaying leaflet closing. These results are additional evidence that an unidentified far-red absorbing pigment could be involved with phytochrome in some far-red-mediated processes.     

Thidiazuron-induced in vitro shoot formation from roots of intact seedlings of Albizzia julibrissin

Seedlings of silktree (Albizzia julibrissin Durrazz.) were grown in vitro on MS-media containing B5 vitamins, 3% sucrose, 0.25% phytagel and various concentrations (0.1–10 M) of thidiazuron (TDZ). Addition of TDZ to the culture medium greatly reduced shoot and root elongation but did not influence shoot production from the cotyledonary node or apex. Within 8–10 days the seedling roots split open, formed large masses of callus, and developed green patches which eventually grew into normal shoots while still within the culture medium containing TDZ at 0.1–1.0 M. Such callus and shoot formation did not occur in control cultures lacking TDZ. At higher TDZ concentrations (2.5–10 M), the green patches formed in the callus did not further develop into shoots. Addition of other cytokinins (kinetin, benzylaminopurine, zeatin) to the culture medium also induced some shoot formation from the roots, but higher concentrations than TDZ were required to induce regeneration. Isopentenyladenine failed to induced shoot formation. Following excision and transfer to MS media with or without 4.9 M IBA, the shoots induced by kinetin or benzylaminopurine rooted 4–7 days earlier than those induced by TDZ, but all excised shoots developed into normal rooted plantlets within 3 weeks.Abbreviations TDZ thidiazuron     

Anxiolytic-like effects of extracts from Albizzia julibrissin bark in the elevated plus-maze in rats

The purpose of the this study was to characterize the putative anxiolytic-like effects of the aqueous extract of Albizzia julibrissin stem bark using the elevated plus maze (EPM) in rats. The water extract of Albizzia julibrissin was orally administered at 10, 50, 100 or 200 mg/kg to adult male SD rats, 1 h before behavioral evaluation in an EPM, respectively. Control rats were treated with an equal volume of saline, and positive control rats buspirone (1 mg/kg). Single or repeated treatment (for 7 days) of the water extract of Albizzia julibrissin (at 100 or 200 mg/kg) significantly increased time-spent and arm entries into the open arms of the EPM, and decreased time-spent and arm entries in the closed arms of the EPM versus saline controls (P < 0.05). However, no changes in the locomotor activity and myorelaxant effect were seen in any group versus the saline control. In addition, the anxiolytic-like effects of Albizzia julibrissin extract were abolished by pindolol (10 mg/kg, i.p), a 5-HT(1A/1B) receptor antagonist. These results suggest that Albizzia julibrissin might proved to be an effective anxiolytic agent, and that it acts via the serotonergic nervous system.     

Circadian Rhythmicity in Excised Samanea Pulvini: II. Resetting the Clock by Phytochrome Conversion

Excised Samanea saman pulvini were incubated in H(2)O or 50 mm sucrose in darkness for 100 to 152 hours except for brief exposures to red or far red light, and angles of opening measured periodically. When pulvini are incubated in H(2)O, the rhythm damps in the open position after two to three cycles irrespective of the light treatments, but when sucrose is available, the now persistent oscillations show large red, far red-regulated effects on phase, amplitude, mesor slope, and entrainment. Single red light pulses rephase the rhythm, with a phase response curve that resembles that reported for other plants and animals; such rephasing is prevented by immediately subsequent far red light, indicating that phytochrome is the photoreceptor. Red light pulses repeated every 24 hours entrain the rhythm, and also prevent damping if presented at an appropriate part of the cycle.     

合欢皮与山合欢皮的理化性质的比较研究

采用紫外分光光度法,薄层色谱法,溶血试验,泡沫反应等,对合欢皮与山合欢皮的理化性质进行了比较研究。结果表明:可以将山合欢皮作合欢皮使用。     

Thidiazuron-induced shoot-bud formation on root segments of Albizzia julibrissin is an apex-controlled, light-independent and calcium-mediated response

Root segments or entire roots of Albizziajulibrissin formed shoot-buds; the former were more responsive thanthe latter. The regeneration capacity of root segments increased with anincreasing distance from the meristem. Shoot regeneration on N₆mineral formulation required either a cytokinin (BAP) or thidiazuron (TDZ); thelatter was more effective than the former, inducing a higher number of shoots ata low concentration (0.1 M) in the light as well as in thedark. The frequency of shoot formation was reduced when the auxin inhibitorsmaleic hydrazide (MH) or triiodobenzoic acid (TIBA) were included, indicating anindirect role of auxin in shoot morphogenesis. Inhibitors of calcium uptake(lanthanum) and calmodulin, trifluoperazine (TFP) or chlorpromazine (CPZ) atvery low levels, resulted in inhibition to reduction in frequency of shootmorphogenesis. This indicates that TDZ-induced shoot formation may be acalcium-mediated response. Increasing the level of calcium in the medium did notpromote shoot formation in the presence of TDZ (0.1 M). At areduced level of calcium, which was ineffective in the presence of low TDZ (0.1M), shoot-buds appeared when the concentration of TDZ wasraised to 1.0 M. This provides indirect evidence that TDZmodulates the tissue level of calcium needed for shoot formation.     

Effects of Age, Water Stress, and 1-Aminocyclopropane-1-carboxylic Acid on Leaflet Movement in Albizzia julibrissin

The movement patterns of Albizzia julibrissin leaflets transferred from light to darkness differ for leaflets of different age: the older the leaflet, the slower and less completely it closes. Water stress, which enhances ethylene synthesis in other plants, and 1-aminocyclopropane-1-carboxylic acid (ACC), precursor of ethylene, both mimic the effect of aging by reducing the rate and extent of dark-induced closure. Brief far-red compared to red irradiation before darkness does not appear to alter the closure of young leaflets, but far-red preirradiation retards the closure of middle-aged and old leaflets floating on water, and middle-aged leaflets treated with ACC. A change in some membrane property and/or cell wall lignification are suggested as possible explanations for the alteration of leaflet movement.