Wheat Coleoptile Sections Research Articles

Resin acids as the potential growth-affecting component of pine oleoresin

The nonvolatile fraction of the oleoresin of <i>Pinus sihestris</i> L. was found to contain substances which inhibit growth of wheat ceoleoptile and oat mesocotyl sections in standard bioassays. The inhibition is mainly confined to the fraction of resin acids. Among the seven authentic resin acids tested, the effects of dehydroabietic and abietic acids were most sifgnificant. Palustric, pimaric and isopimaric acids were not effective in the wheat coleoptile section straight growth test. None of the substances, in the amounts tested, except for extremely high concentration, exerted an inhibitory effect on natural or IAA-induced elongation of pine hypocotyl sections. Neither was an inhibitory effect discovered in the microbiological test with the <i>Aspergillus niger</i> van Tiegh. The results obtained with pine hypocotyl sections, allow the conclusion that resin acids interfering with the results of standard bioassays are probably not effective as inhibitory factors in the regulation of pine tissue growth.

Degradation Studies on Benzoxazinoids. Soil Degradation Dynamics of (2R)-2-O-β-d-Glucopyranosyl-4-hydroxy-(2H)- 1,4-benzoxazin-3(4H)-one (DIBOA-Glc) and Its Degradation Products, Phytotoxic Allelochemicals from Gramineae

Wheat (Triticum aestivum L.) has been found to possess allelopathic potential and studies have been conduced to apply wheat allelopathy for biological weed control. 2,4-Dihydroxy-(2H)-1,4-benzoxazin-3(4H)-one (DIBOA) is a common product found in wheat, corn, and rye exudates and it can be released to the environment by that way. In this report, the stability of DIBOA is studied in two soils from crop lands of wheat cv. Astron and cv. Ritmo. These varieties were selected by their concentrations of DIBOA and 2,4-dihydroxy-7-methoxy-(2H)-1,4-benzoxazin-3(4H)-one (DIMBOA) from aerial parts and by the bioactivities of their aqueous extracts in the growth of wheat coleoptile sections. The degradation rate of DIBOA in these soils was measured in laboratory tests during 90 h by high-pressure liquid chromatography methods. These analyses demonstrate that DIBOA was transformed primarily into 2-benzoxazolinone (BOA). This transformation was similar in both soil types with an average half-life of 43 h. The degradation studies for BOA show its biotransformation to 2-aminophenoxazin-3-one (APO) with a half-life of 2.5 days. Therefore, BOA is an intermediate product in the biotransformation from DIBOA to APO in these wheat crop soils and is consistent with previous findings. APO was not degraded after three months in soil, suggesting that its degradation rate in soil is very slow.

Physiological effects of narciclasine from the mucilage of Narcissus tazetta L. bulbs

An inhibitor was isolated from the secreted mucilage of Narcissus tazetta L. bulbs. Based on X-ray analysis, the inhibitor was identified as narciclasine (NCS), an Amaryllidaceae alkaloid. NCS inhibited seed germination and seedling growth of rice and Chinese cabbage in a dose-dependent manner. NCS interacted with plant hormones in some physiological responses. Indole-3-acetic acid could not overcome the inhibition of elongation of wheat coleoptile sections caused by NCS. NCS suppressed the gibberellin-induced α-amylase production in barley seeds and cytokinin-induced expansion and greening of excised radish cotyledons.

Effect of auxinhormone lanthanide complexes on the growth of wheat coleoptile.

Naphthalene-1-acetic acid (HNAA), dichlorophenoxy acetic acid (HDAA), and indole-3-acetic acid (HIAA) are auxinhormones that can affect the growth of plants. The lanthanide complexes of the above auxinhormone LnA3 x 3H2O (Ln = La3+, Ce3+, Sm3+, Er3+, Yb3+; HA = HNAA, HDAA, HIAA; A = NAA-, DAA-, IAA-) were synthesized and are characterized in this paper. The solubility and IR spectra of these complexes were also studied. Experiments of the effects of LnCl3 x nH2O, HA, and LnA3 x 3H2O on the growth rate of wheat coleoptile sections show, that LnCl3 x nH2O promotes the growth of wheat coleoptile when this compounds concentration is lower than 2 x 10(-5) M and the promotion is very significant when the concentration of Ln3+ is lower than 8 x 10(-6) M. It was also found that the effect of LnA3 x 3H2O on the growth of wheat coleoptile is stronger than that of LnCl3 x nH2O and HA, which indicates that the combination of Ln3+ with HA act synergistically.

Evidence for the presence of a native, non-auxinic rooting promoter in avocado (Persea americana Mill.)

The presence of a rooting promoter in paratially purified extracts of avocado (Persea amricana Mill.) organs has been demonstrated using the mung bean rooting bioassay. Extraction with 80% methanol was followed by partition into diethyl ether, paper chromatography (PC) and 3 steps of thin layer chromatography (TLC). The number of roots induced by the rooting promoter in the absence of exogenous auxin was 5 to 7 times higher than that of the water control and 50% higher than by 4-(indol-3-yl) butyric acid (IBA) at its reported optimum concentration. Rooting of tomato, Coleus and young avocado cuttings was also enhanced by the rooting promoter. The rooting promoter was inhibitory in the wheat coleoptile section elongation bioassay for auxins and had slight inhibitory activity in the split pea stem curvature test.

Relation of gibberellic acid-induced growth of wheat coleoptiles with indole acetic acid

Summary Gibberellic acid (GA3) induced elongation of wheat coleoptile sections and its relation with endogenous indole acetic acid was studied. Growth promotion by GA was reduced to half when oxidation of endogenous IAA was prevented by pretreatment of the coleoptiles with EDTA or a mixture of chlorogenic acid and 2,2′-dipyridyl. The effect of GA was reduced to ¼ when the endogenous methyleneoxindole (MeOx), an oxidation product of IAA, was made unavailable to GA3 during its action. External application of hydroxymethyloxindole (HMO), earliest oxidation product of IAA, helped GA to regain its full activity even when oxidation of endogenous IAA was inhibited. It is concluded that endogenous IAA, more precisely, its oxidation products, were necessary for GA in exhibiting its growth promoting activity on wheat coleoptile sections.

Changes in isoperoxidases induced by hydroxyphenylacetic acids

The effects ofo-, m- andp-hydroxyphenylacetic acids on total peroxidase activity and isoperoxidase patterns of wheat coleoptile sections were studied.o-andm-HOPA reduced the total peroxidase activity whilep-HOPA increased it. Electrophoresis in polyacrylamide gel revealed thato- andm-HOPA diminish the intensity of some anodic and cathodic bands, but thatp-HOPA increases anodic and reduces cathodic isoperoxidases. These results may explain the apparently paradoxical positive effects ofp-HOPA on both growth and total peroxidase activity.

Structure-activity differences between indoleacetic acid auxins on pea and wheat

A series of halogenated indoleacetic acids was assessed for auxin activity on pea stem and wheat coleoptile sections. Activity differences between the two species were found. These are discussed, in terms of differences in receptor models for pea and wheat, with the models differing in the areas covered by the 6- and 7-substituted compounds.

Barium effects inPhaseolus aureus, Cephalandra indica,Canna indica, Beta vulgaris, Triticum aestivum andLactuca sativa

Barium chloride at 0.1 mM concentration inhibited elongation of mungbean (Phaseolus aureus) roots more strongly than elongation of hypocotyls. Root growth was completely inhibited at 80 mM and there was no germination at 100 mM. Respiration rates which were directly proportional to seedling vigour declined at varying degrees at the growth-inhibitory concentrations of BaCl2. Barium retarded senescence in isolated leaf discs ofCephalandra indica by maintaining the chlorophyll level in darkness. The carotenes were similarly protected from degradation by Ba in darkness whereas xanthophylls were retained both in darkness and light. Ba also protected anthocyanin pigments in the staminode discs ofCanna indica flowers and reduced to a variable extent the leakage of betacyanin pigment fromBeta vulgaris root discs caused by various membrane active chemicals. Applied either alone or in combination with IAA, Ba inhibited cell enlargement in wheat (Triticum aestivum) coleoptile sections. Barium-induced inhibition of lettuce (Lactuca sativa) hypocotyl elongation was largely overcome by GA3.

3-Hydroxymethyl Oxindole: Its Auxin Action and Metabolism in Wheat

Summary The role of 3-hydroxymethyl oxindole (HMO), a photooxidation product of indole-3-acetic acid (IAA), in stimulating elongation of wheat coleoptiles, increasing protein and RNA content and stimulating ethylene evolution was studied. HMO was found to be more oligodynamic than IAA. Unlike IAA, the growth promoting effect, increased content of protein and RNA induced by HMO, remained unaffected after pretreatments of the coleoptiles with chemicals inhibiting oxidation of IAA. No stimulation of ethylene evolution was detected either with IAA or with HMO, following pretreatments. A possible cause of this inhibition is discussed. Much more pronounced increases in protein, RNA and even DNA were observed by application of HMO than with IAA in seedlings. HMO induced more ethylene evolution than IAA in both wheat seedlings and coleoptile sections. The changes in the level of IAA-metabolic enzymes, viz. IAA-oxidase, peroxidase and methyleneoxindolereductase were studied after the application of IAA and HMO, with or without pretreatments. The changes in the level of IAA and IAA-metabolic enzymes with age were also studied in shoots and roots of developing wheat seedlings. The possible role of HMO in auxin mediated actions are discussed.

Auxin Activity of 3-Hydroxymethyl Oxindole in Wheat

Summary A plotcoxidation product of indole-3-acetic acid (IAA), 3-hydroxymethyl oxindole (HMO), is as effective as IAA in stimulating elongation of wheat coleoptile sections, even at a lower concentration. IAA fails to show stimulation of growth after pretreatment of the coleoptiles with chemicals inhibiting oxidation of IAA, but the growth promoting effect of HMO remains unaffected by such pretreatments. In time-course experiments also, the stimulatory effect of HMO is same as IAA. HMO prepared from IAA from different sources are effective to the same extent in stimulation of elongation of wheat coleoptiles.

Depolarization of transmembrane potential of corn and wheat coleoptiles under reduced water potential and after IAA application

The influence of IAA and temporarily reduced water potential on the transmembrane potential (PD) of corn and wheat coleoptile sections was investigated. The studies were performed by two different methods: discontinuous PD measurements with microelectrodes in corn coleoptile sections and continuous measurements with microelectrodes in wheat coleoptile sections. Both methods showed a very rapid depolarization of PD within a period of 2 to 5 min. In corn coleoptile sections, a PD oscillation was observed within an average period of 14.5 min after IAA application and of 14.0 min after reduction of water potential. The PD amplitude was about 20 to 25 mV. In wheat coleoptile sections, an oscillation of PD could not be definitely established. After an IAA-induced depolarization period of 4 to 7 min, the initial potential sometimes was restored, while in some other cases, a subsequent hyperpolarization was found although in most cases the depolarization continued. The discussion covers the possibility that a decrease in PD caused by IAA and water stress may induce activation of H+ secretion by a plasmalemma H+ pump.

The action of penicillin in mungbean (Phaseolus aureus L.) seedlings and wheat (Triticum vulgare L.) coleoptile sections

Penicillin caused elongation inhibition of mungbean (Phaseolus aureus L.) seedlings at concentrations above 100 mgl-1. Inhibition of hypocotyl could be reduced to different degrees by manganese, pyruvate, succinate, fumarate, malate, GA3, purines, pyrimidines and nucleosides, whereas the amino acids except cysteine were not effective. Penicillin inhibited neither elongation of wheat coleoptile sections nor the cell enlargement induced by IAA in this tissue. Thus penioillin inhibits intact seedling elongation probably through an Effect on cell division apparently without inhibiting cell enlargement.

Dependence of the detectability of stored growth on the elongation rate in IAA- and acid-induced elongation of wheat coleoptile sections

Dependence of the detectability of stored growth on the elongation rate in IAA- and acid-induced elongation of wheat coleoptile sections

Structures and synthesis of the growth inhibitors batatasins IV and V, and their physiological activities

Two new compounds, batatasins IV and V were isolated from dormant bulbils of Chinese yam ( Dioscorea batatas) and shown to be 2′,3-dihydroxy-5-methoxybibenzyl and 2′-hydroxy-3,4,5-trimethoxybibenzyl, respectively. An analogue, 3,4′-dihydroxy-5-methoxybibenzyl was synthesized. Inhibitory activities of these three compounds as well as batatasin I (6-hydroxy-2,4,7-trimethoxyphenanthrene) and batatasin III (3,3′-dihydroxy-5-methoxy-bibenzyl) in lettuce seed germination, lettuce hypocotyl elongation and wheat coleoptile section elongation tests are described.

The effect of chlormequat on auxin-stimulated elongation of wheat coleoptile sections as influenced by cations

Summary The effect of cations on the auxin-stimulated elongation of wheat coleoptile sections was studied. Ca ++ ions in the incubation medium promoted the auxin-stimulated elongation of wheat coleoptile sections and inhibited leakage of K + and possibly of other ions from the sections into the medium. Chlormequat did not inhibit the gibberellin- or kinetin-stimulated elongation of coleoptiles. This growth regulator inhibited the auxin stimulated elongation of coleoptile sections most strongly in the presence of Ca ++ or Mg ++ ions. Chlormequat did not affect the total contents of K or Ca of these coleoptile sections.

Auxin-like Growth Activity of Phenylacetonitrile

Phenylacetonitrile (PAN) and phenylacetic acid (PAA) showed auxin-like activity by stimulating elongation of wheat-coleoptile sections. Their auxin-like properties were also tested on the elongation of sections cut from hypocotyls of cress and sugar-beet seedlings, from petioles of sugar-beet leaves, and from epicotyls of pea seedlings. They were also tested for their ability to induce adventitious roots on hypocotyls of cress and sugar-beet seedlings and on pea epicotyls. PAN was generally more active than PAA on cress, and PAA more active than PAN on sugar-beet and peas. Steam distillates of cress seedlings contained a neutral substance with auxin-like activity and similar chromatographic properties to PAN.

Comparison of the effect of some phenolic compounds on wheat coleoptile section growth with their effect on iaa-oxidase activity

P-coumaric acid (HCA), 2,4-dichlorophenol (DCP) and resorcionol acted as cofactors for IAA-oxidase isolated from young wheat plants. Ferulic acid (FA) and 3,4-dihydroxybenzoic acid (DHBA) induced a lag phase prior to IAA oxidation. HCA, FA (0.2-1 mg ml-1) and DCP (0.03-1 mg ml-1) strongly inhibited wheat coleoptile section growth. DHBA (0.01-1 mg ml-1) slightly stimulated it and resorcinol was without effect. HCA inhibited IAA-induced growth of coleoptile sections and FA stimulated it at low IAA levels and inhibited it at higher ones. DHBA, DCP and resorcinol did not affect IAA-induced growth of coleoptile sections.

Studies on the Japanese Barnyard Millet as Soiling Crop : III. Mesocotyl elongation in Japanese barnyard millet seedling

The elongation of mesocotyl of Japanese barnyard millet (Echinochloa utilis Ohwi et Yabuno) seedling was remarkable and attained to about 13 cm, though the coleoptile was only about 0.5 cm in length at 30°C in the dark. Decapitation of coleoptile remarkably inhibited the elongation of mesocotyl in proportion to the extent of decapitation. Eluted sections of paper chromatograms from ether extract of coleoptiles of Japanese barnyard millet were used to characterize the growth response of wheat coleoptile sections. At Rf values of 0.1∼0.2, 0.4 and 0.9 in acid fraction an increase of wheat coleoptile elongation was observed, with the increase of 25∼45 per cent over the control. The effects of gibberellin (GA), indole-3-acetic acid (IAA), 2, 3, 5-triiodobenzoic acid (TIBA) and trans-cinnamic acid (TCA) on the growth of seedlings by treatment to sowing bed were tested. GA (1∼1OOppm) had no effect on elongation of mesocotyl. IAA had a little stimulation on the elongation of coleoptile with 10-6M, but mesocotyl elongation was inhibited with 10-5M and 10-6M. TIBA considerably increased the coleoptile elongation with 17.5 ppm, and conversely inhibited the mesocotyl elongation with the same concentration. TCA had also the same effect, although the effect was not remarkable as well as TIBA. GA(10∼1000 ppm) had no promotive effect on elongation of mesocotyl sections. IAA had promotive effect on elongation of mesocotyl sections at the concentration of 10-M and 10-6M. TIBA(1∼10 ppm) had an inhibitory effect on mesocotyl elongation and a stimulative effect on coleoptile elongation in the sections contained both coleoptile and mesocotyl. As the results of marking method and microscopic observation, it became clear that the growing region of mesocotyl was limitted narrow range of about 2 mm lower the coleoptilar node, and the growth of mesocotyl depend on the both cell division and cell elongation

Effect of 2-Chloroethylphosphonic Acid (CEPA) on the Distribution of Growth Regulators in Geotropically Stimulated Vicia faba Roots

Summary In a recent study on Vicia faba roots kept horizontal for 30 min, it was found the concentration of gibberellins to be considerably higher in the upper than in the lower halves of the geotropically stimulated roots, whereas abscisic acid (ABA) attained a higher concentration in the lower than in the upper halves, and thus showed a distribution pattern similar to that usually reported for indoleacetic acid (IAA). In the present investigation the effect of ethylene pretreatment of the roots on the distribution of these growth regulators during subsequent geotropic stimulation was determined. Ethylene treatment was effected by immersing the intact seedling in a solution of 2-chloroethylphosphonic acid (CEPA) at 200 mg/l at pH 6.0 for 1 h prior to stimulation. The contents of both IAA and ABA were determined by wheat coleoptile section assay of purified extracts of the root-halves, whereas gibberellins was determined by lettuce hypocotyl bioassay. As expected the establishment of an asymmetrical distribution of IAA was prevented by the CEPA treatment. Gibberellins and ABA, on the other hand, were distributed as in stimulated roots not pretreated with CEPA. In spite of the presence of an excess of gibberellins in the upper and of ABA in the lower halves, the CEPA-pretreated roots failed to develop geotropic curvatures within 4 h. These results, therefore, provide no evidence for a participation of gibberellins or ABA in the early development of geotropic curvatures in these roots. Some roots of intact seedlings were treated with 100 mg/l (pH 6.0) solution of GA3, ABA, kinetin or IAA for 1 h prior to geotropic stimulation. Both in untreated and GA2,-and ABA-treated samples, 90 to 100% of the roots developed positive geotropic curvatures within 2 h. Since the flooding with GA3 or ABA, assumed to prevent the establishment of an effective transversel gradient by saturating the transport system, did not prevent the development of the curvatures, these results agree with the above conclusion. On the other hand, flooding with kinetin or IAA at 100 mg/l prevented the development of the positive curvatures. Pretreatment with kinetin or IAA at 10 and 50 mgμl did not completely prevent the geotropic reaction but delayed it for several hours.