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1.
Interrelation between the CN-sensitive cytochrome path and the CN-resistant, benzohydroxamic acid (BHM)-sensitive, or n-propylgallate (nPG)-sensitive alternative path in seed respiration during germination was examined using the nondormant upper and lower seeds of Xanthium pensylvanicum Wallr. The operation of both paths was required not only for normal germination of the lower seed but also for KCN- or NaN3-induced germination of both. From the sensitivity to BHM of the germination response, it became obvious that the alternative path exerts its physiological activity as soon as it develops during the early period of water imbibition. Pretreatments with KCN and NaN3 for promoting germination, strikingly decreased only the engagement of the cytochrome path in the subsequent respiration without affecting that of the alternative path. Nevertheless, no germination occurred without the operation of the cytochrome path. This suggested that excess operation of the cytochrome path is detrimental to germination, being maximal following the BHM-sensitive phase.  相似文献   

2.
Abstract At 23°C, both C2H4 and CO2 stimulated the germination of freshly imbibed upper cocklebur (Xanthium pennsylvanicum Wallr.) seeds, but C2H4, unlike CO2, changed to an inhibitor of germination under some soaking conditions. However, when seeds were pre-soaked for more than several hours at 23 °C prior to treatment, C2H4 strongly inhibited their germination at 33 °C, the degree of inhibition increasing with the duration of pre-soaking. Maximum inhibition occurred at 1–3 cm3 m?3 C2H4 when seeds were pre-soaked for 1 week; further increases of C2H4 concentration and pre-soaking period decreased the inhibitory effect. C2H4 was synergistic with CO2 when C2H4 promoted germination, whereas it was antagonistic when inhibitory. Such a transition of the C2H4 action occurred at ca. 27 °C. Also 1-andnocyclopropane-1-carboxylic acid, a C2H4 precursor, inhibited the germination of pre-soaked seeds at 33 °C, although it promoted the germination at 23 °C. When pre-soaked seeds were prepared for germination by chilling at 8 °C for 3 d, the inhibitory effect of C2H4 on the subsequent germination was manifested even at 23 °C. The reversal of the C2H4 action from promotion to inhibition in cocklebur seed germination is discussed in relation to the engagement of two respiratory pathways in the imbibed seeds.  相似文献   

3.
Growth of segments of embryonic axes and cotyledons excisedfrom dormant or nondormant cocklebur (Xanthium pennsylvanicumWallr.) seeds and CO2 and C2H4 production in these segmentswere examined in relation to the effects of temperature, CO2and C2H4. Both the nondormant axes and cotyledons grew evenat low temperatures below 23°C, but the dormant ones failedto grow. There was only little difference in the CO2 evolutionbetween the nondormant and dormant ones, but both the axis andcotyledon segments from the dormant seeds exhibited little orno C2H4 productivity, unlike the nondormant ones, at low temperatures.However, a high temperature of 33°C caused rapid extensiongrowth and C22H4 production even in dormant axes and cotyledons. The inability of dormant axes and cotyledons to grow disappearedcompletely in the presence of C2H4 at fairly low concentrations.Removal of endogenous CO2 and C2H4 reduced the growth in bothaxes and cotyledons, while exogenous CO2 mainly enhaced axialgrowth although exogenous C2H4 strongly stimulated the growthof both organs. Regardless of the dormant status, however, maximumgrowth of these organs occurred when C2H4 was given togetherwith CO2. We suggest that dormancy in cocklebur seeds is dueto the lack of growing ability in both organs, caused by thelack of C2H4 productivity in both dormant axes and cotyledons,particularly in the former. (Received December 2, 1974; )  相似文献   

4.
The effect of propyl-gallate (PG) and benzohydroxamic acid (BHAM),inhibitors of cyanide-resistant, alternative respiration path(AP), on germination were examined using after-ripened upperand lower cocklebur (Xanthium pennsylvanicum Wallr.) seeds pre-soakedat 23?C for various periods. Germination was strongly suppressedby PG or BHAM at concentration above 2 mM. However, germinationwas enhanced by low concentrations of PG or BHAM (0.25 or 0.5mM) which reduced some portions of AP operation. Similarly,the high temperature-induced germination of pre-soaked upperseeds was promoted by the same low concentration range of PGor BHAM, in which PG and BHAM were effective only when appliedat the start of high temperature incubation. The inhibitionof germination by C2H4 at high temperature occurred only whenseeds were exposed to C2H4 during the earlier period of hightemperature incubation, and delayed application tended to promotetheir germination, although most of germinated seeds did notexhibit the normal germination behaviour of predominant radicleprotrusion. If the upper seeds had been subjected to a short-timepre-soaking, the inhibition of high temperature-induced germinationby C2H4 was prevented by the low concentrations of PG or BHAM,although the germination restored was mostly an abnormal, predominantlycotyldonary growth, suggesting that the germination inhibitionby C2H4 may be involved in some step of axial growth or in thegrowth of some specific axial zone. The lower concentrationsof PG or BHAM were promotive to the axial growth even at 33?C.Based on these results, the involvement of AP in cocklebur seedgerminaton is discussed in relation to the differential growthof axial and cotyledonary tissues. (Received May 2, 1986; Accepted October 27, 1986)  相似文献   

5.
Protein Synthesis in Dormant and Non-Dormant Cocklebur Seed Segments   总被引:1,自引:0,他引:1  
Using the axial and cotyledonary segments of lower cocklebur (Xanthium pensylvanicum Wallr.) seeds, protein synthesis as shown by incorporation of radioactive leucine was examined in relation to their dormant status. During the first 9 h of water imbibition, the protein synthesis was higher in the dormant axes than in the non-dormant, after- ripened ones. When imbibed for more than 12 h non-dormant axes had a higher activity than dormant ones. This was also the case with the cotyledonary segments. Cyctoheximide, an inhibitor of protein synthesis, blocked protein synthesis in the axial tissue regardless of its dormant status, and thereby inhibited germination of the non-dormant seeds. In the dormant seeds, however, cycloheximide at 3 mM slightly stimulated germination without stimulating the C2H4 production. Based on these results, it is suggested that in cocklebur seeds there may be some proteinaceous system which is involved in the maintenance of dormancy.  相似文献   

6.
Transition from primary dormancy to secondary dormancy in cocklebur seeds   总被引:1,自引:1,他引:0  
Abstract The transition from primary dormancy to secondary dormancy was examined using upper cocklebur (Xanthium pennsylvanicum Wallr.) seeds. The non-after-ripened seeds with primary dormancy responded to chilling, anoxia, KCN, and NaN3 with an increase in germination. However, their maximal responses to these treatments only occurred after a period of water imbibition, probably a reflection of the increasing growth potential of the axial tissue which was accompanied by the increase in the capacities of respiration and ethylene production. On the other hand, the establishment of secondary dormancy was accompanied by a decrease in respiration and ethylene production of seeds, and in the growth potential of both axial and cotyledonary tissues. The decrease in growth potential of these tissues occurred regardless of whether they were excised from after-ripened seeds or non-after-ripened seeds. It is inferred that the primary dormancy of cocklebur seeds is a state maintained in un-germinated seeds for a long time through a spontaneous transition to secondary dormancy.  相似文献   

7.
Effects of C2H4 and CO2 on respiration of pre-soaked upper cocklebur(Xanthium pennsylvanicum Wallr.) seeds during a pre-germinationperiod were examined in relation to effects of the two gaseson germination. At 33?C, cocklebur seed germination was greatlystimulated. This high temperature-stimulated germination wasseverely inhibited by C2H4, but not by CO2, although both gasesstimulated germination at 23?C. C2H4 promoted seed respirationat 23?C, but its promotive effect decreases with increasingtemperature and disappeared at about 35?C, while CO2 stimulatedrespiration regardless of temperature. CO2 augmented the operationof the CN-sensitive, cytochrome path (CP) regardless of temperature,resulting in an increase in the ratio of the CP flux to a CN-resistant,alternative path (AP) flux. On the other hand, C2H4 augmentedthe operation of both paths, particularly of the AP, at 23?C,where it promoted germination. However, at 33?C where germinationis suppressed by C2H4, C2H4 preferentially stimulated respirationvia the AP, thus leading to an extremely high ratio of AP toCP. The inhibitory effect of C2H4 on germination at 33?C disappearedcompletely in enriched O2, under which conditions CP is knownto be augmented. At 23?C, CO2 and C2H4 acted independently incontrolling seed respiration, but they were antagonistic at33?C. The independent action appeared when the AP flux was verylow relative to the CP flux, while the antagonism appeared whenthe AP flux had risen. This differential action of the two gasesat different temperatures was also observed in the ATP level,adenylate pool size and energy charge of the axial tissues.These results suggest that the germination-controlling actionsof both CO2 and C2H4 are fundamentally manifested through themodification of respiratory systems. However, the germination-inhibitingeffect of C2H4 at 33 ?C was not removed by inhibitors of AP,and there was little difference in the adenylate compounds betweenthe C2H4-treated and non-treated seeds at 33?C. Therefore, thephysiological action of C2H4 can not be explained only in termsof regulation of the respiratory system. (Received January 24, 1986; Accepted November 17, 1986)  相似文献   

8.
To examine in more detail the mechanisms of cocklebur (Xanthium pennsylvanicum Wallr.) seed germination and rice (Oryza sativa L. cv. Sasanishiki) coleoptile elongation that were responsive to both C2H4 and CO2, the effects of NBD (2,5-norbornadiene), a cyclic olefin known as a competitive inhibitor of C2H4, on those phenomena were tested under various conditions. NBD strongly inhibited germination of cocklebur seeds and their axial and cotyledonary growth. The NBD effects were significantly negated by endogenously evolved and exogenously applied CO2 regardless of incubation temperature. Similarly, the inhibitory NBD effect was negated by C2H4 at 23°C, but at 33°C a low concentration (3 1/L) of C2H4 rather enhanced the inhibitory NBD effect. This phenomenon reflected the growth responses of the tip zone of axial tissues in cocklebur seeds to NBD and C2H4, in which both gases were antagonistic in regulating the axial growth at 23°C but additive in inhibiting it at 33°C. Maximal negation of these inhibitory NBD effects was brought about by simultaneous application of CO2 and C2H4. Similarly, elongation of rice coleoptiles was suppressed by NBD, and when they were immature, its inhibitory action was counteracted by both C2H4 and CO2, especially during simultaneous application. However, the inhibitory NBD effect was completely negated by C2H4 applied alone at concentrations above 500 1/L regardless of the physiological age of coleoptiles. These inhibitory NBD effects are additional evidence suggesting that C2H4 acts as a growth regulator in both cocklebur seed germination and rice coleoptile elongation. That NBD was capable of counteracting CO2 action in some cases but was incapable of negating inhibitory C2H4 action, such as that observed in cocklebur seeds, suggests that NBD acts with some side effects besides being a competitive inhibitor of C2H4 actions.  相似文献   

9.
High O2 tensions, CO4, C2H4 and high temperatures were effectivenot only in breaking the dormancy of cocklebur (Xanthium pennsylvanicumWallr.) seeds but also in increasing the germination potentialof the nondormant but small seeds. There were few qualitativedifferences in response to these factors between the dormantand impotent seeds. Unlike CO2, however, enriched O2 and C2H4were stimulative even at the low temperature of 13°C. Germination induced by CO2, C2H4 and high temperature treatmentswas lowered when endogenously evolved C2H4 or CO2 was removed,whereas the effect of O2 enrichment was not affected by theirremoval. CO2 and high temperatures remarkably stimulated C2H4production, whereas O2 enrichment had no such effect. C2H4 productivity was lower in the dormant than non-dormantseeds, suggesting that the after-ripening is characterized byincreasing C2H4 production. (Received August 20, 1974; )  相似文献   

10.
The axial growth of de-coated cocklebur (Xanthium pennsylvanicumWallr.) seeds, whose axes were divided into 4 zones, was examinedin relation to the temperature-dependent shift of the effectof C2H4 on germination. At 23?C, where both C2H4 and CO2 stimulatedgermination, CO2 promoted the axial growth at the radicle tipzone, whereas C2H4 promoted growth in the proximal portion ofthe axis. At 33?C, C2H4 inhibited germination, and stronglysuppressed the growth at the radicle tip, whereas the effectof CO2 did not change. The inhibition of growth at the radicletip zone was alleviated by O2 enrichment, which also reversedthe inhibition of germination. It is thus apparent that thetemperature-dependent shift of the action of C2H4 is associatedwith a temperature-dependent responsiveness of the radicle tipzone to C2H4. Growth of the radicle tip zone was sensitive toNaN3, whereas the proximal portion was sensitive to benzohydroxamicacid, an inhibitor of alternative respiration, suggesting thatthere may be an increase in the operation of the alternativerespiration path along a gradient of axial tissue from the tiptowards the cotyledonary side. The effects of CO2 and C2H4 arediscussed in relation to the different respiratory activitiesin each axial zone of cocklebur seeds. (Received May 9, 1986; Accepted November 6, 1986)  相似文献   

11.
The responsiveness of non-dormant, upper cocklebur (Xanthiumpennsylvanicum Wallr.) seeds to various germination stimulants,such as CO2 C2H4 CS(NH2)2, BA and enriched O2, decreased withincreasing periods of water imbibition and was completely lostin the state of secondary dormancy. Unlike CO2 BA and CS(NH2)2however, C2H2 and enriched O2 effectively prevented the developmentof secondary dormancy, and their combination was the most effectivefor stimulating the germination of seeds which had undergoneimbibition for a long time. CS(NH2)2 and BA were effective,not by themselves but either under anaerobiosis or elevatedO2 tension. Growth of the axial and cotyledonary segments excisedfrom aged seeds remained responsive to these germination stimulantsand could be further stimulated by exogenous C2H2. With imbibitionat a lower temperature, the seeds maintained high germinationin response to various stimulants and a high rate of C2H2 andCO2 production during a long period of water imbibition. Theseresults are discussed in terms of the two possible causes forthe loss of responsiveness or induction of the secondary dormancy. (Received June 27, 1978; )  相似文献   

12.
Abstract. Germination modes of lower seeds of cocklebur (Xanthium pennsylvanicum Wallr.) under different water stresses, prepared with mannitol solution, were examined in relation to gaseous factors. As the concentration of mannitol increased, germination was increasingly inhibited at a mode which was drawn by two straight lines having different slopes and meeting at an angle. One is a sharp line occurring at the lower concentrations of mannitol; the other is a gentle line occurring at higher concentrations of mannitol. The former reflected the growth response of axial tissues to mild water stress, whereas the latter reflected the growth response of cotyledonary tissues to severe water stress. The germination potential of cocklebur seeds increased with increasing temperature. Thus, the seeds were more resistant to water stress at higher than al lower temperatures. This increased germination potential under water stress resulted from the greater growth potential of axial tissues, but not cotyledonary tissues, at higher temperature. Increased O2 levels improved both the reduced axial and cotyledonary growth under water stress. Carbon dioxide predominantly enhanced axial growth under water stress, whereas C2H4 exclusively enhanced cotyledonary growth. Thus, these gases were effective in potentiating germination under water stress. When combined with each other, these gases caused more pronounced growth of the axial and cotyledonary tissues, leading to germination under more severe water stresses. Maximal axial and cotyledonary growth under water stress occurred in the simultaneous presence of CO2, C2H4 and O2, which allowed the germination at higher mannitol concentrations above 0.6 kmol m?3 From these results, it was suggested that cocklebur seeds would override water stress by depending upon both the Corresponding axial growth and the C2H4-responding cotyledonary growth.  相似文献   

13.
The dormancy breaking effect of sodium azide was studied in seeds of several genetically pure lines of Avena fatua L. isolated from field populations. Sodium azide (0.8 and 1 m M ) induced germination in several dormant lines (characterized by long term dormancy) after two weeks of treatment. By about five weeks, germination was nearly complete in azide treated seeds as compared to little or no germination in controls. (2-chloroethyl) trimethylammonium chloride (an inhibitor of gibberellin biosynthesis) completely inhibited the azide effect suggesting that stimulation of germination by azide requires gibberellin biosynthesis. Azide was very effective in breaking dormancy in lines AN-51, AN-86, AN-127 and AN-265, but failed to induce germination in Montana 73. In this line there was a synergism between azide and gibberellic acid in promotion of germination. Thus, at least two metabolic blocks are involved in the stimulation of germination in this line. Salicylhydroxamic acid (an inhibitor of alternative respiration) at 3 m M completely inhibited the germination induced by 1 m M azide. At this concentration, salicylhydroxamic acid did not inhibit germination in 1) genetically nondormant seeds (line SH-430), 2) afterripened seeds of a dormant line (AN-51), and 3) gibberellic acid-treated dormant seeds. These findings suggest that salicylhydroxamic acid-sensitive process(es), presumably alternative respiration, is necessary for the stimulation of germination in the presence of azide, but not in the germination of genetically nondormant, gibberellic acid-treated dormant, or afterripened seeds.  相似文献   

14.
Thermoperiodism in cocklebur seed germination   总被引:4,自引:2,他引:2       下载免费PDF全文
Germination potential in nondormant, upper cocklebur (Xanthium pensylvanicum Wallr.) seeds, which were incapable of germinating under constant temperatures below 25 C in air, was increased by exposure to diurnally alternating temperatures. The cocklebur seeds failed to respond to the temperature fluctuations in the beginning of water imbibition, and their responsiveness appeared only after aerobic presoaking for a limited period or after anaerobic pretreatment for 1 to 3 days.

Maximal germination was obtained after exposure to a thermoperiodic regime of 8 hours at 23 C and 16 hours at 8 C. A process occurring during the high temperature phase was aerobic and had to precede the inductive low temperature phase, its effect increasing with temperature. Critical minimum length of the inductive low temperature phase changed with the duration of a preceding anaerobiosis, for instance about 4 hours after 1 day anaerobiosis, but about 2 hours after 2 days. Percentage of subsequent germination was in proportion to the number of thermoperiodic cycles. A process of the inductive low temperature phase was not perturbed by inserting a brief higher temperature period into its phase; indeed, such insertion rather increased germination potential when performed in the earlier parts of the inductive low temperature phase. The effect of the low temperature survived for 13 to 17 hours during the higher temperature period.

  相似文献   

15.
Ethylene Production in Pea and Cocklebur Seeds of Differing Vigour   总被引:1,自引:0,他引:1  
Relationships between seed vigour and ethylene (C2H4) productionwere studied using C2H4-responsive fatty cocklebur seeds (Xanthiumpennsyhanicum Wallr.) and C2H4-insensitive starchy pea seeds(Pisum sativum L. cv. Alaska), which had been harvested in differentyears and subjected to different storage conditions. In bothspecies, the seeds with the highest vigour evolved the largestamounts of C2H4 during a period of water imbibition. The reductionof C2H4 production in cocklebur seeds occurred concomitantlywith the reduction in the growth potentials of both axial andcotyledonary tissues. Similarly, the activity of ACC-C2H4 conversionincreased with soaking, and was greater in seeds of high vigourcompared with those of low vigour. However, the change in ACCcontent in pea seeds differed from that in cocklebur seeds.That is, pea seeds with high vigour accumulated less ACC duringan imbibition period than those with low vigour. From theseresults it was suggested that the inferior C2H4 production bylow vigour pea seeds is mainly attributable to low ACC-C2H4conversion, whereas that by low vigour cocklebur seeds is dueto the shortage of ACC supply in addition to the reduced ACC-C2H4conversion. However, germination of deteriorated cocklebur seedswas not restored by exposure to ACC or C2H4, suggesting thatthe loss of seed vigour reduces the responsiveness of seedsto C2H4 as well as C2H4 production. Key words: Pea, cocklebur, seed vigour, ethylene production, 1-aminocyclopropane-1-carboxylic acid  相似文献   

16.
A possible involvement of ß-cyanoalanine synthase(CAS: EC 4.4.1.9 [EC] ) in germination processes of seeds was demonstratedusing pre-soaked upper seeds of cocklebur (Xanthium pennsylvanicumWallr.). Pretreatment in anoxia not only with KCN but also cysteine,as the substrates for CAS, stimulated the subsequent germinationof cocklebur seeds in air. However, the effect of cysteine wasmanifested even in air when applied together with C2H4, andits effect was further enhanced in combination with KCN. Thegermination-stimulating effect of KCN was intensified by C2H4only when 02 was present. In contrast, serine, another substrateof CAS, was effective in air only when combined with C2H4 and/orKCN. The addition of cysteine greatly reduced the cyanogenicglycoside content of seeds, but increased HCN evolution. Onthe other hand, glutathione did not have any effect on cockleburseed germination, HCN evolution or bound cyanogen content, suggestingthat cysteine is not acting as a reducing reagent. It is suggestedthat CAS regulates the process of cocklebur seed germinationby the dual action of enlarging the pool of amino acids andsupplying sulphydryl bases, the latter being more determinatelyimportant. Serine is effective only via the former action, whilecysteine would act via both. Key words: Cyanide, cyanogenic glycoside, ß-cyanoalanine synthase, seed germination, Xanthium pennsylvanicum  相似文献   

17.
Summary C2H4 production of the embryonic axes and cotyledons excised from dormant and non-dormant cocklebur (Xanthium pennsylvanicum Wallr.) seeds was examined in relation to ambient O2 tensions. There were two kinds of C2H4-producing systems, quasi-anaerobic and aerobic, in both organs. Regardless of the organ, the former activity was high in the dormant state and, particularly in axes, declined with after-ripening. On the other hand, the latter activity was almost insignificant in the dormant state, but increased with release from dormancy and the non-dormant axes exclusively produced C2H4 through this system. In the cotyledons, however, the former was still predominant even after they were fully after-ripened. Thus, the C2H4-producing systems were different in the seed organ and in the dormancy state.  相似文献   

18.
Esashi, Y., Fuwa, Nn Kojima, K. and Hase, S. 1986. Light actionsin the germination of cocklebur seeds. IV. Disappearance ofred light-requirement for the germination of upper seeds subjectto anoxia, chilling, cyanide or azide pretreatmenL—J.exp. Bot. 37: 1652–1662. The effects on the germination of positively photoblastic uppercocklebur (X anthium pennsylvanicum Wallr.) seeds by pretreatingwith anoxia, chilling, cyanide or azide, which stimulates theirdark germination, were examined in relation to light actions.Prior to experiments, seeds were pre-soaked at 23 °C inthe dark for 1 or 2 weeks to remove the pre-existing Pfr. Whenthe prctreatment conditions were suboptimal for germinationinduction, the stimulating effects of the pretreatments on germinationduring a subsequent dark period at 23 °C were manifest onlywhen seeds were irradiated with red light before or after thepretreatment Red light promotion was reversed by blue or far-redlight treatment. However, both prc-chilling for 6 d at 8 °Cand prctreatment with 1· 5 mol m – 3 NaN3 for 2d could induce full germination without red light exposure.On the other hand, both pre-exposure to anoxia for 8 d and pretreatmentwith 30 mol m–3 KCN could induce the dark germinationonly when germination occurred at 33 °C which is known toaugment the ratio of an alternative respiration flux to a cytochromeone. Moreover, the dark germination in response to these inductionswere strongly inhibited by the inhibitors of alternative respiration,propyl gallate and benzohydroxamic acid, applied during a subsequentdark period. It was thus suggested that Pfr has some relationto the operation of two respiration systems of cocklebur seeds,but it is not indispensable to germination of this positivelyphotoblastic seed. Key words: Anoxia, azide, blue light, chilling cyanide, dark germination, far-red light, red light, seed germination, X anthium pennsylvanicum  相似文献   

19.
Esashi, Y., Hase, S. and Kojima, K. 1987. Light actions in thegermination of cocklebur seeds. V. Effects of ethylene, carbondioxide and oxygen on germination in relation to light.–J.exp. Bot. 38: 702–710. Effects of ethylene, CO2 and O2 on the germination of after-ripenedupper cocklebur (Xanthium pennsylvanicum Wallr.) seeds wereexamined in relation to pre-irradiation by red (R) or far-red(FR) light In order to remove the pre-existing Pfr, seeds weresoaked in the dark for various periods prior to light irradiationand gas treatments. Regardless of light, 0.3 Pa C2H4 promotedgermination at 23 ?C, but it strongly inhibited germinationwhen applied at 33 ?C, the optimal temperature for the germinationof this seed. However, delayed application of C2H4 during 33?C incubation stimulated germination independently of lightin a similar manner to that seen at 23 ?C. It is, therefore,suggested that the germination-regulating action of C2H4 iscompletely independent of phytochrome. In contrast, the germination-promoting effect of 3–0 kPaCO2 was pronounced only when the seeds were previously irradiatedby R, regardless of temperature, suggesting that CO2 actionto promote germination depends upon Pfr. A synergism betweenCO2 and C2H4 at 23 ?C was observed only in the germination ofseeds pre-irradiated by R, while at 33 ?C an antagonism occurredindependently of light. The stimulation of C2H4 production byCO2 was most striking in the cotyledonary tissue pre-irradiatedby R. However, the R-dependent enhancement of CO2-stimulatedC2H4 production was negated by the subsequent FR and it wasnot found in the presence of 1-aminocyclopropane-1-carboxylicacid (ACC). Moreover, the R dependency of the germination-promotingCO2 effect disappeared in the presence of C2H4. The R-dependentC2H4 production enhanced by CO2 may thus be involved, at leastpartially, in some step of conversion from methionine to ACC. The germination-promoting effect of C2H4, but not CO2, was enhancedby O2 enrichment regardless of light. However, the germination-promotingeffect of pure O2 itself appeared to depend upon pre-irradiationwith R Key words: Carbon dioxide, cocklebur seed, ethylene, far-red light, germination, oxygen, red light, Xanthium pennsyloanicum  相似文献   

20.
Esashi Y  Katoh H 《Plant physiology》1977,59(2):117-121
Germination of nondormant but impotent small cocklebur seeds (Xanthium pennsylvanicum Wallr.) was promoted profoundly with thiourea or benzyladenine, and slightly with gibberellic acid. Gibberellic acid was ineffective in causing the germination of dormant cocklebur seeds, although thiourea and benzyladenine were effective. Experiments with excised seed pieces showed that the promotive effects of thiourea, benzyladenine, and gibberellic acid on cocklebur seed germination were associated with the enhancement of growth of seed parts; thiourea stimulated predominantly the axial growth, whereas benzyladenine stimulated predominantly the cotyledonary growth.  相似文献   

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