Inhibitory Effects of Methyl Jasmonate on the Germination and Ethylene Production in Cocklebur Seeds

Methyl jasmonate (JA-Me) inhibited the germination of cocklebur (Xanthium pennsylvanicum Wallr.) seeds. The inhibition of the germination of cocklebur seeds treated with JA-Me at concentrations less than 300 μm was nullified by ethylene applied exogenously, although the inhibitory effect of 1,000 μm JA-Me was not recovered completely even by high concentrations of ethylene (10,000 μL/liter). JA-Me inhibited ethylene production before seed germination. The level of 1-aminocyclopropane-1-carboxylic acid (ACC) in the cotyledonary tissues treated with JA-Me decreased but not the level of 1-(malonylamino)cyclopropane-1-carboxylic acid (MACC). JA-Me inhibited the conversion of ACC to ethylene in the tissues. These results suggested that JA-Me inhibits ethylene production by prevention of ACC oxidation in addition to ACC synthesis. We believe that the inhibition of ethylene production by JA-Me results in the retardation of the germination of cocklebur seeds. Received June 4, 1997; accepted October 23, 1997     

Methyl Jasmonate Induces Gums and Stimulates Anthocyanin Accumulation in Peach Shoots

The effect of methyl jasmonate (JA-Me) on the induction of gum was studied in relation to the action of ethylene in peach (Prunus persica Batsch cv. Benishimizu) shoots. JA-Me applied at concentrations of 0.1–2.5% (w/w) in lanolin paste to current growing or older shoots substantially induced gums 3 days after treatment. The amount of gums exuded increased depending on the dose of JA-Me. Ethephon (2-chloroethyl- phosphonic acid) at 1 or 2% (w/w) in lanolin induced gum and strongly enhanced the promoting effect of JA-Me on gum formation. JA-Me also induced anthocyanin accumulation in current growing shoots, but ethephon did not. Anthocyanin accumulation in response to JA-Me at a concentration of 10 mg/liter or higher was observed also in the cut shoots of peach. Ethephon (100 mg/liter) substantially inhibited anthocyanin accumulation induced by JA-Me. These facts suggest that JA-Me plays an important role in gum formation as well as ethylene and in anthocyanin accumulation and that these processes are not necessarily accompanied by each other in peach shoots. Received January 26, 1998; accepted March 4, 1998     

Gum Formation by Methyl Jasmonate in Tulip Shoots is Stimulated by Ethylene

The promotive effect of methyl jasmonate (JA-Me) on the induction of gum in tulip shoots (Tulipa gesneriana L. cvs. Gudoshnik and Apeldoorn) was studied in the presence of ethylene. Gum formation in the stem and the basal part of the leaves was induced by JA-Me (1% w/w in lanolin) and stimulated strongly by the simultaneous application of 1 or 5 mm 1-aminocyclopropane-1-carboxylic acid (ACC). JA-Me at a concentration of 0.1% did not induce gum, but that together with ACC at a concentration of 1 or 5 mm induced it substantially. Although JA-Me stimulated ethylene production substantially in the stem of intact tulips, ethephon (1% w/w) or ACC (1 or 5 mm) did not induce gum formation in tulip shoots. JA-Me induced gum formation in tulip shoots even in the presence of aminooxyacetic acid or cobalt ions. Moreover, gum formation was also observed in the cut shoot applied with JA-Me as a solution at concentrations of 0.23 mm or more. These results strongly suggest that JA-Me is required for gum formation in tulip shoots, and ethylene probably makes the tissues of shoots sensitive to JA-Me. Received March 23, 1998; accepted June 10, 1998     

Exogenous ethylene inhibits sprout growth in onion bulbs

Background and Aims

Exogenous ethylene has recently gained commercial interest as a sprouting inhibitor of onion bulbs. The role of ethylene in dormancy and sprouting of onions, however, is not known.

Methods

A cultivar (Allium cepa ‘Copra’) with a true period of dormancy was used. Dormant and sprouting states of onion bulbs were treated with supposedly saturating doses of ethylene or with the ethylene-action inhibitor 1-methylcyclopropene (1-MCP). Initial sprouting was determined during storage at 18 °C by monitoring leaf blade elongation in a specific size class of leaf sheaths. Changes in ATP content and sucrose synthase activity in the sprout leaves, indicators of the sprouting state, were determined. CO₂ and ethylene production of onion bulbs during storage were recorded.

Key results

Exogenous ethylene suppressed sprout growth of both dormant and already sprouting onion bulbs by inhibiting leaf blade elongation. In contrast to this growth-inhibiting effect, ethylene stimulated CO₂ production by the bulbs about 2-fold. The duration of dormancy was not significantly affected by exogenous ethylene. However, treatment of dormant bulbs with 1-MCP caused premature sprouting.

Conclusions

Exogenous ethylene proved to be a powerful inhibitor of sprout growth in onion bulbs. The dormancy breaking effect of 1-MCP indicates a regulatory role of endogenous ethylene in onion bulb dormancy.Key words: Bulb dormancy, Allium cepa, onion, sprout growth, ethylene, CO₂ production, respiration, 1-methylcyclopropene     

Methyl jasmonate stimulates the formation and the accumulation of anthocyanin in <Emphasis Type="Italic">Kalanchoe blossfeldiana</Emphasis>

Methyl jasmonate (JA-Me) at concentrations of 0.1, 0.5 and 1.0 % (w/w) greatly stimulated anthocyanins accumulation in shoots of young plants of Kalanchoe blossfeldiana when it was applied around the stem as a lanolin paste. Stimulatory effect of JA-Me was evidently observed as early as two days after treatment. Anthocyanins were formed in the main and lateral shoots, including petioles, both below and above portions of the treatment. When leaves were removed from the plant, almost no anthocyanin formation was observed. It should be mentioned that leaves are necessary for the anthocyanin accumulation in stems induced by JA-Me.     

Effect of Gibberellin on Growth, Protein Secretion, and Starch Accumulation in Maize Endosperm Suspension Cells

The physiologic effect of gibberellins (GA) in seed development is poorly understood. We examined the effect of gibberellic acid (GA₃) on growth, protein secretion, and starch accumulation in cultured maize (Zea mays L.) endosperm suspension cells. GA₃ (5 and 30 μm) increased the fresh weight, dry weight, and protein content of the cultured cells, but the effect of GA₃ at 50 μm was not significantly different. However, the protein content in the culture medium was increased by these three concentrations of GA₃. The effect of GA₃ on the amount of cellular structural polysaccharides was not significant, but GA₃ had a dramatic effect on the starch content. At 5 μm, GA₃ caused an increase in the starch content, but at 50 μm the starch accumulation was reduced. Chlorocholine chloride (CCC), an inhibitor of GA biosynthesis, significantly increased the starch content and decreased the structural polysaccharide content of the cultured cells. The effects of CCC at 500 μm on the starch and polysaccharide content were partially reversed by 5 μm GA₃ applied exogenously. Based on these results we suggest that GA does not favor starch accumulation in the cell cultures and that the addition of lower concentrations of GA₃ in the medium may provide an improved balance among the endogenous GA in the cultured cells. Received October 31, 1995; accepted March 25, 1997     

Membrane Potassium Channels and Human Bladder Tumor Cells: II. Growth Properties

These experiments were done to determine the effect of glibenclamide and diazoxide on the growth of human bladder carcinoma (HTB-9) cells in vitro. Cell growth was assayed by cell counts, protein accumulation, and ³H-thymidine uptake. Glibenclamide added at 75 and 150 μm for 48 hr reduced cell proliferation. Dose-inhibition curves showed that glibenclamide added for 48 hr reduced cell growth at concentrations as low as 1 μm (IC₅₀= 73 μm) when growth was assayed in the absence of added serum. This μM-effect on cell growth was in agreement with the dose range in which glibenclamide decreased open probability of membrane K_ATP channels. Addition of glibenclamide for 48 hr also altered the distribution of cells within stages of the cell cycle as determined by flow cytometry using 10⁻⁵ m bromodeoxyuridine. Glibenclamide (100 μm) increased the percentage of cells in G₀/G₁ from 33.6% (vehicle control) to 38.3% (P < 0.05), and it reduced the percentage of cells in S phase from 38.3% to 30.6%. On the other hand, diazoxide, which opens membrane K_ATP channels in HTB-9 cells, stimulated growth measured by protein accumulation, but it did not increase the cell number. We conclude that the sulfonylurea receptor and the corresponding membrane K_ATP channel are involved in mechanisms controlling HTB-9 cell growth. However, K_ATP is not rate-limiting among the signaling mechanisms or molecular switches that regulate the cell cycle. Received: 12 June 1997/Revised: 21 October 1997     

Requirement for Ethylene Synthesis and Action during Relief of Thermoinhibition of Lettuce Seed Germination by Combinations of Gibberellic Acid, Kinetin, and Carbon Dioxide

Application of exogenous ethylene in combination with gibberellic acid (GA₃), kinetin (KIN), and/or CO₂ has been reported to induce germination of lettuce seeds at supraoptimal temperatures. However, it is not clear whether endogenous ethylene also plays a mediatory role when germination under these conditions is induced by treatment regimes that do not include ethylene. Therefore, possible involvement of endogenous ethylene during the relief of thermoinhibition of lettuce (Lactuca sativa L. cv Grand Rapids) seed germination at 32°C was investigated. Combinations of GA₃ (0.5 millimolar), KIN (0.05 millimolar), and CO₂ (10%) were used to induce germination. Little germination occurred in controls or upon treatment with ethylene, KIN, or CO₂. Neither KIN nor CO₂ affected the rate of ethylene production by seeds. Both germination and ethylene production were slightly promoted by GA₃. Treatments with GA₃+CO₂, GA₃+KIN, or GA₃+CO₂+KIN resulted in approximately 10-to 40-fold increases in ethylene production and 50 to 100% promotion of germination as compared to controls. Initial ethylene evolution from the treated seeds was greater than from the controls and a major surge in ethylene evolution occurred at the time of visible germination. Application of 1 millimolar 2-aminoethoxyvinyl glycine (AVG), an inhibitor of ethylene synthesis, in combination with any of above three treatments inhibited the ethylene production to below control levels. This was accompanied by a marked decline in germination percentage. Germination was also inhibited by 2,5-norbornadiene (0.25-2 milliliters per liter), a competitive inhibitor of ethylene action. Application of exogenous ethylene (1-100 microliters per liter) overcame the inhibitory effects of AVG and 2,5-norbornadiene on germination. The results demonstrate that endogenous ethylene synthesis and action are essential for the alleviation of thermoinhibition of lettuce seeds by combinations of GA₃, KIN, and CO₂. It also appears that these treatment combinations do not act exclusively via promotion of ethylene evolution as the application of exogenous ethylene alone did not promote germination.     

Mediation of a plant response to malformin by ethylene

Malformin and ethylene stimulate abscission of the primary leaves of Phaseolus aureus Roxb. in the dark, and abscission stimulation by both compounds is inhibited by indeleacetic acid and CO₂. Ethylene production by malformin-treated buds is stimulated within 4 hours. and up to 8 days, after treatment. Malformin-induced growth disturbances in P. vulgaris L. and abscission in P. aureus are considered mediated by ethylene. Although root curvatures of Zea mays L. are induced by both malformin and ethylene, and malformin is inhibited by CO₂, ethylene production is not stimulated by malformin. A role of ethylene in root curvatures induced by malformin is neither proposed nor disproved.     

A Possible Role for Jasmonic Acid in Adaptation of Barley Seedlings to Salinity Stress

The changes caused by NaCl salinity and jasmonic acid (JA) treatment (8 days) on growth and photosynthesis of barley plants (Hordeum vulgare L., var. Alfa) have been studied. Gas exchange measurements and analysis of enzyme activities were used to study the reactions of photosynthesis to salinity and JA. Both 100 mm NaCl and 25 μm JA treatment led to a noticeable decrease in both the initial slope of the curves representing net photosynthetic rate vs intercellular CO₂ concentration and the maximal rate of photosynthesis. The calculated values of the intercellular CO₂ concentration, CO₂ compensation point, and maximal carboxylating efficiency of ribulose-1,5-bisphosphate carboxylase support the suggestion that biochemical factors are involved in the response of photosynthesis to JA and salinity stress. The activities of phosphoenolpyruvate carboxylase and carbonic anhydrase increased more than twofold. Pretreatment with JA for 4 days before salinization diminished the inhibitory effect of high salt concentration on the growth and photosynthesis. The results are discussed in terms of a possible role of JA in increasing salinity tolerance of the barley plants. Received September 8, 1997; accepted May 19, 1998     

Hormonal Effects on Growth and Morphology of Normal and Hairy Roots of Hyoscyamus muticus

Treatment of normal and Agrobacterium rhizogenes-transformed root cultures of Hyoscyamus muticus with three different auxins, indole-3-acetic acid (IAA), indole-3-butyric acid (IBA), and naphthaleneacetic acid (NAA), revealed that the response varied considerably among auxins, between transformed and normal roots, and depending on the parameter. In normal roots all three auxins provoked abundant branching, with IBA and NAA being the most effective at 2.5 and 0.5 μm, respectively, whereas IAA was most effective at low concentrations (0.05 and 0.1 μm). In transformed roots exogenously supplied auxins were generally inhibitory or, at best, without effect on growth and branching. Only 0.01 μm IAA significantly enhanced lateral root number, whereas at the higher concentrations IBA, although inhibitory, was the least effective auxin. In both root types IBA had little effect on primary root growth, but normal roots were more sensitive to IAA and NAA. These results suggest a different sensitivity to auxins of normal and transformed roots since there was no significant difference in endogenous free and conjugated IAA content nor in IAA uptake capacity. Ethylene production and biosynthesis were approximately threefold higher in hairy roots, but production could be stimulated up to tenfold that of control levels in normal roots by supplying NAA or 1-aminocyclopropane-1-carboxylic acid (ACC). Treatment with 2.5 μm NAA, but not IAA or IBA, also enhanced ethylene biosynthesis in normal roots but not in transformed ones. ACC and malonyl-1-aminocyclopropane-1-carboxylic acid accumulated to detectable levels only after treatment with an auxin (NAA). Received March 3, 1997; accepted May 28, 1997     

Dual effects of ethylene on potato dormancy and sprout growth

Dormant potato tubers (Solanum tuberosum L.) of two cultivars were treated with various concentrations of ethylene gas for various exposure periods. As has been shown by others, ethylene caused a rapid but transient increase in respiration rate, which appeared to be independent of any effects on dormancy. All concentrations tested caused accelerated sprouting, 2 microliters per liter being the most effective. Ethylene exerts a dual effect on potato tubers: it markedly shortens the duration of rest, but it inhibits elongation of the sprouts during extended treatment. Comparing these results with published work on seeds, bulbs, and corms suggests that ethylene must have a significant but as yet unexplained role in rest and dormancy. However, since the most effective ethylene treatment did not equal the response elicited by treatment with ethylene chlorhydrin, other factors must also contribute to termination of rest.     

Senescence of Flag Leaves and Ears of Wheat Hastened by Methyl Jasmonate

Treatment of flag leaves and ears of wheat plants with MJ (jasmonic acid methylester) (10⁻⁵ and 10⁻⁴ m) did not increase ethylene production, but it did accelerate senescence as indicated by the loss of chlorophyll. MJ also caused the closure of stomata, and consequently the rates of transpiration and photosynthesis decreased. Early maturity shortened the grain filling period, so the thousand grain weight was lower. Although ethylene elicited the same physiologic effects, the syndrome of senescence by MJ is independent of the former. We conclude that senescence and death in wheat are far from being elucidated; however, MJ and ethylene seem to participate in the phenomenon. Received July 10, 1997; accepted January 5, 1998     

Endogenous ethylene and reversing methyl jasmonate inhibition of Amaranthus caudatus seed germination by benzyladenine or gibberellin

BA at 10^–5 M, GA₃ at 3×10^–4 M or GA₄₊₇ at 3×10^–5 M partially or largely reversed the inhibition of Amaranthus caudatus seed germination due to JA-Me. BA or GA₃ did not affect ethylene production and ACC oxidase activity in vivo in the presence of JA-Me before radicle protrusion. However, both increased ethylene production after 72 h of incubation, when the reversal of the JA-Me inhibition of seed germination was observed. AVG at 3×10^–4 M decreased ethylene production when it was applied simultaneously with BA and JA-Me or GA₃ and JA-Me, but it had no effect on seed germination. NBD almost completely reversed the stimulatory effect of BA, GA₃ or GA₄₊₇ on the germination of seeds in the presence of JA-Me. Exogenous ethylene reversed the inhibitory effect of NBD. The results indicate that action of endogenous ethylene is involved in the response of JA-Me inhibited seeds to BA or GA_s.     

Involvement of ethylene in the morphological and developmental response of rice to elevated atmospheric CO2 concentrations

We tested the hypothesis that increased carbohydrate flux under elevatedCO₂ regulates accelerated development using rice (Oryzasativa L. cv. Jarrah). Plants were grown either in flooded soil orsolution culture at either 360 or 700 L CO₂L^–1. Total dry mass, shoot elongation rates (SER),tiller appearance rates (TAR) and ethylene release from intact rice seedlingswere measured from 5 to 42 days after planting (DAP). At maturity, shoot andsheath length, tiller number and grain mass were also measured. ElevatedCO₂ had a profound effect on growth, morphology and development andthe effects were more pronounced during the early growth phase. Total aboveground biomass increased at elevated CO₂ and this was accounted for by enhanced tiller number. Grain yield was increased by 56% under elevated CO₂mainly due to increased tiller number and hence panicle number. TAR and SERwereenhanced at elevated CO₂ but SER increased only untill 25 DAP.Elevated CO₂ stimulated a 2-3-fold increase in endogenous andACC-mediated ethylene release but the ACC concentration in the leaves waslittleaffected showing that rates of ACC synthesis matched its oxidation. Inhibitionof ethylene action by 1-aminocyclopropane (1-MCP) had a more pronouncedinhibitory effect on ethylene release in plants that were grown at 700 ascompared to 360 L CO₂ L^–1. Feedingsucrose to intact plants enhanced ethylene synthesis and these results areconsistent with the hypothesis that increased accumulation of sucrose atelevated CO₂ may enhance expression of genes in the ethylenebiosynthetic pathway. We conclude that increase in ethylene release may becentral in promoting accelerated development under elevated CO₂ andthis coincides with the release of auxiliary buds and accelerated rates oftiller appearance hence increased grain yield at elevated CO₂.     

A comparison of the submergence response of deepwater and non-deepwater rice

Twelve cultivars of rice (Oryza sativa L.), representing deepwater, short-statured, and semidwarf types, were tested for their response to submergence. The magnitude of the response varied between cultivars; however, all cultivars responded to submergence by rapid growth once internodal elongation had started. Three of these cultivars were tested for elongation capacity at four ages. The deepwater rice was capable of rapid internodal elongation in response to submergence at 4 weeks of age. Growth of the short-statured and semidwarf cultivars was not stimulated by submergence until about 10 weeks of age. In air, the internodes of deepwater rice grew slower than did those of the short-statured and semidwarf cultivars. We also investigated the elongation response of stem sections of all 12 cultivars to an atmosphere containing 3% O₂, 6% CO₂, 91% N₂ (all by volume), and 1 microliter per liter ethylene. We found that the response of each of the non-deepwater cultivars was qualitatively and quantitatively similar to that of the deepwater rice.     

Acclimation of Two Tomato Species to High Atmospheric CO(2): I. Sugar and Starch Concentrations

Lycopersicon esculentum Mill. cv Vedettos and Lycopersicon chmielewskii Rick, LA 1028, were exposed to two CO₂ concentrations (330 or 900 microliters per liter) for 10 weeks. Tomato plants grown at 900 microliters per liter contained more starch and more sugars than the control. However, we found no significant accumulation of starch and sugars in the young leaves of L. esculentum exposed to high CO₂. Carbon exchange rates were significantly higher in CO₂-enriched plants for the first few weeks of treatment but thereafter decreased as tomato plants acclimated to high atmospheric CO₂. This indicates that the long-term decline of photosynthetic efficiency of leaf 5 cannot be attributed to an accumulation of sugar and/or starch. The average concentration of starch in leaves 5 and 9 was always higher in L. esculentum than in L. chmielewskii (151.7% higher). A higher proportion of photosynthates was directed into starch for L. esculentum than for L. chmielewskii. However, these characteristics did not improve the long-term photosynthetic efficiency of L. chmielewskii grown at high CO₂ when compared with L. esculentum. The chloroplasts of tomato plants exposed to the higher CO₂ concentration exhibited a marked accumulation of starch. The results reported here suggest that starch and/or sugar accumulation under high CO₂ cannot entirely explain the loss of photosynthetic efficiency of high CO₂-grown plants.     

Light Stimulation of Ethylene Release from Leaves of Gomphrena globosa L

The effect of light and CO₂ on both the endogenous and 1-aminocyclopropane-1-carboxylic acid (ACC)-dependent ethylene evolution from metabolically active detached leaves and leaf discs of Gomphrena globosa L. is reported. Treatment with varying concentrations of ACC did not appear to inhibit photosynthesis, respiration, or stomatal behavior. In all treatments, more ethylene was released into a closed flask from ACC-treated tissue, but the pattern of ethylene release with respect to light/dark/CO₂ treatments was the same.

Leaf tissue in the light with a source of CO₂ sufficient to maintain photosynthesis always generates 3 to 4 times more ethylene than tissue in the dark. Conversely, the lowest rate of ethylene release occurs when leaf tissue is illuminated and photosynthetic activity depletes the CO₂ to the compensation point. Ethylene release in the dark is also stimulated by CO₂ either added to the flask as bicarbonate or generated by dark respiration. Ethylene release increases dramatically and in parallel with photosynthesis at increasing light intensities in this C₄ plant. Ethylene release appears dependent on CO₂ both in the light and in the dark. Therefore, it is suggested that the important factor regulating the evolution of ethylene gas from leaves of Gomphrena may be CO₂ metabolism rather than light per se.

     

Inhibition by calcium of senescence of detached cucumber cotyledons: effect on ethylene and hydroperoxide production

The effect of Ca on senescence was followed in detached cucumber (Cucumis sativus L.) cotyledons floating on various solutions in the dark. Compared with those in water, cotyledons in 10⁻⁴ molar CaCl₂ exhibited reduced chlorophyll loss and H₂O₂ production, reduced and delayed ethylene production, and did not undergo a burst in CO₂ production. In contrast, Mg had little effect on cotyledon senescence, whereas K stimulated chlorophyll loss but did not increase H₂O₂ accumulation of ethylene and CO₂ production. This reduction in the rate of senescence by Ca could also be achieved by increasing the endogenous levels of Ca in the cotyledons before excision, although the reduction was less than that with Ca in the external solution. The addition of H₂O₂ to the solutions on which cotyledons were floated stimulated chlorophyll breakdown, but effects on ethylene and CO₂ were not consistent.     

Effect of silver ion, carbon dioxide, and oxygen on ethylene action and metabolism

The relationship between ethylene action and metabolism was investigated in the etiolated pea seedling (Pisum sativum L. cv. Alaska) by inhibiting ethylene action with Ag⁺, high CO₂, and low O₂ and then determining if ethylene metabolism was inhibited in a similar manner. Ag⁺ (100 milligrams per liter) was clearly the most potent antiethylene treatment. Ag⁺ pretreatment inhibited the growth retarding action of 0.2 microliters per liter ethylene by 48% and it also inhibited the incorporation of 0.2 microliters per liter ¹⁴C₂H₄ into pea tips by the same amount. As the ethylene concentration was increased from 0.2 to 30 microliters per liter, the effectiveness of Ag⁺ in reducing ethylene action and metabolism declined in a similar fashion. Although Ag⁺ significantly inhibited the incorporation of ¹⁴C₂H₄ into tissue metabolites, the oxidation of ¹⁴C₂H₄ to ¹⁴CO₂ was unaffected in the same tissue.