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1.
The effect of the ethylene antagonists norbornadiene and silver nitrate and the ethylene precursor l-aminocyclopropane-l-carboxylic acid (ACC) on Zea mays plant regeneration was studied. A 12-fold increase in plant regeneration, as measured by number of plants obtained per gram fresh weight from callus cultures of maize inbreds Pa91 and H99, was obtained by 250 M norbornadiene and 100 M silver nitrate treatments. An increase in amout of nonregenerable tissue and a 68% decrease in plant regeneration were associated with callus treated with 1 mM ACC. Ethylene emanation from 1 mM ACC treated callus reached a maximum of 170 nl g–1 h–1 after 3 days compared to 7 nl g–1 h–1 for the control. The free proline content was up to 80% lower in 1 mM ACC treated callus grown for 30 days on medium with or without 12 mM proline, respectively, as compared to each control. These studies indicate that ethylene action inhibitors such as norbornadiene and silver nitrate can be used to increase plant regeneration efficiency from maize callus cultures.Abbreviations ACC l-aminocyclopropane-l-carboxylic acid - gfw gram fresh weight  相似文献   

2.
Induction of secondary somatic embryogenesis was studied with hybridlarch (Larix x leptoeuropaea)cotyledonary somatic embryos obtained after 3, 4, 5 and 6 weeks of culture on amaturation medium supplemented with abscisic acid. Almost all 3-week maturedcotyledonary somatic embryos can develop embryonal masses whereas only 78, 27and 12% of them are able to do so after 4, 5 and 6 weeks of maturation,respectively. During the first week of culture on the induction medium, somaticembryos with high embryogenic potential (i.e. 3-weekmatured) release little ethylene (less than 1.5 nL h–1g–1 FW), whereas those which have almost completelylosttheir ability to induce embryonal masses (i.e. 6-weekmatured) produce much more ethylene. Thereafter, ethylene production by bothtypes of embryos is very similar at around 5–6 nLh–1 g–1 FW. Enrichment of theatmosphere with ethylene, or addition of 2-chloroethylphosphonic acid(ethephon)or ACC in the induction medium strongly reduced the induction of secondarysomatic embryogenesis. Moreover, inhibitors of ethylene action(AgNO3and 2,5-norbornadiene) improved the development of embryonal masses fromsomaticembryos, particularly from the 6-week maturated ones. The results obtainedclearly suggest that ethylene is involved in the regulation of somaticembryogenesis in hybrid larch. The possible relationship between somaticembryogenic potential and ethylene biosynthesis by the explants or sensitivityof the latter to ethylene is discussed.  相似文献   

3.
Effects of 1-MCP on the vase life and ethylene response of cut flowers   总被引:1,自引:0,他引:1  
Pretreatment for 6 h with low concentrations of 1-MCP (1-Methylcyclopropene, formerly designated as SIS-X), a cyclic ethylene analog, inhibits the normal wilting response of cut carnations exposed continuously to 0.4 l·l–1 ethylene. The response to 1-MCP was a function of treatment concentration and time. Treatment with 1-MCP was as effective in inhibiting ethylene effects as treatment with the anionic silver thiosulfate complex (STS), the standard commercial treatment. Other ethylene-sensitive cut flowers responded similarly to carnations. In the presence of 1 l·l–1 ethylene, the vase life of 1-MCP-treated flowers was up to 4 times that of the controls.Abbreviations 1-MCP 1-Methylcyclopropene - STS silver thiosulfate  相似文献   

4.
1-Methylcyclopropene (1-MCP), formerly designated as Sis-X, has been shown to be an effective inhibitor of ethylene responses in carnation flowers in either the light or the dark. The binding appears to be to the receptor and to be permanent. A 6 h treatment at 2.5 nl l–1 is sufficient to protect against ethylene, and 0.5 nl l–1 is sufficient if exposure is for 24 h. As carnation flowers age, a little higher concentration appears to be needed. Most of the natural increase in ethylene production during senescence is prevented by treatment with 1-MCP. A closely related compound, methylenecyclopropane shows ethylene activity. A tritium labelled 1-MCP (60 mCi mmol–1) has been prepared. A higher specific activity is needed for more critical studies.  相似文献   

5.
The ethylene antagonists, 2,5-norbornadiene (NBD) and silver nitrate, were used to probe the involvement of endogenous ethylene in the natural degreening of citrus fruit. Mature-green, detached Shamouti orange (Citrus sinensis L. Osbeck) fruit were treated with NBD vapor or dipped in solutions of silver nitrate. More than 80% of the chlorophyll was lost from control fruit after 8 days. NBD (0.11 mmole/liter) inhibited the loss of chlorophyll by 60%. NBD also antagonized the degreening induced by exogenous ethylene by 50%. Silver nitrate (0.1 mM) inhibited the loss of chlorophyll by 55%. Ethylene evolution of mature, green detached fruit was <2 nl.fruit-1.h-1 (ca. 13.5 nl.Kg-1FW.h-1) and did not change significantly for 7 days after harvest. NBD concentrations up to 0.22 mmole/liter did not enhance ethylene evolution. Not with-standing the extremely low amounts of ethylene evolved, the inhibition of degreening by NBD and silver nitrate suggests that endogenous ethylene is involved in the control of this process in mature citrus fruit.  相似文献   

6.
The kinetic parameters of in vivo ethylene metabolism by seedlings of Pisum sativum L. cv. Alaska have been determined. The oxidation of ethylene to CO2, (Ox) and the incorporation of ethylene into the tissue (TI) were both shown to display Michaelis-Menten kinetics (Km Ox = 0.9 × 10–6 M liquid phase, Vmax Ox = 2.4 × 10–10 moles g dry mass h–1 Km TI = 1.6 × 10–6 M liquid phase, Vmax TI = 4.5 × 10–10 moles g–1 dry mass h–1). Propylene competitively inhibited both Ox (Ki = 7.0 × 10–6 M) and TI (Ki = 3.7 × 10–7 M). A system comparable to Ox was absent from imbibed cotyledons of Vicia faba L. cv. Aquadulce even at saturating concentrations of ethylene similar to those used in kinetic analysis on Pisum. Silver ions were shown to inhibit TI but promoted Ox, while carbon dioxide inhibited Ox but promoted TI. Kinetic data on both these effects are presented. Data on the effect of a range of concentrations of CO2 on TI and Ox are also presented.To whom editorial correspondence should be sent  相似文献   

7.
A family of 10 competing, unstructured models has been developed to model cell growth, substrate consumption, and product formation of the pyruvate producing strain Escherichia coli YYC202 ldhA::Kan strain used in fed-batch processes. The strain is completely blocked in its ability to convert pyruvate into acetyl-CoA or acetate (using glucose as the carbon source) resulting in an acetate auxotrophy during growth in glucose minimal medium. Parameter estimation was carried out using data from fed-batch fermentation performed at constant glucose feed rates of qVG=10 mL h–1. Acetate was fed according to the previously developed feeding strategy. While the model identification was realized by least-square fit, the model discrimination was based on the model selection criterion (MSC). The validation of model parameters was performed applying data from two different fed-batch experiments with glucose feed rate qVG=20 and 30 mL h–1, respectively. Consequently, the most suitable model was identified that reflected the pyruvate and biomass curves adequately by considering a pyruvate inhibited growth (Jerusalimsky approach) and pyruvate inhibited product formation (described by modified Luedeking–Piret/Levenspiel term).List of symbols cA acetate concentration (g L–1) - cA,0 acetate concentration in the feed (g L–1) - cG glucose concentration (g L–1) - cG,0 glucose concentration in the feed (g L–1) - cP pyruvate concentration (g L–1) - cP,max critical pyruvate concentration above which reaction cannot proceed (g L–1) - cX biomass concentration (g L–1) - KI inhibition constant for pyruvate production (g L–1) - KIA inhibition constant for biomass growth on acetate (g L–1) - KP saturation constant for pyruvate production (g L–1) - KP inhibition constant of Jerusalimsky (g L–1) - KSA Monod growth constant for acetate (g L–1) - KSG Monod growth constant for glucose (g L–1) - mA maintenance coefficient for growth on acetate (g g–1 h–1) - mG maintenance coefficient for growth on glucose (g g–1 h–1) - n constant of extended Monod kinetics (Levenspiel) (–) - qV volumetric flow rate (L h–1) - qVA volumetric flow rate of acetate (L h–1) - qVG volumetric flow rate of glucose (L h–1) - rA specific rate of acetate consumption (g g–1 h–1) - rG specific rate of glucose consumption (g g–1 h–1) - rP specific rate of pyruvate production (g g–1 h–1) - rP,max maximum specific rate of pyruvate production (g g–1 h–1) - t time (h) - V reaction (broth) volume (L) - YP/G yield coefficient pyruvate from glucose (g g–1) - YX/A yield coefficient biomass from acetate (g g–1) - YX/A,max maximum yield coefficient biomass from acetate (g g–1) - YX/G yield coefficient biomass from glucose (g g–1) - YX/G,max maximum yield coefficient biomass from glucose (g g–1) - growth associated product formation coefficient (g g–1) - non-growth associated product formation coefficient (g g–1 h–1) - specific growth rate (h–1) - max maximum specific growth rate (h–1)  相似文献   

8.
The effect of age of radish seedlings on changes in chlorophyll concentration caused by ethylene was examined. Ethylene was produced at 2–4 nl g–1 h–1 following excision of cotyledons from 5-to 20-day-old seedlings. The youngest cotyledons maintained this rate, whereas ethylene synthesis declined by as much as 80% during a 24-h period in older cotyledons. The youngest cotyledons continued to accumulate chlorophyll in the dark, but after 7 days cotyledons lost chlorophyll and the proportion of chlorophyll lost increased with age. Ethylene promoted, and norbornadiene inhibited, this loss of chlorophyll; in combined treatments the effects of ethylene and norbornadiene were competitive. The maximal rate of chlorophyll loss occurred in 1l L–1 ethylene; extrapolation of the response to concentration indicated that half-maximum loss would occur at 0.005–0.01 l L–1 ethylene. In cotyledons from 20-day-old seedlings, chlorophyll degradation occurred mainly after 24 h from excision and transfer to the dark. Chlorophyll degradation during 48 h in the dark was affected by norbornadiene or ethylene applied from 0–24 h or from 24–48 h.  相似文献   

9.
The effects of medium strategies [maintenance (M), intermediary (G), and production (P) medium] on cell growth, anthraquinone (AQ) production, hydrogen peroxide (H2O2) level, lipid peroxidation, and antioxidant vitamins in Morinda elliptica cell suspension cultures were investigated. These were compared with third-stage leaf and 1-month-old callus culture. With P medium strategy, cell growth at 49 g l–1, intracellular AQ content at 42 mg g–1 DW, and H2O2 level at 9 mol g–1 FW medium were the highest as compared to the others. However, the extent of lipid peroxidation at 40.4 nmol g–1 FW and total carotenoids at 13.3 mg g–1 FW for cultures in P medium were comparable to that in the leaf, which had registered sevenfold lower AQ and 2.2-fold lower H2O2 levels. Vitamin C content at 30–120 g g–1 FW in all culture systems was almost half the leaf content. On the other hand, vitamin E content was around 400–500 g g–1 FW in 7-day-old cultures from all medium strategies and reduced to 50–150 g g–1 FW on day 14 and 21; as compared to 60 g g–1 FW in callus and 200 g g–1 FW in the leaf. This study suggests that medium strategies and cell growth phase in cell culture could influence the competition between primary and secondary metabolism, oxidative stresses and antioxidative measures. When compared with the leaf metabolism, these activities are dynamic depending on the types and availability of antioxidants.Abbreviations AQ Anthraquinone - DW Dry cell weight - FW Fresh cell weight - G Intermediary medium - M Maintenance medium - MDA Malondialdehyde - P Production medium - ROS Reactive oxygen species - TBA Thiobarbituric acid - td Doubling time  相似文献   

10.
Water stress induced an increase in endogenous concentrations of ABA in Lavandula stoechas L. plants to 13100 pmol ABA g–1 FW, which may contribute to the maintenance of water relations between the second and the third day of water stress treatment. After the third day, a sharp decrease in ABA levels was observed to 2630 pmol ABA g–1 FW, together with a decrease in water content and water potential and a loss of plant response to water stress. Water deficit did not induce an increase in endogenous ABA concentration, which remained at 514 pmol ABA g–1 FW in Rosmarinus officinalis L., which is more sclerophyllous than L. stoechas. Nevertheless, the relative water content of Rosmarinus officinalis L. after seven days of water stress decreased more than 40% and reached values of –3.2 MPa. R. officinalis showed lower levels of ABA, but significantly higher levels of IAA and ZR than L. stoechas (4 times and 6 times respectively in well watered-plants). The increase in ABA levels is not a common mechanism in these two Mediterranean shrubs which survive under water stress conditions.Abbreviations ABA abscisic acid - d days of water stress treatment - DW dry weight - FW fresh weight - IAA indole-3-acetic acid - RP Reversed Phase - RWC relative water content - TW turgid weight - WC water content - ZR zeatin riboside - water potential  相似文献   

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