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Corbineau F, Xia Q, Bailly C, El-Maarouf-Bouteau H. Ethylene, a key factor in the regulation of seed dormancy. FRONTIERS IN PLANT SCIENCE 2014; 5:539. [PMID: 25346747 PMCID: PMC4193209 DOI: 10.3389/fpls.2014.00539] [Citation(s) in RCA: 128] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/14/2014] [Accepted: 09/22/2014] [Indexed: 05/04/2023]
Abstract
Ethylene is an important component of the gaseous environment, and regulates numerous plant developmental processes including seed germination and seedling establishment. Dormancy, the inability to germinate in apparently favorable conditions, has been demonstrated to be regulated by the hormonal balance between abscisic acid (ABA) and gibberellins (GAs). Ethylene plays a key role in dormancy release in numerous species, the effective concentrations allowing the germination of dormant seeds ranging between 0.1 and 200 μL L(-1). Studies using inhibitors of ethylene biosynthesis or of ethylene action and analysis of mutant lines altered in genes involved in the ethylene signaling pathway (etr1, ein2, ain1, etr1, and erf1) demonstrate the involvement of ethylene in the regulation of germination and dormancy. Ethylene counteracts ABA effects through a regulation of ABA metabolism and signaling pathways. Moreover, ethylene insensitive mutants in Arabidopsis are more sensitive to ABA and the seeds are more dormant. Numerous data also show an interaction between ABA, GAs and ethylene metabolism and signaling pathways. It has been increasingly demonstrated that reactive oxygen species (ROS) may play a significant role in the regulation of seed germination interacting with hormonal signaling pathways. In the present review the responsiveness of seeds to ethylene will be described, and the key role of ethylene in the regulation of seed dormancy via a crosstalk between hormones and other signals will be discussed.
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Affiliation(s)
- Françoise Corbineau
- Biologie des Semences (Seed Biology), UMR7622 CNRS-UPMC, Sorbonne Universités – Université Pierre et Marie Curie-ParisParis, France
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Saini HS, Consolacion ED, Bassi PK, Spencer MS. Control processes in the induction and relief of thermoinhibition of lettuce seed germination : actions of phytochrome and endogenous ethylene. PLANT PHYSIOLOGY 1989; 90:311-5. [PMID: 16666755 PMCID: PMC1061715 DOI: 10.1104/pp.90.1.311] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Germination of lettuce seeds (Lactuca sativa L. cv Grand Rapids) in the dark was nearly 100% at 20 degrees C but was inhibited at 27 degrees C and higher temperatures (thermoinhibition). A single 5-minute exposure to red light completely overcame the inhibition at temperatures up to 28 degrees C, above which the effectiveness of single light exposures gradually declined to reach a negligible level at 32 degrees C. However, the promotive effect of light could be extended to 34 degrees C by repeated irradiations. At any one temperature, increased frequency of irradiations increased germination percentage, and with each degree increase in temperature, increasingly frequent irradiations were necessary to elicit maximal germination. Loss of the effectiveness of single irradiations with increase in temperature may result either from acceleration of the thermal reversion of the far red-absorbing form of phytochrome or decrease in seed sensitivity toward a given percentage of the far red-absorbing form of phytochrome. Using continuous red light to induce germination, the role of endogenous C(2)H(4) in germination at 32 degrees C was studied. Ethylene evolution from irradiated seeds began to increase 2 hours prior to radicle protrusion, whereas the dark-incubated (nongerminating) seeds produced a low, constant amount of C(2)H(4) throughout the 24 hour incubation period. Inhibition of C(2)H(4) synthesis with 2-aminoethoxyvinyl glycine and/or inhibition of C(2)H(4) action with 2,5-norbornadiene blocked the promotive effect of light. Exogenous C(2)H(4) overcame these blockages. The results showed that participation by endogenous C(2)H(4) was essential for the light-induced relief of thermoinhibition of lettuce seed germination. However, light did not act exclusively via C(2)H(4) since exogenous C(2)H(4) alone in darkness did not promote germination.
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Affiliation(s)
- H S Saini
- Institut botanique, Université de Montréal, 4101, rue Sherbrooke est, Montréal, Qc. Canada, H1X 2B2
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Esashi Y, Kawabe K, Isuzugawa K, Ishizawa K. Interrelations between Carbon Dioxide and Ethylene on the Stimulation of Cocklebur Seed Germination. PLANT PHYSIOLOGY 1988; 86:39-43. [PMID: 16665889 PMCID: PMC1054424 DOI: 10.1104/pp.86.1.39] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Interrelations between CO(2) and C(2)H(4) on promotion of seed germination were examined in more detail at 23 degrees C with presoaked upper seeds of Xanthium pennsylvanicum Wallr. The germination-promoting effect of C(2)H(4) decreased gradually as its application time was delayed during a soaking period, whereas CO(2) was most promotive in application at 5 days of soaking, then its effect declined. CO(2) and C(2)H(4) were additive in earlier soaking periods and synergistic in later periods. Such changes in germination behavior in response to CO(2) and/or C(2)H(4) during a soaking period were closely associated with growth responsiveness of the axial tissues, but not of the cotyledonary ones. Growth responsiveness of axial tissues to CO(2) or C(2)H(4) disappeared finally during a soaking period, but their extinct responsiveness to any one of these gases was almost fully restored in the simultaneous presence of the other. The extinct responsiveness to CO(2) was partially recovered by a preexposure to C(2)H(4). This suggests that in the later period of soaking, unlike the case in a very early period of soaking, the C(2)H(4)-sensitive phase for seed germination precedes the CO(2)-sensitive phase in which CO(2) potentiated axial growth. The restoration of CO(2) responsiveness in axial growth occurred not only after C(2)H(4) treatment but also after exposure to 8 or 33 degrees C or after KCN treatment. Thus, secondarily dormant Xanthium seeds could germinate in response to CO(2) alone, when they were previously exposed for shortterms not only to C(2)H(4) but also 8 degrees C, 33 degrees C, or KCN.
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Affiliation(s)
- Y Esashi
- Department of Biological Science, Tohoku University,Kawauchi, Sendai 980, Japan
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Saini HS, Consolacion ED, Bassi PK, Spencer MS. Requirement for Ethylene Synthesis and Action during Relief of Thermoinhibition of Lettuce Seed Germination by Combinations of Gibberellic Acid, Kinetin, and Carbon Dioxide. PLANT PHYSIOLOGY 1986; 81:950-3. [PMID: 16664963 PMCID: PMC1075465 DOI: 10.1104/pp.81.4.950] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Application of exogenous ethylene in combination with gibberellic acid (GA(3)), kinetin (KIN), and/or CO(2) 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 degrees C was investigated. Combinations of GA(3) (0.5 millimolar), KIN (0.05 millimolar), and CO(2) (10%) were used to induce germination. Little germination occurred in controls or upon treatment with ethylene, KIN, or CO(2). Neither KIN nor CO(2) affected the rate of ethylene production by seeds. Both germination and ethylene production were slightly promoted by GA(3). Treatments with GA(3)+CO(2), GA(3)+KIN, or GA(3)+CO(2)+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 GA(3), KIN, and CO(2). 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.
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Affiliation(s)
- H S Saini
- Department of Plant Science, University of Alberta, Edmonton, Alberta, Canada T6G 2P5
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Bufler G. Ethylene-promoted conversion of 1-aminocyclopropane-1-carboxylic Acid to ethylene in peel of apple at various stages of fruit development. PLANT PHYSIOLOGY 1986; 80:539-43. [PMID: 16664658 PMCID: PMC1075151 DOI: 10.1104/pp.80.2.539] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Internal ethylene concentration, ability to convert 1-amino-cyclopropane-1-carboxylic acid (ACC) to ethylene (ethylene-forming enzyme [EFE] activity) and ACC content in the peel of apples (Malus domestica Borkh., cv Golden Delicious) increased only slightly during fruit maturation on the tree. Treatment of immature apples with 100 microliters ethylene per liter for 24 hours increased EFE activity in the peel tissue, but did not induce an increase in ethylene production. This ability of apple peel tissue to respond to ethylene with elevated EFE activity increased exponentially during maturation on the tree. After harvest of mature preclimacteric apples previously treated with aminoethoxyvinyl-glycine, 0.05 microliter per liter ethylene did not immediately cause a rapid increase of development in EFE activity in peel tissue. However, 0.5 microliter per liter ethylene and higher concentrations did. The ethylene concentration for half-maximal promotion of EFE development was estimated to be approximately 0.9 microliter per liter. CO(2) partially inhibited the rapid increase of ethylene-promoted development of EFE activity. It is suggested that ethylene-promoted CO(2) production is involved in the regulation of autocatalytic ethylene production in apples.
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Affiliation(s)
- G Bufler
- Institut für Obst-, Gemüse-, und Weinbau (370), Universität Hohenheim, 7000 Stuttgart 70, Federal Republic of Germany
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Jones J, Hall M. Studies on the requirement for carbon dioxide and ethylene for germination of Spergula arvensis seeds. ACTA ACUST UNITED AC 1979. [DOI: 10.1016/0304-4211(79)90012-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Negm FB, Smith OE. Effects of ethylene and carbon dioxide on the germination of osmotically inhibited lettuce seed. PLANT PHYSIOLOGY 1978; 62:473-6. [PMID: 16660541 PMCID: PMC1092153 DOI: 10.1104/pp.62.4.473] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Lettuce seeds (Lactuca sativa L.) used in this study germinated 98% at 25 C in light or dark. Their germination was completely inhibited by 0.20 m NaCl, 0.35 m mannitol, or polyethylene glycol 6000 (-7 bars) under continuous light when germination tests were made in Petri dishes. Approximately 50% germination occurred in sealed flasks due to endogenously produced C(2)H(4) and CO(2). Removal of either or both gases prevented germination. In the presence of endogenous CO(2), addition of C(2)H(4) (0.5 to 16 microliters/liter) stimulated 95 to 100% germination (after 5 days) only in the light, but the rate of germination was dependent on C(2)H(4) concentration. At 16 microliters/liter C(2)H(4), full germination occurred within 72 hours. Addition of up to 3.2% CO(2) had no adverse effect on the C(2)H(4) action. Higher concentrations or the complete absence of CO(2) reduced both rate and total germination. CO(2) alone was ineffective.Under these osmotic conditions the promotive effect of C(2)H(4) was under the control of phytochrome.
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Affiliation(s)
- F B Negm
- Department of Horticulture, Washington State University, Pullman, Washington 99164
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Tisserat B, Murashige T. Probable indentity of substances in citrus that repress asexual embryogenesis. IN VITRO 1977; 13:785-9. [PMID: 590971 DOI: 10.1007/bf02627858] [Citation(s) in RCA: 32] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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Tisserat B, Murashige T. Effects of ethephon, ethylene, and 2,4-dichlorophenoxyacetic Acid on asexual embryogenesis in vitro. PLANT PHYSIOLOGY 1977; 60:437-9. [PMID: 16660109 PMCID: PMC542632 DOI: 10.1104/pp.60.3.437] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Asexual embryogenesis in Daucus carota L. ;Queen Anne's Lace' callus was suppressed by Ethephon, ethylene, and 2,4-dichlorophenoxyacetic acid (2,4-D). The Ethephon effect could be attributed to volatile and nonvolatile substances. The volatile component was probably entirely ethylene. Ethylene was liberated in the cultures in direct proportion to Ethephon added to the medium. Autoclaving of Ethephon caused a substantial decrease of measurable ethylene. Continuous exposure of callus to 5 mul/l ethylene depressed somatic cell embryogenesis, but not markedly. Depression of embryogenesis by 2,4-D was unrelated to ethylene evolution.
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Affiliation(s)
- B Tisserat
- Department of Plant Sciences, University of California, Riverside, California 92521
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Janes HW, Loercher L. Effects of red light and ethylene on growth of etiolated lettuce seedlings. PLANT PHYSIOLOGY 1976; 57:420-3. [PMID: 16659495 PMCID: PMC542038 DOI: 10.1104/pp.57.3.420] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Low concentrations of ethylene inhibit hypocotyl elongation of etiolated lettuce seedlings (Lactuca sativa cv. Grand Rapids), whereas red light does not inhibit it. The plumular hook tightens in response to either ethylene or red light. A combination of these two factors gives an additive response. Red light has no effect on ethylene production and red light will cause hook closure even under hypobaric pressure which removes endogenous ethylene. This suggests that ethylene and red light act independently in causing hook closure.These findings differ from those about etiolated beans where red light causes a decrease in ethylene production and a straightening of the plumular hook.
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Affiliation(s)
- H W Janes
- Department of Biology, Rutgers University, Camden, New Jersey 08102
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Keys RD, Smith OE, Kumamoto J, Lyon JL. Effect of Gibberellic Acid, Kinetin, and Ethylene plus Carbon Dioxide on the Thermodormancy of Lettuce Seed (Lactuca sativa L. cv. Mesa 659). PLANT PHYSIOLOGY 1975; 56:826-9. [PMID: 16659403 PMCID: PMC541933 DOI: 10.1104/pp.56.6.826] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
The effects of gibberellic acid and kinetin with ethylene plus carbon dioxide on the thermodormancy of lettuce seeds (Lactuca sativa L. cv. Mesa 659) at 35 C in the dark were studied. The combination of gibberellic acid plus kinetin with ethylene plus carbon dioxide was most effective in overcoming thermodormancy in these Great Lakes type seeds, alleviating any induced light requirement. Gibberellic acid action required at least a minimal level of ethylene plus carbon dioxide. Kinetin action was independent of ethylene plus carbon dioxide but interacted with the gases when the gases were added. A schematic representation of the interaction is presented.
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Affiliation(s)
- R D Keys
- Department of Plant Sciences, University of California, Riverside, California 92502
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Ching TM. Temperature regulation of germination in crimson clover seeds. PLANT PHYSIOLOGY 1975; 56:768-71. [PMID: 16659391 PMCID: PMC541921 DOI: 10.1104/pp.56.6.768] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Seeds of Dixie crimson clover (Trifolium incarnatum cv. Dixie) completed germination in 36 hours at 20 C. At 10 C germination was delayed by 24 hours. At 30 C only 20% germinated and the rest remained viable for a long time but not germinable. Different patterns of adenylate energy state and zymograms of acid phosphatase and esterase were observed from seeds grown under the three temperatures for 24 hours. Varied specific activities of protease, alpha-amylase, ATPase, RNase, acid phosphatase, glutamine synthetase, and fumarase were also found. Protein-synthesizing ability was proportional to temperature. These data indicate that temperature regulates seed germination at multiple sites.
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Affiliation(s)
- T M Ching
- Department of Crop Science, Oregon State University, Corvallis, Oregon 97331
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Bassi PK, Tregunna EB, Purohit AN. Carbon dioxide requirements for phytochrome action in photoperiodism and seed germination. PLANT PHYSIOLOGY 1975; 56:335-6. [PMID: 16659297 PMCID: PMC541814 DOI: 10.1104/pp.56.2.335] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
The effect of interrupting darkness with red light in the presence or absence of 0.03% CO(2) was studied in relation to flowering of Xanthium pennsylvanicum and germination of light-sensitive lettuce seeds. The results indicate that CO(2) is essential for red light to be effective in either process.
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Affiliation(s)
- P K Bassi
- Department of Botany, University of British Columbia, Vancouver, V6T 1W5 British Columbia, Canada
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Mingo-Castel AM, Negm FB, Smith OE. Effect of carbon dioxide and ethylene on tuberization of isolated potato stolons cultured in vitro. PLANT PHYSIOLOGY 1974; 53:798-801. [PMID: 16658793 PMCID: PMC541451 DOI: 10.1104/pp.53.6.798] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Carbon dioxide stimulates tuberization of isolated potato (Solanum tuberosum L.) stolons cultured in vitro. The stimulatory effect is inhibited by C(2)H(4) which is by itself also inhibitory of tuberization. Furthermore, C(2)H(4) inhibits kinetin-induced tuber initiation. Both the formation and elongation of roots are inhibited by C(2)H(4). The antagonistic actions of CO(2) and C(2)H(4) on tuberization are discussed.
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Affiliation(s)
- A M Mingo-Castel
- Department of Plant Sciences, University of California, Riverside, California 92502
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Park WM, Chen SS. Patterns of food utilization by the germinating lettuce seeds. PLANT PHYSIOLOGY 1974; 53:64-6. [PMID: 16658653 PMCID: PMC541333 DOI: 10.1104/pp.53.1.64] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
The embryo excised from seed of Grand Rapids lettuce (Lactuca sativa L.) can be cultured in distilled water. Complete digestion of the endosperm and transfer of nutrients from the endosperm to the embryo occur in the germinating seed with fat as the source of food. The fat is utilized for respiration, synthesis of amino acids, and to a degree, converted to sucrose. (14)C-Glucose administered to the seed is quickly converted to sucrose in the endosperm and translocated to the embryo. Radioactivity associated with the glucose remains predominantly in the carbohydrate fraction, and much of it is incorporated into what is believed to be cell wall polysaccharides. Relatively little isotope is distributed in the amino or organic acids.
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Affiliation(s)
- W M Park
- Department of Biological Sciences, University of Illinois at Chicago Circle, Chicago, Illinois 60680
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Rijven A. Ethylene and carbon dioxide in the growth regulation of isolated cotyledons of fenugreek (Trigonella foenum graecum L.) in darkness. ACTA ACUST UNITED AC 1974. [DOI: 10.1016/0304-4211(74)90038-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Craker LE, Wetherbee PJ. Ethylene, carbon dioxide, and anthocyanin synthesis. PLANT PHYSIOLOGY 1973; 52:177-9. [PMID: 16658523 PMCID: PMC366464 DOI: 10.1104/pp.52.2.177] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Affiliation(s)
- L E Craker
- Suburban Experiment Station, University of Massachusetts, Waltham, Massachusetts 02154
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Negm FB, Smith OE, Kumamoto J. The role of phytochrome in an interaction with ethylene and carbon dioxide in overcoming lettuce seed thermodormancy. PLANT PHYSIOLOGY 1973; 51:1089-94. [PMID: 16658472 PMCID: PMC366411 DOI: 10.1104/pp.51.6.1089] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Ethylene and CO(2) were used to control induction of germination in thermodormant lettuce seed (Lactuca sativa L.). These experiments ultimately showed that germination depends on the presence of an active form of the phytochrome. The phytochrome system is functional and stable at 35 C, a temperature which completely inhibits germination. Phytochrome responses to red or far red light and darkness showed that this inhibition of germination under light must be due to some other block(s) rather than to a direct inactivation of the phytochrome system itself. A postred radiation increase in lettuce seed germination that is not reversed by far red light was observed. The CO(2) requirement for C(2)H(4) action is not due to a change in the medium's pH; addition of C(2)H(4) plus CO(2) at the start of imbibition did not result in as much germination as when they were added several hours after imbibition. This reduction in germination, when the gases are added at the start of imbibiton, is due to CO(2).
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Affiliation(s)
- F B Negm
- Department of Plant Sciences, University of California, Riverside, California 92502
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Ketring DL, Morgan PW. Physiology of Oil Seeds: IV. Role of Endogenous Ethylene and Inhibitory Regulators during Natural and Induced Afterripening of Dormant Virginia-type Peanut Seeds. PLANT PHYSIOLOGY 1972; 50:382-7. [PMID: 16658179 PMCID: PMC366147 DOI: 10.1104/pp.50.3.382] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
To further elucidate the regulation of dormancy release, we followed the natural afterripening of Virginia-type peanut (Arachis hypogaea L.) seeds from about the 5th to 40th week after harvest. Seeds were kept at low temperature (3 +/- 2 C) until just prior to testing for germination, ethylene production, and internal ethylene concentration. Germination tended to fluctuate but did not increase significantly during the first 30 weeks; internal ethylene concentrations and ethylene production remained comparatively low during this time. When the seeds were placed at room temperature during the 30th to 40th weeks after harvest, there was a large increase in germination, 49% and 47% for apical and basal seeds, respectively. The data confirm our previous suggestion that production rates of 2.0 to 3.0 nanoliters per gram fresh weight per hour are necessary to provide internal ethylene concentrations at activation levels which cause a substantial increase of germination. Activation levels internally must be more than 0.4 microliter per liter and 0.9 microliter per liter for some apical and basal seeds, respectively, since dormant-imbibed seeds containing these concentrations did not germinate. Abscisic acid inhibited germination and ethylene production of afterripened seeds. Kinetin reversed the effects of ABA and this was correlated with its ability to stimulate ethylene production by the seeds. Ethylene also reversed the effects of abscisic acid. Carbon dioxide did not compete with ethylene action in this system. The data indicate that ethylene and an inhibitor, possibly abscisic acid, interact to control dormant peanut seed germination. The inability of CO(2) to inhibit competitively the action of ethylene on dormancy release, as it does other ethylene effects, suggests that the primary site of action of ethylene in peanut seeds is different from the site for other plant responses to ethylene.
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Affiliation(s)
- D L Ketring
- Department of Plant Sciences, Texas A&M University, College Station, Texas 77843
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