Oat Coleoptiles Research Articles

Biosynthetic pathway of indole-3-acetic acid in ectomycorrhizal fungi collected from northern Thailand.

Indole-3-acetic acid (IAA) is an imperative phytohormone for plant growth and development. Ectomycorrhizal fungi (ECM) are able to produce IAA. However, only a few studies on IAA biosynthesis pathways in ECM fungi have been reported. This study aimed to investigate the IAA biosynthesis pathway of six ECM cultures including Astraeus odoratus, Gyrodon suthepensis, Phlebopus portentosus, Pisolithus albus, Pisolithus orientalis and Scleroderma suthepense. The results showed that all ECM fungi produced IAA in liquid medium that had been supplemented with L-tryptophan. Notably, fungal IAA levels vary for different fungal species. The detection of indole-3-lactic acid and indole-3-ethanol in the crude culture extracts of all ECM fungi indicated an enzymatic reduction of indole-3-pyruvic acid and indole-3-acetaldehyde, respectively in the IAA biosynthesis via the indole-3-pyruvic acid pathway. Moreover, the tryptophan aminotransferase activity confirmed that all ECM fungi synthesize IAA through the indole-3-pyruvic acid pathway. Additionally, the elongation of rice and oat coleoptiles was stimulated by crude culture extract. This is the first report of the biosynthesis pathway of IAA in the tested ECM fungi.

A unified model of shoot tropism in plants: photo-, gravi- and Propio-ception.

Land plants rely mainly on gravitropism and phototropism to control their posture and spatial orientation. In natural conditions, these two major tropisms act concurrently to create a photogravitropic equilibrium in the responsive organ. Recently, a parsimonious model was developed that accurately predicted the complete gravitropic and proprioceptive control over the movement of different organs in different species in response to gravitational stimuli. Here we show that the framework of this unifying graviproprioceptive model can be readily extended to include phototropism. The interaction between gravitropism and phototropism results in an alignment of the apical part of the organ toward a photogravitropic set-point angle. This angle is determined by a combination of the two directional stimuli, gravity and light, weighted by the ratio between the gravi- and photo-sensitivities of the plant organ. In the model, two dimensionless numbers, the graviproprioceptive number B and the photograviceptive number M, control the dynamics and the shapes of the movement. The extended model agrees well with two sets of detailed quantitative data on photogravitropic equilibrium in oat coleoptiles. It is demonstrated that the influence of light intensity I can be included in the model in a power-law-dependent relationship M(I). The numbers B and M and the related photograviceptive number D are all quantitative genetic traits that can be measured in a straightforward manner, opening the way to the phenotyping of molecular and mechanical aspects of shoot tropism.

Physiological and biochemical effects of morphactin IT 3233 on callus and tumour tissues of Nicotiana tabacum L. cultured in vitro. IV. IAA oxidase activity. Oat coleoptile biotest

IAA oxidase activity in callus and tumour tissue of tobacco subjected to the action of morphactin IT 3233 for shorter and longer periods was determined. Control tumour tissue shows an activity higher by about 40 per cent as compared with that of callus tissue. Morphactin applied for a short time (24-h incubation) does not change the activity of the enzyme. When application is prolonged, a considerable enhancement (up to 140%) of the enzyme activity in callus tissue is observed in dependence on the morphactin concentration. In tumour tissues the activity is stimulated by 45 per cent as compared to control. Oat coleoptile elongation growth induced by IAA is limited to 40 per cent when morphactin is added in the concentrations used for tobacco tissue cultures. The possibility of the morphactin action on tissue growth via IAA metabolism is discussed.

The influence of electrical charge and indolebutyric acid on rooting of willow cuttings

Willow cuttings were treated by direct electrical current (DEC), with a negative or a positive electrode inserted inside them, and with the other being outside. Both directions of DEC flow between electrodes stimulated rooting as actively as growth stimulators. The mung bean or oat coleoptile straight growth test showed that the cuttings released some growth promoters into the surrounding water. However, the simultaneous release of some undetected rooting inhibitors was not excluded. The experiment, shows the possibility of changing the chemical regulatory mechanisms of tissues by the use of weak, direct electrical current which causes, the migration of particular substance{s) into or from a definite tissue or organ.

Galanthamine, an anti-cholinesterase drug, effects plant growth and development in Artemisia tridentata Nutt. via modulation of auxin and neurotransmitter signaling

Galanthamine is a naturally occurring acetylcholinesterase (AchE) inhibitor that has been well established as a drug for treatment of mild to moderate Alzheimer disease, but the role of the compound in plant metabolism is not known. The current study was designed to investigate whether galanthamine could redirect morphogenesis of Artemisia tridentata Nutt. cultures by altering concentration of endogenous neurosignaling molecules acetylcholine (Ach), auxin (IAA), melatonin (Mel), and serotonin (5HT). Exposure of axenic A. tridentata cultures to 10 µM galanthamine decreased the concentration of endogenous Ach, IAA, MEL, and AchE, and altered plant growth in a manner reminiscent of 2–4D toxicity. Galanthamine itself demonstrated IAA activity in an oat coleoptile elongation bioassay, 20 µM galanthamine showed no significant difference compared with 5 μM IAA or 5 μM 1-Naphthaleneacetic acid (NAA). Metabolomic analysis detected between 20,921 to 27,891 compounds in A. tridentata plantlets and showed greater commonality between control and 5 µM treatments. Furthermore, metabolomic analysis putatively identified coumarins scopoletin/isoscopoletin, and scopolin in A. tridentata leaf extracts and these metabolites linearly increased in response to galanthamine treatments. Overall, these data indicate that galanthamine is an allelopathic phytochemical and support the hypothesis that neurologically active compounds in plants help ensure plant survival and adaptation to environmental challenges.

Phytochrome and endogenous gibberellin-like substances in etiolated and irradiated oat seedlings

The level of gibberellin-like substances was investigated in oat coleoptiles with different stationary states of phytochrome and in leaf segments which had been etiolated and irradiated with red light. Etiolated coleoptiles and leaves containing maximum amounts of the PR form of phytochrome were characterized by an increased level of bound gibberellins. Irradiation with red light resulting in the photoconversion of phytochrome into the Pt R form caused the appearance of a high content of free gibberellins. It seems that the releasing the hormones from bound forms correlated with the formation of phytochrome PFR may be an important aspect of the mechanism of phytochrome action in the processes of seedling deetiolation. The interrelation between phytochrome and plant hormones in the control of photomorphogenesis of young monocotyledonous seedlings is also discussed.

Acropetal effects of IAA upon the wave-like pattern in the basipetal efflux of natural growth substances of Fraxinus excelsior L.

Basipetal efflux of natural growth substances from the cambial region of a successive series of short sections of the stem of <em>Fraxinus excelsior</em> L. was measured by Went's oat coleoptile curvature bioassay. A wave-like pattern of stimulation by natural growth substances collected after efflux of only 10 min in agar containing 0.56 µM synthetic IAA was observed, confirming to earlier findings in other species. Both inhibitory and stimulatory effects were recorded, however, the oscillations were manifested in stimulation, which is probably due to natural auxin. IAA applied for 1 h directly to the cut surface of the lateral branch, distal to the stem segment used for the measurements of natural auxin efflux, caused acropetal modulations of the wave-like pattern. The results seem to indicate that the auxin-wave system analogous to that already described for other trees operates also in the cambial region of the <em>Fraxinus excelsior</em> L. stem. Modulations of such waves caused by IAA (seen as phase shift) can be propagated acropetally at a rate excluding direct action of molecules of auxin at the site of measurement.

Bioassay for investigation of auxin transport in single cell layers

Auxin was collected from the cambial region of <em>Pinus sylvestris</em> by applying agar strips to the cut surfaces of stem sections which comprised a single layer of 2 to 4-mm long, mainly intact fusiform cells. Sections of the agar strips were either bioassayed immediately to determine their auxin content or stored for several months at -80<sup>o</sup>C, extracted with 80% MeOH and redissolved in hot agar prior to bioassay. Auxin concentrations were determined by Went's oat coleoptile test, as described by Funke, which was modified considerably to give highly reproducible results. The modifications proved essential for good replication of results and are described in detail together with the use of the bioassay to determine changes in cambial cell polarity during ageing and senescence in <em>P. sylvestris</em>.

Plant lighting system with five wavelength-band light-emitting diodes providing photon flux density and mixing ratio control

BackgroundPlant growth and development depend on the availability of light. Lighting systems therefore play crucial roles in plant studies. Recent advancements of light-emitting diode (LED) technologies provide abundant opportunities to study various plant light responses. The LED merits include solidity, longevity, small element volume, radiant flux controllability, and monochromaticity. To apply these merits in plant light response studies, a lighting system must provide precisely controlled light spectra that are useful for inducing various plant responses.ResultsWe have developed a plant lighting system that irradiated a 0.18 m2 area with a highly uniform distribution of photon flux density (PFD). The average photosynthetic PFD (PPFD) in the irradiated area was 438 micro-mol m–2 s–1 (coefficient of variation 9.6%), which is appropriate for growing leafy vegetables. The irradiated light includes violet, blue, orange-red, red, and far-red wavelength bands created by LEDs of five types. The PFD and mixing ratio of the five wavelength-band lights are controllable using a computer and drive circuits. The phototropic response of oat coleoptiles was investigated to evaluate plant sensitivity to the light control quality of the lighting system. Oat coleoptiles irradiated for 23 h with a uniformly distributed spectral PFD (SPFD) of 1 micro-mol m–2 s–1 nm–1 at every peak wavelength (405, 460, 630, 660, and 735 nm) grew almost straight upwards. When they were irradiated with an SPFD gradient of blue light (460 nm peak wavelength), the coleoptiles showed a phototropic curvature in the direction of the greater SPFD of blue light. The greater SPFD gradient induced the greater curvature of coleoptiles. The relation between the phototropic curvature (deg) and the blue-light SPFD gradient (micro-mol m–2 s–1 nm–1 m–1) was 2 deg per 1 micro-mol m–2 s–1 nm–1 m–1.ConclusionsThe plant lighting system, with a computer with a graphical user interface program, can control the PFD and mixing ratios of five wavelength-band lights. A highly uniform PFD distribution was achieved, although an intentionally distorted PFD gradient was also created. Phototropic responses of oat coleoptiles to the blue light gradient demonstrated the merit of fine controllability of this plant lighting system.

FRENK ÜZÜMLERİNDE {Ribes nigrum LL. Ribes rubrum L.) ÇİÇEKLENMEYLE BÜNYESEL HORMANLAR ARASINDAKİ İLİŞKİLER

ozet Bu calisma, Erzurum sartlarinda Mulka, Rosenthais ve Silvergieter Frenkuzumu cesitlerine, tomurcuklarin tesekkul doneminden ciceklerin acilmasina kadar gecen devrede, bunyesel hormonlarin nasil bir degisim gosterdigini belirleyebilmek amaciyla yapilmistir. Tomurcuklardaki buyumeyi engelleyici maddeler yaz ortasinda nispeten yuksek bulunmus ve bunlarin etkilerinin Eylul ortasina dogru azaldigi ve Kasim, Ocak, hatta Subatta bile etkilerin yuksek oldugu belirlenmistir. Engelleyici maddelerde Aralik ayindan itibaren nispi bir azalma baslamis ve bunlarin etkinlikleri Nisan ayinda minimuma dusmustur. Buyumeyi uyartici maddelerin ise Mart ayindan itibaren etkili olmaya basladiklari saptanmistir. SUMMARY The Relation Between Blooming and. Endogenous Hormones in Currants (Ribes nigrum L., Ribes rubrum L.). This study was carried out to determine the changing of the endogenous hormones from bud formation to blooming period in Mulka, Rosenthals, and Silvegieter currant cvs. grown in Erzurum conditions. Bud samples were extracted with methanol, lsopropil alcohol: ammonia: water (8:1:1 v/v) was used as tank solution for. paper chromatography. Oat coleoptile test was used to determine the Rf value of growth inhibitors and promoters. The influence of growth inhibitors and promoters was changed month from according to the oat coleoptile test. The growth promoters were found in the sections of .Rf -0.1-0.1 and 0.7-U.9 It was observed that the most effective sections of Rf for growth inhibitors was between 0.3-0.5 values. The effect of growth inhibitors was high during mid-summer. But they declined from mid-summer to mid-September. However they began to increase again from mid-September to December. It was found that the effect of growth inhibitors was high even in January. But this effect declined steadily and it was the minimum in April. On the other hand the effect of growth promoters began to increase steadily from mid-March to on. The influence of growth inhibitors was less in Rosenthals and Silvegrieter than Mulka on 10 th of April which was the date of bud burst for previous cvs.

ChemInform Abstract: Synthesis, Biological Activity and Metabolism of N-Hydroxytryptophan.

Abstract N -Hydroxytryptophan (α-hydroxyamino-β-indolyl-3-propionic acid) was chemically synthesized. On a mole basis, its relative biological activity in comparison with indole-3-acetic acid at sub-optimal concentrations is: oat coleoptile curvature test=0.129; oat first internode test=0.089 and linseed root growth inhibition test=0.022. Infiltration of N -hydroxytryptophan into oat coleoptile sections leads to the production of indoleacetaldehyde oxime, indoleacetaldehyde and indoleacetic acid. It is suggested that tryptophan could be metabolized in oat coleoptiles to indole-3-acetic acid via N -hydroxytryptophan, indoleacetaldehyde oxime and indoleacetaldehyde.

Soluble sugar availability of aerobically germinated barley, oat and rice coleoptiles in anoxia

Physiological and metabolic responses to anoxia were compared for aerobically germinated seedlings of barley ( Hordeum vulgare), oat ( Avena sativa) and rice ( Oryza sativa). Coleoptile growth of barley, oat and rice seedlings was suppressed by a 24 h-anoxic stress, but the growth of the rice coleoptiles was much greater than that of the barley and oat coleoptiles. ATP concentration in the anoxic rice coleoptiles was greater than that in the anoxic barley and oat coleoptiles. Concentrations of ethanol and activity of alcohol dehydrogenase (ADH) in the anoxic rice coleoptiles were also greater than those of the anoxic barley and oat coleoptiles, suggesting that ethanolic fermentation may be more active in the rice coleoptiles than in the barley and oat coleoptiles, where glycolysis and ethanolic fermentation are the main source of ATP production. Soluble sugar concentration in the anoxic rice coleoptiles was greater than that of the anoxic barley and oat coleoptiles. However, α-amylase, which catabolizes reserve starch to soluble sugars, was active in anoxic barley, oat and rice endosperms, and soluble sugar concentration in the anoxic barley, oat and rice endosperms was not significantly different. Therefore, anoxia stress may inhibit soluble sugar transport from the endosperms to the coleoptiles in barley and oat more than in rice. Since the availability of soluble sugar is essential for operation of glycolysis and fermentation in plant cells, ability for sugar transport from the endosperms to the coleoptiles may be one means to distinguish the coleoptile growth of these plant species in anoxia and anoxia tolerance of these plants.

Nucleoside diphosphate kinase isoforms regulated by phytochrome A isolated from oat coleoptiles.

Nucleoside diphosphate kinase (NDPK) (EC 2.7.4.6), the enzyme transferring the phosphate residue from ATP to nucleoside diphosphates, is localized mainly in the cytoplasm and mitochondria and in smaller amounts in cell nuclei and the microsomal fraction. Exposure of etiolated oat seedlings to red light causes an increase of the enzyme activity by about 42% in nuclear fraction, 7% in etioplastic and 14% in postetioplastic fraction. Endogenous phytochrome A, as visualized by an immunochemical method, translocates from the cytoplasm into the nucleus upon red, far-red or white light activation. Nuclei purified from oat seedlings contain two, and the postnuclear fraction four easily separated forms of NDPK. One of the nuclear isoforms (I(n)) and one isoform isolated from the postnuclear fraction (II(pn)) are activated by red light in the presence of phytochrome A purified from etiolated oat coleoptiles. Both phytochrome A-activated NDPKs purified to electrophoretic homogeneity have the same molecular mass (17-18 kDa) determined by SDS/PAGE. Both enzymes in the native form have similar molecular masses (71 and 63 kDa).

Conformation and mobility of the arabinan and galactan side-chains of pectin

The function of the arabinan and galactan side-chains of pectin remains unknown. We describe 13C NMR experiments designed to yield spectra from the most mobile polymer components of hydrated cell walls isolated from a range of plant species. In pectin-rich cell walls, these corresponded to the pectic side-chains. The arabinan side-chains were in general more mobile than the galactans, but the long galactan side-chains of potato pectin showed high mobility. Due to motional line-narrowing effects these arabinan and galactan chains gave 13C NMR spectra of higher resolution than has previously been observed from ‘solid’ biopolymers. These spectra were similar to those reported for the arabinan and galactan polymers in the solution state, implying time-averaged conformations resembling those found in solution. The mobility of the highly esterified galacturonan in citrus cell walls overlapped with the lower end of the mobility range characteristic of the pectic side-chains. The cellulose-rich cell walls of flax phloem fibres gave spectra of low intensity corresponding to mobile type II arabinogalactans. Cell walls from oat coleoptiles appeared to contain no polymers as mobile as the pectic arabinans and galactans in primary cell walls of the other species examined. These properties of the pectic side-chains suggest a role in interacting with water.

Melatonin acts as a growth‐stimulating compound in some monocot species

In a recent study melatonin (N-acetyl-5-methoxytryptamine), a well-investigated animal molecule but minimally studied in plants, was seen to have a physiological role as growth-promoting molecule in lupin hypocotyls. In the present study, the role of melatonin as a growth promoter is extended to coleoptiles of canary grass, wheat, barley and oat, in which it shows a relative auxinic activity [with respect to indole-3-acetic acid (IAA), the main auxin in plants] of between 10 and 55%. In addition, melatonin is seen to have an important inhibitory growth effect on roots similar to that played by auxin. The quantitation by liquid chromatography with electrochemical detection and identification by tandem mass spectrometry of melatonin and IAA in etiolated coleoptiles of the monocots assayed showed that both compounds are present in similar levels in these tissues. These results point to the co-existence of auxin and melatonin in tissues and raises the possibility of their co-participation in some physiological actions as auxinic hormones in plants.

Uridine and the Control of Phototropism in Oat (Avena sativa L.) Coleoptiles

The short-term growth response of oat (Avena sativa L.) coleoptiles to exogenously applied uridine was studied both in excised apical segments and in the intact seedlings. In both cases growth of coleoptile tissue was inhibited by uridine. The inhibition of coleoptile growth consistently occurred 20–30 min after uridine treatment, which is within the lag period of their phototropic response. Asymmetric application of uridine to coleoptiles in the intact seedlings resulted in their bending toward the direction to which uridine was applied in the absence of light stimulus. These findings suggest that uridine or its metabolites, plays an important role in the phototropism of oat coleoptiles and provide support to the Bruinsma–Hasegawa theory as an alternative to the Cholodny–Went theory for explaining phototropism.

Changes in ion fluxes during phototropic bending of etiolated oat coleoptiles.

This work has been conducted to assist theoretical modelling of the different stages of the blue light (BL)-induced phototropic signalling pathway and ion transport activity across plant membranes. Ion fluxes (Ca(2+), H(+), K(+) and Cl(-)) in etiolated oat coleoptiles have been measured continuously before and during unilateral BL exposure. Changes in ion fluxes at the illuminated (light) and shadowed (dark) sides of etiolated oat coleoptiles (Avena sativa) were studied using a non-invasive ion-selective microelectrode technique (MIFE). The bending response was also measured continuously, and correlations between the changes in various ion fluxes and bending response have been investigated. For each ion the difference (Delta) between the magnitudes of flux at the light and dark sides of the coleoptile was calculated. Plants that demonstrated a phototropic bending response also demonstrated Ca(2+) influx into the light side approximately 20 min after the start of BL exposure. This is regarded as part of the perception and transduction stages of the BL-induced signal cascade. The first 10 min of bending were associated with substantial influx of H(+), K(+) and Cl(-) into the light (concave) side of the coleoptiles. The data suggest that Ca(2+) participates in the signalling stage of the BL-induced phototropism, whereas the phototropic bending response is linked to changes in the transport of H(+), K(+) and Cl(-).

Purification and properties of apoplastic amylase from oat (Avena sativa) seedlings.

The protein fraction extracted with a high ionic strength buffer from the cell wall preparation of oat (Avena sativa L.) coleoptiles and first leaves contained starch-degrading (amylase) activity. The activity of apoplastic amylase in the coleoptiles and first leaves continued to increase in parallel with organ growth. One of the apoplastic amylases recovered from shoot cell wall preparations was purified by sequential ion exchange and gel filtration chromatography, and the catalytic properties of the enzyme were analysed. The purified enzyme gave a single 25 kDa protein band on SDS-PAGE. The enzyme exhibited maximum activity at pH 5.0 against maltooligosaccharides. The purified enzyme hydrolysed soluble starch and maltooligosaccharides larger than tetraose at maltose unit, but did not hydrolyse beta-limit dextrin or p-nitrophenyl-alpha-d-glucopyranoside. These results as well as the findings that the molecular size and the catalytic properties of the purified enzyme are different from those of known amylases obtained from Gramineae caryopses suggest that this enzyme is a novel type of beta-amylase present in cell walls of vigorously elongating Gramineae shoot organs.

Ethanol sensitivity of rice and oat coleoptiles.

The ability to avoid the ethanol-induced injury was evaluated in rice (Oryza sativa L.) and oat (Avena sativa L.) coleoptiles. The growth of the rice and oat coleoptiles was inhibited by ethanol exogenously applied at concentrations greater than 200 and 30 mM, respectively. At 300 mM ethanol, oat coleoptiles were brown and flaccid but rice coleoptiles did not show any visible symptoms of toxicity. The acetaldehyde level in rice and oat coleoptiles was increased by exogenously applied ethanol and the increases were greater in oat than in rice coleoptiles under aerobic and anaerobic conditions. At 300 mM ethanol, the acetaldehyde concentrations in the rice and oat coleoptiles were 46 and 87 nmol g-1 FW under aerobic conditions, respectively, and 52 and 124 nmol g-1 FW under anaerobic conditions, respectively. The activity of alcohol dehydrogenase (ADH; EC 1.1.1.1) in the direction of ethanol to acetaldehyde was greater in oat than in rice coleoptiles and ADH protein in oat coleoptiles was more induced by exogenously applied ethanol than that in rice coleoptiles. These results suggest that in vivo conversion rate of ethanol to acetaldehyde by ADH is lower in rice than oat coleoptiles, which may be one of the reasons that ethanol sensitivity of rice is much lower than that of oat coleoptiles. The great ability of rice to avoid the ethanol-induced injuries may contribute its anoxia tolerance when glycolysis and ethanolic fermentation replace the Krebs cycle as the main source of energy under anaerobic conditions.

Anoxia tolerance and ethanol sensitivity of rice and oat coleoptiles

Anoxia tolerance and ethanol sensitivity of rice (Oryza sativa L.) and oat (Avena sativa L.) seedlings were evaluated to clarify their growth habit in anoxia. Anoxic stress inhibited elongation and dry weight gain of coleoptiles of the oat and rice seedlings; however, the inhibition of the oat coleoptiles was much greater than that of the rice coleoptiles. Anoxic stress increased endogenous ethanol concentration and alcohol dehydrogenase activity in oat and rice coleoptiles and their increases in the rice coleoptiles were much greater than those in the oat coleoptiles. At concentrations greater than 30 mM and 300 mM, exogenously applied ethanol inhibited the elongation and weight gain for the oat and the rice coleoptiles, respectively, and the inhibition was increased with increasing ethanol concentrations with marked inhibition being achieved on the oat coleoptiles. These results suggest that anoxia tolerance and induction of ethanolic fermentation in anoxia may be greater in rice than oat, and ethanol sensitivity of rice may be lower than that of oat.